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mballoc.c

/*
 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
 * Written by Alex Tomas <alex@clusterfs.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public Licens
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 */


/*
 * mballoc.c contains the multiblocks allocation routines
 */

#include "mballoc.h"
#include <trace/events/ext4.h>

/*
 * MUSTDO:
 *   - test ext4_ext_search_left() and ext4_ext_search_right()
 *   - search for metadata in few groups
 *
 * TODO v4:
 *   - normalization should take into account whether file is still open
 *   - discard preallocations if no free space left (policy?)
 *   - don't normalize tails
 *   - quota
 *   - reservation for superuser
 *
 * TODO v3:
 *   - bitmap read-ahead (proposed by Oleg Drokin aka green)
 *   - track min/max extents in each group for better group selection
 *   - mb_mark_used() may allocate chunk right after splitting buddy
 *   - tree of groups sorted by number of free blocks
 *   - error handling
 */

/*
 * The allocation request involve request for multiple number of blocks
 * near to the goal(block) value specified.
 *
 * During initialization phase of the allocator we decide to use the
 * group preallocation or inode preallocation depending on the size of
 * the file. The size of the file could be the resulting file size we
 * would have after allocation, or the current file size, which ever
 * is larger. If the size is less than sbi->s_mb_stream_request we
 * select to use the group preallocation. The default value of
 * s_mb_stream_request is 16 blocks. This can also be tuned via
 * /sys/fs/ext4/<partition>/mb_stream_req. The value is represented in
 * terms of number of blocks.
 *
 * The main motivation for having small file use group preallocation is to
 * ensure that we have small files closer together on the disk.
 *
 * First stage the allocator looks at the inode prealloc list,
 * ext4_inode_info->i_prealloc_list, which contains list of prealloc
 * spaces for this particular inode. The inode prealloc space is
 * represented as:
 *
 * pa_lstart -> the logical start block for this prealloc space
 * pa_pstart -> the physical start block for this prealloc space
 * pa_len    -> lenght for this prealloc space
 * pa_free   ->  free space available in this prealloc space
 *
 * The inode preallocation space is used looking at the _logical_ start
 * block. If only the logical file block falls within the range of prealloc
 * space we will consume the particular prealloc space. This make sure that
 * that the we have contiguous physical blocks representing the file blocks
 *
 * The important thing to be noted in case of inode prealloc space is that
 * we don't modify the values associated to inode prealloc space except
 * pa_free.
 *
 * If we are not able to find blocks in the inode prealloc space and if we
 * have the group allocation flag set then we look at the locality group
 * prealloc space. These are per CPU prealloc list repreasented as
 *
 * ext4_sb_info.s_locality_groups[smp_processor_id()]
 *
 * The reason for having a per cpu locality group is to reduce the contention
 * between CPUs. It is possible to get scheduled at this point.
 *
 * The locality group prealloc space is used looking at whether we have
 * enough free space (pa_free) withing the prealloc space.
 *
 * If we can't allocate blocks via inode prealloc or/and locality group
 * prealloc then we look at the buddy cache. The buddy cache is represented
 * by ext4_sb_info.s_buddy_cache (struct inode) whose file offset gets
 * mapped to the buddy and bitmap information regarding different
 * groups. The buddy information is attached to buddy cache inode so that
 * we can access them through the page cache. The information regarding
 * each group is loaded via ext4_mb_load_buddy.  The information involve
 * block bitmap and buddy information. The information are stored in the
 * inode as:
 *
 *  {                        page                        }
 *  [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...
 *
 *
 * one block each for bitmap and buddy information.  So for each group we
 * take up 2 blocks. A page can contain blocks_per_page (PAGE_CACHE_SIZE /
 * blocksize) blocks.  So it can have information regarding groups_per_page
 * which is blocks_per_page/2
 *
 * The buddy cache inode is not stored on disk. The inode is thrown
 * away when the filesystem is unmounted.
 *
 * We look for count number of blocks in the buddy cache. If we were able
 * to locate that many free blocks we return with additional information
 * regarding rest of the contiguous physical block available
 *
 * Before allocating blocks via buddy cache we normalize the request
 * blocks. This ensure we ask for more blocks that we needed. The extra
 * blocks that we get after allocation is added to the respective prealloc
 * list. In case of inode preallocation we follow a list of heuristics
 * based on file size. This can be found in ext4_mb_normalize_request. If
 * we are doing a group prealloc we try to normalize the request to
 * sbi->s_mb_group_prealloc. Default value of s_mb_group_prealloc is
 * 512 blocks. This can be tuned via
 * /sys/fs/ext4/<partition/mb_group_prealloc. The value is represented in
 * terms of number of blocks. If we have mounted the file system with -O
 * stripe=<value> option the group prealloc request is normalized to the
 * stripe value (sbi->s_stripe)
 *
 * The regular allocator(using the buddy cache) supports few tunables.
 *
 * /sys/fs/ext4/<partition>/mb_min_to_scan
 * /sys/fs/ext4/<partition>/mb_max_to_scan
 * /sys/fs/ext4/<partition>/mb_order2_req
 *
 * The regular allocator uses buddy scan only if the request len is power of
 * 2 blocks and the order of allocation is >= sbi->s_mb_order2_reqs. The
 * value of s_mb_order2_reqs can be tuned via
 * /sys/fs/ext4/<partition>/mb_order2_req.  If the request len is equal to
 * stripe size (sbi->s_stripe), we try to search for contigous block in
 * stripe size. This should result in better allocation on RAID setups. If
 * not, we search in the specific group using bitmap for best extents. The
 * tunable min_to_scan and max_to_scan control the behaviour here.
 * min_to_scan indicate how long the mballoc __must__ look for a best
 * extent and max_to_scan indicates how long the mballoc __can__ look for a
 * best extent in the found extents. Searching for the blocks starts with
 * the group specified as the goal value in allocation context via
 * ac_g_ex. Each group is first checked based on the criteria whether it
 * can used for allocation. ext4_mb_good_group explains how the groups are
 * checked.
 *
 * Both the prealloc space are getting populated as above. So for the first
 * request we will hit the buddy cache which will result in this prealloc
 * space getting filled. The prealloc space is then later used for the
 * subsequent request.
 */

/*
 * mballoc operates on the following data:
 *  - on-disk bitmap
 *  - in-core buddy (actually includes buddy and bitmap)
 *  - preallocation descriptors (PAs)
 *
 * there are two types of preallocations:
 *  - inode
 *    assiged to specific inode and can be used for this inode only.
 *    it describes part of inode's space preallocated to specific
 *    physical blocks. any block from that preallocated can be used
 *    independent. the descriptor just tracks number of blocks left
 *    unused. so, before taking some block from descriptor, one must
 *    make sure corresponded logical block isn't allocated yet. this
 *    also means that freeing any block within descriptor's range
 *    must discard all preallocated blocks.
 *  - locality group
 *    assigned to specific locality group which does not translate to
 *    permanent set of inodes: inode can join and leave group. space
 *    from this type of preallocation can be used for any inode. thus
 *    it's consumed from the beginning to the end.
 *
 * relation between them can be expressed as:
 *    in-core buddy = on-disk bitmap + preallocation descriptors
 *
 * this mean blocks mballoc considers used are:
 *  - allocated blocks (persistent)
 *  - preallocated blocks (non-persistent)
 *
 * consistency in mballoc world means that at any time a block is either
 * free or used in ALL structures. notice: "any time" should not be read
 * literally -- time is discrete and delimited by locks.
 *
 *  to keep it simple, we don't use block numbers, instead we count number of
 *  blocks: how many blocks marked used/free in on-disk bitmap, buddy and PA.
 *
 * all operations can be expressed as:
 *  - init buddy:             buddy = on-disk + PAs
 *  - new PA:                       buddy += N; PA = N
 *  - use inode PA:                 on-disk += N; PA -= N
 *  - discard inode PA              buddy -= on-disk - PA; PA = 0
 *  - use locality group PA         on-disk += N; PA -= N
 *  - discard locality group PA           buddy -= PA; PA = 0
 *  note: 'buddy -= on-disk - PA' is used to show that on-disk bitmap
 *        is used in real operation because we can't know actual used
 *        bits from PA, only from on-disk bitmap
 *
 * if we follow this strict logic, then all operations above should be atomic.
 * given some of them can block, we'd have to use something like semaphores
 * killing performance on high-end SMP hardware. let's try to relax it using
 * the following knowledge:
 *  1) if buddy is referenced, it's already initialized
 *  2) while block is used in buddy and the buddy is referenced,
 *     nobody can re-allocate that block
 *  3) we work on bitmaps and '+' actually means 'set bits'. if on-disk has
 *     bit set and PA claims same block, it's OK. IOW, one can set bit in
 *     on-disk bitmap if buddy has same bit set or/and PA covers corresponded
 *     block
 *
 * so, now we're building a concurrency table:
 *  - init buddy vs.
 *    - new PA
 *      blocks for PA are allocated in the buddy, buddy must be referenced
 *      until PA is linked to allocation group to avoid concurrent buddy init
 *    - use inode PA
 *      we need to make sure that either on-disk bitmap or PA has uptodate data
 *      given (3) we care that PA-=N operation doesn't interfere with init
 *    - discard inode PA
 *      the simplest way would be to have buddy initialized by the discard
 *    - use locality group PA
 *      again PA-=N must be serialized with init
 *    - discard locality group PA
 *      the simplest way would be to have buddy initialized by the discard
 *  - new PA vs.
 *    - use inode PA
 *      i_data_sem serializes them
 *    - discard inode PA
 *      discard process must wait until PA isn't used by another process
 *    - use locality group PA
 *      some mutex should serialize them
 *    - discard locality group PA
 *      discard process must wait until PA isn't used by another process
 *  - use inode PA
 *    - use inode PA
 *      i_data_sem or another mutex should serializes them
 *    - discard inode PA
 *      discard process must wait until PA isn't used by another process
 *    - use locality group PA
 *      nothing wrong here -- they're different PAs covering different blocks
 *    - discard locality group PA
 *      discard process must wait until PA isn't used by another process
 *
 * now we're ready to make few consequences:
 *  - PA is referenced and while it is no discard is possible
 *  - PA is referenced until block isn't marked in on-disk bitmap
 *  - PA changes only after on-disk bitmap
 *  - discard must not compete with init. either init is done before
 *    any discard or they're serialized somehow
 *  - buddy init as sum of on-disk bitmap and PAs is done atomically
 *
 * a special case when we've used PA to emptiness. no need to modify buddy
 * in this case, but we should care about concurrent init
 *
 */

 /*
 * Logic in few words:
 *
 *  - allocation:
 *    load group
 *    find blocks
 *    mark bits in on-disk bitmap
 *    release group
 *
 *  - use preallocation:
 *    find proper PA (per-inode or group)
 *    load group
 *    mark bits in on-disk bitmap
 *    release group
 *    release PA
 *
 *  - free:
 *    load group
 *    mark bits in on-disk bitmap
 *    release group
 *
 *  - discard preallocations in group:
 *    mark PAs deleted
 *    move them onto local list
 *    load on-disk bitmap
 *    load group
 *    remove PA from object (inode or locality group)
 *    mark free blocks in-core
 *
 *  - discard inode's preallocations:
 */

/*
 * Locking rules
 *
 * Locks:
 *  - bitlock on a group      (group)
 *  - object (inode/locality) (object)
 *  - per-pa lock       (pa)
 *
 * Paths:
 *  - new pa
 *    object
 *    group
 *
 *  - find and use pa:
 *    pa
 *
 *  - release consumed pa:
 *    pa
 *    group
 *    object
 *
 *  - generate in-core bitmap:
 *    group
 *        pa
 *
 *  - discard all for given object (inode, locality group):
 *    object
 *        pa
 *    group
 *
 *  - discard all for given group:
 *    group
 *        pa
 *    group
 *        object
 *
 */
static struct kmem_cache *ext4_pspace_cachep;
static struct kmem_cache *ext4_ac_cachep;
static struct kmem_cache *ext4_free_ext_cachep;
static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
                              ext4_group_t group);
static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
                                    ext4_group_t group);
static void release_blocks_on_commit(journal_t *journal, transaction_t *txn);

static inline void *mb_correct_addr_and_bit(int *bit, void *addr)
{
#if BITS_PER_LONG == 64
      *bit += ((unsigned long) addr & 7UL) << 3;
      addr = (void *) ((unsigned long) addr & ~7UL);
#elif BITS_PER_LONG == 32
      *bit += ((unsigned long) addr & 3UL) << 3;
      addr = (void *) ((unsigned long) addr & ~3UL);
#else
#error "how many bits you are?!"
#endif
      return addr;
}

static inline int mb_test_bit(int bit, void *addr)
{
      /*
       * ext4_test_bit on architecture like powerpc
       * needs unsigned long aligned address
       */
      addr = mb_correct_addr_and_bit(&bit, addr);
      return ext4_test_bit(bit, addr);
}

static inline void mb_set_bit(int bit, void *addr)
{
      addr = mb_correct_addr_and_bit(&bit, addr);
      ext4_set_bit(bit, addr);
}

static inline void mb_clear_bit(int bit, void *addr)
{
      addr = mb_correct_addr_and_bit(&bit, addr);
      ext4_clear_bit(bit, addr);
}

static inline int mb_find_next_zero_bit(void *addr, int max, int start)
{
      int fix = 0, ret, tmpmax;
      addr = mb_correct_addr_and_bit(&fix, addr);
      tmpmax = max + fix;
      start += fix;

      ret = ext4_find_next_zero_bit(addr, tmpmax, start) - fix;
      if (ret > max)
            return max;
      return ret;
}

static inline int mb_find_next_bit(void *addr, int max, int start)
{
      int fix = 0, ret, tmpmax;
      addr = mb_correct_addr_and_bit(&fix, addr);
      tmpmax = max + fix;
      start += fix;

      ret = ext4_find_next_bit(addr, tmpmax, start) - fix;
      if (ret > max)
            return max;
      return ret;
}

static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
{
      char *bb;

      BUG_ON(EXT4_MB_BITMAP(e4b) == EXT4_MB_BUDDY(e4b));
      BUG_ON(max == NULL);

      if (order > e4b->bd_blkbits + 1) {
            *max = 0;
            return NULL;
      }

      /* at order 0 we see each particular block */
      *max = 1 << (e4b->bd_blkbits + 3);
      if (order == 0)
            return EXT4_MB_BITMAP(e4b);

      bb = EXT4_MB_BUDDY(e4b) + EXT4_SB(e4b->bd_sb)->s_mb_offsets[order];
      *max = EXT4_SB(e4b->bd_sb)->s_mb_maxs[order];

      return bb;
}

#ifdef DOUBLE_CHECK
static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b,
                     int first, int count)
{
      int i;
      struct super_block *sb = e4b->bd_sb;

      if (unlikely(e4b->bd_info->bb_bitmap == NULL))
            return;
      assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));
      for (i = 0; i < count; i++) {
            if (!mb_test_bit(first + i, e4b->bd_info->bb_bitmap)) {
                  ext4_fsblk_t blocknr;
                  blocknr = e4b->bd_group * EXT4_BLOCKS_PER_GROUP(sb);
                  blocknr += first + i;
                  blocknr +=
                      le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
                  ext4_grp_locked_error(sb, e4b->bd_group,
                           __func__, "double-free of inode"
                           " %lu's block %llu(bit %u in group %u)",
                           inode ? inode->i_ino : 0, blocknr,
                           first + i, e4b->bd_group);
            }
            mb_clear_bit(first + i, e4b->bd_info->bb_bitmap);
      }
}

static void mb_mark_used_double(struct ext4_buddy *e4b, int first, int count)
{
      int i;

      if (unlikely(e4b->bd_info->bb_bitmap == NULL))
            return;
      assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
      for (i = 0; i < count; i++) {
            BUG_ON(mb_test_bit(first + i, e4b->bd_info->bb_bitmap));
            mb_set_bit(first + i, e4b->bd_info->bb_bitmap);
      }
}

static void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
{
      if (memcmp(e4b->bd_info->bb_bitmap, bitmap, e4b->bd_sb->s_blocksize)) {
            unsigned char *b1, *b2;
            int i;
            b1 = (unsigned char *) e4b->bd_info->bb_bitmap;
            b2 = (unsigned char *) bitmap;
            for (i = 0; i < e4b->bd_sb->s_blocksize; i++) {
                  if (b1[i] != b2[i]) {
                        printk(KERN_ERR "corruption in group %u "
                               "at byte %u(%u): %x in copy != %x "
                               "on disk/prealloc\n",
                               e4b->bd_group, i, i * 8, b1[i], b2[i]);
                        BUG();
                  }
            }
      }
}

#else
static inline void mb_free_blocks_double(struct inode *inode,
                        struct ext4_buddy *e4b, int first, int count)
{
      return;
}
static inline void mb_mark_used_double(struct ext4_buddy *e4b,
                                    int first, int count)
{
      return;
}
static inline void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
{
      return;
}
#endif

#ifdef AGGRESSIVE_CHECK

#define MB_CHECK_ASSERT(assert)                                   \
do {                                                  \
      if (!(assert)) {                                \
            printk(KERN_EMERG                         \
                  "Assertion failure in %s() at %s:%d: \"%s\"\n", \
                  function, file, line, # assert);          \
            BUG();                                          \
      }                                               \
} while (0)

static int __mb_check_buddy(struct ext4_buddy *e4b, char *file,
                        const char *function, int line)
{
      struct super_block *sb = e4b->bd_sb;
      int order = e4b->bd_blkbits + 1;
      int max;
      int max2;
      int i;
      int j;
      int k;
      int count;
      struct ext4_group_info *grp;
      int fragments = 0;
      int fstart;
      struct list_head *cur;
      void *buddy;
      void *buddy2;

      {
            static int mb_check_counter;
            if (mb_check_counter++ % 100 != 0)
                  return 0;
      }

      while (order > 1) {
            buddy = mb_find_buddy(e4b, order, &max);
            MB_CHECK_ASSERT(buddy);
            buddy2 = mb_find_buddy(e4b, order - 1, &max2);
            MB_CHECK_ASSERT(buddy2);
            MB_CHECK_ASSERT(buddy != buddy2);
            MB_CHECK_ASSERT(max * 2 == max2);

            count = 0;
            for (i = 0; i < max; i++) {

                  if (mb_test_bit(i, buddy)) {
                        /* only single bit in buddy2 may be 1 */
                        if (!mb_test_bit(i << 1, buddy2)) {
                              MB_CHECK_ASSERT(
                                    mb_test_bit((i<<1)+1, buddy2));
                        } else if (!mb_test_bit((i << 1) + 1, buddy2)) {
                              MB_CHECK_ASSERT(
                                    mb_test_bit(i << 1, buddy2));
                        }
                        continue;
                  }

                  /* both bits in buddy2 must be 0 */
                  MB_CHECK_ASSERT(mb_test_bit(i << 1, buddy2));
                  MB_CHECK_ASSERT(mb_test_bit((i << 1) + 1, buddy2));

                  for (j = 0; j < (1 << order); j++) {
                        k = (i * (1 << order)) + j;
                        MB_CHECK_ASSERT(
                              !mb_test_bit(k, EXT4_MB_BITMAP(e4b)));
                  }
                  count++;
            }
            MB_CHECK_ASSERT(e4b->bd_info->bb_counters[order] == count);
            order--;
      }

      fstart = -1;
      buddy = mb_find_buddy(e4b, 0, &max);
      for (i = 0; i < max; i++) {
            if (!mb_test_bit(i, buddy)) {
                  MB_CHECK_ASSERT(i >= e4b->bd_info->bb_first_free);
                  if (fstart == -1) {
                        fragments++;
                        fstart = i;
                  }
                  continue;
            }
            fstart = -1;
            /* check used bits only */
            for (j = 0; j < e4b->bd_blkbits + 1; j++) {
                  buddy2 = mb_find_buddy(e4b, j, &max2);
                  k = i >> j;
                  MB_CHECK_ASSERT(k < max2);
                  MB_CHECK_ASSERT(mb_test_bit(k, buddy2));
            }
      }
      MB_CHECK_ASSERT(!EXT4_MB_GRP_NEED_INIT(e4b->bd_info));
      MB_CHECK_ASSERT(e4b->bd_info->bb_fragments == fragments);

      grp = ext4_get_group_info(sb, e4b->bd_group);
      buddy = mb_find_buddy(e4b, 0, &max);
      list_for_each(cur, &grp->bb_prealloc_list) {
            ext4_group_t groupnr;
            struct ext4_prealloc_space *pa;
            pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
            ext4_get_group_no_and_offset(sb, pa->pa_pstart, &groupnr, &k);
            MB_CHECK_ASSERT(groupnr == e4b->bd_group);
            for (i = 0; i < pa->pa_len; i++)
                  MB_CHECK_ASSERT(mb_test_bit(k + i, buddy));
      }
      return 0;
}
#undef MB_CHECK_ASSERT
#define mb_check_buddy(e4b) __mb_check_buddy(e4b,     \
                              __FILE__, __func__, __LINE__)
#else
#define mb_check_buddy(e4b)
#endif

/* FIXME!! need more doc */
static void ext4_mb_mark_free_simple(struct super_block *sb,
                        void *buddy, unsigned first, int len,
                              struct ext4_group_info *grp)
{
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      unsigned short min;
      unsigned short max;
      unsigned short chunk;
      unsigned short border;

      BUG_ON(len > EXT4_BLOCKS_PER_GROUP(sb));

      border = 2 << sb->s_blocksize_bits;

      while (len > 0) {
            /* find how many blocks can be covered since this position */
            max = ffs(first | border) - 1;

            /* find how many blocks of power 2 we need to mark */
            min = fls(len) - 1;

            if (max < min)
                  min = max;
            chunk = 1 << min;

            /* mark multiblock chunks only */
            grp->bb_counters[min]++;
            if (min > 0)
                  mb_clear_bit(first >> min,
                             buddy + sbi->s_mb_offsets[min]);

            len -= chunk;
            first += chunk;
      }
}

static noinline_for_stack
void ext4_mb_generate_buddy(struct super_block *sb,
                        void *buddy, void *bitmap, ext4_group_t group)
{
      struct ext4_group_info *grp = ext4_get_group_info(sb, group);
      unsigned short max = EXT4_BLOCKS_PER_GROUP(sb);
      unsigned short i = 0;
      unsigned short first;
      unsigned short len;
      unsigned free = 0;
      unsigned fragments = 0;
      unsigned long long period = get_cycles();

      /* initialize buddy from bitmap which is aggregation
       * of on-disk bitmap and preallocations */
      i = mb_find_next_zero_bit(bitmap, max, 0);
      grp->bb_first_free = i;
      while (i < max) {
            fragments++;
            first = i;
            i = mb_find_next_bit(bitmap, max, i);
            len = i - first;
            free += len;
            if (len > 1)
                  ext4_mb_mark_free_simple(sb, buddy, first, len, grp);
            else
                  grp->bb_counters[0]++;
            if (i < max)
                  i = mb_find_next_zero_bit(bitmap, max, i);
      }
      grp->bb_fragments = fragments;

      if (free != grp->bb_free) {
            ext4_grp_locked_error(sb, group,  __func__,
                  "EXT4-fs: group %u: %u blocks in bitmap, %u in gd",
                  group, free, grp->bb_free);
            /*
             * If we intent to continue, we consider group descritor
             * corrupt and update bb_free using bitmap value
             */
            grp->bb_free = free;
      }

      clear_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));

      period = get_cycles() - period;
      spin_lock(&EXT4_SB(sb)->s_bal_lock);
      EXT4_SB(sb)->s_mb_buddies_generated++;
      EXT4_SB(sb)->s_mb_generation_time += period;
      spin_unlock(&EXT4_SB(sb)->s_bal_lock);
}

/* The buddy information is attached the buddy cache inode
 * for convenience. The information regarding each group
 * is loaded via ext4_mb_load_buddy. The information involve
 * block bitmap and buddy information. The information are
 * stored in the inode as
 *
 * {                        page                        }
 * [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...
 *
 *
 * one block each for bitmap and buddy information.
 * So for each group we take up 2 blocks. A page can
 * contain blocks_per_page (PAGE_CACHE_SIZE / blocksize)  blocks.
 * So it can have information regarding groups_per_page which
 * is blocks_per_page/2
 */

static int ext4_mb_init_cache(struct page *page, char *incore)
{
      ext4_group_t ngroups;
      int blocksize;
      int blocks_per_page;
      int groups_per_page;
      int err = 0;
      int i;
      ext4_group_t first_group;
      int first_block;
      struct super_block *sb;
      struct buffer_head *bhs;
      struct buffer_head **bh;
      struct inode *inode;
      char *data;
      char *bitmap;

      mb_debug("init page %lu\n", page->index);

      inode = page->mapping->host;
      sb = inode->i_sb;
      ngroups = ext4_get_groups_count(sb);
      blocksize = 1 << inode->i_blkbits;
      blocks_per_page = PAGE_CACHE_SIZE / blocksize;

      groups_per_page = blocks_per_page >> 1;
      if (groups_per_page == 0)
            groups_per_page = 1;

      /* allocate buffer_heads to read bitmaps */
      if (groups_per_page > 1) {
            err = -ENOMEM;
            i = sizeof(struct buffer_head *) * groups_per_page;
            bh = kzalloc(i, GFP_NOFS);
            if (bh == NULL)
                  goto out;
      } else
            bh = &bhs;

      first_group = page->index * blocks_per_page / 2;

      /* read all groups the page covers into the cache */
      for (i = 0; i < groups_per_page; i++) {
            struct ext4_group_desc *desc;

            if (first_group + i >= ngroups)
                  break;

            err = -EIO;
            desc = ext4_get_group_desc(sb, first_group + i, NULL);
            if (desc == NULL)
                  goto out;

            err = -ENOMEM;
            bh[i] = sb_getblk(sb, ext4_block_bitmap(sb, desc));
            if (bh[i] == NULL)
                  goto out;

            if (bitmap_uptodate(bh[i]))
                  continue;

            lock_buffer(bh[i]);
            if (bitmap_uptodate(bh[i])) {
                  unlock_buffer(bh[i]);
                  continue;
            }
            ext4_lock_group(sb, first_group + i);
            if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
                  ext4_init_block_bitmap(sb, bh[i],
                                    first_group + i, desc);
                  set_bitmap_uptodate(bh[i]);
                  set_buffer_uptodate(bh[i]);
                  ext4_unlock_group(sb, first_group + i);
                  unlock_buffer(bh[i]);
                  continue;
            }
            ext4_unlock_group(sb, first_group + i);
            if (buffer_uptodate(bh[i])) {
                  /*
                   * if not uninit if bh is uptodate,
                   * bitmap is also uptodate
                   */
                  set_bitmap_uptodate(bh[i]);
                  unlock_buffer(bh[i]);
                  continue;
            }
            get_bh(bh[i]);
            /*
             * submit the buffer_head for read. We can
             * safely mark the bitmap as uptodate now.
             * We do it here so the bitmap uptodate bit
             * get set with buffer lock held.
             */
            set_bitmap_uptodate(bh[i]);
            bh[i]->b_end_io = end_buffer_read_sync;
            submit_bh(READ, bh[i]);
            mb_debug("read bitmap for group %u\n", first_group + i);
      }

      /* wait for I/O completion */
      for (i = 0; i < groups_per_page && bh[i]; i++)
            wait_on_buffer(bh[i]);

      err = -EIO;
      for (i = 0; i < groups_per_page && bh[i]; i++)
            if (!buffer_uptodate(bh[i]))
                  goto out;

      err = 0;
      first_block = page->index * blocks_per_page;
      /* init the page  */
      memset(page_address(page), 0xff, PAGE_CACHE_SIZE);
      for (i = 0; i < blocks_per_page; i++) {
            int group;
            struct ext4_group_info *grinfo;

            group = (first_block + i) >> 1;
            if (group >= ngroups)
                  break;

            /*
             * data carry information regarding this
             * particular group in the format specified
             * above
             *
             */
            data = page_address(page) + (i * blocksize);
            bitmap = bh[group - first_group]->b_data;

            /*
             * We place the buddy block and bitmap block
             * close together
             */
            if ((first_block + i) & 1) {
                  /* this is block of buddy */
                  BUG_ON(incore == NULL);
                  mb_debug("put buddy for group %u in page %lu/%x\n",
                        group, page->index, i * blocksize);
                  grinfo = ext4_get_group_info(sb, group);
                  grinfo->bb_fragments = 0;
                  memset(grinfo->bb_counters, 0,
                         sizeof(unsigned short)*(sb->s_blocksize_bits+2));
                  /*
                   * incore got set to the group block bitmap below
                   */
                  ext4_lock_group(sb, group);
                  ext4_mb_generate_buddy(sb, data, incore, group);
                  ext4_unlock_group(sb, group);
                  incore = NULL;
            } else {
                  /* this is block of bitmap */
                  BUG_ON(incore != NULL);
                  mb_debug("put bitmap for group %u in page %lu/%x\n",
                        group, page->index, i * blocksize);

                  /* see comments in ext4_mb_put_pa() */
                  ext4_lock_group(sb, group);
                  memcpy(data, bitmap, blocksize);

                  /* mark all preallocated blks used in in-core bitmap */
                  ext4_mb_generate_from_pa(sb, data, group);
                  ext4_mb_generate_from_freelist(sb, data, group);
                  ext4_unlock_group(sb, group);

                  /* set incore so that the buddy information can be
                   * generated using this
                   */
                  incore = data;
            }
      }
      SetPageUptodate(page);

out:
      if (bh) {
            for (i = 0; i < groups_per_page && bh[i]; i++)
                  brelse(bh[i]);
            if (bh != &bhs)
                  kfree(bh);
      }
      return err;
}

static noinline_for_stack int
ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
                              struct ext4_buddy *e4b)
{
      int blocks_per_page;
      int block;
      int pnum;
      int poff;
      struct page *page;
      int ret;
      struct ext4_group_info *grp;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct inode *inode = sbi->s_buddy_cache;

      mb_debug("load group %u\n", group);

      blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
      grp = ext4_get_group_info(sb, group);

      e4b->bd_blkbits = sb->s_blocksize_bits;
      e4b->bd_info = ext4_get_group_info(sb, group);
      e4b->bd_sb = sb;
      e4b->bd_group = group;
      e4b->bd_buddy_page = NULL;
      e4b->bd_bitmap_page = NULL;
      e4b->alloc_semp = &grp->alloc_sem;

      /* Take the read lock on the group alloc
       * sem. This would make sure a parallel
       * ext4_mb_init_group happening on other
       * groups mapped by the page is blocked
       * till we are done with allocation
       */
      down_read(e4b->alloc_semp);

      /*
       * the buddy cache inode stores the block bitmap
       * and buddy information in consecutive blocks.
       * So for each group we need two blocks.
       */
      block = group * 2;
      pnum = block / blocks_per_page;
      poff = block % blocks_per_page;

      /* we could use find_or_create_page(), but it locks page
       * what we'd like to avoid in fast path ... */
      page = find_get_page(inode->i_mapping, pnum);
      if (page == NULL || !PageUptodate(page)) {
            if (page)
                  /*
                   * drop the page reference and try
                   * to get the page with lock. If we
                   * are not uptodate that implies
                   * somebody just created the page but
                   * is yet to initialize the same. So
                   * wait for it to initialize.
                   */
                  page_cache_release(page);
            page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
            if (page) {
                  BUG_ON(page->mapping != inode->i_mapping);
                  if (!PageUptodate(page)) {
                        ret = ext4_mb_init_cache(page, NULL);
                        if (ret) {
                              unlock_page(page);
                              goto err;
                        }
                        mb_cmp_bitmaps(e4b, page_address(page) +
                                     (poff * sb->s_blocksize));
                  }
                  unlock_page(page);
            }
      }
      if (page == NULL || !PageUptodate(page)) {
            ret = -EIO;
            goto err;
      }
      e4b->bd_bitmap_page = page;
      e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
      mark_page_accessed(page);

      block++;
      pnum = block / blocks_per_page;
      poff = block % blocks_per_page;

      page = find_get_page(inode->i_mapping, pnum);
      if (page == NULL || !PageUptodate(page)) {
            if (page)
                  page_cache_release(page);
            page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
            if (page) {
                  BUG_ON(page->mapping != inode->i_mapping);
                  if (!PageUptodate(page)) {
                        ret = ext4_mb_init_cache(page, e4b->bd_bitmap);
                        if (ret) {
                              unlock_page(page);
                              goto err;
                        }
                  }
                  unlock_page(page);
            }
      }
      if (page == NULL || !PageUptodate(page)) {
            ret = -EIO;
            goto err;
      }
      e4b->bd_buddy_page = page;
      e4b->bd_buddy = page_address(page) + (poff * sb->s_blocksize);
      mark_page_accessed(page);

      BUG_ON(e4b->bd_bitmap_page == NULL);
      BUG_ON(e4b->bd_buddy_page == NULL);

      return 0;

err:
      if (e4b->bd_bitmap_page)
            page_cache_release(e4b->bd_bitmap_page);
      if (e4b->bd_buddy_page)
            page_cache_release(e4b->bd_buddy_page);
      e4b->bd_buddy = NULL;
      e4b->bd_bitmap = NULL;

      /* Done with the buddy cache */
      up_read(e4b->alloc_semp);
      return ret;
}

static void ext4_mb_release_desc(struct ext4_buddy *e4b)
{
      if (e4b->bd_bitmap_page)
            page_cache_release(e4b->bd_bitmap_page);
      if (e4b->bd_buddy_page)
            page_cache_release(e4b->bd_buddy_page);
      /* Done with the buddy cache */
      if (e4b->alloc_semp)
            up_read(e4b->alloc_semp);
}


static int mb_find_order_for_block(struct ext4_buddy *e4b, int block)
{
      int order = 1;
      void *bb;

      BUG_ON(EXT4_MB_BITMAP(e4b) == EXT4_MB_BUDDY(e4b));
      BUG_ON(block >= (1 << (e4b->bd_blkbits + 3)));

      bb = EXT4_MB_BUDDY(e4b);
      while (order <= e4b->bd_blkbits + 1) {
            block = block >> 1;
            if (!mb_test_bit(block, bb)) {
                  /* this block is part of buddy of order 'order' */
                  return order;
            }
            bb += 1 << (e4b->bd_blkbits - order);
            order++;
      }
      return 0;
}

static void mb_clear_bits(void *bm, int cur, int len)
{
      __u32 *addr;

      len = cur + len;
      while (cur < len) {
            if ((cur & 31) == 0 && (len - cur) >= 32) {
                  /* fast path: clear whole word at once */
                  addr = bm + (cur >> 3);
                  *addr = 0;
                  cur += 32;
                  continue;
            }
            mb_clear_bit(cur, bm);
            cur++;
      }
}

static void mb_set_bits(void *bm, int cur, int len)
{
      __u32 *addr;

      len = cur + len;
      while (cur < len) {
            if ((cur & 31) == 0 && (len - cur) >= 32) {
                  /* fast path: set whole word at once */
                  addr = bm + (cur >> 3);
                  *addr = 0xffffffff;
                  cur += 32;
                  continue;
            }
            mb_set_bit(cur, bm);
            cur++;
      }
}

static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
                    int first, int count)
{
      int block = 0;
      int max = 0;
      int order;
      void *buddy;
      void *buddy2;
      struct super_block *sb = e4b->bd_sb;

      BUG_ON(first + count > (sb->s_blocksize << 3));
      assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));
      mb_check_buddy(e4b);
      mb_free_blocks_double(inode, e4b, first, count);

      e4b->bd_info->bb_free += count;
      if (first < e4b->bd_info->bb_first_free)
            e4b->bd_info->bb_first_free = first;

      /* let's maintain fragments counter */
      if (first != 0)
            block = !mb_test_bit(first - 1, EXT4_MB_BITMAP(e4b));
      if (first + count < EXT4_SB(sb)->s_mb_maxs[0])
            max = !mb_test_bit(first + count, EXT4_MB_BITMAP(e4b));
      if (block && max)
            e4b->bd_info->bb_fragments--;
      else if (!block && !max)
            e4b->bd_info->bb_fragments++;

      /* let's maintain buddy itself */
      while (count-- > 0) {
            block = first++;
            order = 0;

            if (!mb_test_bit(block, EXT4_MB_BITMAP(e4b))) {
                  ext4_fsblk_t blocknr;
                  blocknr = e4b->bd_group * EXT4_BLOCKS_PER_GROUP(sb);
                  blocknr += block;
                  blocknr +=
                      le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
                  ext4_grp_locked_error(sb, e4b->bd_group,
                           __func__, "double-free of inode"
                           " %lu's block %llu(bit %u in group %u)",
                           inode ? inode->i_ino : 0, blocknr, block,
                           e4b->bd_group);
            }
            mb_clear_bit(block, EXT4_MB_BITMAP(e4b));
            e4b->bd_info->bb_counters[order]++;

            /* start of the buddy */
            buddy = mb_find_buddy(e4b, order, &max);

            do {
                  block &= ~1UL;
                  if (mb_test_bit(block, buddy) ||
                              mb_test_bit(block + 1, buddy))
                        break;

                  /* both the buddies are free, try to coalesce them */
                  buddy2 = mb_find_buddy(e4b, order + 1, &max);

                  if (!buddy2)
                        break;

                  if (order > 0) {
                        /* for special purposes, we don't set
                         * free bits in bitmap */
                        mb_set_bit(block, buddy);
                        mb_set_bit(block + 1, buddy);
                  }
                  e4b->bd_info->bb_counters[order]--;
                  e4b->bd_info->bb_counters[order]--;

                  block = block >> 1;
                  order++;
                  e4b->bd_info->bb_counters[order]++;

                  mb_clear_bit(block, buddy2);
                  buddy = buddy2;
            } while (1);
      }
      mb_check_buddy(e4b);
}

static int mb_find_extent(struct ext4_buddy *e4b, int order, int block,
                        int needed, struct ext4_free_extent *ex)
{
      int next = block;
      int max;
      int ord;
      void *buddy;

      assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
      BUG_ON(ex == NULL);

      buddy = mb_find_buddy(e4b, order, &max);
      BUG_ON(buddy == NULL);
      BUG_ON(block >= max);
      if (mb_test_bit(block, buddy)) {
            ex->fe_len = 0;
            ex->fe_start = 0;
            ex->fe_group = 0;
            return 0;
      }

      /* FIXME dorp order completely ? */
      if (likely(order == 0)) {
            /* find actual order */
            order = mb_find_order_for_block(e4b, block);
            block = block >> order;
      }

      ex->fe_len = 1 << order;
      ex->fe_start = block << order;
      ex->fe_group = e4b->bd_group;

      /* calc difference from given start */
      next = next - ex->fe_start;
      ex->fe_len -= next;
      ex->fe_start += next;

      while (needed > ex->fe_len &&
             (buddy = mb_find_buddy(e4b, order, &max))) {

            if (block + 1 >= max)
                  break;

            next = (block + 1) * (1 << order);
            if (mb_test_bit(next, EXT4_MB_BITMAP(e4b)))
                  break;

            ord = mb_find_order_for_block(e4b, next);

            order = ord;
            block = next >> order;
            ex->fe_len += 1 << order;
      }

      BUG_ON(ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3)));
      return ex->fe_len;
}

static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
{
      int ord;
      int mlen = 0;
      int max = 0;
      int cur;
      int start = ex->fe_start;
      int len = ex->fe_len;
      unsigned ret = 0;
      int len0 = len;
      void *buddy;

      BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3));
      BUG_ON(e4b->bd_group != ex->fe_group);
      assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
      mb_check_buddy(e4b);
      mb_mark_used_double(e4b, start, len);

      e4b->bd_info->bb_free -= len;
      if (e4b->bd_info->bb_first_free == start)
            e4b->bd_info->bb_first_free += len;

      /* let's maintain fragments counter */
      if (start != 0)
            mlen = !mb_test_bit(start - 1, EXT4_MB_BITMAP(e4b));
      if (start + len < EXT4_SB(e4b->bd_sb)->s_mb_maxs[0])
            max = !mb_test_bit(start + len, EXT4_MB_BITMAP(e4b));
      if (mlen && max)
            e4b->bd_info->bb_fragments++;
      else if (!mlen && !max)
            e4b->bd_info->bb_fragments--;

      /* let's maintain buddy itself */
      while (len) {
            ord = mb_find_order_for_block(e4b, start);

            if (((start >> ord) << ord) == start && len >= (1 << ord)) {
                  /* the whole chunk may be allocated at once! */
                  mlen = 1 << ord;
                  buddy = mb_find_buddy(e4b, ord, &max);
                  BUG_ON((start >> ord) >= max);
                  mb_set_bit(start >> ord, buddy);
                  e4b->bd_info->bb_counters[ord]--;
                  start += mlen;
                  len -= mlen;
                  BUG_ON(len < 0);
                  continue;
            }

            /* store for history */
            if (ret == 0)
                  ret = len | (ord << 16);

            /* we have to split large buddy */
            BUG_ON(ord <= 0);
            buddy = mb_find_buddy(e4b, ord, &max);
            mb_set_bit(start >> ord, buddy);
            e4b->bd_info->bb_counters[ord]--;

            ord--;
            cur = (start >> ord) & ~1U;
            buddy = mb_find_buddy(e4b, ord, &max);
            mb_clear_bit(cur, buddy);
            mb_clear_bit(cur + 1, buddy);
            e4b->bd_info->bb_counters[ord]++;
            e4b->bd_info->bb_counters[ord]++;
      }

      mb_set_bits(EXT4_MB_BITMAP(e4b), ex->fe_start, len0);
      mb_check_buddy(e4b);

      return ret;
}

/*
 * Must be called under group lock!
 */
static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
                              struct ext4_buddy *e4b)
{
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
      int ret;

      BUG_ON(ac->ac_b_ex.fe_group != e4b->bd_group);
      BUG_ON(ac->ac_status == AC_STATUS_FOUND);

      ac->ac_b_ex.fe_len = min(ac->ac_b_ex.fe_len, ac->ac_g_ex.fe_len);
      ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical;
      ret = mb_mark_used(e4b, &ac->ac_b_ex);

      /* preallocation can change ac_b_ex, thus we store actually
       * allocated blocks for history */
      ac->ac_f_ex = ac->ac_b_ex;

      ac->ac_status = AC_STATUS_FOUND;
      ac->ac_tail = ret & 0xffff;
      ac->ac_buddy = ret >> 16;

      /*
       * take the page reference. We want the page to be pinned
       * so that we don't get a ext4_mb_init_cache_call for this
       * group until we update the bitmap. That would mean we
       * double allocate blocks. The reference is dropped
       * in ext4_mb_release_context
       */
      ac->ac_bitmap_page = e4b->bd_bitmap_page;
      get_page(ac->ac_bitmap_page);
      ac->ac_buddy_page = e4b->bd_buddy_page;
      get_page(ac->ac_buddy_page);
      /* on allocation we use ac to track the held semaphore */
      ac->alloc_semp =  e4b->alloc_semp;
      e4b->alloc_semp = NULL;
      /* store last allocated for subsequent stream allocation */
      if ((ac->ac_flags & EXT4_MB_HINT_DATA)) {
            spin_lock(&sbi->s_md_lock);
            sbi->s_mb_last_group = ac->ac_f_ex.fe_group;
            sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
            spin_unlock(&sbi->s_md_lock);
      }
}

/*
 * regular allocator, for general purposes allocation
 */

static void ext4_mb_check_limits(struct ext4_allocation_context *ac,
                              struct ext4_buddy *e4b,
                              int finish_group)
{
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
      struct ext4_free_extent *bex = &ac->ac_b_ex;
      struct ext4_free_extent *gex = &ac->ac_g_ex;
      struct ext4_free_extent ex;
      int max;

      if (ac->ac_status == AC_STATUS_FOUND)
            return;
      /*
       * We don't want to scan for a whole year
       */
      if (ac->ac_found > sbi->s_mb_max_to_scan &&
                  !(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
            ac->ac_status = AC_STATUS_BREAK;
            return;
      }

      /*
       * Haven't found good chunk so far, let's continue
       */
      if (bex->fe_len < gex->fe_len)
            return;

      if ((finish_group || ac->ac_found > sbi->s_mb_min_to_scan)
                  && bex->fe_group == e4b->bd_group) {
            /* recheck chunk's availability - we don't know
             * when it was found (within this lock-unlock
             * period or not) */
            max = mb_find_extent(e4b, 0, bex->fe_start, gex->fe_len, &ex);
            if (max >= gex->fe_len) {
                  ext4_mb_use_best_found(ac, e4b);
                  return;
            }
      }
}

/*
 * The routine checks whether found extent is good enough. If it is,
 * then the extent gets marked used and flag is set to the context
 * to stop scanning. Otherwise, the extent is compared with the
 * previous found extent and if new one is better, then it's stored
 * in the context. Later, the best found extent will be used, if
 * mballoc can't find good enough extent.
 *
 * FIXME: real allocation policy is to be designed yet!
 */
static void ext4_mb_measure_extent(struct ext4_allocation_context *ac,
                              struct ext4_free_extent *ex,
                              struct ext4_buddy *e4b)
{
      struct ext4_free_extent *bex = &ac->ac_b_ex;
      struct ext4_free_extent *gex = &ac->ac_g_ex;

      BUG_ON(ex->fe_len <= 0);
      BUG_ON(ex->fe_len > EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
      BUG_ON(ex->fe_start >= EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
      BUG_ON(ac->ac_status != AC_STATUS_CONTINUE);

      ac->ac_found++;

      /*
       * The special case - take what you catch first
       */
      if (unlikely(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
            *bex = *ex;
            ext4_mb_use_best_found(ac, e4b);
            return;
      }

      /*
       * Let's check whether the chuck is good enough
       */
      if (ex->fe_len == gex->fe_len) {
            *bex = *ex;
            ext4_mb_use_best_found(ac, e4b);
            return;
      }

      /*
       * If this is first found extent, just store it in the context
       */
      if (bex->fe_len == 0) {
            *bex = *ex;
            return;
      }

      /*
       * If new found extent is better, store it in the context
       */
      if (bex->fe_len < gex->fe_len) {
            /* if the request isn't satisfied, any found extent
             * larger than previous best one is better */
            if (ex->fe_len > bex->fe_len)
                  *bex = *ex;
      } else if (ex->fe_len > gex->fe_len) {
            /* if the request is satisfied, then we try to find
             * an extent that still satisfy the request, but is
             * smaller than previous one */
            if (ex->fe_len < bex->fe_len)
                  *bex = *ex;
      }

      ext4_mb_check_limits(ac, e4b, 0);
}

static noinline_for_stack
int ext4_mb_try_best_found(struct ext4_allocation_context *ac,
                              struct ext4_buddy *e4b)
{
      struct ext4_free_extent ex = ac->ac_b_ex;
      ext4_group_t group = ex.fe_group;
      int max;
      int err;

      BUG_ON(ex.fe_len <= 0);
      err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
      if (err)
            return err;

      ext4_lock_group(ac->ac_sb, group);
      max = mb_find_extent(e4b, 0, ex.fe_start, ex.fe_len, &ex);

      if (max > 0) {
            ac->ac_b_ex = ex;
            ext4_mb_use_best_found(ac, e4b);
      }

      ext4_unlock_group(ac->ac_sb, group);
      ext4_mb_release_desc(e4b);

      return 0;
}

static noinline_for_stack
int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,
                        struct ext4_buddy *e4b)
{
      ext4_group_t group = ac->ac_g_ex.fe_group;
      int max;
      int err;
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
      struct ext4_super_block *es = sbi->s_es;
      struct ext4_free_extent ex;

      if (!(ac->ac_flags & EXT4_MB_HINT_TRY_GOAL))
            return 0;

      err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
      if (err)
            return err;

      ext4_lock_group(ac->ac_sb, group);
      max = mb_find_extent(e4b, 0, ac->ac_g_ex.fe_start,
                       ac->ac_g_ex.fe_len, &ex);

      if (max >= ac->ac_g_ex.fe_len && ac->ac_g_ex.fe_len == sbi->s_stripe) {
            ext4_fsblk_t start;

            start = (e4b->bd_group * EXT4_BLOCKS_PER_GROUP(ac->ac_sb)) +
                  ex.fe_start + le32_to_cpu(es->s_first_data_block);
            /* use do_div to get remainder (would be 64-bit modulo) */
            if (do_div(start, sbi->s_stripe) == 0) {
                  ac->ac_found++;
                  ac->ac_b_ex = ex;
                  ext4_mb_use_best_found(ac, e4b);
            }
      } else if (max >= ac->ac_g_ex.fe_len) {
            BUG_ON(ex.fe_len <= 0);
            BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
            BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
            ac->ac_found++;
            ac->ac_b_ex = ex;
            ext4_mb_use_best_found(ac, e4b);
      } else if (max > 0 && (ac->ac_flags & EXT4_MB_HINT_MERGE)) {
            /* Sometimes, caller may want to merge even small
             * number of blocks to an existing extent */
            BUG_ON(ex.fe_len <= 0);
            BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
            BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
            ac->ac_found++;
            ac->ac_b_ex = ex;
            ext4_mb_use_best_found(ac, e4b);
      }
      ext4_unlock_group(ac->ac_sb, group);
      ext4_mb_release_desc(e4b);

      return 0;
}

/*
 * The routine scans buddy structures (not bitmap!) from given order
 * to max order and tries to find big enough chunk to satisfy the req
 */
static noinline_for_stack
void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
                              struct ext4_buddy *e4b)
{
      struct super_block *sb = ac->ac_sb;
      struct ext4_group_info *grp = e4b->bd_info;
      void *buddy;
      int i;
      int k;
      int max;

      BUG_ON(ac->ac_2order <= 0);
      for (i = ac->ac_2order; i <= sb->s_blocksize_bits + 1; i++) {
            if (grp->bb_counters[i] == 0)
                  continue;

            buddy = mb_find_buddy(e4b, i, &max);
            BUG_ON(buddy == NULL);

            k = mb_find_next_zero_bit(buddy, max, 0);
            BUG_ON(k >= max);

            ac->ac_found++;

            ac->ac_b_ex.fe_len = 1 << i;
            ac->ac_b_ex.fe_start = k << i;
            ac->ac_b_ex.fe_group = e4b->bd_group;

            ext4_mb_use_best_found(ac, e4b);

            BUG_ON(ac->ac_b_ex.fe_len != ac->ac_g_ex.fe_len);

            if (EXT4_SB(sb)->s_mb_stats)
                  atomic_inc(&EXT4_SB(sb)->s_bal_2orders);

            break;
      }
}

/*
 * The routine scans the group and measures all found extents.
 * In order to optimize scanning, caller must pass number of
 * free blocks in the group, so the routine can know upper limit.
 */
static noinline_for_stack
void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
                              struct ext4_buddy *e4b)
{
      struct super_block *sb = ac->ac_sb;
      void *bitmap = EXT4_MB_BITMAP(e4b);
      struct ext4_free_extent ex;
      int i;
      int free;

      free = e4b->bd_info->bb_free;
      BUG_ON(free <= 0);

      i = e4b->bd_info->bb_first_free;

      while (free && ac->ac_status == AC_STATUS_CONTINUE) {
            i = mb_find_next_zero_bit(bitmap,
                                    EXT4_BLOCKS_PER_GROUP(sb), i);
            if (i >= EXT4_BLOCKS_PER_GROUP(sb)) {
                  /*
                   * IF we have corrupt bitmap, we won't find any
                   * free blocks even though group info says we
                   * we have free blocks
                   */
                  ext4_grp_locked_error(sb, e4b->bd_group,
                              __func__, "%d free blocks as per "
                              "group info. But bitmap says 0",
                              free);
                  break;
            }

            mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex);
            BUG_ON(ex.fe_len <= 0);
            if (free < ex.fe_len) {
                  ext4_grp_locked_error(sb, e4b->bd_group,
                              __func__, "%d free blocks as per "
                              "group info. But got %d blocks",
                              free, ex.fe_len);
                  /*
                   * The number of free blocks differs. This mostly
                   * indicate that the bitmap is corrupt. So exit
                   * without claiming the space.
                   */
                  break;
            }

            ext4_mb_measure_extent(ac, &ex, e4b);

            i += ex.fe_len;
            free -= ex.fe_len;
      }

      ext4_mb_check_limits(ac, e4b, 1);
}

/*
 * This is a special case for storages like raid5
 * we try to find stripe-aligned chunks for stripe-size requests
 * XXX should do so at least for multiples of stripe size as well
 */
static noinline_for_stack
void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
                         struct ext4_buddy *e4b)
{
      struct super_block *sb = ac->ac_sb;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      void *bitmap = EXT4_MB_BITMAP(e4b);
      struct ext4_free_extent ex;
      ext4_fsblk_t first_group_block;
      ext4_fsblk_t a;
      ext4_grpblk_t i;
      int max;

      BUG_ON(sbi->s_stripe == 0);

      /* find first stripe-aligned block in group */
      first_group_block = e4b->bd_group * EXT4_BLOCKS_PER_GROUP(sb)
            + le32_to_cpu(sbi->s_es->s_first_data_block);
      a = first_group_block + sbi->s_stripe - 1;
      do_div(a, sbi->s_stripe);
      i = (a * sbi->s_stripe) - first_group_block;

      while (i < EXT4_BLOCKS_PER_GROUP(sb)) {
            if (!mb_test_bit(i, bitmap)) {
                  max = mb_find_extent(e4b, 0, i, sbi->s_stripe, &ex);
                  if (max >= sbi->s_stripe) {
                        ac->ac_found++;
                        ac->ac_b_ex = ex;
                        ext4_mb_use_best_found(ac, e4b);
                        break;
                  }
            }
            i += sbi->s_stripe;
      }
}

static int ext4_mb_good_group(struct ext4_allocation_context *ac,
                        ext4_group_t group, int cr)
{
      unsigned free, fragments;
      unsigned i, bits;
      int flex_size = ext4_flex_bg_size(EXT4_SB(ac->ac_sb));
      struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);

      BUG_ON(cr < 0 || cr >= 4);
      BUG_ON(EXT4_MB_GRP_NEED_INIT(grp));

      free = grp->bb_free;
      fragments = grp->bb_fragments;
      if (free == 0)
            return 0;
      if (fragments == 0)
            return 0;

      switch (cr) {
      case 0:
            BUG_ON(ac->ac_2order == 0);

            /* Avoid using the first bg of a flexgroup for data files */
            if ((ac->ac_flags & EXT4_MB_HINT_DATA) &&
                (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) &&
                ((group % flex_size) == 0))
                  return 0;

            bits = ac->ac_sb->s_blocksize_bits + 1;
            for (i = ac->ac_2order; i <= bits; i++)
                  if (grp->bb_counters[i] > 0)
                        return 1;
            break;
      case 1:
            if ((free / fragments) >= ac->ac_g_ex.fe_len)
                  return 1;
            break;
      case 2:
            if (free >= ac->ac_g_ex.fe_len)
                  return 1;
            break;
      case 3:
            return 1;
      default:
            BUG();
      }

      return 0;
}

/*
 * lock the group_info alloc_sem of all the groups
 * belonging to the same buddy cache page. This
 * make sure other parallel operation on the buddy
 * cache doesn't happen  whild holding the buddy cache
 * lock
 */
int ext4_mb_get_buddy_cache_lock(struct super_block *sb, ext4_group_t group)
{
      int i;
      int block, pnum;
      int blocks_per_page;
      int groups_per_page;
      ext4_group_t ngroups = ext4_get_groups_count(sb);
      ext4_group_t first_group;
      struct ext4_group_info *grp;

      blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
      /*
       * the buddy cache inode stores the block bitmap
       * and buddy information in consecutive blocks.
       * So for each group we need two blocks.
       */
      block = group * 2;
      pnum = block / blocks_per_page;
      first_group = pnum * blocks_per_page / 2;

      groups_per_page = blocks_per_page >> 1;
      if (groups_per_page == 0)
            groups_per_page = 1;
      /* read all groups the page covers into the cache */
      for (i = 0; i < groups_per_page; i++) {

            if ((first_group + i) >= ngroups)
                  break;
            grp = ext4_get_group_info(sb, first_group + i);
            /* take all groups write allocation
             * semaphore. This make sure there is
             * no block allocation going on in any
             * of that groups
             */
            down_write_nested(&grp->alloc_sem, i);
      }
      return i;
}

void ext4_mb_put_buddy_cache_lock(struct super_block *sb,
                              ext4_group_t group, int locked_group)
{
      int i;
      int block, pnum;
      int blocks_per_page;
      ext4_group_t first_group;
      struct ext4_group_info *grp;

      blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
      /*
       * the buddy cache inode stores the block bitmap
       * and buddy information in consecutive blocks.
       * So for each group we need two blocks.
       */
      block = group * 2;
      pnum = block / blocks_per_page;
      first_group = pnum * blocks_per_page / 2;
      /* release locks on all the groups */
      for (i = 0; i < locked_group; i++) {

            grp = ext4_get_group_info(sb, first_group + i);
            /* take all groups write allocation
             * semaphore. This make sure there is
             * no block allocation going on in any
             * of that groups
             */
            up_write(&grp->alloc_sem);
      }

}

static noinline_for_stack
int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
{

      int ret;
      void *bitmap;
      int blocks_per_page;
      int block, pnum, poff;
      int num_grp_locked = 0;
      struct ext4_group_info *this_grp;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct inode *inode = sbi->s_buddy_cache;
      struct page *page = NULL, *bitmap_page = NULL;

      mb_debug("init group %lu\n", group);
      blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
      this_grp = ext4_get_group_info(sb, group);
      /*
       * This ensures we don't add group
       * to this buddy cache via resize
       */
      num_grp_locked =  ext4_mb_get_buddy_cache_lock(sb, group);
      if (!EXT4_MB_GRP_NEED_INIT(this_grp)) {
            /*
             * somebody initialized the group
             * return without doing anything
             */
            ret = 0;
            goto err;
      }
      /*
       * the buddy cache inode stores the block bitmap
       * and buddy information in consecutive blocks.
       * So for each group we need two blocks.
       */
      block = group * 2;
      pnum = block / blocks_per_page;
      poff = block % blocks_per_page;
      page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
      if (page) {
            BUG_ON(page->mapping != inode->i_mapping);
            ret = ext4_mb_init_cache(page, NULL);
            if (ret) {
                  unlock_page(page);
                  goto err;
            }
            unlock_page(page);
      }
      if (page == NULL || !PageUptodate(page)) {
            ret = -EIO;
            goto err;
      }
      mark_page_accessed(page);
      bitmap_page = page;
      bitmap = page_address(page) + (poff * sb->s_blocksize);

      /* init buddy cache */
      block++;
      pnum = block / blocks_per_page;
      poff = block % blocks_per_page;
      page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
      if (page == bitmap_page) {
            /*
             * If both the bitmap and buddy are in
             * the same page we don't need to force
             * init the buddy
             */
            unlock_page(page);
      } else if (page) {
            BUG_ON(page->mapping != inode->i_mapping);
            ret = ext4_mb_init_cache(page, bitmap);
            if (ret) {
                  unlock_page(page);
                  goto err;
            }
            unlock_page(page);
      }
      if (page == NULL || !PageUptodate(page)) {
            ret = -EIO;
            goto err;
      }
      mark_page_accessed(page);
err:
      ext4_mb_put_buddy_cache_lock(sb, group, num_grp_locked);
      if (bitmap_page)
            page_cache_release(bitmap_page);
      if (page)
            page_cache_release(page);
      return ret;
}

static noinline_for_stack int
ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
{
      ext4_group_t ngroups, group, i;
      int cr;
      int err = 0;
      int bsbits;
      struct ext4_sb_info *sbi;
      struct super_block *sb;
      struct ext4_buddy e4b;
      loff_t size, isize;

      sb = ac->ac_sb;
      sbi = EXT4_SB(sb);
      ngroups = ext4_get_groups_count(sb);
      BUG_ON(ac->ac_status == AC_STATUS_FOUND);

      /* first, try the goal */
      err = ext4_mb_find_by_goal(ac, &e4b);
      if (err || ac->ac_status == AC_STATUS_FOUND)
            goto out;

      if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
            goto out;

      /*
       * ac->ac2_order is set only if the fe_len is a power of 2
       * if ac2_order is set we also set criteria to 0 so that we
       * try exact allocation using buddy.
       */
      i = fls(ac->ac_g_ex.fe_len);
      ac->ac_2order = 0;
      /*
       * We search using buddy data only if the order of the request
       * is greater than equal to the sbi_s_mb_order2_reqs
       * You can tune it via /sys/fs/ext4/<partition>/mb_order2_req
       */
      if (i >= sbi->s_mb_order2_reqs) {
            /*
             * This should tell if fe_len is exactly power of 2
             */
            if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0)
                  ac->ac_2order = i - 1;
      }

      bsbits = ac->ac_sb->s_blocksize_bits;
      /* if stream allocation is enabled, use global goal */
      size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
      isize = i_size_read(ac->ac_inode) >> bsbits;
      if (size < isize)
            size = isize;

      if (size < sbi->s_mb_stream_request &&
                  (ac->ac_flags & EXT4_MB_HINT_DATA)) {
            /* TBD: may be hot point */
            spin_lock(&sbi->s_md_lock);
            ac->ac_g_ex.fe_group = sbi->s_mb_last_group;
            ac->ac_g_ex.fe_start = sbi->s_mb_last_start;
            spin_unlock(&sbi->s_md_lock);
      }
      /* Let's just scan groups to find more-less suitable blocks */
      cr = ac->ac_2order ? 0 : 1;
      /*
       * cr == 0 try to get exact allocation,
       * cr == 3  try to get anything
       */
repeat:
      for (; cr < 4 && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
            ac->ac_criteria = cr;
            /*
             * searching for the right group start
             * from the goal value specified
             */
            group = ac->ac_g_ex.fe_group;

            for (i = 0; i < ngroups; group++, i++) {
                  struct ext4_group_info *grp;
                  struct ext4_group_desc *desc;

                  if (group == ngroups)
                        group = 0;

                  /* quick check to skip empty groups */
                  grp = ext4_get_group_info(sb, group);
                  if (grp->bb_free == 0)
                        continue;

                  /*
                   * if the group is already init we check whether it is
                   * a good group and if not we don't load the buddy
                   */
                  if (EXT4_MB_GRP_NEED_INIT(grp)) {
                        /*
                         * we need full data about the group
                         * to make a good selection
                         */
                        err = ext4_mb_init_group(sb, group);
                        if (err)
                              goto out;
                  }

                  /*
                   * If the particular group doesn't satisfy our
                   * criteria we continue with the next group
                   */
                  if (!ext4_mb_good_group(ac, group, cr))
                        continue;

                  err = ext4_mb_load_buddy(sb, group, &e4b);
                  if (err)
                        goto out;

                  ext4_lock_group(sb, group);
                  if (!ext4_mb_good_group(ac, group, cr)) {
                        /* someone did allocation from this group */
                        ext4_unlock_group(sb, group);
                        ext4_mb_release_desc(&e4b);
                        continue;
                  }

                  ac->ac_groups_scanned++;
                  desc = ext4_get_group_desc(sb, group, NULL);
                  if (cr == 0)
                        ext4_mb_simple_scan_group(ac, &e4b);
                  else if (cr == 1 &&
                              ac->ac_g_ex.fe_len == sbi->s_stripe)
                        ext4_mb_scan_aligned(ac, &e4b);
                  else
                        ext4_mb_complex_scan_group(ac, &e4b);

                  ext4_unlock_group(sb, group);
                  ext4_mb_release_desc(&e4b);

                  if (ac->ac_status != AC_STATUS_CONTINUE)
                        break;
            }
      }

      if (ac->ac_b_ex.fe_len > 0 && ac->ac_status != AC_STATUS_FOUND &&
          !(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
            /*
             * We've been searching too long. Let's try to allocate
             * the best chunk we've found so far
             */

            ext4_mb_try_best_found(ac, &e4b);
            if (ac->ac_status != AC_STATUS_FOUND) {
                  /*
                   * Someone more lucky has already allocated it.
                   * The only thing we can do is just take first
                   * found block(s)
                  printk(KERN_DEBUG "EXT4-fs: someone won our chunk\n");
                   */
                  ac->ac_b_ex.fe_group = 0;
                  ac->ac_b_ex.fe_start = 0;
                  ac->ac_b_ex.fe_len = 0;
                  ac->ac_status = AC_STATUS_CONTINUE;
                  ac->ac_flags |= EXT4_MB_HINT_FIRST;
                  cr = 3;
                  atomic_inc(&sbi->s_mb_lost_chunks);
                  goto repeat;
            }
      }
out:
      return err;
}

#ifdef EXT4_MB_HISTORY
02099 struct ext4_mb_proc_session {
      struct ext4_mb_history *history;
      struct super_block *sb;
      int start;
      int max;
};

static void *ext4_mb_history_skip_empty(struct ext4_mb_proc_session *s,
                              struct ext4_mb_history *hs,
                              int first)
{
      if (hs == s->history + s->max)
            hs = s->history;
      if (!first && hs == s->history + s->start)
            return NULL;
      while (hs->orig.fe_len == 0) {
            hs++;
            if (hs == s->history + s->max)
                  hs = s->history;
            if (hs == s->history + s->start)
                  return NULL;
      }
      return hs;
}

static void *ext4_mb_seq_history_start(struct seq_file *seq, loff_t *pos)
{
      struct ext4_mb_proc_session *s = seq->private;
      struct ext4_mb_history *hs;
      int l = *pos;

      if (l == 0)
            return SEQ_START_TOKEN;
      hs = ext4_mb_history_skip_empty(s, s->history + s->start, 1);
      if (!hs)
            return NULL;
      while (--l && (hs = ext4_mb_history_skip_empty(s, ++hs, 0)) != NULL);
      return hs;
}

static void *ext4_mb_seq_history_next(struct seq_file *seq, void *v,
                              loff_t *pos)
{
      struct ext4_mb_proc_session *s = seq->private;
      struct ext4_mb_history *hs = v;

      ++*pos;
      if (v == SEQ_START_TOKEN)
            return ext4_mb_history_skip_empty(s, s->history + s->start, 1);
      else
            return ext4_mb_history_skip_empty(s, ++hs, 0);
}

static int ext4_mb_seq_history_show(struct seq_file *seq, void *v)
{
      char buf[25], buf2[25], buf3[25], *fmt;
      struct ext4_mb_history *hs = v;

      if (v == SEQ_START_TOKEN) {
            seq_printf(seq, "%-5s %-8s %-23s %-23s %-23s %-5s "
                        "%-5s %-2s %-5s %-5s %-5s %-6s\n",
                    "pid", "inode", "original", "goal", "result", "found",
                     "grps", "cr", "flags", "merge", "tail", "broken");
            return 0;
      }

      if (hs->op == EXT4_MB_HISTORY_ALLOC) {
            fmt = "%-5u %-8u %-23s %-23s %-23s %-5u %-5u %-2u "
                  "%-5u %-5s %-5u %-6u\n";
            sprintf(buf2, "%u/%d/%u@%u", hs->result.fe_group,
                  hs->result.fe_start, hs->result.fe_len,
                  hs->result.fe_logical);
            sprintf(buf, "%u/%d/%u@%u", hs->orig.fe_group,
                  hs->orig.fe_start, hs->orig.fe_len,
                  hs->orig.fe_logical);
            sprintf(buf3, "%u/%d/%u@%u", hs->goal.fe_group,
                  hs->goal.fe_start, hs->goal.fe_len,
                  hs->goal.fe_logical);
            seq_printf(seq, fmt, hs->pid, hs->ino, buf, buf3, buf2,
                        hs->found, hs->groups, hs->cr, hs->flags,
                        hs->merged ? "M" : "", hs->tail,
                        hs->buddy ? 1 << hs->buddy : 0);
      } else if (hs->op == EXT4_MB_HISTORY_PREALLOC) {
            fmt = "%-5u %-8u %-23s %-23s %-23s\n";
            sprintf(buf2, "%u/%d/%u@%u", hs->result.fe_group,
                  hs->result.fe_start, hs->result.fe_len,
                  hs->result.fe_logical);
            sprintf(buf, "%u/%d/%u@%u", hs->orig.fe_group,
                  hs->orig.fe_start, hs->orig.fe_len,
                  hs->orig.fe_logical);
            seq_printf(seq, fmt, hs->pid, hs->ino, buf, "", buf2);
      } else if (hs->op == EXT4_MB_HISTORY_DISCARD) {
            sprintf(buf2, "%u/%d/%u", hs->result.fe_group,
                  hs->result.fe_start, hs->result.fe_len);
            seq_printf(seq, "%-5u %-8u %-23s discard\n",
                        hs->pid, hs->ino, buf2);
      } else if (hs->op == EXT4_MB_HISTORY_FREE) {
            sprintf(buf2, "%u/%d/%u", hs->result.fe_group,
                  hs->result.fe_start, hs->result.fe_len);
            seq_printf(seq, "%-5u %-8u %-23s free\n",
                        hs->pid, hs->ino, buf2);
      }
      return 0;
}

static void ext4_mb_seq_history_stop(struct seq_file *seq, void *v)
{
}

static struct seq_operations ext4_mb_seq_history_ops = {
      .start  = ext4_mb_seq_history_start,
      .next   = ext4_mb_seq_history_next,
      .stop   = ext4_mb_seq_history_stop,
      .show   = ext4_mb_seq_history_show,
};

static int ext4_mb_seq_history_open(struct inode *inode, struct file *file)
{
      struct super_block *sb = PDE(inode)->data;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct ext4_mb_proc_session *s;
      int rc;
      int size;

      if (unlikely(sbi->s_mb_history == NULL))
            return -ENOMEM;
      s = kmalloc(sizeof(*s), GFP_KERNEL);
      if (s == NULL)
            return -ENOMEM;
      s->sb = sb;
      size = sizeof(struct ext4_mb_history) * sbi->s_mb_history_max;
      s->history = kmalloc(size, GFP_KERNEL);
      if (s->history == NULL) {
            kfree(s);
            return -ENOMEM;
      }

      spin_lock(&sbi->s_mb_history_lock);
      memcpy(s->history, sbi->s_mb_history, size);
      s->max = sbi->s_mb_history_max;
      s->start = sbi->s_mb_history_cur % s->max;
      spin_unlock(&sbi->s_mb_history_lock);

      rc = seq_open(file, &ext4_mb_seq_history_ops);
      if (rc == 0) {
            struct seq_file *m = (struct seq_file *)file->private_data;
            m->private = s;
      } else {
            kfree(s->history);
            kfree(s);
      }
      return rc;

}

static int ext4_mb_seq_history_release(struct inode *inode, struct file *file)
{
      struct seq_file *seq = (struct seq_file *)file->private_data;
      struct ext4_mb_proc_session *s = seq->private;
      kfree(s->history);
      kfree(s);
      return seq_release(inode, file);
}

static ssize_t ext4_mb_seq_history_write(struct file *file,
                        const char __user *buffer,
                        size_t count, loff_t *ppos)
{
      struct seq_file *seq = (struct seq_file *)file->private_data;
      struct ext4_mb_proc_session *s = seq->private;
      struct super_block *sb = s->sb;
      char str[32];
      int value;

      if (count >= sizeof(str)) {
            printk(KERN_ERR "EXT4-fs: %s string too long, max %u bytes\n",
                        "mb_history", (int)sizeof(str));
            return -EOVERFLOW;
      }

      if (copy_from_user(str, buffer, count))
            return -EFAULT;

      value = simple_strtol(str, NULL, 0);
      if (value < 0)
            return -ERANGE;
      EXT4_SB(sb)->s_mb_history_filter = value;

      return count;
}

static struct file_operations ext4_mb_seq_history_fops = {
      .owner            = THIS_MODULE,
      .open       = ext4_mb_seq_history_open,
      .read       = seq_read,
      .write            = ext4_mb_seq_history_write,
      .llseek           = seq_lseek,
      .release    = ext4_mb_seq_history_release,
};

static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
{
      struct super_block *sb = seq->private;
      ext4_group_t group;

      if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
            return NULL;
      group = *pos + 1;
      return (void *) ((unsigned long) group);
}

static void *ext4_mb_seq_groups_next(struct seq_file *seq, void *v, loff_t *pos)
{
      struct super_block *sb = seq->private;
      ext4_group_t group;

      ++*pos;
      if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
            return NULL;
      group = *pos + 1;
      return (void *) ((unsigned long) group);
}

static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
{
      struct super_block *sb = seq->private;
      ext4_group_t group = (ext4_group_t) ((unsigned long) v);
      int i;
      int err;
      struct ext4_buddy e4b;
      struct sg {
            struct ext4_group_info info;
            unsigned short counters[16];
      } sg;

      group--;
      if (group == 0)
            seq_printf(seq, "#%-5s: %-5s %-5s %-5s "
                        "[ %-5s %-5s %-5s %-5s %-5s %-5s %-5s "
                          "%-5s %-5s %-5s %-5s %-5s %-5s %-5s ]\n",
                     "group", "free", "frags", "first",
                     "2^0", "2^1", "2^2", "2^3", "2^4", "2^5", "2^6",
                     "2^7", "2^8", "2^9", "2^10", "2^11", "2^12", "2^13");

      i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
            sizeof(struct ext4_group_info);
      err = ext4_mb_load_buddy(sb, group, &e4b);
      if (err) {
            seq_printf(seq, "#%-5u: I/O error\n", group);
            return 0;
      }
      ext4_lock_group(sb, group);
      memcpy(&sg, ext4_get_group_info(sb, group), i);
      ext4_unlock_group(sb, group);
      ext4_mb_release_desc(&e4b);

      seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,
                  sg.info.bb_fragments, sg.info.bb_first_free);
      for (i = 0; i <= 13; i++)
            seq_printf(seq, " %-5u", i <= sb->s_blocksize_bits + 1 ?
                        sg.info.bb_counters[i] : 0);
      seq_printf(seq, " ]\n");

      return 0;
}

static void ext4_mb_seq_groups_stop(struct seq_file *seq, void *v)
{
}

static struct seq_operations ext4_mb_seq_groups_ops = {
      .start  = ext4_mb_seq_groups_start,
      .next   = ext4_mb_seq_groups_next,
      .stop   = ext4_mb_seq_groups_stop,
      .show   = ext4_mb_seq_groups_show,
};

static int ext4_mb_seq_groups_open(struct inode *inode, struct file *file)
{
      struct super_block *sb = PDE(inode)->data;
      int rc;

      rc = seq_open(file, &ext4_mb_seq_groups_ops);
      if (rc == 0) {
            struct seq_file *m = (struct seq_file *)file->private_data;
            m->private = sb;
      }
      return rc;

}

static struct file_operations ext4_mb_seq_groups_fops = {
      .owner            = THIS_MODULE,
      .open       = ext4_mb_seq_groups_open,
      .read       = seq_read,
      .llseek           = seq_lseek,
      .release    = seq_release,
};

static void ext4_mb_history_release(struct super_block *sb)
{
      struct ext4_sb_info *sbi = EXT4_SB(sb);

      if (sbi->s_proc != NULL) {
            remove_proc_entry("mb_groups", sbi->s_proc);
            if (sbi->s_mb_history_max)
                  remove_proc_entry("mb_history", sbi->s_proc);
      }
      kfree(sbi->s_mb_history);
}

static void ext4_mb_history_init(struct super_block *sb)
{
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      int i;

      if (sbi->s_proc != NULL) {
            if (sbi->s_mb_history_max)
                  proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
                               &ext4_mb_seq_history_fops, sb);
            proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
                         &ext4_mb_seq_groups_fops, sb);
      }

      sbi->s_mb_history_cur = 0;
      spin_lock_init(&sbi->s_mb_history_lock);
      i = sbi->s_mb_history_max * sizeof(struct ext4_mb_history);
      sbi->s_mb_history = i ? kzalloc(i, GFP_KERNEL) : NULL;
      /* if we can't allocate history, then we simple won't use it */
}

static noinline_for_stack void
ext4_mb_store_history(struct ext4_allocation_context *ac)
{
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
      struct ext4_mb_history h;

      if (sbi->s_mb_history == NULL)
            return;

      if (!(ac->ac_op & sbi->s_mb_history_filter))
            return;

      h.op = ac->ac_op;
      h.pid = current->pid;
      h.ino = ac->ac_inode ? ac->ac_inode->i_ino : 0;
      h.orig = ac->ac_o_ex;
      h.result = ac->ac_b_ex;
      h.flags = ac->ac_flags;
      h.found = ac->ac_found;
      h.groups = ac->ac_groups_scanned;
      h.cr = ac->ac_criteria;
      h.tail = ac->ac_tail;
      h.buddy = ac->ac_buddy;
      h.merged = 0;
      if (ac->ac_op == EXT4_MB_HISTORY_ALLOC) {
            if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&
                        ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)
                  h.merged = 1;
            h.goal = ac->ac_g_ex;
            h.result = ac->ac_f_ex;
      }

      spin_lock(&sbi->s_mb_history_lock);
      memcpy(sbi->s_mb_history + sbi->s_mb_history_cur, &h, sizeof(h));
      if (++sbi->s_mb_history_cur >= sbi->s_mb_history_max)
            sbi->s_mb_history_cur = 0;
      spin_unlock(&sbi->s_mb_history_lock);
}

#else
#define ext4_mb_history_release(sb)
#define ext4_mb_history_init(sb)
#endif


/* Create and initialize ext4_group_info data for the given group. */
int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
                    struct ext4_group_desc *desc)
{
      int i, len;
      int metalen = 0;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct ext4_group_info **meta_group_info;

      /*
       * First check if this group is the first of a reserved block.
       * If it's true, we have to allocate a new table of pointers
       * to ext4_group_info structures
       */
      if (group % EXT4_DESC_PER_BLOCK(sb) == 0) {
            metalen = sizeof(*meta_group_info) <<
                  EXT4_DESC_PER_BLOCK_BITS(sb);
            meta_group_info = kmalloc(metalen, GFP_KERNEL);
            if (meta_group_info == NULL) {
                  printk(KERN_ERR "EXT4-fs: can't allocate mem for a "
                         "buddy group\n");
                  goto exit_meta_group_info;
            }
            sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)] =
                  meta_group_info;
      }

      /*
       * calculate needed size. if change bb_counters size,
       * don't forget about ext4_mb_generate_buddy()
       */
      len = offsetof(typeof(**meta_group_info),
                   bb_counters[sb->s_blocksize_bits + 2]);

      meta_group_info =
            sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)];
      i = group & (EXT4_DESC_PER_BLOCK(sb) - 1);

      meta_group_info[i] = kzalloc(len, GFP_KERNEL);
      if (meta_group_info[i] == NULL) {
            printk(KERN_ERR "EXT4-fs: can't allocate buddy mem\n");
            goto exit_group_info;
      }
      set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT,
            &(meta_group_info[i]->bb_state));

      /*
       * initialize bb_free to be able to skip
       * empty groups without initialization
       */
      if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
            meta_group_info[i]->bb_free =
                  ext4_free_blocks_after_init(sb, group, desc);
      } else {
            meta_group_info[i]->bb_free =
                  ext4_free_blks_count(sb, desc);
      }

      INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
      init_rwsem(&meta_group_info[i]->alloc_sem);
      meta_group_info[i]->bb_free_root.rb_node = NULL;;

#ifdef DOUBLE_CHECK
      {
            struct buffer_head *bh;
            meta_group_info[i]->bb_bitmap =
                  kmalloc(sb->s_blocksize, GFP_KERNEL);
            BUG_ON(meta_group_info[i]->bb_bitmap == NULL);
            bh = ext4_read_block_bitmap(sb, group);
            BUG_ON(bh == NULL);
            memcpy(meta_group_info[i]->bb_bitmap, bh->b_data,
                  sb->s_blocksize);
            put_bh(bh);
      }
#endif

      return 0;

exit_group_info:
      /* If a meta_group_info table has been allocated, release it now */
      if (group % EXT4_DESC_PER_BLOCK(sb) == 0)
            kfree(sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)]);
exit_meta_group_info:
      return -ENOMEM;
} /* ext4_mb_add_groupinfo */

/*
 * Update an existing group.
 * This function is used for online resize
 */
void ext4_mb_update_group_info(struct ext4_group_info *grp, ext4_grpblk_t add)
{
      grp->bb_free += add;
}

static int ext4_mb_init_backend(struct super_block *sb)
{
      ext4_group_t ngroups = ext4_get_groups_count(sb);
      ext4_group_t i;
      int metalen;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct ext4_super_block *es = sbi->s_es;
      int num_meta_group_infos;
      int num_meta_group_infos_max;
      int array_size;
      struct ext4_group_info **meta_group_info;
      struct ext4_group_desc *desc;

      /* This is the number of blocks used by GDT */
      num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -
                        1) >> EXT4_DESC_PER_BLOCK_BITS(sb);

      /*
       * This is the total number of blocks used by GDT including
       * the number of reserved blocks for GDT.
       * The s_group_info array is allocated with this value
       * to allow a clean online resize without a complex
       * manipulation of pointer.
       * The drawback is the unused memory when no resize
       * occurs but it's very low in terms of pages
       * (see comments below)
       * Need to handle this properly when META_BG resizing is allowed
       */
      num_meta_group_infos_max = num_meta_group_infos +
                        le16_to_cpu(es->s_reserved_gdt_blocks);

      /*
       * array_size is the size of s_group_info array. We round it
       * to the next power of two because this approximation is done
       * internally by kmalloc so we can have some more memory
       * for free here (e.g. may be used for META_BG resize).
       */
      array_size = 1;
      while (array_size < sizeof(*sbi->s_group_info) *
             num_meta_group_infos_max)
            array_size = array_size << 1;
      /* An 8TB filesystem with 64-bit pointers requires a 4096 byte
       * kmalloc. A 128kb malloc should suffice for a 256TB filesystem.
       * So a two level scheme suffices for now. */
      sbi->s_group_info = kmalloc(array_size, GFP_KERNEL);
      if (sbi->s_group_info == NULL) {
            printk(KERN_ERR "EXT4-fs: can't allocate buddy meta group\n");
            return -ENOMEM;
      }
      sbi->s_buddy_cache = new_inode(sb);
      if (sbi->s_buddy_cache == NULL) {
            printk(KERN_ERR "EXT4-fs: can't get new inode\n");
            goto err_freesgi;
      }
      EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;

      metalen = sizeof(*meta_group_info) << EXT4_DESC_PER_BLOCK_BITS(sb);
      for (i = 0; i < num_meta_group_infos; i++) {
            if ((i + 1) == num_meta_group_infos)
                  metalen = sizeof(*meta_group_info) *
                        (ngroups -
                              (i << EXT4_DESC_PER_BLOCK_BITS(sb)));
            meta_group_info = kmalloc(metalen, GFP_KERNEL);
            if (meta_group_info == NULL) {
                  printk(KERN_ERR "EXT4-fs: can't allocate mem for a "
                         "buddy group\n");
                  goto err_freemeta;
            }
            sbi->s_group_info[i] = meta_group_info;
      }

      for (i = 0; i < ngroups; i++) {
            desc = ext4_get_group_desc(sb, i, NULL);
            if (desc == NULL) {
                  printk(KERN_ERR
                        "EXT4-fs: can't read descriptor %u\n", i);
                  goto err_freebuddy;
            }
            if (ext4_mb_add_groupinfo(sb, i, desc) != 0)
                  goto err_freebuddy;
      }

      return 0;

err_freebuddy:
      while (i-- > 0)
            kfree(ext4_get_group_info(sb, i));
      i = num_meta_group_infos;
err_freemeta:
      while (i-- > 0)
            kfree(sbi->s_group_info[i]);
      iput(sbi->s_buddy_cache);
err_freesgi:
      kfree(sbi->s_group_info);
      return -ENOMEM;
}

int ext4_mb_init(struct super_block *sb, int needs_recovery)
{
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      unsigned i, j;
      unsigned offset;
      unsigned max;
      int ret;

      i = (sb->s_blocksize_bits + 2) * sizeof(unsigned short);

      sbi->s_mb_offsets = kmalloc(i, GFP_KERNEL);
      if (sbi->s_mb_offsets == NULL) {
            return -ENOMEM;
      }

      i = (sb->s_blocksize_bits + 2) * sizeof(unsigned int);
      sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
      if (sbi->s_mb_maxs == NULL) {
            kfree(sbi->s_mb_offsets);
            return -ENOMEM;
      }

      /* order 0 is regular bitmap */
      sbi->s_mb_maxs[0] = sb->s_blocksize << 3;
      sbi->s_mb_offsets[0] = 0;

      i = 1;
      offset = 0;
      max = sb->s_blocksize << 2;
      do {
            sbi->s_mb_offsets[i] = offset;
            sbi->s_mb_maxs[i] = max;
            offset += 1 << (sb->s_blocksize_bits - i);
            max = max >> 1;
            i++;
      } while (i <= sb->s_blocksize_bits + 1);

      /* init file for buddy data */
      ret = ext4_mb_init_backend(sb);
      if (ret != 0) {
            kfree(sbi->s_mb_offsets);
            kfree(sbi->s_mb_maxs);
            return ret;
      }

      spin_lock_init(&sbi->s_md_lock);
      spin_lock_init(&sbi->s_bal_lock);

      sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;
      sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;
      sbi->s_mb_stats = MB_DEFAULT_STATS;
      sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
      sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;
      sbi->s_mb_history_filter = EXT4_MB_HISTORY_DEFAULT;
      sbi->s_mb_group_prealloc = MB_DEFAULT_GROUP_PREALLOC;

      sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
      if (sbi->s_locality_groups == NULL) {
            kfree(sbi->s_mb_offsets);
            kfree(sbi->s_mb_maxs);
            return -ENOMEM;
      }
      for_each_possible_cpu(i) {
            struct ext4_locality_group *lg;
            lg = per_cpu_ptr(sbi->s_locality_groups, i);
            mutex_init(&lg->lg_mutex);
            for (j = 0; j < PREALLOC_TB_SIZE; j++)
                  INIT_LIST_HEAD(&lg->lg_prealloc_list[j]);
            spin_lock_init(&lg->lg_prealloc_lock);
      }

      ext4_mb_history_init(sb);

      if (sbi->s_journal)
            sbi->s_journal->j_commit_callback = release_blocks_on_commit;

      printk(KERN_INFO "EXT4-fs: mballoc enabled\n");
      return 0;
}

/* need to called with the ext4 group lock held */
static void ext4_mb_cleanup_pa(struct ext4_group_info *grp)
{
      struct ext4_prealloc_space *pa;
      struct list_head *cur, *tmp;
      int count = 0;

      list_for_each_safe(cur, tmp, &grp->bb_prealloc_list) {
            pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
            list_del(&pa->pa_group_list);
            count++;
            kmem_cache_free(ext4_pspace_cachep, pa);
      }
      if (count)
            mb_debug("mballoc: %u PAs left\n", count);

}

int ext4_mb_release(struct super_block *sb)
{
      ext4_group_t ngroups = ext4_get_groups_count(sb);
      ext4_group_t i;
      int num_meta_group_infos;
      struct ext4_group_info *grinfo;
      struct ext4_sb_info *sbi = EXT4_SB(sb);

      if (sbi->s_group_info) {
            for (i = 0; i < ngroups; i++) {
                  grinfo = ext4_get_group_info(sb, i);
#ifdef DOUBLE_CHECK
                  kfree(grinfo->bb_bitmap);
#endif
                  ext4_lock_group(sb, i);
                  ext4_mb_cleanup_pa(grinfo);
                  ext4_unlock_group(sb, i);
                  kfree(grinfo);
            }
            num_meta_group_infos = (ngroups +
                        EXT4_DESC_PER_BLOCK(sb) - 1) >>
                  EXT4_DESC_PER_BLOCK_BITS(sb);
            for (i = 0; i < num_meta_group_infos; i++)
                  kfree(sbi->s_group_info[i]);
            kfree(sbi->s_group_info);
      }
      kfree(sbi->s_mb_offsets);
      kfree(sbi->s_mb_maxs);
      if (sbi->s_buddy_cache)
            iput(sbi->s_buddy_cache);
      if (sbi->s_mb_stats) {
            printk(KERN_INFO
                   "EXT4-fs: mballoc: %u blocks %u reqs (%u success)\n",
                        atomic_read(&sbi->s_bal_allocated),
                        atomic_read(&sbi->s_bal_reqs),
                        atomic_read(&sbi->s_bal_success));
            printk(KERN_INFO
                  "EXT4-fs: mballoc: %u extents scanned, %u goal hits, "
                        "%u 2^N hits, %u breaks, %u lost\n",
                        atomic_read(&sbi->s_bal_ex_scanned),
                        atomic_read(&sbi->s_bal_goals),
                        atomic_read(&sbi->s_bal_2orders),
                        atomic_read(&sbi->s_bal_breaks),
                        atomic_read(&sbi->s_mb_lost_chunks));
            printk(KERN_INFO
                   "EXT4-fs: mballoc: %lu generated and it took %Lu\n",
                        sbi->s_mb_buddies_generated++,
                        sbi->s_mb_generation_time);
            printk(KERN_INFO
                   "EXT4-fs: mballoc: %u preallocated, %u discarded\n",
                        atomic_read(&sbi->s_mb_preallocated),
                        atomic_read(&sbi->s_mb_discarded));
      }

      free_percpu(sbi->s_locality_groups);
      ext4_mb_history_release(sb);

      return 0;
}

/*
 * This function is called by the jbd2 layer once the commit has finished,
 * so we know we can free the blocks that were released with that commit.
 */
static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
{
      struct super_block *sb = journal->j_private;
      struct ext4_buddy e4b;
      struct ext4_group_info *db;
      int err, count = 0, count2 = 0;
      struct ext4_free_data *entry;
      ext4_fsblk_t discard_block;
      struct list_head *l, *ltmp;

      list_for_each_safe(l, ltmp, &txn->t_private_list) {
            entry = list_entry(l, struct ext4_free_data, list);

            mb_debug("gonna free %u blocks in group %u (0x%p):",
                   entry->count, entry->group, entry);

            err = ext4_mb_load_buddy(sb, entry->group, &e4b);
            /* we expect to find existing buddy because it's pinned */
            BUG_ON(err != 0);

            db = e4b.bd_info;
            /* there are blocks to put in buddy to make them really free */
            count += entry->count;
            count2++;
            ext4_lock_group(sb, entry->group);
            /* Take it out of per group rb tree */
            rb_erase(&entry->node, &(db->bb_free_root));
            mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);

            if (!db->bb_free_root.rb_node) {
                  /* No more items in the per group rb tree
                   * balance refcounts from ext4_mb_free_metadata()
                   */
                  page_cache_release(e4b.bd_buddy_page);
                  page_cache_release(e4b.bd_bitmap_page);
            }
            ext4_unlock_group(sb, entry->group);
            discard_block = (ext4_fsblk_t) entry->group * EXT4_BLOCKS_PER_GROUP(sb)
                  + entry->start_blk
                  + le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
            trace_ext4_discard_blocks(sb, (unsigned long long)discard_block,
                                entry->count);
            sb_issue_discard(sb, discard_block, entry->count);

            kmem_cache_free(ext4_free_ext_cachep, entry);
            ext4_mb_release_desc(&e4b);
      }

      mb_debug("freed %u blocks in %u structures\n", count, count2);
}

int __init init_ext4_mballoc(void)
{
      ext4_pspace_cachep =
            kmem_cache_create("ext4_prealloc_space",
                             sizeof(struct ext4_prealloc_space),
                             0, SLAB_RECLAIM_ACCOUNT, NULL);
      if (ext4_pspace_cachep == NULL)
            return -ENOMEM;

      ext4_ac_cachep =
            kmem_cache_create("ext4_alloc_context",
                             sizeof(struct ext4_allocation_context),
                             0, SLAB_RECLAIM_ACCOUNT, NULL);
      if (ext4_ac_cachep == NULL) {
            kmem_cache_destroy(ext4_pspace_cachep);
            return -ENOMEM;
      }

      ext4_free_ext_cachep =
            kmem_cache_create("ext4_free_block_extents",
                             sizeof(struct ext4_free_data),
                             0, SLAB_RECLAIM_ACCOUNT, NULL);
      if (ext4_free_ext_cachep == NULL) {
            kmem_cache_destroy(ext4_pspace_cachep);
            kmem_cache_destroy(ext4_ac_cachep);
            return -ENOMEM;
      }
      return 0;
}

void exit_ext4_mballoc(void)
{
      /* 
       * Wait for completion of call_rcu()'s on ext4_pspace_cachep
       * before destroying the slab cache.
       */
      rcu_barrier();
      kmem_cache_destroy(ext4_pspace_cachep);
      kmem_cache_destroy(ext4_ac_cachep);
      kmem_cache_destroy(ext4_free_ext_cachep);
}


/*
 * Check quota and mark choosed space (ac->ac_b_ex) non-free in bitmaps
 * Returns 0 if success or error code
 */
static noinline_for_stack int
ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
                        handle_t *handle, unsigned int reserv_blks)
{
      struct buffer_head *bitmap_bh = NULL;
      struct ext4_super_block *es;
      struct ext4_group_desc *gdp;
      struct buffer_head *gdp_bh;
      struct ext4_sb_info *sbi;
      struct super_block *sb;
      ext4_fsblk_t block;
      int err, len;

      BUG_ON(ac->ac_status != AC_STATUS_FOUND);
      BUG_ON(ac->ac_b_ex.fe_len <= 0);

      sb = ac->ac_sb;
      sbi = EXT4_SB(sb);
      es = sbi->s_es;


      err = -EIO;
      bitmap_bh = ext4_read_block_bitmap(sb, ac->ac_b_ex.fe_group);
      if (!bitmap_bh)
            goto out_err;

      err = ext4_journal_get_write_access(handle, bitmap_bh);
      if (err)
            goto out_err;

      err = -EIO;
      gdp = ext4_get_group_desc(sb, ac->ac_b_ex.fe_group, &gdp_bh);
      if (!gdp)
            goto out_err;

      ext4_debug("using block group %u(%d)\n", ac->ac_b_ex.fe_group,
                  ext4_free_blks_count(sb, gdp));

      err = ext4_journal_get_write_access(handle, gdp_bh);
      if (err)
            goto out_err;

      block = ac->ac_b_ex.fe_group * EXT4_BLOCKS_PER_GROUP(sb)
            + ac->ac_b_ex.fe_start
            + le32_to_cpu(es->s_first_data_block);

      len = ac->ac_b_ex.fe_len;
      if (!ext4_data_block_valid(sbi, block, len)) {
            ext4_error(sb, __func__,
                     "Allocating blocks %llu-%llu which overlap "
                     "fs metadata\n", block, block+len);
            /* File system mounted not to panic on error
             * Fix the bitmap and repeat the block allocation
             * We leak some of the blocks here.
             */
            ext4_lock_group(sb, ac->ac_b_ex.fe_group);
            mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
                      ac->ac_b_ex.fe_len);
            ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
            err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
            if (!err)
                  err = -EAGAIN;
            goto out_err;
      }

      ext4_lock_group(sb, ac->ac_b_ex.fe_group);
#ifdef AGGRESSIVE_CHECK
      {
            int i;
            for (i = 0; i < ac->ac_b_ex.fe_len; i++) {
                  BUG_ON(mb_test_bit(ac->ac_b_ex.fe_start + i,
                                    bitmap_bh->b_data));
            }
      }
#endif
      mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,ac->ac_b_ex.fe_len);
      if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
            gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
            ext4_free_blks_set(sb, gdp,
                              ext4_free_blocks_after_init(sb,
                              ac->ac_b_ex.fe_group, gdp));
      }
      len = ext4_free_blks_count(sb, gdp) - ac->ac_b_ex.fe_len;
      ext4_free_blks_set(sb, gdp, len);
      gdp->bg_checksum = ext4_group_desc_csum(sbi, ac->ac_b_ex.fe_group, gdp);

      ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
      percpu_counter_sub(&sbi->s_freeblocks_counter, ac->ac_b_ex.fe_len);
      /*
       * Now reduce the dirty block count also. Should not go negative
       */
      if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
            /* release all the reserved blocks if non delalloc */
            percpu_counter_sub(&sbi->s_dirtyblocks_counter, reserv_blks);
      else {
            percpu_counter_sub(&sbi->s_dirtyblocks_counter,
                                    ac->ac_b_ex.fe_len);
            /* convert reserved quota blocks to real quota blocks */
            vfs_dq_claim_block(ac->ac_inode, ac->ac_b_ex.fe_len);
      }

      if (sbi->s_log_groups_per_flex) {
            ext4_group_t flex_group = ext4_flex_group(sbi,
                                            ac->ac_b_ex.fe_group);
            atomic_sub(ac->ac_b_ex.fe_len,
                     &sbi->s_flex_groups[flex_group].free_blocks);
      }

      err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
      if (err)
            goto out_err;
      err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);

out_err:
      sb->s_dirt = 1;
      brelse(bitmap_bh);
      return err;
}

/*
 * here we normalize request for locality group
 * Group request are normalized to s_strip size if we set the same via mount
 * option. If not we set it to s_mb_group_prealloc which can be configured via
 * /sys/fs/ext4/<partition>/mb_group_prealloc
 *
 * XXX: should we try to preallocate more than the group has now?
 */
static void ext4_mb_normalize_group_request(struct ext4_allocation_context *ac)
{
      struct super_block *sb = ac->ac_sb;
      struct ext4_locality_group *lg = ac->ac_lg;

      BUG_ON(lg == NULL);
      if (EXT4_SB(sb)->s_stripe)
            ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_stripe;
      else
            ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc;
      mb_debug("#%u: goal %u blocks for locality group\n",
            current->pid, ac->ac_g_ex.fe_len);
}

/*
 * Normalization means making request better in terms of
 * size and alignment
 */
static noinline_for_stack void
ext4_mb_normalize_request(struct ext4_allocation_context *ac,
                        struct ext4_allocation_request *ar)
{
      int bsbits, max;
      ext4_lblk_t end;
      loff_t size, orig_size, start_off;
      ext4_lblk_t start, orig_start;
      struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
      struct ext4_prealloc_space *pa;

      /* do normalize only data requests, metadata requests
         do not need preallocation */
      if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
            return;

      /* sometime caller may want exact blocks */
      if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
            return;

      /* caller may indicate that preallocation isn't
       * required (it's a tail, for example) */
      if (ac->ac_flags & EXT4_MB_HINT_NOPREALLOC)
            return;

      if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC) {
            ext4_mb_normalize_group_request(ac);
            return ;
      }

      bsbits = ac->ac_sb->s_blocksize_bits;

      /* first, let's learn actual file size
       * given current request is allocated */
      size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
      size = size << bsbits;
      if (size < i_size_read(ac->ac_inode))
            size = i_size_read(ac->ac_inode);

      /* max size of free chunks */
      max = 2 << bsbits;

#define NRL_CHECK_SIZE(req, size, max, chunk_size)    \
            (req <= (size) || max <= (chunk_size))

      /* first, try to predict filesize */
      /* XXX: should this table be tunable? */
      start_off = 0;
      if (size <= 16 * 1024) {
            size = 16 * 1024;
      } else if (size <= 32 * 1024) {
            size = 32 * 1024;
      } else if (size <= 64 * 1024) {
            size = 64 * 1024;
      } else if (size <= 128 * 1024) {
            size = 128 * 1024;
      } else if (size <= 256 * 1024) {
            size = 256 * 1024;
      } else if (size <= 512 * 1024) {
            size = 512 * 1024;
      } else if (size <= 1024 * 1024) {
            size = 1024 * 1024;
      } else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, 2 * 1024)) {
            start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
                                    (21 - bsbits)) << 21;
            size = 2 * 1024 * 1024;
      } else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, 4 * 1024)) {
            start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
                                          (22 - bsbits)) << 22;
            size = 4 * 1024 * 1024;
      } else if (NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,
                              (8<<20)>>bsbits, max, 8 * 1024)) {
            start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
                                          (23 - bsbits)) << 23;
            size = 8 * 1024 * 1024;
      } else {
            start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
            size    = ac->ac_o_ex.fe_len << bsbits;
      }
      orig_size = size = size >> bsbits;
      orig_start = start = start_off >> bsbits;

      /* don't cover already allocated blocks in selected range */
      if (ar->pleft && start <= ar->lleft) {
            size -= ar->lleft + 1 - start;
            start = ar->lleft + 1;
      }
      if (ar->pright && start + size - 1 >= ar->lright)
            size -= start + size - ar->lright;

      end = start + size;

      /* check we don't cross already preallocated blocks */
      rcu_read_lock();
      list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
            ext4_lblk_t pa_end;

            if (pa->pa_deleted)
                  continue;
            spin_lock(&pa->pa_lock);
            if (pa->pa_deleted) {
                  spin_unlock(&pa->pa_lock);
                  continue;
            }

            pa_end = pa->pa_lstart + pa->pa_len;

            /* PA must not overlap original request */
            BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
                  ac->ac_o_ex.fe_logical < pa->pa_lstart));

            /* skip PA normalized request doesn't overlap with */
            if (pa->pa_lstart >= end) {
                  spin_unlock(&pa->pa_lock);
                  continue;
            }
            if (pa_end <= start) {
                  spin_unlock(&pa->pa_lock);
                  continue;
            }
            BUG_ON(pa->pa_lstart <= start && pa_end >= end);

            if (pa_end <= ac->ac_o_ex.fe_logical) {
                  BUG_ON(pa_end < start);
                  start = pa_end;
            }

            if (pa->pa_lstart > ac->ac_o_ex.fe_logical) {
                  BUG_ON(pa->pa_lstart > end);
                  end = pa->pa_lstart;
            }
            spin_unlock(&pa->pa_lock);
      }
      rcu_read_unlock();
      size = end - start;

      /* XXX: extra loop to check we really don't overlap preallocations */
      rcu_read_lock();
      list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
            ext4_lblk_t pa_end;
            spin_lock(&pa->pa_lock);
            if (pa->pa_deleted == 0) {
                  pa_end = pa->pa_lstart + pa->pa_len;
                  BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
            }
            spin_unlock(&pa->pa_lock);
      }
      rcu_read_unlock();

      if (start + size <= ac->ac_o_ex.fe_logical &&
                  start > ac->ac_o_ex.fe_logical) {
            printk(KERN_ERR "start %lu, size %lu, fe_logical %lu\n",
                  (unsigned long) start, (unsigned long) size,
                  (unsigned long) ac->ac_o_ex.fe_logical);
      }
      BUG_ON(start + size <= ac->ac_o_ex.fe_logical &&
                  start > ac->ac_o_ex.fe_logical);
      BUG_ON(size <= 0 || size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb));

      /* now prepare goal request */

      /* XXX: is it better to align blocks WRT to logical
       * placement or satisfy big request as is */
      ac->ac_g_ex.fe_logical = start;
      ac->ac_g_ex.fe_len = size;

      /* define goal start in order to merge */
      if (ar->pright && (ar->lright == (start + size))) {
            /* merge to the right */
            ext4_get_group_no_and_offset(ac->ac_sb, ar->pright - size,
                                    &ac->ac_f_ex.fe_group,
                                    &ac->ac_f_ex.fe_start);
            ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
      }
      if (ar->pleft && (ar->lleft + 1 == start)) {
            /* merge to the left */
            ext4_get_group_no_and_offset(ac->ac_sb, ar->pleft + 1,
                                    &ac->ac_f_ex.fe_group,
                                    &ac->ac_f_ex.fe_start);
            ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
      }

      mb_debug("goal: %u(was %u) blocks at %u\n", (unsigned) size,
            (unsigned) orig_size, (unsigned) start);
}

static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
{
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

      if (sbi->s_mb_stats && ac->ac_g_ex.fe_len > 1) {
            atomic_inc(&sbi->s_bal_reqs);
            atomic_add(ac->ac_b_ex.fe_len, &sbi->s_bal_allocated);
            if (ac->ac_o_ex.fe_len >= ac->ac_g_ex.fe_len)
                  atomic_inc(&sbi->s_bal_success);
            atomic_add(ac->ac_found, &sbi->s_bal_ex_scanned);
            if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&
                        ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)
                  atomic_inc(&sbi->s_bal_goals);
            if (ac->ac_found > sbi->s_mb_max_to_scan)
                  atomic_inc(&sbi->s_bal_breaks);
      }

      ext4_mb_store_history(ac);
}

/*
 * use blocks preallocated to inode
 */
static void ext4_mb_use_inode_pa(struct ext4_allocation_context *ac,
                        struct ext4_prealloc_space *pa)
{
      ext4_fsblk_t start;
      ext4_fsblk_t end;
      int len;

      /* found preallocated blocks, use them */
      start = pa->pa_pstart + (ac->ac_o_ex.fe_logical - pa->pa_lstart);
      end = min(pa->pa_pstart + pa->pa_len, start + ac->ac_o_ex.fe_len);
      len = end - start;
      ext4_get_group_no_and_offset(ac->ac_sb, start, &ac->ac_b_ex.fe_group,
                              &ac->ac_b_ex.fe_start);
      ac->ac_b_ex.fe_len = len;
      ac->ac_status = AC_STATUS_FOUND;
      ac->ac_pa = pa;

      BUG_ON(start < pa->pa_pstart);
      BUG_ON(start + len > pa->pa_pstart + pa->pa_len);
      BUG_ON(pa->pa_free < len);
      pa->pa_free -= len;

      mb_debug("use %llu/%u from inode pa %p\n", start, len, pa);
}

/*
 * use blocks preallocated to locality group
 */
static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
                        struct ext4_prealloc_space *pa)
{
      unsigned int len = ac->ac_o_ex.fe_len;

      ext4_get_group_no_and_offset(ac->ac_sb, pa->pa_pstart,
                              &ac->ac_b_ex.fe_group,
                              &ac->ac_b_ex.fe_start);
      ac->ac_b_ex.fe_len = len;
      ac->ac_status = AC_STATUS_FOUND;
      ac->ac_pa = pa;

      /* we don't correct pa_pstart or pa_plen here to avoid
       * possible race when the group is being loaded concurrently
       * instead we correct pa later, after blocks are marked
       * in on-disk bitmap -- see ext4_mb_release_context()
       * Other CPUs are prevented from allocating from this pa by lg_mutex
       */
      mb_debug("use %u/%u from group pa %p\n", pa->pa_lstart-len, len, pa);
}

/*
 * Return the prealloc space that have minimal distance
 * from the goal block. @cpa is the prealloc
 * space that is having currently known minimal distance
 * from the goal block.
 */
static struct ext4_prealloc_space *
ext4_mb_check_group_pa(ext4_fsblk_t goal_block,
                  struct ext4_prealloc_space *pa,
                  struct ext4_prealloc_space *cpa)
{
      ext4_fsblk_t cur_distance, new_distance;

      if (cpa == NULL) {
            atomic_inc(&pa->pa_count);
            return pa;
      }
      cur_distance = abs(goal_block - cpa->pa_pstart);
      new_distance = abs(goal_block - pa->pa_pstart);

      if (cur_distance < new_distance)
            return cpa;

      /* drop the previous reference */
      atomic_dec(&cpa->pa_count);
      atomic_inc(&pa->pa_count);
      return pa;
}

/*
 * search goal blocks in preallocated space
 */
static noinline_for_stack int
ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
{
      int order, i;
      struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
      struct ext4_locality_group *lg;
      struct ext4_prealloc_space *pa, *cpa = NULL;
      ext4_fsblk_t goal_block;

      /* only data can be preallocated */
      if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
            return 0;

      /* first, try per-file preallocation */
      rcu_read_lock();
      list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {

            /* all fields in this condition don't change,
             * so we can skip locking for them */
            if (ac->ac_o_ex.fe_logical < pa->pa_lstart ||
                  ac->ac_o_ex.fe_logical >= pa->pa_lstart + pa->pa_len)
                  continue;

            /* found preallocated blocks, use them */
            spin_lock(&pa->pa_lock);
            if (pa->pa_deleted == 0 && pa->pa_free) {
                  atomic_inc(&pa->pa_count);
                  ext4_mb_use_inode_pa(ac, pa);
                  spin_unlock(&pa->pa_lock);
                  ac->ac_criteria = 10;
                  rcu_read_unlock();
                  return 1;
            }
            spin_unlock(&pa->pa_lock);
      }
      rcu_read_unlock();

      /* can we use group allocation? */
      if (!(ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC))
            return 0;

      /* inode may have no locality group for some reason */
      lg = ac->ac_lg;
      if (lg == NULL)
            return 0;
      order  = fls(ac->ac_o_ex.fe_len) - 1;
      if (order > PREALLOC_TB_SIZE - 1)
            /* The max size of hash table is PREALLOC_TB_SIZE */
            order = PREALLOC_TB_SIZE - 1;

      goal_block = ac->ac_g_ex.fe_group * EXT4_BLOCKS_PER_GROUP(ac->ac_sb) +
                 ac->ac_g_ex.fe_start +
                 le32_to_cpu(EXT4_SB(ac->ac_sb)->s_es->s_first_data_block);
      /*
       * search for the prealloc space that is having
       * minimal distance from the goal block.
       */
      for (i = order; i < PREALLOC_TB_SIZE; i++) {
            rcu_read_lock();
            list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[i],
                              pa_inode_list) {
                  spin_lock(&pa->pa_lock);
                  if (pa->pa_deleted == 0 &&
                              pa->pa_free >= ac->ac_o_ex.fe_len) {

                        cpa = ext4_mb_check_group_pa(goal_block,
                                                pa, cpa);
                  }
                  spin_unlock(&pa->pa_lock);
            }
            rcu_read_unlock();
      }
      if (cpa) {
            ext4_mb_use_group_pa(ac, cpa);
            ac->ac_criteria = 20;
            return 1;
      }
      return 0;
}

/*
 * the function goes through all block freed in the group
 * but not yet committed and marks them used in in-core bitmap.
 * buddy must be generated from this bitmap
 * Need to be called with the ext4 group lock held
 */
static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
                                    ext4_group_t group)
{
      struct rb_node *n;
      struct ext4_group_info *grp;
      struct ext4_free_data *entry;

      grp = ext4_get_group_info(sb, group);
      n = rb_first(&(grp->bb_free_root));

      while (n) {
            entry = rb_entry(n, struct ext4_free_data, node);
            mb_set_bits(bitmap, entry->start_blk, entry->count);
            n = rb_next(n);
      }
      return;
}

/*
 * the function goes through all preallocation in this group and marks them
 * used in in-core bitmap. buddy must be generated from this bitmap
 * Need to be called with ext4 group lock held
 */
static noinline_for_stack
void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
                              ext4_group_t group)
{
      struct ext4_group_info *grp = ext4_get_group_info(sb, group);
      struct ext4_prealloc_space *pa;
      struct list_head *cur;
      ext4_group_t groupnr;
      ext4_grpblk_t start;
      int preallocated = 0;
      int count = 0;
      int len;

      /* all form of preallocation discards first load group,
       * so the only competing code is preallocation use.
       * we don't need any locking here
       * notice we do NOT ignore preallocations with pa_deleted
       * otherwise we could leave used blocks available for
       * allocation in buddy when concurrent ext4_mb_put_pa()
       * is dropping preallocation
       */
      list_for_each(cur, &grp->bb_prealloc_list) {
            pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
            spin_lock(&pa->pa_lock);
            ext4_get_group_no_and_offset(sb, pa->pa_pstart,
                                   &groupnr, &start);
            len = pa->pa_len;
            spin_unlock(&pa->pa_lock);
            if (unlikely(len == 0))
                  continue;
            BUG_ON(groupnr != group);
            mb_set_bits(bitmap, start, len);
            preallocated += len;
            count++;
      }
      mb_debug("prellocated %u for group %u\n", preallocated, group);
}

static void ext4_mb_pa_callback(struct rcu_head *head)
{
      struct ext4_prealloc_space *pa;
      pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu);
      kmem_cache_free(ext4_pspace_cachep, pa);
}

/*
 * drops a reference to preallocated space descriptor
 * if this was the last reference and the space is consumed
 */
static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
                  struct super_block *sb, struct ext4_prealloc_space *pa)
{
      ext4_group_t grp;
      ext4_fsblk_t grp_blk;

      if (!atomic_dec_and_test(&pa->pa_count) || pa->pa_free != 0)
            return;

      /* in this short window concurrent discard can set pa_deleted */
      spin_lock(&pa->pa_lock);
      if (pa->pa_deleted == 1) {
            spin_unlock(&pa->pa_lock);
            return;
      }

      pa->pa_deleted = 1;
      spin_unlock(&pa->pa_lock);

      grp_blk = pa->pa_pstart;
      /* 
       * If doing group-based preallocation, pa_pstart may be in the
       * next group when pa is used up
       */
      if (pa->pa_type == MB_GROUP_PA)
            grp_blk--;

      ext4_get_group_no_and_offset(sb, grp_blk, &grp, NULL);

      /*
       * possible race:
       *
       *  P1 (buddy init)                 P2 (regular allocation)
       *                            find block B in PA
       *  copy on-disk bitmap to buddy
       *                            mark B in on-disk bitmap
       *                            drop PA from group
       *  mark all PAs in buddy
       *
       * thus, P1 initializes buddy with B available. to prevent this
       * we make "copy" and "mark all PAs" atomic and serialize "drop PA"
       * against that pair
       */
      ext4_lock_group(sb, grp);
      list_del(&pa->pa_group_list);
      ext4_unlock_group(sb, grp);

      spin_lock(pa->pa_obj_lock);
      list_del_rcu(&pa->pa_inode_list);
      spin_unlock(pa->pa_obj_lock);

      call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
}

/*
 * creates new preallocated space for given inode
 */
static noinline_for_stack int
ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
{
      struct super_block *sb = ac->ac_sb;
      struct ext4_prealloc_space *pa;
      struct ext4_group_info *grp;
      struct ext4_inode_info *ei;

      /* preallocate only when found space is larger then requested */
      BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
      BUG_ON(ac->ac_status != AC_STATUS_FOUND);
      BUG_ON(!S_ISREG(ac->ac_inode->i_mode));

      pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
      if (pa == NULL)
            return -ENOMEM;

      if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) {
            int winl;
            int wins;
            int win;
            int offs;

            /* we can't allocate as much as normalizer wants.
             * so, found space must get proper lstart
             * to cover original request */
            BUG_ON(ac->ac_g_ex.fe_logical > ac->ac_o_ex.fe_logical);
            BUG_ON(ac->ac_g_ex.fe_len < ac->ac_o_ex.fe_len);

            /* we're limited by original request in that
             * logical block must be covered any way
             * winl is window we can move our chunk within */
            winl = ac->ac_o_ex.fe_logical - ac->ac_g_ex.fe_logical;

            /* also, we should cover whole original request */
            wins = ac->ac_b_ex.fe_len - ac->ac_o_ex.fe_len;

            /* the smallest one defines real window */
            win = min(winl, wins);

            offs = ac->ac_o_ex.fe_logical % ac->ac_b_ex.fe_len;
            if (offs && offs < win)
                  win = offs;

            ac->ac_b_ex.fe_logical = ac->ac_o_ex.fe_logical - win;
            BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical);
            BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len);
      }

      /* preallocation can change ac_b_ex, thus we store actually
       * allocated blocks for history */
      ac->ac_f_ex = ac->ac_b_ex;

      pa->pa_lstart = ac->ac_b_ex.fe_logical;
      pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
      pa->pa_len = ac->ac_b_ex.fe_len;
      pa->pa_free = pa->pa_len;
      atomic_set(&pa->pa_count, 1);
      spin_lock_init(&pa->pa_lock);
      INIT_LIST_HEAD(&pa->pa_inode_list);
      INIT_LIST_HEAD(&pa->pa_group_list);
      pa->pa_deleted = 0;
      pa->pa_type = MB_INODE_PA;

      mb_debug("new inode pa %p: %llu/%u for %u\n", pa,
                  pa->pa_pstart, pa->pa_len, pa->pa_lstart);
      trace_ext4_mb_new_inode_pa(ac, pa);

      ext4_mb_use_inode_pa(ac, pa);
      atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);

      ei = EXT4_I(ac->ac_inode);
      grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);

      pa->pa_obj_lock = &ei->i_prealloc_lock;
      pa->pa_inode = ac->ac_inode;

      ext4_lock_group(sb, ac->ac_b_ex.fe_group);
      list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
      ext4_unlock_group(sb, ac->ac_b_ex.fe_group);

      spin_lock(pa->pa_obj_lock);
      list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
      spin_unlock(pa->pa_obj_lock);

      return 0;
}

/*
 * creates new preallocated space for locality group inodes belongs to
 */
static noinline_for_stack int
ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
{
      struct super_block *sb = ac->ac_sb;
      struct ext4_locality_group *lg;
      struct ext4_prealloc_space *pa;
      struct ext4_group_info *grp;

      /* preallocate only when found space is larger then requested */
      BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
      BUG_ON(ac->ac_status != AC_STATUS_FOUND);
      BUG_ON(!S_ISREG(ac->ac_inode->i_mode));

      BUG_ON(ext4_pspace_cachep == NULL);
      pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
      if (pa == NULL)
            return -ENOMEM;

      /* preallocation can change ac_b_ex, thus we store actually
       * allocated blocks for history */
      ac->ac_f_ex = ac->ac_b_ex;

      pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
      pa->pa_lstart = pa->pa_pstart;
      pa->pa_len = ac->ac_b_ex.fe_len;
      pa->pa_free = pa->pa_len;
      atomic_set(&pa->pa_count, 1);
      spin_lock_init(&pa->pa_lock);
      INIT_LIST_HEAD(&pa->pa_inode_list);
      INIT_LIST_HEAD(&pa->pa_group_list);
      pa->pa_deleted = 0;
      pa->pa_type = MB_GROUP_PA;

      mb_debug("new group pa %p: %llu/%u for %u\n", pa,
                  pa->pa_pstart, pa->pa_len, pa->pa_lstart);
      trace_ext4_mb_new_group_pa(ac, pa);

      ext4_mb_use_group_pa(ac, pa);
      atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);

      grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
      lg = ac->ac_lg;
      BUG_ON(lg == NULL);

      pa->pa_obj_lock = &lg->lg_prealloc_lock;
      pa->pa_inode = NULL;

      ext4_lock_group(sb, ac->ac_b_ex.fe_group);
      list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
      ext4_unlock_group(sb, ac->ac_b_ex.fe_group);

      /*
       * We will later add the new pa to the right bucket
       * after updating the pa_free in ext4_mb_release_context
       */
      return 0;
}

static int ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
{
      int err;

      if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
            err = ext4_mb_new_group_pa(ac);
      else
            err = ext4_mb_new_inode_pa(ac);
      return err;
}

/*
 * finds all unused blocks in on-disk bitmap, frees them in
 * in-core bitmap and buddy.
 * @pa must be unlinked from inode and group lists, so that
 * nobody else can find/use it.
 * the caller MUST hold group/inode locks.
 * TODO: optimize the case when there are no in-core structures yet
 */
static noinline_for_stack int
ext4_mb_release_inode_pa(struct ext4_buddy *e4b, struct buffer_head *bitmap_bh,
                  struct ext4_prealloc_space *pa,
                  struct ext4_allocation_context *ac)
{
      struct super_block *sb = e4b->bd_sb;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      unsigned int end;
      unsigned int next;
      ext4_group_t group;
      ext4_grpblk_t bit;
      unsigned long long grp_blk_start;
      sector_t start;
      int err = 0;
      int free = 0;

      BUG_ON(pa->pa_deleted == 0);
      ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
      grp_blk_start = pa->pa_pstart - bit;
      BUG_ON(group != e4b->bd_group && pa->pa_len != 0);
      end = bit + pa->pa_len;

      if (ac) {
            ac->ac_sb = sb;
            ac->ac_inode = pa->pa_inode;
            ac->ac_op = EXT4_MB_HISTORY_DISCARD;
      }

      while (bit < end) {
            bit = mb_find_next_zero_bit(bitmap_bh->b_data, end, bit);
            if (bit >= end)
                  break;
            next = mb_find_next_bit(bitmap_bh->b_data, end, bit);
            start = group * EXT4_BLOCKS_PER_GROUP(sb) + bit +
                        le32_to_cpu(sbi->s_es->s_first_data_block);
            mb_debug("    free preallocated %u/%u in group %u\n",
                        (unsigned) start, (unsigned) next - bit,
                        (unsigned) group);
            free += next - bit;

            if (ac) {
                  ac->ac_b_ex.fe_group = group;
                  ac->ac_b_ex.fe_start = bit;
                  ac->ac_b_ex.fe_len = next - bit;
                  ac->ac_b_ex.fe_logical = 0;
                  ext4_mb_store_history(ac);
            }

            trace_ext4_mb_release_inode_pa(ac, pa, grp_blk_start + bit,
                                     next - bit);
            mb_free_blocks(pa->pa_inode, e4b, bit, next - bit);
            bit = next + 1;
      }
      if (free != pa->pa_free) {
            printk(KERN_CRIT "pa %p: logic %lu, phys. %lu, len %lu\n",
                  pa, (unsigned long) pa->pa_lstart,
                  (unsigned long) pa->pa_pstart,
                  (unsigned long) pa->pa_len);
            ext4_grp_locked_error(sb, group,
                              __func__, "free %u, pa_free %u",
                              free, pa->pa_free);
            /*
             * pa is already deleted so we use the value obtained
             * from the bitmap and continue.
             */
      }
      atomic_add(free, &sbi->s_mb_discarded);

      return err;
}

static noinline_for_stack int
ext4_mb_release_group_pa(struct ext4_buddy *e4b,
                        struct ext4_prealloc_space *pa,
                        struct ext4_allocation_context *ac)
{
      struct super_block *sb = e4b->bd_sb;
      ext4_group_t group;
      ext4_grpblk_t bit;

      if (ac)
            ac->ac_op = EXT4_MB_HISTORY_DISCARD;

      trace_ext4_mb_release_group_pa(ac, pa);
      BUG_ON(pa->pa_deleted == 0);
      ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
      BUG_ON(group != e4b->bd_group && pa->pa_len != 0);
      mb_free_blocks(pa->pa_inode, e4b, bit, pa->pa_len);
      atomic_add(pa->pa_len, &EXT4_SB(sb)->s_mb_discarded);

      if (ac) {
            ac->ac_sb = sb;
            ac->ac_inode = NULL;
            ac->ac_b_ex.fe_group = group;
            ac->ac_b_ex.fe_start = bit;
            ac->ac_b_ex.fe_len = pa->pa_len;
            ac->ac_b_ex.fe_logical = 0;
            ext4_mb_store_history(ac);
      }

      return 0;
}

/*
 * releases all preallocations in given group
 *
 * first, we need to decide discard policy:
 * - when do we discard
 *   1) ENOSPC
 * - how many do we discard
 *   1) how many requested
 */
static noinline_for_stack int
ext4_mb_discard_group_preallocations(struct super_block *sb,
                              ext4_group_t group, int needed)
{
      struct ext4_group_info *grp = ext4_get_group_info(sb, group);
      struct buffer_head *bitmap_bh = NULL;
      struct ext4_prealloc_space *pa, *tmp;
      struct ext4_allocation_context *ac;
      struct list_head list;
      struct ext4_buddy e4b;
      int err;
      int busy = 0;
      int free = 0;

      mb_debug("discard preallocation for group %u\n", group);

      if (list_empty(&grp->bb_prealloc_list))
            return 0;

      bitmap_bh = ext4_read_block_bitmap(sb, group);
      if (bitmap_bh == NULL) {
            ext4_error(sb, __func__, "Error in reading block "
                        "bitmap for %u", group);
            return 0;
      }

      err = ext4_mb_load_buddy(sb, group, &e4b);
      if (err) {
            ext4_error(sb, __func__, "Error in loading buddy "
                        "information for %u", group);
            put_bh(bitmap_bh);
            return 0;
      }

      if (needed == 0)
            needed = EXT4_BLOCKS_PER_GROUP(sb) + 1;

      INIT_LIST_HEAD(&list);
      ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
      if (ac)
            ac->ac_sb = sb;
repeat:
      ext4_lock_group(sb, group);
      list_for_each_entry_safe(pa, tmp,
                        &grp->bb_prealloc_list, pa_group_list) {
            spin_lock(&pa->pa_lock);
            if (atomic_read(&pa->pa_count)) {
                  spin_unlock(&pa->pa_lock);
                  busy = 1;
                  continue;
            }
            if (pa->pa_deleted) {
                  spin_unlock(&pa->pa_lock);
                  continue;
            }

            /* seems this one can be freed ... */
            pa->pa_deleted = 1;

            /* we can trust pa_free ... */
            free += pa->pa_free;

            spin_unlock(&pa->pa_lock);

            list_del(&pa->pa_group_list);
            list_add(&pa->u.pa_tmp_list, &list);
      }

      /* if we still need more blocks and some PAs were used, try again */
      if (free < needed && busy) {
            busy = 0;
            ext4_unlock_group(sb, group);
            /*
             * Yield the CPU here so that we don't get soft lockup
             * in non preempt case.
             */
            yield();
            goto repeat;
      }

      /* found anything to free? */
      if (list_empty(&list)) {
            BUG_ON(free != 0);
            goto out;
      }

      /* now free all selected PAs */
      list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {

            /* remove from object (inode or locality group) */
            spin_lock(pa->pa_obj_lock);
            list_del_rcu(&pa->pa_inode_list);
            spin_unlock(pa->pa_obj_lock);

            if (pa->pa_type == MB_GROUP_PA)
                  ext4_mb_release_group_pa(&e4b, pa, ac);
            else
                  ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa, ac);

            list_del(&pa->u.pa_tmp_list);
            call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
      }

out:
      ext4_unlock_group(sb, group);
      if (ac)
            kmem_cache_free(ext4_ac_cachep, ac);
      ext4_mb_release_desc(&e4b);
      put_bh(bitmap_bh);
      return free;
}

/*
 * releases all non-used preallocated blocks for given inode
 *
 * It's important to discard preallocations under i_data_sem
 * We don't want another block to be served from the prealloc
 * space when we are discarding the inode prealloc space.
 *
 * FIXME!! Make sure it is valid at all the call sites
 */
void ext4_discard_preallocations(struct inode *inode)
{
      struct ext4_inode_info *ei = EXT4_I(inode);
      struct super_block *sb = inode->i_sb;
      struct buffer_head *bitmap_bh = NULL;
      struct ext4_prealloc_space *pa, *tmp;
      struct ext4_allocation_context *ac;
      ext4_group_t group = 0;
      struct list_head list;
      struct ext4_buddy e4b;
      int err;

      if (!S_ISREG(inode->i_mode)) {
            /*BUG_ON(!list_empty(&ei->i_prealloc_list));*/
            return;
      }

      mb_debug("discard preallocation for inode %lu\n", inode->i_ino);
      trace_ext4_discard_preallocations(inode);

      INIT_LIST_HEAD(&list);

      ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
      if (ac) {
            ac->ac_sb = sb;
            ac->ac_inode = inode;
      }
repeat:
      /* first, collect all pa's in the inode */
      spin_lock(&ei->i_prealloc_lock);
      while (!list_empty(&ei->i_prealloc_list)) {
            pa = list_entry(ei->i_prealloc_list.next,
                        struct ext4_prealloc_space, pa_inode_list);
            BUG_ON(pa->pa_obj_lock != &ei->i_prealloc_lock);
            spin_lock(&pa->pa_lock);
            if (atomic_read(&pa->pa_count)) {
                  /* this shouldn't happen often - nobody should
                   * use preallocation while we're discarding it */
                  spin_unlock(&pa->pa_lock);
                  spin_unlock(&ei->i_prealloc_lock);
                  printk(KERN_ERR "uh-oh! used pa while discarding\n");
                  WARN_ON(1);
                  schedule_timeout_uninterruptible(HZ);
                  goto repeat;

            }
            if (pa->pa_deleted == 0) {
                  pa->pa_deleted = 1;
                  spin_unlock(&pa->pa_lock);
                  list_del_rcu(&pa->pa_inode_list);
                  list_add(&pa->u.pa_tmp_list, &list);
                  continue;
            }

            /* someone is deleting pa right now */
            spin_unlock(&pa->pa_lock);
            spin_unlock(&ei->i_prealloc_lock);

            /* we have to wait here because pa_deleted
             * doesn't mean pa is already unlinked from
             * the list. as we might be called from
             * ->clear_inode() the inode will get freed
             * and concurrent thread which is unlinking
             * pa from inode's list may access already
             * freed memory, bad-bad-bad */

            /* XXX: if this happens too often, we can
             * add a flag to force wait only in case
             * of ->clear_inode(), but not in case of
             * regular truncate */
            schedule_timeout_uninterruptible(HZ);
            goto repeat;
      }
      spin_unlock(&ei->i_prealloc_lock);

      list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
            BUG_ON(pa->pa_type != MB_INODE_PA);
            ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL);

            err = ext4_mb_load_buddy(sb, group, &e4b);
            if (err) {
                  ext4_error(sb, __func__, "Error in loading buddy "
                              "information for %u", group);
                  continue;
            }

            bitmap_bh = ext4_read_block_bitmap(sb, group);
            if (bitmap_bh == NULL) {
                  ext4_error(sb, __func__, "Error in reading block "
                              "bitmap for %u", group);
                  ext4_mb_release_desc(&e4b);
                  continue;
            }

            ext4_lock_group(sb, group);
            list_del(&pa->pa_group_list);
            ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa, ac);
            ext4_unlock_group(sb, group);

            ext4_mb_release_desc(&e4b);
            put_bh(bitmap_bh);

            list_del(&pa->u.pa_tmp_list);
            call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
      }
      if (ac)
            kmem_cache_free(ext4_ac_cachep, ac);
}

/*
 * finds all preallocated spaces and return blocks being freed to them
 * if preallocated space becomes full (no block is used from the space)
 * then the function frees space in buddy
 * XXX: at the moment, truncate (which is the only way to free blocks)
 * discards all preallocations
 */
static void ext4_mb_return_to_preallocation(struct inode *inode,
                              struct ext4_buddy *e4b,
                              sector_t block, int count)
{
      BUG_ON(!list_empty(&EXT4_I(inode)->i_prealloc_list));
}
#ifdef MB_DEBUG
static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
{
      struct super_block *sb = ac->ac_sb;
      ext4_group_t ngroups, i;

      printk(KERN_ERR "EXT4-fs: Can't allocate:"
                  " Allocation context details:\n");
      printk(KERN_ERR "EXT4-fs: status %d flags %d\n",
                  ac->ac_status, ac->ac_flags);
      printk(KERN_ERR "EXT4-fs: orig %lu/%lu/%lu@%lu, goal %lu/%lu/%lu@%lu, "
                  "best %lu/%lu/%lu@%lu cr %d\n",
                  (unsigned long)ac->ac_o_ex.fe_group,
                  (unsigned long)ac->ac_o_ex.fe_start,
                  (unsigned long)ac->ac_o_ex.fe_len,
                  (unsigned long)ac->ac_o_ex.fe_logical,
                  (unsigned long)ac->ac_g_ex.fe_group,
                  (unsigned long)ac->ac_g_ex.fe_start,
                  (unsigned long)ac->ac_g_ex.fe_len,
                  (unsigned long)ac->ac_g_ex.fe_logical,
                  (unsigned long)ac->ac_b_ex.fe_group,
                  (unsigned long)ac->ac_b_ex.fe_start,
                  (unsigned long)ac->ac_b_ex.fe_len,
                  (unsigned long)ac->ac_b_ex.fe_logical,
                  (int)ac->ac_criteria);
      printk(KERN_ERR "EXT4-fs: %lu scanned, %d found\n", ac->ac_ex_scanned,
            ac->ac_found);
      printk(KERN_ERR "EXT4-fs: groups: \n");
      ngroups = ext4_get_groups_count(sb);
      for (i = 0; i < ngroups; i++) {
            struct ext4_group_info *grp = ext4_get_group_info(sb, i);
            struct ext4_prealloc_space *pa;
            ext4_grpblk_t start;
            struct list_head *cur;
            ext4_lock_group(sb, i);
            list_for_each(cur, &grp->bb_prealloc_list) {
                  pa = list_entry(cur, struct ext4_prealloc_space,
                              pa_group_list);
                  spin_lock(&pa->pa_lock);
                  ext4_get_group_no_and_offset(sb, pa->pa_pstart,
                                         NULL, &start);
                  spin_unlock(&pa->pa_lock);
                  printk(KERN_ERR "PA:%lu:%d:%u \n", i,
                                          start, pa->pa_len);
            }
            ext4_unlock_group(sb, i);

            if (grp->bb_free == 0)
                  continue;
            printk(KERN_ERR "%lu: %d/%d \n",
                   i, grp->bb_free, grp->bb_fragments);
      }
      printk(KERN_ERR "\n");
}
#else
static inline void ext4_mb_show_ac(struct ext4_allocation_context *ac)
{
      return;
}
#endif

/*
 * We use locality group preallocation for small size file. The size of the
 * file is determined by the current size or the resulting size after
 * allocation which ever is larger
 *
 * One can tune this size via /sys/fs/ext4/<partition>/mb_stream_req
 */
static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
{
      struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
      int bsbits = ac->ac_sb->s_blocksize_bits;
      loff_t size, isize;

      if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
            return;

      size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
      isize = i_size_read(ac->ac_inode) >> bsbits;
      size = max(size, isize);

      /* don't use group allocation for large files */
      if (size >= sbi->s_mb_stream_request)
            return;

      if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
            return;

      BUG_ON(ac->ac_lg != NULL);
      /*
       * locality group prealloc space are per cpu. The reason for having
       * per cpu locality group is to reduce the contention between block
       * request from multiple CPUs.
       */
      ac->ac_lg = per_cpu_ptr(sbi->s_locality_groups, raw_smp_processor_id());

      /* we're going to use group allocation */
      ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;

      /* serialize all allocations in the group */
      mutex_lock(&ac->ac_lg->lg_mutex);
}

static noinline_for_stack int
ext4_mb_initialize_context(struct ext4_allocation_context *ac,
                        struct ext4_allocation_request *ar)
{
      struct super_block *sb = ar->inode->i_sb;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct ext4_super_block *es = sbi->s_es;
      ext4_group_t group;
      unsigned int len;
      ext4_fsblk_t goal;
      ext4_grpblk_t block;

      /* we can't allocate > group size */
      len = ar->len;

      /* just a dirty hack to filter too big requests  */
      if (len >= EXT4_BLOCKS_PER_GROUP(sb) - 10)
            len = EXT4_BLOCKS_PER_GROUP(sb) - 10;

      /* start searching from the goal */
      goal = ar->goal;
      if (goal < le32_to_cpu(es->s_first_data_block) ||
                  goal >= ext4_blocks_count(es))
            goal = le32_to_cpu(es->s_first_data_block);
      ext4_get_group_no_and_offset(sb, goal, &group, &block);

      /* set up allocation goals */
      memset(ac, 0, sizeof(struct ext4_allocation_context));
      ac->ac_b_ex.fe_logical = ar->logical;
      ac->ac_status = AC_STATUS_CONTINUE;
      ac->ac_sb = sb;
      ac->ac_inode = ar->inode;
      ac->ac_o_ex.fe_logical = ar->logical;
      ac->ac_o_ex.fe_group = group;
      ac->ac_o_ex.fe_start = block;
      ac->ac_o_ex.fe_len = len;
      ac->ac_g_ex.fe_logical = ar->logical;
      ac->ac_g_ex.fe_group = group;
      ac->ac_g_ex.fe_start = block;
      ac->ac_g_ex.fe_len = len;
      ac->ac_flags = ar->flags;

      /* we have to define context: we'll we work with a file or
       * locality group. this is a policy, actually */
      ext4_mb_group_or_file(ac);

      mb_debug("init ac: %u blocks @ %u, goal %u, flags %x, 2^%d, "
                  "left: %u/%u, right %u/%u to %swritable\n",
                  (unsigned) ar->len, (unsigned) ar->logical,
                  (unsigned) ar->goal, ac->ac_flags, ac->ac_2order,
                  (unsigned) ar->lleft, (unsigned) ar->pleft,
                  (unsigned) ar->lright, (unsigned) ar->pright,
                  atomic_read(&ar->inode->i_writecount) ? "" : "non-");
      return 0;

}

static noinline_for_stack void
ext4_mb_discard_lg_preallocations(struct super_block *sb,
                              struct ext4_locality_group *lg,
                              int order, int total_entries)
{
      ext4_group_t group = 0;
      struct ext4_buddy e4b;
      struct list_head discard_list;
      struct ext4_prealloc_space *pa, *tmp;
      struct ext4_allocation_context *ac;

      mb_debug("discard locality group preallocation\n");

      INIT_LIST_HEAD(&discard_list);
      ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
      if (ac)
            ac->ac_sb = sb;

      spin_lock(&lg->lg_prealloc_lock);
      list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[order],
                                    pa_inode_list) {
            spin_lock(&pa->pa_lock);
            if (atomic_read(&pa->pa_count)) {
                  /*
                   * This is the pa that we just used
                   * for block allocation. So don't
                   * free that
                   */
                  spin_unlock(&pa->pa_lock);
                  continue;
            }
            if (pa->pa_deleted) {
                  spin_unlock(&pa->pa_lock);
                  continue;
            }
            /* only lg prealloc space */
            BUG_ON(pa->pa_type != MB_GROUP_PA);

            /* seems this one can be freed ... */
            pa->pa_deleted = 1;
            spin_unlock(&pa->pa_lock);

            list_del_rcu(&pa->pa_inode_list);
            list_add(&pa->u.pa_tmp_list, &discard_list);

            total_entries--;
            if (total_entries <= 5) {
                  /*
                   * we want to keep only 5 entries
                   * allowing it to grow to 8. This
                   * mak sure we don't call discard
                   * soon for this list.
                   */
                  break;
            }
      }
      spin_unlock(&lg->lg_prealloc_lock);

      list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {

            ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL);
            if (ext4_mb_load_buddy(sb, group, &e4b)) {
                  ext4_error(sb, __func__, "Error in loading buddy "
                              "information for %u", group);
                  continue;
            }
            ext4_lock_group(sb, group);
            list_del(&pa->pa_group_list);
            ext4_mb_release_group_pa(&e4b, pa, ac);
            ext4_unlock_group(sb, group);

            ext4_mb_release_desc(&e4b);
            list_del(&pa->u.pa_tmp_list);
            call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
      }
      if (ac)
            kmem_cache_free(ext4_ac_cachep, ac);
}

/*
 * We have incremented pa_count. So it cannot be freed at this
 * point. Also we hold lg_mutex. So no parallel allocation is
 * possible from this lg. That means pa_free cannot be updated.
 *
 * A parallel ext4_mb_discard_group_preallocations is possible.
 * which can cause the lg_prealloc_list to be updated.
 */

static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
{
      int order, added = 0, lg_prealloc_count = 1;
      struct super_block *sb = ac->ac_sb;
      struct ext4_locality_group *lg = ac->ac_lg;
      struct ext4_prealloc_space *tmp_pa, *pa = ac->ac_pa;

      order = fls(pa->pa_free) - 1;
      if (order > PREALLOC_TB_SIZE - 1)
            /* The max size of hash table is PREALLOC_TB_SIZE */
            order = PREALLOC_TB_SIZE - 1;
      /* Add the prealloc space to lg */
      rcu_read_lock();
      list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[order],
                                    pa_inode_list) {
            spin_lock(&tmp_pa->pa_lock);
            if (tmp_pa->pa_deleted) {
                  spin_unlock(&tmp_pa->pa_lock);
                  continue;
            }
            if (!added && pa->pa_free < tmp_pa->pa_free) {
                  /* Add to the tail of the previous entry */
                  list_add_tail_rcu(&pa->pa_inode_list,
                                    &tmp_pa->pa_inode_list);
                  added = 1;
                  /*
                   * we want to count the total
                   * number of entries in the list
                   */
            }
            spin_unlock(&tmp_pa->pa_lock);
            lg_prealloc_count++;
      }
      if (!added)
            list_add_tail_rcu(&pa->pa_inode_list,
                              &lg->lg_prealloc_list[order]);
      rcu_read_unlock();

      /* Now trim the list to be not more than 8 elements */
      if (lg_prealloc_count > 8) {
            ext4_mb_discard_lg_preallocations(sb, lg,
                                    order, lg_prealloc_count);
            return;
      }
      return ;
}

/*
 * release all resource we used in allocation
 */
static int ext4_mb_release_context(struct ext4_allocation_context *ac)
{
      struct ext4_prealloc_space *pa = ac->ac_pa;
      if (pa) {
            if (pa->pa_type == MB_GROUP_PA) {
                  /* see comment in ext4_mb_use_group_pa() */
                  spin_lock(&pa->pa_lock);
                  pa->pa_pstart += ac->ac_b_ex.fe_len;
                  pa->pa_lstart += ac->ac_b_ex.fe_len;
                  pa->pa_free -= ac->ac_b_ex.fe_len;
                  pa->pa_len -= ac->ac_b_ex.fe_len;
                  spin_unlock(&pa->pa_lock);
            }
      }
      if (ac->alloc_semp)
            up_read(ac->alloc_semp);
      if (pa) {
            /*
             * We want to add the pa to the right bucket.
             * Remove it from the list and while adding
             * make sure the list to which we are adding
             * doesn't grow big.  We need to release
             * alloc_semp before calling ext4_mb_add_n_trim()
             */
            if ((pa->pa_type == MB_GROUP_PA) && likely(pa->pa_free)) {
                  spin_lock(pa->pa_obj_lock);
                  list_del_rcu(&pa->pa_inode_list);
                  spin_unlock(pa->pa_obj_lock);
                  ext4_mb_add_n_trim(ac);
            }
            ext4_mb_put_pa(ac, ac->ac_sb, pa);
      }
      if (ac->ac_bitmap_page)
            page_cache_release(ac->ac_bitmap_page);
      if (ac->ac_buddy_page)
            page_cache_release(ac->ac_buddy_page);
      if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
            mutex_unlock(&ac->ac_lg->lg_mutex);
      ext4_mb_collect_stats(ac);
      return 0;
}

static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
{
      ext4_group_t i, ngroups = ext4_get_groups_count(sb);
      int ret;
      int freed = 0;

      trace_ext4_mb_discard_preallocations(sb, needed);
      for (i = 0; i < ngroups && needed > 0; i++) {
            ret = ext4_mb_discard_group_preallocations(sb, i, needed);
            freed += ret;
            needed -= ret;
      }

      return freed;
}

/*
 * Main entry point into mballoc to allocate blocks
 * it tries to use preallocation first, then falls back
 * to usual allocation
 */
ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
                         struct ext4_allocation_request *ar, int *errp)
{
      int freed;
      struct ext4_allocation_context *ac = NULL;
      struct ext4_sb_info *sbi;
      struct super_block *sb;
      ext4_fsblk_t block = 0;
      unsigned int inquota = 0;
      unsigned int reserv_blks = 0;

      sb = ar->inode->i_sb;
      sbi = EXT4_SB(sb);

      trace_ext4_request_blocks(ar);

      /*
       * For delayed allocation, we could skip the ENOSPC and
       * EDQUOT check, as blocks and quotas have been already
       * reserved when data being copied into pagecache.
       */
      if (EXT4_I(ar->inode)->i_delalloc_reserved_flag)
            ar->flags |= EXT4_MB_DELALLOC_RESERVED;
      else {
            /* Without delayed allocation we need to verify
             * there is enough free blocks to do block allocation
             * and verify allocation doesn't exceed the quota limits.
             */
            while (ar->len && ext4_claim_free_blocks(sbi, ar->len)) {
                  /* let others to free the space */
                  yield();
                  ar->len = ar->len >> 1;
            }
            if (!ar->len) {
                  *errp = -ENOSPC;
                  return 0;
            }
            reserv_blks = ar->len;
            while (ar->len && vfs_dq_alloc_block(ar->inode, ar->len)) {
                  ar->flags |= EXT4_MB_HINT_NOPREALLOC;
                  ar->len--;
            }
            inquota = ar->len;
            if (ar->len == 0) {
                  *errp = -EDQUOT;
                  goto out3;
            }
      }

      ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
      if (!ac) {
            ar->len = 0;
            *errp = -ENOMEM;
            goto out1;
      }

      *errp = ext4_mb_initialize_context(ac, ar);
      if (*errp) {
            ar->len = 0;
            goto out2;
      }

      ac->ac_op = EXT4_MB_HISTORY_PREALLOC;
      if (!ext4_mb_use_preallocated(ac)) {
            ac->ac_op = EXT4_MB_HISTORY_ALLOC;
            ext4_mb_normalize_request(ac, ar);
repeat:
            /* allocate space in core */
            ext4_mb_regular_allocator(ac);

            /* as we've just preallocated more space than
             * user requested orinally, we store allocated
             * space in a special descriptor */
            if (ac->ac_status == AC_STATUS_FOUND &&
                        ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)
                  ext4_mb_new_preallocation(ac);
      }
      if (likely(ac->ac_status == AC_STATUS_FOUND)) {
            *errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_blks);
            if (*errp ==  -EAGAIN) {
                  /*
                   * drop the reference that we took
                   * in ext4_mb_use_best_found
                   */
                  ext4_mb_release_context(ac);
                  ac->ac_b_ex.fe_group = 0;
                  ac->ac_b_ex.fe_start = 0;
                  ac->ac_b_ex.fe_len = 0;
                  ac->ac_status = AC_STATUS_CONTINUE;
                  goto repeat;
            } else if (*errp) {
                  ac->ac_b_ex.fe_len = 0;
                  ar->len = 0;
                  ext4_mb_show_ac(ac);
            } else {
                  block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
                  ar->len = ac->ac_b_ex.fe_len;
            }
      } else {
            freed  = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
            if (freed)
                  goto repeat;
            *errp = -ENOSPC;
            ac->ac_b_ex.fe_len = 0;
            ar->len = 0;
            ext4_mb_show_ac(ac);
      }

      ext4_mb_release_context(ac);

out2:
      kmem_cache_free(ext4_ac_cachep, ac);
out1:
      if (inquota && ar->len < inquota)
            vfs_dq_free_block(ar->inode, inquota - ar->len);
out3:
      if (!ar->len) {
            if (!EXT4_I(ar->inode)->i_delalloc_reserved_flag)
                  /* release all the reserved blocks if non delalloc */
                  percpu_counter_sub(&sbi->s_dirtyblocks_counter,
                                    reserv_blks);
      }

      trace_ext4_allocate_blocks(ar, (unsigned long long)block);

      return block;
}

/*
 * We can merge two free data extents only if the physical blocks
 * are contiguous, AND the extents were freed by the same transaction,
 * AND the blocks are associated with the same group.
 */
static int can_merge(struct ext4_free_data *entry1,
                  struct ext4_free_data *entry2)
{
      if ((entry1->t_tid == entry2->t_tid) &&
          (entry1->group == entry2->group) &&
          ((entry1->start_blk + entry1->count) == entry2->start_blk))
            return 1;
      return 0;
}

static noinline_for_stack int
ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
                  struct ext4_free_data *new_entry)
{
      ext4_grpblk_t block;
      struct ext4_free_data *entry;
      struct ext4_group_info *db = e4b->bd_info;
      struct super_block *sb = e4b->bd_sb;
      struct ext4_sb_info *sbi = EXT4_SB(sb);
      struct rb_node **n = &db->bb_free_root.rb_node, *node;
      struct rb_node *parent = NULL, *new_node;

      BUG_ON(!ext4_handle_valid(handle));
      BUG_ON(e4b->bd_bitmap_page == NULL);
      BUG_ON(e4b->bd_buddy_page == NULL);

      new_node = &new_entry->node;
      block = new_entry->start_blk;

      if (!*n) {
            /* first free block exent. We need to
               protect buddy cache from being freed,
             * otherwise we'll refresh it from
             * on-disk bitmap and lose not-yet-available
             * blocks */
            page_cache_get(e4b->bd_buddy_page);
            page_cache_get(e4b->bd_bitmap_page);
      }
      while (*n) {
            parent = *n;
            entry = rb_entry(parent, struct ext4_free_data, node);
            if (block < entry->start_blk)
                  n = &(*n)->rb_left;
            else if (block >= (entry->start_blk + entry->count))
                  n = &(*n)->rb_right;
            else {
                  ext4_grp_locked_error(sb, e4b->bd_group, __func__,
                              "Double free of blocks %d (%d %d)",
                              block, entry->start_blk, entry->count);
                  return 0;
            }
      }

      rb_link_node(new_node, parent, n);
      rb_insert_color(new_node, &db->bb_free_root);

      /* Now try to see the extent can be merged to left and right */
      node = rb_prev(new_node);
      if (node) {
            entry = rb_entry(node, struct ext4_free_data, node);
            if (can_merge(entry, new_entry)) {
                  new_entry->start_blk = entry->start_blk;
                  new_entry->count += entry->count;
                  rb_erase(node, &(db->bb_free_root));
                  spin_lock(&sbi->s_md_lock);
                  list_del(&entry->list);
                  spin_unlock(&sbi->s_md_lock);
                  kmem_cache_free(ext4_free_ext_cachep, entry);
            }
      }

      node = rb_next(new_node);
      if (node) {
            entry = rb_entry(node, struct ext4_free_data, node);
            if (can_merge(new_entry, entry)) {
                  new_entry->count += entry->count;
                  rb_erase(node, &(db->bb_free_root));
                  spin_lock(&sbi->s_md_lock);
                  list_del(&entry->list);
                  spin_unlock(&sbi->s_md_lock);
                  kmem_cache_free(ext4_free_ext_cachep, entry);
            }
      }
      /* Add the extent to transaction's private list */
      spin_lock(&sbi->s_md_lock);
      list_add(&new_entry->list, &handle->h_transaction->t_private_list);
      spin_unlock(&sbi->s_md_lock);
      return 0;
}

/*
 * Main entry point into mballoc to free blocks
 */
void ext4_mb_free_blocks(handle_t *handle, struct inode *inode,
                  ext4_fsblk_t block, unsigned long count,
                  int metadata, unsigned long *freed)
{
      struct buffer_head *bitmap_bh = NULL;
      struct super_block *sb = inode->i_sb;
      struct ext4_allocation_context *ac = NULL;
      struct ext4_group_desc *gdp;
      struct ext4_super_block *es;
      unsigned int overflow;
      ext4_grpblk_t bit;
      struct buffer_head *gd_bh;
      ext4_group_t block_group;
      struct ext4_sb_info *sbi;
      struct ext4_buddy e4b;
      int err = 0;
      int ret;

      *freed = 0;

      sbi = EXT4_SB(sb);
      es = EXT4_SB(sb)->s_es;
      if (block < le32_to_cpu(es->s_first_data_block) ||
          block + count < block ||
          block + count > ext4_blocks_count(es)) {
            ext4_error(sb, __func__,
                      "Freeing blocks not in datazone - "
                      "block = %llu, count = %lu", block, count);
            goto error_return;
      }

      ext4_debug("freeing block %llu\n", block);
      trace_ext4_free_blocks(inode, block, count, metadata);

      ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
      if (ac) {
            ac->ac_op = EXT4_MB_HISTORY_FREE;
            ac->ac_inode = inode;
            ac->ac_sb = sb;
      }

do_more:
      overflow = 0;
      ext4_get_group_no_and_offset(sb, block, &block_group, &bit);

      /*
       * Check to see if we are freeing blocks across a group
       * boundary.
       */
      if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
            overflow = bit + count - EXT4_BLOCKS_PER_GROUP(sb);
            count -= overflow;
      }
      bitmap_bh = ext4_read_block_bitmap(sb, block_group);
      if (!bitmap_bh) {
            err = -EIO;
            goto error_return;
      }
      gdp = ext4_get_group_desc(sb, block_group, &gd_bh);
      if (!gdp) {
            err = -EIO;
            goto error_return;
      }

      if (in_range(ext4_block_bitmap(sb, gdp), block, count) ||
          in_range(ext4_inode_bitmap(sb, gdp), block, count) ||
          in_range(block, ext4_inode_table(sb, gdp),
                  EXT4_SB(sb)->s_itb_per_group) ||
          in_range(block + count - 1, ext4_inode_table(sb, gdp),
                  EXT4_SB(sb)->s_itb_per_group)) {

            ext4_error(sb, __func__,
                     "Freeing blocks in system zone - "
                     "Block = %llu, count = %lu", block, count);
            /* err = 0. ext4_std_error should be a no op */
            goto error_return;
      }

      BUFFER_TRACE(bitmap_bh, "getting write access");
      err = ext4_journal_get_write_access(handle, bitmap_bh);
      if (err)
            goto error_return;

      /*
       * We are about to modify some metadata.  Call the journal APIs
       * to unshare ->b_data if a currently-committing transaction is
       * using it
       */
      BUFFER_TRACE(gd_bh, "get_write_access");
      err = ext4_journal_get_write_access(handle, gd_bh);
      if (err)
            goto error_return;
#ifdef AGGRESSIVE_CHECK
      {
            int i;
            for (i = 0; i < count; i++)
                  BUG_ON(!mb_test_bit(bit + i, bitmap_bh->b_data));
      }
#endif
      if (ac) {
            ac->ac_b_ex.fe_group = block_group;
            ac->ac_b_ex.fe_start = bit;
            ac->ac_b_ex.fe_len = count;
            ext4_mb_store_history(ac);
      }

      err = ext4_mb_load_buddy(sb, block_group, &e4b);
      if (err)
            goto error_return;
      if (metadata && ext4_handle_valid(handle)) {
            struct ext4_free_data *new_entry;
            /*
             * blocks being freed are metadata. these blocks shouldn't
             * be used until this transaction is committed
             */
            new_entry  = kmem_cache_alloc(ext4_free_ext_cachep, GFP_NOFS);
            new_entry->start_blk = bit;
            new_entry->group  = block_group;
            new_entry->count = count;
            new_entry->t_tid = handle->h_transaction->t_tid;

            ext4_lock_group(sb, block_group);
            mb_clear_bits(bitmap_bh->b_data, bit, count);
            ext4_mb_free_metadata(handle, &e4b, new_entry);
      } else {
            /* need to update group_info->bb_free and bitmap
             * with group lock held. generate_buddy look at
             * them with group lock_held
             */
            ext4_lock_group(sb, block_group);
            mb_clear_bits(bitmap_bh->b_data, bit, count);
            mb_free_blocks(inode, &e4b, bit, count);
            ext4_mb_return_to_preallocation(inode, &e4b, block, count);
      }

      ret = ext4_free_blks_count(sb, gdp) + count;
      ext4_free_blks_set(sb, gdp, ret);
      gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
      ext4_unlock_group(sb, block_group);
      percpu_counter_add(&sbi->s_freeblocks_counter, count);

      if (sbi->s_log_groups_per_flex) {
            ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
            atomic_add(count, &sbi->s_flex_groups[flex_group].free_blocks);
      }

      ext4_mb_release_desc(&e4b);

      *freed += count;

      /* We dirtied the bitmap block */
      BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
      err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);

      /* And the group descriptor block */
      BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
      ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
      if (!err)
            err = ret;

      if (overflow && !err) {
            block += count;
            count = overflow;
            put_bh(bitmap_bh);
            goto do_more;
      }
      sb->s_dirt = 1;
error_return:
      brelse(bitmap_bh);
      ext4_std_error(sb, err);
      if (ac)
            kmem_cache_free(ext4_ac_cachep, ac);
      return;
}

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