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tree-log.c

/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 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
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "locking.h"
#include "print-tree.h"
#include "compat.h"
#include "tree-log.h"

/* magic values for the inode_only field in btrfs_log_inode:
 *
 * LOG_INODE_ALL means to log everything
 * LOG_INODE_EXISTS means to log just enough to recreate the inode
 * during log replay
 */
#define LOG_INODE_ALL 0
#define LOG_INODE_EXISTS 1

/*
 * directory trouble cases
 *
 * 1) on rename or unlink, if the inode being unlinked isn't in the fsync
 * log, we must force a full commit before doing an fsync of the directory
 * where the unlink was done.
 * ---> record transid of last unlink/rename per directory
 *
 * mkdir foo/some_dir
 * normal commit
 * rename foo/some_dir foo2/some_dir
 * mkdir foo/some_dir
 * fsync foo/some_dir/some_file
 *
 * The fsync above will unlink the original some_dir without recording
 * it in its new location (foo2).  After a crash, some_dir will be gone
 * unless the fsync of some_file forces a full commit
 *
 * 2) we must log any new names for any file or dir that is in the fsync
 * log. ---> check inode while renaming/linking.
 *
 * 2a) we must log any new names for any file or dir during rename
 * when the directory they are being removed from was logged.
 * ---> check inode and old parent dir during rename
 *
 *  2a is actually the more important variant.  With the extra logging
 *  a crash might unlink the old name without recreating the new one
 *
 * 3) after a crash, we must go through any directories with a link count
 * of zero and redo the rm -rf
 *
 * mkdir f1/foo
 * normal commit
 * rm -rf f1/foo
 * fsync(f1)
 *
 * The directory f1 was fully removed from the FS, but fsync was never
 * called on f1, only its parent dir.  After a crash the rm -rf must
 * be replayed.  This must be able to recurse down the entire
 * directory tree.  The inode link count fixup code takes care of the
 * ugly details.
 */

/*
 * stages for the tree walking.  The first
 * stage (0) is to only pin down the blocks we find
 * the second stage (1) is to make sure that all the inodes
 * we find in the log are created in the subvolume.
 *
 * The last stage is to deal with directories and links and extents
 * and all the other fun semantics
 */
#define LOG_WALK_PIN_ONLY 0
#define LOG_WALK_REPLAY_INODES 1
#define LOG_WALK_REPLAY_ALL 2

static int btrfs_log_inode(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root, struct inode *inode,
                       int inode_only);
static int link_to_fixup_dir(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct btrfs_path *path, u64 objectid);
static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_root *log,
                               struct btrfs_path *path,
                               u64 dirid, int del_all);

/*
 * tree logging is a special write ahead log used to make sure that
 * fsyncs and O_SYNCs can happen without doing full tree commits.
 *
 * Full tree commits are expensive because they require commonly
 * modified blocks to be recowed, creating many dirty pages in the
 * extent tree an 4x-6x higher write load than ext3.
 *
 * Instead of doing a tree commit on every fsync, we use the
 * key ranges and transaction ids to find items for a given file or directory
 * that have changed in this transaction.  Those items are copied into
 * a special tree (one per subvolume root), that tree is written to disk
 * and then the fsync is considered complete.
 *
 * After a crash, items are copied out of the log-tree back into the
 * subvolume tree.  Any file data extents found are recorded in the extent
 * allocation tree, and the log-tree freed.
 *
 * The log tree is read three times, once to pin down all the extents it is
 * using in ram and once, once to create all the inodes logged in the tree
 * and once to do all the other items.
 */

/*
 * start a sub transaction and setup the log tree
 * this increments the log tree writer count to make the people
 * syncing the tree wait for us to finish
 */
static int start_log_trans(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root)
{
      int ret;

      mutex_lock(&root->log_mutex);
      if (root->log_root) {
            root->log_batch++;
            atomic_inc(&root->log_writers);
            mutex_unlock(&root->log_mutex);
            return 0;
      }
      mutex_lock(&root->fs_info->tree_log_mutex);
      if (!root->fs_info->log_root_tree) {
            ret = btrfs_init_log_root_tree(trans, root->fs_info);
            BUG_ON(ret);
      }
      if (!root->log_root) {
            ret = btrfs_add_log_tree(trans, root);
            BUG_ON(ret);
      }
      mutex_unlock(&root->fs_info->tree_log_mutex);
      root->log_batch++;
      atomic_inc(&root->log_writers);
      mutex_unlock(&root->log_mutex);
      return 0;
}

/*
 * returns 0 if there was a log transaction running and we were able
 * to join, or returns -ENOENT if there were not transactions
 * in progress
 */
static int join_running_log_trans(struct btrfs_root *root)
{
      int ret = -ENOENT;

      smp_mb();
      if (!root->log_root)
            return -ENOENT;

      mutex_lock(&root->log_mutex);
      if (root->log_root) {
            ret = 0;
            atomic_inc(&root->log_writers);
      }
      mutex_unlock(&root->log_mutex);
      return ret;
}

/*
 * This either makes the current running log transaction wait
 * until you call btrfs_end_log_trans() or it makes any future
 * log transactions wait until you call btrfs_end_log_trans()
 */
int btrfs_pin_log_trans(struct btrfs_root *root)
{
      int ret = -ENOENT;

      mutex_lock(&root->log_mutex);
      atomic_inc(&root->log_writers);
      mutex_unlock(&root->log_mutex);
      return ret;
}

/*
 * indicate we're done making changes to the log tree
 * and wake up anyone waiting to do a sync
 */
int btrfs_end_log_trans(struct btrfs_root *root)
{
      if (atomic_dec_and_test(&root->log_writers)) {
            smp_mb();
            if (waitqueue_active(&root->log_writer_wait))
                  wake_up(&root->log_writer_wait);
      }
      return 0;
}


/*
 * the walk control struct is used to pass state down the chain when
 * processing the log tree.  The stage field tells us which part
 * of the log tree processing we are currently doing.  The others
 * are state fields used for that specific part
 */
struct walk_control {
      /* should we free the extent on disk when done?  This is used
       * at transaction commit time while freeing a log tree
       */
      int free;

      /* should we write out the extent buffer?  This is used
       * while flushing the log tree to disk during a sync
       */
      int write;

      /* should we wait for the extent buffer io to finish?  Also used
       * while flushing the log tree to disk for a sync
       */
      int wait;

      /* pin only walk, we record which extents on disk belong to the
       * log trees
       */
      int pin;

      /* what stage of the replay code we're currently in */
      int stage;

      /* the root we are currently replaying */
      struct btrfs_root *replay_dest;

      /* the trans handle for the current replay */
      struct btrfs_trans_handle *trans;

      /* the function that gets used to process blocks we find in the
       * tree.  Note the extent_buffer might not be up to date when it is
       * passed in, and it must be checked or read if you need the data
       * inside it
       */
      int (*process_func)(struct btrfs_root *log, struct extent_buffer *eb,
                      struct walk_control *wc, u64 gen);
};

/*
 * process_func used to pin down extents, write them or wait on them
 */
static int process_one_buffer(struct btrfs_root *log,
                        struct extent_buffer *eb,
                        struct walk_control *wc, u64 gen)
{
      if (wc->pin)
            btrfs_update_pinned_extents(log->fs_info->extent_root,
                                  eb->start, eb->len, 1);

      if (btrfs_buffer_uptodate(eb, gen)) {
            if (wc->write)
                  btrfs_write_tree_block(eb);
            if (wc->wait)
                  btrfs_wait_tree_block_writeback(eb);
      }
      return 0;
}

/*
 * Item overwrite used by replay and tree logging.  eb, slot and key all refer
 * to the src data we are copying out.
 *
 * root is the tree we are copying into, and path is a scratch
 * path for use in this function (it should be released on entry and
 * will be released on exit).
 *
 * If the key is already in the destination tree the existing item is
 * overwritten.  If the existing item isn't big enough, it is extended.
 * If it is too large, it is truncated.
 *
 * If the key isn't in the destination yet, a new item is inserted.
 */
static noinline int overwrite_item(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root,
                           struct btrfs_path *path,
                           struct extent_buffer *eb, int slot,
                           struct btrfs_key *key)
{
      int ret;
      u32 item_size;
      u64 saved_i_size = 0;
      int save_old_i_size = 0;
      unsigned long src_ptr;
      unsigned long dst_ptr;
      int overwrite_root = 0;

      if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
            overwrite_root = 1;

      item_size = btrfs_item_size_nr(eb, slot);
      src_ptr = btrfs_item_ptr_offset(eb, slot);

      /* look for the key in the destination tree */
      ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
      if (ret == 0) {
            char *src_copy;
            char *dst_copy;
            u32 dst_size = btrfs_item_size_nr(path->nodes[0],
                                      path->slots[0]);
            if (dst_size != item_size)
                  goto insert;

            if (item_size == 0) {
                  btrfs_release_path(root, path);
                  return 0;
            }
            dst_copy = kmalloc(item_size, GFP_NOFS);
            src_copy = kmalloc(item_size, GFP_NOFS);

            read_extent_buffer(eb, src_copy, src_ptr, item_size);

            dst_ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
            read_extent_buffer(path->nodes[0], dst_copy, dst_ptr,
                           item_size);
            ret = memcmp(dst_copy, src_copy, item_size);

            kfree(dst_copy);
            kfree(src_copy);
            /*
             * they have the same contents, just return, this saves
             * us from cowing blocks in the destination tree and doing
             * extra writes that may not have been done by a previous
             * sync
             */
            if (ret == 0) {
                  btrfs_release_path(root, path);
                  return 0;
            }

      }
insert:
      btrfs_release_path(root, path);
      /* try to insert the key into the destination tree */
      ret = btrfs_insert_empty_item(trans, root, path,
                              key, item_size);

      /* make sure any existing item is the correct size */
      if (ret == -EEXIST) {
            u32 found_size;
            found_size = btrfs_item_size_nr(path->nodes[0],
                                    path->slots[0]);
            if (found_size > item_size) {
                  btrfs_truncate_item(trans, root, path, item_size, 1);
            } else if (found_size < item_size) {
                  ret = btrfs_extend_item(trans, root, path,
                                    item_size - found_size);
                  BUG_ON(ret);
            }
      } else if (ret) {
            BUG();
      }
      dst_ptr = btrfs_item_ptr_offset(path->nodes[0],
                              path->slots[0]);

      /* don't overwrite an existing inode if the generation number
       * was logged as zero.  This is done when the tree logging code
       * is just logging an inode to make sure it exists after recovery.
       *
       * Also, don't overwrite i_size on directories during replay.
       * log replay inserts and removes directory items based on the
       * state of the tree found in the subvolume, and i_size is modified
       * as it goes
       */
      if (key->type == BTRFS_INODE_ITEM_KEY && ret == -EEXIST) {
            struct btrfs_inode_item *src_item;
            struct btrfs_inode_item *dst_item;

            src_item = (struct btrfs_inode_item *)src_ptr;
            dst_item = (struct btrfs_inode_item *)dst_ptr;

            if (btrfs_inode_generation(eb, src_item) == 0)
                  goto no_copy;

            if (overwrite_root &&
                S_ISDIR(btrfs_inode_mode(eb, src_item)) &&
                S_ISDIR(btrfs_inode_mode(path->nodes[0], dst_item))) {
                  save_old_i_size = 1;
                  saved_i_size = btrfs_inode_size(path->nodes[0],
                                          dst_item);
            }
      }

      copy_extent_buffer(path->nodes[0], eb, dst_ptr,
                     src_ptr, item_size);

      if (save_old_i_size) {
            struct btrfs_inode_item *dst_item;
            dst_item = (struct btrfs_inode_item *)dst_ptr;
            btrfs_set_inode_size(path->nodes[0], dst_item, saved_i_size);
      }

      /* make sure the generation is filled in */
      if (key->type == BTRFS_INODE_ITEM_KEY) {
            struct btrfs_inode_item *dst_item;
            dst_item = (struct btrfs_inode_item *)dst_ptr;
            if (btrfs_inode_generation(path->nodes[0], dst_item) == 0) {
                  btrfs_set_inode_generation(path->nodes[0], dst_item,
                                       trans->transid);
            }
      }
no_copy:
      btrfs_mark_buffer_dirty(path->nodes[0]);
      btrfs_release_path(root, path);
      return 0;
}

/*
 * simple helper to read an inode off the disk from a given root
 * This can only be called for subvolume roots and not for the log
 */
static noinline struct inode *read_one_inode(struct btrfs_root *root,
                                   u64 objectid)
{
      struct btrfs_key key;
      struct inode *inode;

      key.objectid = objectid;
      key.type = BTRFS_INODE_ITEM_KEY;
      key.offset = 0;
      inode = btrfs_iget(root->fs_info->sb, &key, root);
      if (IS_ERR(inode)) {
            inode = NULL;
      } else if (is_bad_inode(inode)) {
            iput(inode);
            inode = NULL;
      }
      return inode;
}

/* replays a single extent in 'eb' at 'slot' with 'key' into the
 * subvolume 'root'.  path is released on entry and should be released
 * on exit.
 *
 * extents in the log tree have not been allocated out of the extent
 * tree yet.  So, this completes the allocation, taking a reference
 * as required if the extent already exists or creating a new extent
 * if it isn't in the extent allocation tree yet.
 *
 * The extent is inserted into the file, dropping any existing extents
 * from the file that overlap the new one.
 */
static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_path *path,
                              struct extent_buffer *eb, int slot,
                              struct btrfs_key *key)
{
      int found_type;
      u64 mask = root->sectorsize - 1;
      u64 extent_end;
      u64 alloc_hint;
      u64 start = key->offset;
      u64 saved_nbytes;
      struct btrfs_file_extent_item *item;
      struct inode *inode = NULL;
      unsigned long size;
      int ret = 0;

      item = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
      found_type = btrfs_file_extent_type(eb, item);

      if (found_type == BTRFS_FILE_EXTENT_REG ||
          found_type == BTRFS_FILE_EXTENT_PREALLOC)
            extent_end = start + btrfs_file_extent_num_bytes(eb, item);
      else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
            size = btrfs_file_extent_inline_len(eb, item);
            extent_end = (start + size + mask) & ~mask;
      } else {
            ret = 0;
            goto out;
      }

      inode = read_one_inode(root, key->objectid);
      if (!inode) {
            ret = -EIO;
            goto out;
      }

      /*
       * first check to see if we already have this extent in the
       * file.  This must be done before the btrfs_drop_extents run
       * so we don't try to drop this extent.
       */
      ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
                               start, 0);

      if (ret == 0 &&
          (found_type == BTRFS_FILE_EXTENT_REG ||
           found_type == BTRFS_FILE_EXTENT_PREALLOC)) {
            struct btrfs_file_extent_item cmp1;
            struct btrfs_file_extent_item cmp2;
            struct btrfs_file_extent_item *existing;
            struct extent_buffer *leaf;

            leaf = path->nodes[0];
            existing = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_file_extent_item);

            read_extent_buffer(eb, &cmp1, (unsigned long)item,
                           sizeof(cmp1));
            read_extent_buffer(leaf, &cmp2, (unsigned long)existing,
                           sizeof(cmp2));

            /*
             * we already have a pointer to this exact extent,
             * we don't have to do anything
             */
            if (memcmp(&cmp1, &cmp2, sizeof(cmp1)) == 0) {
                  btrfs_release_path(root, path);
                  goto out;
            }
      }
      btrfs_release_path(root, path);

      saved_nbytes = inode_get_bytes(inode);
      /* drop any overlapping extents */
      ret = btrfs_drop_extents(trans, root, inode,
                   start, extent_end, extent_end, start, &alloc_hint);
      BUG_ON(ret);

      if (found_type == BTRFS_FILE_EXTENT_REG ||
          found_type == BTRFS_FILE_EXTENT_PREALLOC) {
            u64 offset;
            unsigned long dest_offset;
            struct btrfs_key ins;

            ret = btrfs_insert_empty_item(trans, root, path, key,
                                    sizeof(*item));
            BUG_ON(ret);
            dest_offset = btrfs_item_ptr_offset(path->nodes[0],
                                        path->slots[0]);
            copy_extent_buffer(path->nodes[0], eb, dest_offset,
                        (unsigned long)item,  sizeof(*item));

            ins.objectid = btrfs_file_extent_disk_bytenr(eb, item);
            ins.offset = btrfs_file_extent_disk_num_bytes(eb, item);
            ins.type = BTRFS_EXTENT_ITEM_KEY;
            offset = key->offset - btrfs_file_extent_offset(eb, item);

            if (ins.objectid > 0) {
                  u64 csum_start;
                  u64 csum_end;
                  LIST_HEAD(ordered_sums);
                  /*
                   * is this extent already allocated in the extent
                   * allocation tree?  If so, just add a reference
                   */
                  ret = btrfs_lookup_extent(root, ins.objectid,
                                    ins.offset);
                  if (ret == 0) {
                        ret = btrfs_inc_extent_ref(trans, root,
                                    ins.objectid, ins.offset,
                                    0, root->root_key.objectid,
                                    key->objectid, offset);
                  } else {
                        /*
                         * insert the extent pointer in the extent
                         * allocation tree
                         */
                        ret = btrfs_alloc_logged_file_extent(trans,
                                    root, root->root_key.objectid,
                                    key->objectid, offset, &ins);
                        BUG_ON(ret);
                  }
                  btrfs_release_path(root, path);

                  if (btrfs_file_extent_compression(eb, item)) {
                        csum_start = ins.objectid;
                        csum_end = csum_start + ins.offset;
                  } else {
                        csum_start = ins.objectid +
                              btrfs_file_extent_offset(eb, item);
                        csum_end = csum_start +
                              btrfs_file_extent_num_bytes(eb, item);
                  }

                  ret = btrfs_lookup_csums_range(root->log_root,
                                    csum_start, csum_end - 1,
                                    &ordered_sums);
                  BUG_ON(ret);
                  while (!list_empty(&ordered_sums)) {
                        struct btrfs_ordered_sum *sums;
                        sums = list_entry(ordered_sums.next,
                                    struct btrfs_ordered_sum,
                                    list);
                        ret = btrfs_csum_file_blocks(trans,
                                    root->fs_info->csum_root,
                                    sums);
                        BUG_ON(ret);
                        list_del(&sums->list);
                        kfree(sums);
                  }
            } else {
                  btrfs_release_path(root, path);
            }
      } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
            /* inline extents are easy, we just overwrite them */
            ret = overwrite_item(trans, root, path, eb, slot, key);
            BUG_ON(ret);
      }

      inode_set_bytes(inode, saved_nbytes);
      btrfs_update_inode(trans, root, inode);
out:
      if (inode)
            iput(inode);
      return ret;
}

/*
 * when cleaning up conflicts between the directory names in the
 * subvolume, directory names in the log and directory names in the
 * inode back references, we may have to unlink inodes from directories.
 *
 * This is a helper function to do the unlink of a specific directory
 * item
 */
static noinline int drop_one_dir_item(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_path *path,
                              struct inode *dir,
                              struct btrfs_dir_item *di)
{
      struct inode *inode;
      char *name;
      int name_len;
      struct extent_buffer *leaf;
      struct btrfs_key location;
      int ret;

      leaf = path->nodes[0];

      btrfs_dir_item_key_to_cpu(leaf, di, &location);
      name_len = btrfs_dir_name_len(leaf, di);
      name = kmalloc(name_len, GFP_NOFS);
      read_extent_buffer(leaf, name, (unsigned long)(di + 1), name_len);
      btrfs_release_path(root, path);

      inode = read_one_inode(root, location.objectid);
      BUG_ON(!inode);

      ret = link_to_fixup_dir(trans, root, path, location.objectid);
      BUG_ON(ret);

      ret = btrfs_unlink_inode(trans, root, dir, inode, name, name_len);
      BUG_ON(ret);
      kfree(name);

      iput(inode);
      return ret;
}

/*
 * helper function to see if a given name and sequence number found
 * in an inode back reference are already in a directory and correctly
 * point to this inode
 */
static noinline int inode_in_dir(struct btrfs_root *root,
                         struct btrfs_path *path,
                         u64 dirid, u64 objectid, u64 index,
                         const char *name, int name_len)
{
      struct btrfs_dir_item *di;
      struct btrfs_key location;
      int match = 0;

      di = btrfs_lookup_dir_index_item(NULL, root, path, dirid,
                               index, name, name_len, 0);
      if (di && !IS_ERR(di)) {
            btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
            if (location.objectid != objectid)
                  goto out;
      } else
            goto out;
      btrfs_release_path(root, path);

      di = btrfs_lookup_dir_item(NULL, root, path, dirid, name, name_len, 0);
      if (di && !IS_ERR(di)) {
            btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
            if (location.objectid != objectid)
                  goto out;
      } else
            goto out;
      match = 1;
out:
      btrfs_release_path(root, path);
      return match;
}

/*
 * helper function to check a log tree for a named back reference in
 * an inode.  This is used to decide if a back reference that is
 * found in the subvolume conflicts with what we find in the log.
 *
 * inode backreferences may have multiple refs in a single item,
 * during replay we process one reference at a time, and we don't
 * want to delete valid links to a file from the subvolume if that
 * link is also in the log.
 */
static noinline int backref_in_log(struct btrfs_root *log,
                           struct btrfs_key *key,
                           char *name, int namelen)
{
      struct btrfs_path *path;
      struct btrfs_inode_ref *ref;
      unsigned long ptr;
      unsigned long ptr_end;
      unsigned long name_ptr;
      int found_name_len;
      int item_size;
      int ret;
      int match = 0;

      path = btrfs_alloc_path();
      ret = btrfs_search_slot(NULL, log, key, path, 0, 0);
      if (ret != 0)
            goto out;

      item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
      ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
      ptr_end = ptr + item_size;
      while (ptr < ptr_end) {
            ref = (struct btrfs_inode_ref *)ptr;
            found_name_len = btrfs_inode_ref_name_len(path->nodes[0], ref);
            if (found_name_len == namelen) {
                  name_ptr = (unsigned long)(ref + 1);
                  ret = memcmp_extent_buffer(path->nodes[0], name,
                                       name_ptr, namelen);
                  if (ret == 0) {
                        match = 1;
                        goto out;
                  }
            }
            ptr = (unsigned long)(ref + 1) + found_name_len;
      }
out:
      btrfs_free_path(path);
      return match;
}


/*
 * replay one inode back reference item found in the log tree.
 * eb, slot and key refer to the buffer and key found in the log tree.
 * root is the destination we are replaying into, and path is for temp
 * use by this function.  (it should be released on return).
 */
static noinline int add_inode_ref(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root,
                          struct btrfs_root *log,
                          struct btrfs_path *path,
                          struct extent_buffer *eb, int slot,
                          struct btrfs_key *key)
{
      struct inode *dir;
      int ret;
      struct btrfs_key location;
      struct btrfs_inode_ref *ref;
      struct btrfs_dir_item *di;
      struct inode *inode;
      char *name;
      int namelen;
      unsigned long ref_ptr;
      unsigned long ref_end;

      location.objectid = key->objectid;
      location.type = BTRFS_INODE_ITEM_KEY;
      location.offset = 0;

      /*
       * it is possible that we didn't log all the parent directories
       * for a given inode.  If we don't find the dir, just don't
       * copy the back ref in.  The link count fixup code will take
       * care of the rest
       */
      dir = read_one_inode(root, key->offset);
      if (!dir)
            return -ENOENT;

      inode = read_one_inode(root, key->objectid);
      BUG_ON(!inode);

      ref_ptr = btrfs_item_ptr_offset(eb, slot);
      ref_end = ref_ptr + btrfs_item_size_nr(eb, slot);

again:
      ref = (struct btrfs_inode_ref *)ref_ptr;

      namelen = btrfs_inode_ref_name_len(eb, ref);
      name = kmalloc(namelen, GFP_NOFS);
      BUG_ON(!name);

      read_extent_buffer(eb, name, (unsigned long)(ref + 1), namelen);

      /* if we already have a perfect match, we're done */
      if (inode_in_dir(root, path, dir->i_ino, inode->i_ino,
                   btrfs_inode_ref_index(eb, ref),
                   name, namelen)) {
            goto out;
      }

      /*
       * look for a conflicting back reference in the metadata.
       * if we find one we have to unlink that name of the file
       * before we add our new link.  Later on, we overwrite any
       * existing back reference, and we don't want to create
       * dangling pointers in the directory.
       */
conflict_again:
      ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
      if (ret == 0) {
            char *victim_name;
            int victim_name_len;
            struct btrfs_inode_ref *victim_ref;
            unsigned long ptr;
            unsigned long ptr_end;
            struct extent_buffer *leaf = path->nodes[0];

            /* are we trying to overwrite a back ref for the root directory
             * if so, just jump out, we're done
             */
            if (key->objectid == key->offset)
                  goto out_nowrite;

            /* check all the names in this back reference to see
             * if they are in the log.  if so, we allow them to stay
             * otherwise they must be unlinked as a conflict
             */
            ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
            ptr_end = ptr + btrfs_item_size_nr(leaf, path->slots[0]);
            while (ptr < ptr_end) {
                  victim_ref = (struct btrfs_inode_ref *)ptr;
                  victim_name_len = btrfs_inode_ref_name_len(leaf,
                                                   victim_ref);
                  victim_name = kmalloc(victim_name_len, GFP_NOFS);
                  BUG_ON(!victim_name);

                  read_extent_buffer(leaf, victim_name,
                                 (unsigned long)(victim_ref + 1),
                                 victim_name_len);

                  if (!backref_in_log(log, key, victim_name,
                                  victim_name_len)) {
                        btrfs_inc_nlink(inode);
                        btrfs_release_path(root, path);

                        ret = btrfs_unlink_inode(trans, root, dir,
                                           inode, victim_name,
                                           victim_name_len);
                        kfree(victim_name);
                        btrfs_release_path(root, path);
                        goto conflict_again;
                  }
                  kfree(victim_name);
                  ptr = (unsigned long)(victim_ref + 1) + victim_name_len;
            }
            BUG_ON(ret);
      }
      btrfs_release_path(root, path);

      /* look for a conflicting sequence number */
      di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino,
                               btrfs_inode_ref_index(eb, ref),
                               name, namelen, 0);
      if (di && !IS_ERR(di)) {
            ret = drop_one_dir_item(trans, root, path, dir, di);
            BUG_ON(ret);
      }
      btrfs_release_path(root, path);


      /* look for a conflicting name */
      di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
                           name, namelen, 0);
      if (di && !IS_ERR(di)) {
            ret = drop_one_dir_item(trans, root, path, dir, di);
            BUG_ON(ret);
      }
      btrfs_release_path(root, path);

      /* insert our name */
      ret = btrfs_add_link(trans, dir, inode, name, namelen, 0,
                       btrfs_inode_ref_index(eb, ref));
      BUG_ON(ret);

      btrfs_update_inode(trans, root, inode);

out:
      ref_ptr = (unsigned long)(ref + 1) + namelen;
      kfree(name);
      if (ref_ptr < ref_end)
            goto again;

      /* finally write the back reference in the inode */
      ret = overwrite_item(trans, root, path, eb, slot, key);
      BUG_ON(ret);

out_nowrite:
      btrfs_release_path(root, path);
      iput(dir);
      iput(inode);
      return 0;
}

/*
 * There are a few corners where the link count of the file can't
 * be properly maintained during replay.  So, instead of adding
 * lots of complexity to the log code, we just scan the backrefs
 * for any file that has been through replay.
 *
 * The scan will update the link count on the inode to reflect the
 * number of back refs found.  If it goes down to zero, the iput
 * will free the inode.
 */
static noinline int fixup_inode_link_count(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct inode *inode)
{
      struct btrfs_path *path;
      int ret;
      struct btrfs_key key;
      u64 nlink = 0;
      unsigned long ptr;
      unsigned long ptr_end;
      int name_len;

      key.objectid = inode->i_ino;
      key.type = BTRFS_INODE_REF_KEY;
      key.offset = (u64)-1;

      path = btrfs_alloc_path();

      while (1) {
            ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
            if (ret < 0)
                  break;
            if (ret > 0) {
                  if (path->slots[0] == 0)
                        break;
                  path->slots[0]--;
            }
            btrfs_item_key_to_cpu(path->nodes[0], &key,
                              path->slots[0]);
            if (key.objectid != inode->i_ino ||
                key.type != BTRFS_INODE_REF_KEY)
                  break;
            ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
            ptr_end = ptr + btrfs_item_size_nr(path->nodes[0],
                                       path->slots[0]);
            while (ptr < ptr_end) {
                  struct btrfs_inode_ref *ref;

                  ref = (struct btrfs_inode_ref *)ptr;
                  name_len = btrfs_inode_ref_name_len(path->nodes[0],
                                              ref);
                  ptr = (unsigned long)(ref + 1) + name_len;
                  nlink++;
            }

            if (key.offset == 0)
                  break;
            key.offset--;
            btrfs_release_path(root, path);
      }
      btrfs_release_path(root, path);
      if (nlink != inode->i_nlink) {
            inode->i_nlink = nlink;
            btrfs_update_inode(trans, root, inode);
      }
      BTRFS_I(inode)->index_cnt = (u64)-1;

      if (inode->i_nlink == 0 && S_ISDIR(inode->i_mode)) {
            ret = replay_dir_deletes(trans, root, NULL, path,
                               inode->i_ino, 1);
            BUG_ON(ret);
      }
      btrfs_free_path(path);

      return 0;
}

static noinline int fixup_inode_link_counts(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
                                  struct btrfs_path *path)
{
      int ret;
      struct btrfs_key key;
      struct inode *inode;

      key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
      key.type = BTRFS_ORPHAN_ITEM_KEY;
      key.offset = (u64)-1;
      while (1) {
            ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
            if (ret < 0)
                  break;

            if (ret == 1) {
                  if (path->slots[0] == 0)
                        break;
                  path->slots[0]--;
            }

            btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
            if (key.objectid != BTRFS_TREE_LOG_FIXUP_OBJECTID ||
                key.type != BTRFS_ORPHAN_ITEM_KEY)
                  break;

            ret = btrfs_del_item(trans, root, path);
            BUG_ON(ret);

            btrfs_release_path(root, path);
            inode = read_one_inode(root, key.offset);
            BUG_ON(!inode);

            ret = fixup_inode_link_count(trans, root, inode);
            BUG_ON(ret);

            iput(inode);

            /*
             * fixup on a directory may create new entries,
             * make sure we always look for the highset possible
             * offset
             */
            key.offset = (u64)-1;
      }
      btrfs_release_path(root, path);
      return 0;
}


/*
 * record a given inode in the fixup dir so we can check its link
 * count when replay is done.  The link count is incremented here
 * so the inode won't go away until we check it
 */
static noinline int link_to_fixup_dir(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_path *path,
                              u64 objectid)
{
      struct btrfs_key key;
      int ret = 0;
      struct inode *inode;

      inode = read_one_inode(root, objectid);
      BUG_ON(!inode);

      key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
      btrfs_set_key_type(&key, BTRFS_ORPHAN_ITEM_KEY);
      key.offset = objectid;

      ret = btrfs_insert_empty_item(trans, root, path, &key, 0);

      btrfs_release_path(root, path);
      if (ret == 0) {
            btrfs_inc_nlink(inode);
            btrfs_update_inode(trans, root, inode);
      } else if (ret == -EEXIST) {
            ret = 0;
      } else {
            BUG();
      }
      iput(inode);

      return ret;
}

/*
 * when replaying the log for a directory, we only insert names
 * for inodes that actually exist.  This means an fsync on a directory
 * does not implicitly fsync all the new files in it
 */
static noinline int insert_one_name(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            struct btrfs_path *path,
                            u64 dirid, u64 index,
                            char *name, int name_len, u8 type,
                            struct btrfs_key *location)
{
      struct inode *inode;
      struct inode *dir;
      int ret;

      inode = read_one_inode(root, location->objectid);
      if (!inode)
            return -ENOENT;

      dir = read_one_inode(root, dirid);
      if (!dir) {
            iput(inode);
            return -EIO;
      }
      ret = btrfs_add_link(trans, dir, inode, name, name_len, 1, index);

      /* FIXME, put inode into FIXUP list */

      iput(inode);
      iput(dir);
      return ret;
}

/*
 * take a single entry in a log directory item and replay it into
 * the subvolume.
 *
 * if a conflicting item exists in the subdirectory already,
 * the inode it points to is unlinked and put into the link count
 * fix up tree.
 *
 * If a name from the log points to a file or directory that does
 * not exist in the FS, it is skipped.  fsyncs on directories
 * do not force down inodes inside that directory, just changes to the
 * names or unlinks in a directory.
 */
static noinline int replay_one_name(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            struct btrfs_path *path,
                            struct extent_buffer *eb,
                            struct btrfs_dir_item *di,
                            struct btrfs_key *key)
{
      char *name;
      int name_len;
      struct btrfs_dir_item *dst_di;
      struct btrfs_key found_key;
      struct btrfs_key log_key;
      struct inode *dir;
      u8 log_type;
      int exists;
      int ret;

      dir = read_one_inode(root, key->objectid);
      BUG_ON(!dir);

      name_len = btrfs_dir_name_len(eb, di);
      name = kmalloc(name_len, GFP_NOFS);
      log_type = btrfs_dir_type(eb, di);
      read_extent_buffer(eb, name, (unsigned long)(di + 1),
               name_len);

      btrfs_dir_item_key_to_cpu(eb, di, &log_key);
      exists = btrfs_lookup_inode(trans, root, path, &log_key, 0);
      if (exists == 0)
            exists = 1;
      else
            exists = 0;
      btrfs_release_path(root, path);

      if (key->type == BTRFS_DIR_ITEM_KEY) {
            dst_di = btrfs_lookup_dir_item(trans, root, path, key->objectid,
                               name, name_len, 1);
      } else if (key->type == BTRFS_DIR_INDEX_KEY) {
            dst_di = btrfs_lookup_dir_index_item(trans, root, path,
                                         key->objectid,
                                         key->offset, name,
                                         name_len, 1);
      } else {
            BUG();
      }
      if (!dst_di || IS_ERR(dst_di)) {
            /* we need a sequence number to insert, so we only
             * do inserts for the BTRFS_DIR_INDEX_KEY types
             */
            if (key->type != BTRFS_DIR_INDEX_KEY)
                  goto out;
            goto insert;
      }

      btrfs_dir_item_key_to_cpu(path->nodes[0], dst_di, &found_key);
      /* the existing item matches the logged item */
      if (found_key.objectid == log_key.objectid &&
          found_key.type == log_key.type &&
          found_key.offset == log_key.offset &&
          btrfs_dir_type(path->nodes[0], dst_di) == log_type) {
            goto out;
      }

      /*
       * don't drop the conflicting directory entry if the inode
       * for the new entry doesn't exist
       */
      if (!exists)
            goto out;

      ret = drop_one_dir_item(trans, root, path, dir, dst_di);
      BUG_ON(ret);

      if (key->type == BTRFS_DIR_INDEX_KEY)
            goto insert;
out:
      btrfs_release_path(root, path);
      kfree(name);
      iput(dir);
      return 0;

insert:
      btrfs_release_path(root, path);
      ret = insert_one_name(trans, root, path, key->objectid, key->offset,
                        name, name_len, log_type, &log_key);

      BUG_ON(ret && ret != -ENOENT);
      goto out;
}

/*
 * find all the names in a directory item and reconcile them into
 * the subvolume.  Only BTRFS_DIR_ITEM_KEY types will have more than
 * one name in a directory item, but the same code gets used for
 * both directory index types
 */
static noinline int replay_one_dir_item(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_path *path,
                              struct extent_buffer *eb, int slot,
                              struct btrfs_key *key)
{
      int ret;
      u32 item_size = btrfs_item_size_nr(eb, slot);
      struct btrfs_dir_item *di;
      int name_len;
      unsigned long ptr;
      unsigned long ptr_end;

      ptr = btrfs_item_ptr_offset(eb, slot);
      ptr_end = ptr + item_size;
      while (ptr < ptr_end) {
            di = (struct btrfs_dir_item *)ptr;
            name_len = btrfs_dir_name_len(eb, di);
            ret = replay_one_name(trans, root, path, eb, di, key);
            BUG_ON(ret);
            ptr = (unsigned long)(di + 1);
            ptr += name_len;
      }
      return 0;
}

/*
 * directory replay has two parts.  There are the standard directory
 * items in the log copied from the subvolume, and range items
 * created in the log while the subvolume was logged.
 *
 * The range items tell us which parts of the key space the log
 * is authoritative for.  During replay, if a key in the subvolume
 * directory is in a logged range item, but not actually in the log
 * that means it was deleted from the directory before the fsync
 * and should be removed.
 */
static noinline int find_dir_range(struct btrfs_root *root,
                           struct btrfs_path *path,
                           u64 dirid, int key_type,
                           u64 *start_ret, u64 *end_ret)
{
      struct btrfs_key key;
      u64 found_end;
      struct btrfs_dir_log_item *item;
      int ret;
      int nritems;

      if (*start_ret == (u64)-1)
            return 1;

      key.objectid = dirid;
      key.type = key_type;
      key.offset = *start_ret;

      ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
      if (ret < 0)
            goto out;
      if (ret > 0) {
            if (path->slots[0] == 0)
                  goto out;
            path->slots[0]--;
      }
      if (ret != 0)
            btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);

      if (key.type != key_type || key.objectid != dirid) {
            ret = 1;
            goto next;
      }
      item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                        struct btrfs_dir_log_item);
      found_end = btrfs_dir_log_end(path->nodes[0], item);

      if (*start_ret >= key.offset && *start_ret <= found_end) {
            ret = 0;
            *start_ret = key.offset;
            *end_ret = found_end;
            goto out;
      }
      ret = 1;
next:
      /* check the next slot in the tree to see if it is a valid item */
      nritems = btrfs_header_nritems(path->nodes[0]);
      if (path->slots[0] >= nritems) {
            ret = btrfs_next_leaf(root, path);
            if (ret)
                  goto out;
      } else {
            path->slots[0]++;
      }

      btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);

      if (key.type != key_type || key.objectid != dirid) {
            ret = 1;
            goto out;
      }
      item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                        struct btrfs_dir_log_item);
      found_end = btrfs_dir_log_end(path->nodes[0], item);
      *start_ret = key.offset;
      *end_ret = found_end;
      ret = 0;
out:
      btrfs_release_path(root, path);
      return ret;
}

/*
 * this looks for a given directory item in the log.  If the directory
 * item is not in the log, the item is removed and the inode it points
 * to is unlinked
 */
static noinline int check_item_in_log(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_root *log,
                              struct btrfs_path *path,
                              struct btrfs_path *log_path,
                              struct inode *dir,
                              struct btrfs_key *dir_key)
{
      int ret;
      struct extent_buffer *eb;
      int slot;
      u32 item_size;
      struct btrfs_dir_item *di;
      struct btrfs_dir_item *log_di;
      int name_len;
      unsigned long ptr;
      unsigned long ptr_end;
      char *name;
      struct inode *inode;
      struct btrfs_key location;

again:
      eb = path->nodes[0];
      slot = path->slots[0];
      item_size = btrfs_item_size_nr(eb, slot);
      ptr = btrfs_item_ptr_offset(eb, slot);
      ptr_end = ptr + item_size;
      while (ptr < ptr_end) {
            di = (struct btrfs_dir_item *)ptr;
            name_len = btrfs_dir_name_len(eb, di);
            name = kmalloc(name_len, GFP_NOFS);
            if (!name) {
                  ret = -ENOMEM;
                  goto out;
            }
            read_extent_buffer(eb, name, (unsigned long)(di + 1),
                          name_len);
            log_di = NULL;
            if (log && dir_key->type == BTRFS_DIR_ITEM_KEY) {
                  log_di = btrfs_lookup_dir_item(trans, log, log_path,
                                           dir_key->objectid,
                                           name, name_len, 0);
            } else if (log && dir_key->type == BTRFS_DIR_INDEX_KEY) {
                  log_di = btrfs_lookup_dir_index_item(trans, log,
                                         log_path,
                                         dir_key->objectid,
                                         dir_key->offset,
                                         name, name_len, 0);
            }
            if (!log_di || IS_ERR(log_di)) {
                  btrfs_dir_item_key_to_cpu(eb, di, &location);
                  btrfs_release_path(root, path);
                  btrfs_release_path(log, log_path);
                  inode = read_one_inode(root, location.objectid);
                  BUG_ON(!inode);

                  ret = link_to_fixup_dir(trans, root,
                                    path, location.objectid);
                  BUG_ON(ret);
                  btrfs_inc_nlink(inode);
                  ret = btrfs_unlink_inode(trans, root, dir, inode,
                                     name, name_len);
                  BUG_ON(ret);
                  kfree(name);
                  iput(inode);

                  /* there might still be more names under this key
                   * check and repeat if required
                   */
                  ret = btrfs_search_slot(NULL, root, dir_key, path,
                                    0, 0);
                  if (ret == 0)
                        goto again;
                  ret = 0;
                  goto out;
            }
            btrfs_release_path(log, log_path);
            kfree(name);

            ptr = (unsigned long)(di + 1);
            ptr += name_len;
      }
      ret = 0;
out:
      btrfs_release_path(root, path);
      btrfs_release_path(log, log_path);
      return ret;
}

/*
 * deletion replay happens before we copy any new directory items
 * out of the log or out of backreferences from inodes.  It
 * scans the log to find ranges of keys that log is authoritative for,
 * and then scans the directory to find items in those ranges that are
 * not present in the log.
 *
 * Anything we don't find in the log is unlinked and removed from the
 * directory.
 */
static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_root *log,
                               struct btrfs_path *path,
                               u64 dirid, int del_all)
{
      u64 range_start;
      u64 range_end;
      int key_type = BTRFS_DIR_LOG_ITEM_KEY;
      int ret = 0;
      struct btrfs_key dir_key;
      struct btrfs_key found_key;
      struct btrfs_path *log_path;
      struct inode *dir;

      dir_key.objectid = dirid;
      dir_key.type = BTRFS_DIR_ITEM_KEY;
      log_path = btrfs_alloc_path();
      if (!log_path)
            return -ENOMEM;

      dir = read_one_inode(root, dirid);
      /* it isn't an error if the inode isn't there, that can happen
       * because we replay the deletes before we copy in the inode item
       * from the log
       */
      if (!dir) {
            btrfs_free_path(log_path);
            return 0;
      }
again:
      range_start = 0;
      range_end = 0;
      while (1) {
            if (del_all)
                  range_end = (u64)-1;
            else {
                  ret = find_dir_range(log, path, dirid, key_type,
                                   &range_start, &range_end);
                  if (ret != 0)
                        break;
            }

            dir_key.offset = range_start;
            while (1) {
                  int nritems;
                  ret = btrfs_search_slot(NULL, root, &dir_key, path,
                                    0, 0);
                  if (ret < 0)
                        goto out;

                  nritems = btrfs_header_nritems(path->nodes[0]);
                  if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret)
                              break;
                  }
                  btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                                    path->slots[0]);
                  if (found_key.objectid != dirid ||
                      found_key.type != dir_key.type)
                        goto next_type;

                  if (found_key.offset > range_end)
                        break;

                  ret = check_item_in_log(trans, root, log, path,
                                    log_path, dir,
                                    &found_key);
                  BUG_ON(ret);
                  if (found_key.offset == (u64)-1)
                        break;
                  dir_key.offset = found_key.offset + 1;
            }
            btrfs_release_path(root, path);
            if (range_end == (u64)-1)
                  break;
            range_start = range_end + 1;
      }

next_type:
      ret = 0;
      if (key_type == BTRFS_DIR_LOG_ITEM_KEY) {
            key_type = BTRFS_DIR_LOG_INDEX_KEY;
            dir_key.type = BTRFS_DIR_INDEX_KEY;
            btrfs_release_path(root, path);
            goto again;
      }
out:
      btrfs_release_path(root, path);
      btrfs_free_path(log_path);
      iput(dir);
      return ret;
}

/*
 * the process_func used to replay items from the log tree.  This
 * gets called in two different stages.  The first stage just looks
 * for inodes and makes sure they are all copied into the subvolume.
 *
 * The second stage copies all the other item types from the log into
 * the subvolume.  The two stage approach is slower, but gets rid of
 * lots of complexity around inodes referencing other inodes that exist
 * only in the log (references come from either directory items or inode
 * back refs).
 */
static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
                       struct walk_control *wc, u64 gen)
{
      int nritems;
      struct btrfs_path *path;
      struct btrfs_root *root = wc->replay_dest;
      struct btrfs_key key;
      u32 item_size;
      int level;
      int i;
      int ret;

      btrfs_read_buffer(eb, gen);

      level = btrfs_header_level(eb);

      if (level != 0)
            return 0;

      path = btrfs_alloc_path();
      BUG_ON(!path);

      nritems = btrfs_header_nritems(eb);
      for (i = 0; i < nritems; i++) {
            btrfs_item_key_to_cpu(eb, &key, i);
            item_size = btrfs_item_size_nr(eb, i);

            /* inode keys are done during the first stage */
            if (key.type == BTRFS_INODE_ITEM_KEY &&
                wc->stage == LOG_WALK_REPLAY_INODES) {
                  struct inode *inode;
                  struct btrfs_inode_item *inode_item;
                  u32 mode;

                  inode_item = btrfs_item_ptr(eb, i,
                                  struct btrfs_inode_item);
                  mode = btrfs_inode_mode(eb, inode_item);
                  if (S_ISDIR(mode)) {
                        ret = replay_dir_deletes(wc->trans,
                               root, log, path, key.objectid, 0);
                        BUG_ON(ret);
                  }
                  ret = overwrite_item(wc->trans, root, path,
                                   eb, i, &key);
                  BUG_ON(ret);

                  /* for regular files, truncate away
                   * extents past the new EOF
                   */
                  if (S_ISREG(mode)) {
                        inode = read_one_inode(root,
                                           key.objectid);
                        BUG_ON(!inode);

                        ret = btrfs_truncate_inode_items(wc->trans,
                              root, inode, inode->i_size,
                              BTRFS_EXTENT_DATA_KEY);
                        BUG_ON(ret);

                        /* if the nlink count is zero here, the iput
                         * will free the inode.  We bump it to make
                         * sure it doesn't get freed until the link
                         * count fixup is done
                         */
                        if (inode->i_nlink == 0) {
                              btrfs_inc_nlink(inode);
                              btrfs_update_inode(wc->trans,
                                             root, inode);
                        }
                        iput(inode);
                  }
                  ret = link_to_fixup_dir(wc->trans, root,
                                    path, key.objectid);
                  BUG_ON(ret);
            }
            if (wc->stage < LOG_WALK_REPLAY_ALL)
                  continue;

            /* these keys are simply copied */
            if (key.type == BTRFS_XATTR_ITEM_KEY) {
                  ret = overwrite_item(wc->trans, root, path,
                                   eb, i, &key);
                  BUG_ON(ret);
            } else if (key.type == BTRFS_INODE_REF_KEY) {
                  ret = add_inode_ref(wc->trans, root, log, path,
                                  eb, i, &key);
                  BUG_ON(ret && ret != -ENOENT);
            } else if (key.type == BTRFS_EXTENT_DATA_KEY) {
                  ret = replay_one_extent(wc->trans, root, path,
                                    eb, i, &key);
                  BUG_ON(ret);
            } else if (key.type == BTRFS_DIR_ITEM_KEY ||
                     key.type == BTRFS_DIR_INDEX_KEY) {
                  ret = replay_one_dir_item(wc->trans, root, path,
                                      eb, i, &key);
                  BUG_ON(ret);
            }
      }
      btrfs_free_path(path);
      return 0;
}

static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root,
                           struct btrfs_path *path, int *level,
                           struct walk_control *wc)
{
      u64 root_owner;
      u64 root_gen;
      u64 bytenr;
      u64 ptr_gen;
      struct extent_buffer *next;
      struct extent_buffer *cur;
      struct extent_buffer *parent;
      u32 blocksize;
      int ret = 0;

      WARN_ON(*level < 0);
      WARN_ON(*level >= BTRFS_MAX_LEVEL);

      while (*level > 0) {
            WARN_ON(*level < 0);
            WARN_ON(*level >= BTRFS_MAX_LEVEL);
            cur = path->nodes[*level];

            if (btrfs_header_level(cur) != *level)
                  WARN_ON(1);

            if (path->slots[*level] >=
                btrfs_header_nritems(cur))
                  break;

            bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
            ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
            blocksize = btrfs_level_size(root, *level - 1);

            parent = path->nodes[*level];
            root_owner = btrfs_header_owner(parent);
            root_gen = btrfs_header_generation(parent);

            next = btrfs_find_create_tree_block(root, bytenr, blocksize);

            wc->process_func(root, next, wc, ptr_gen);

            if (*level == 1) {
                  path->slots[*level]++;
                  if (wc->free) {
                        btrfs_read_buffer(next, ptr_gen);

                        btrfs_tree_lock(next);
                        clean_tree_block(trans, root, next);
                        btrfs_set_lock_blocking(next);
                        btrfs_wait_tree_block_writeback(next);
                        btrfs_tree_unlock(next);

                        WARN_ON(root_owner !=
                              BTRFS_TREE_LOG_OBJECTID);
                        ret = btrfs_free_reserved_extent(root,
                                           bytenr, blocksize);
                        BUG_ON(ret);
                  }
                  free_extent_buffer(next);
                  continue;
            }
            btrfs_read_buffer(next, ptr_gen);

            WARN_ON(*level <= 0);
            if (path->nodes[*level-1])
                  free_extent_buffer(path->nodes[*level-1]);
            path->nodes[*level-1] = next;
            *level = btrfs_header_level(next);
            path->slots[*level] = 0;
            cond_resched();
      }
      WARN_ON(*level < 0);
      WARN_ON(*level >= BTRFS_MAX_LEVEL);

      if (path->nodes[*level] == root->node)
            parent = path->nodes[*level];
      else
            parent = path->nodes[*level + 1];

      bytenr = path->nodes[*level]->start;

      blocksize = btrfs_level_size(root, *level);
      root_owner = btrfs_header_owner(parent);
      root_gen = btrfs_header_generation(parent);

      wc->process_func(root, path->nodes[*level], wc,
                   btrfs_header_generation(path->nodes[*level]));

      if (wc->free) {
            next = path->nodes[*level];
            btrfs_tree_lock(next);
            clean_tree_block(trans, root, next);
            btrfs_set_lock_blocking(next);
            btrfs_wait_tree_block_writeback(next);
            btrfs_tree_unlock(next);

            WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
            ret = btrfs_free_reserved_extent(root, bytenr, blocksize);
            BUG_ON(ret);
      }
      free_extent_buffer(path->nodes[*level]);
      path->nodes[*level] = NULL;
      *level += 1;

      cond_resched();
      return 0;
}

static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         struct btrfs_path *path, int *level,
                         struct walk_control *wc)
{
      u64 root_owner;
      u64 root_gen;
      int i;
      int slot;
      int ret;

      for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
            slot = path->slots[i];
            if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
                  struct extent_buffer *node;
                  node = path->nodes[i];
                  path->slots[i]++;
                  *level = i;
                  WARN_ON(*level == 0);
                  return 0;
            } else {
                  struct extent_buffer *parent;
                  if (path->nodes[*level] == root->node)
                        parent = path->nodes[*level];
                  else
                        parent = path->nodes[*level + 1];

                  root_owner = btrfs_header_owner(parent);
                  root_gen = btrfs_header_generation(parent);
                  wc->process_func(root, path->nodes[*level], wc,
                         btrfs_header_generation(path->nodes[*level]));
                  if (wc->free) {
                        struct extent_buffer *next;

                        next = path->nodes[*level];

                        btrfs_tree_lock(next);
                        clean_tree_block(trans, root, next);
                        btrfs_set_lock_blocking(next);
                        btrfs_wait_tree_block_writeback(next);
                        btrfs_tree_unlock(next);

                        WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
                        ret = btrfs_free_reserved_extent(root,
                                    path->nodes[*level]->start,
                                    path->nodes[*level]->len);
                        BUG_ON(ret);
                  }
                  free_extent_buffer(path->nodes[*level]);
                  path->nodes[*level] = NULL;
                  *level = i + 1;
            }
      }
      return 1;
}

/*
 * drop the reference count on the tree rooted at 'snap'.  This traverses
 * the tree freeing any blocks that have a ref count of zero after being
 * decremented.
 */
static int walk_log_tree(struct btrfs_trans_handle *trans,
                   struct btrfs_root *log, struct walk_control *wc)
{
      int ret = 0;
      int wret;
      int level;
      struct btrfs_path *path;
      int i;
      int orig_level;

      path = btrfs_alloc_path();
      BUG_ON(!path);

      level = btrfs_header_level(log->node);
      orig_level = level;
      path->nodes[level] = log->node;
      extent_buffer_get(log->node);
      path->slots[level] = 0;

      while (1) {
            wret = walk_down_log_tree(trans, log, path, &level, wc);
            if (wret > 0)
                  break;
            if (wret < 0)
                  ret = wret;

            wret = walk_up_log_tree(trans, log, path, &level, wc);
            if (wret > 0)
                  break;
            if (wret < 0)
                  ret = wret;
      }

      /* was the root node processed? if not, catch it here */
      if (path->nodes[orig_level]) {
            wc->process_func(log, path->nodes[orig_level], wc,
                   btrfs_header_generation(path->nodes[orig_level]));
            if (wc->free) {
                  struct extent_buffer *next;

                  next = path->nodes[orig_level];

                  btrfs_tree_lock(next);
                  clean_tree_block(trans, log, next);
                  btrfs_set_lock_blocking(next);
                  btrfs_wait_tree_block_writeback(next);
                  btrfs_tree_unlock(next);

                  WARN_ON(log->root_key.objectid !=
                        BTRFS_TREE_LOG_OBJECTID);
                  ret = btrfs_free_reserved_extent(log, next->start,
                                           next->len);
                  BUG_ON(ret);
            }
      }

      for (i = 0; i <= orig_level; i++) {
            if (path->nodes[i]) {
                  free_extent_buffer(path->nodes[i]);
                  path->nodes[i] = NULL;
            }
      }
      btrfs_free_path(path);
      return ret;
}

/*
 * helper function to update the item for a given subvolumes log root
 * in the tree of log roots
 */
static int update_log_root(struct btrfs_trans_handle *trans,
                     struct btrfs_root *log)
{
      int ret;

      if (log->log_transid == 1) {
            /* insert root item on the first sync */
            ret = btrfs_insert_root(trans, log->fs_info->log_root_tree,
                        &log->root_key, &log->root_item);
      } else {
            ret = btrfs_update_root(trans, log->fs_info->log_root_tree,
                        &log->root_key, &log->root_item);
      }
      return ret;
}

static int wait_log_commit(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, unsigned long transid)
{
      DEFINE_WAIT(wait);
      int index = transid % 2;

      /*
       * we only allow two pending log transactions at a time,
       * so we know that if ours is more than 2 older than the
       * current transaction, we're done
       */
      do {
            prepare_to_wait(&root->log_commit_wait[index],
                        &wait, TASK_UNINTERRUPTIBLE);
            mutex_unlock(&root->log_mutex);

            if (root->fs_info->last_trans_log_full_commit !=
                trans->transid && root->log_transid < transid + 2 &&
                atomic_read(&root->log_commit[index]))
                  schedule();

            finish_wait(&root->log_commit_wait[index], &wait);
            mutex_lock(&root->log_mutex);
      } while (root->log_transid < transid + 2 &&
             atomic_read(&root->log_commit[index]));
      return 0;
}

static int wait_for_writer(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root)
{
      DEFINE_WAIT(wait);
      while (atomic_read(&root->log_writers)) {
            prepare_to_wait(&root->log_writer_wait,
                        &wait, TASK_UNINTERRUPTIBLE);
            mutex_unlock(&root->log_mutex);
            if (root->fs_info->last_trans_log_full_commit !=
                trans->transid && atomic_read(&root->log_writers))
                  schedule();
            mutex_lock(&root->log_mutex);
            finish_wait(&root->log_writer_wait, &wait);
      }
      return 0;
}

/*
 * btrfs_sync_log does sends a given tree log down to the disk and
 * updates the super blocks to record it.  When this call is done,
 * you know that any inodes previously logged are safely on disk only
 * if it returns 0.
 *
 * Any other return value means you need to call btrfs_commit_transaction.
 * Some of the edge cases for fsyncing directories that have had unlinks
 * or renames done in the past mean that sometimes the only safe
 * fsync is to commit the whole FS.  When btrfs_sync_log returns -EAGAIN,
 * that has happened.
 */
int btrfs_sync_log(struct btrfs_trans_handle *trans,
               struct btrfs_root *root)
{
      int index1;
      int index2;
      int ret;
      struct btrfs_root *log = root->log_root;
      struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;

      mutex_lock(&root->log_mutex);
      index1 = root->log_transid % 2;
      if (atomic_read(&root->log_commit[index1])) {
            wait_log_commit(trans, root, root->log_transid);
            mutex_unlock(&root->log_mutex);
            return 0;
      }
      atomic_set(&root->log_commit[index1], 1);

      /* wait for previous tree log sync to complete */
      if (atomic_read(&root->log_commit[(index1 + 1) % 2]))
            wait_log_commit(trans, root, root->log_transid - 1);

      while (1) {
            unsigned long batch = root->log_batch;
            mutex_unlock(&root->log_mutex);
            schedule_timeout_uninterruptible(1);
            mutex_lock(&root->log_mutex);

            wait_for_writer(trans, root);
            if (batch == root->log_batch)
                  break;
      }

      /* bail out if we need to do a full commit */
      if (root->fs_info->last_trans_log_full_commit == trans->transid) {
            ret = -EAGAIN;
            mutex_unlock(&root->log_mutex);
            goto out;
      }

      ret = btrfs_write_and_wait_marked_extents(log, &log->dirty_log_pages);
      BUG_ON(ret);

      btrfs_set_root_node(&log->root_item, log->node);

      root->log_batch = 0;
      root->log_transid++;
      log->log_transid = root->log_transid;
      smp_mb();
      /*
       * log tree has been flushed to disk, new modifications of
       * the log will be written to new positions. so it's safe to
       * allow log writers to go in.
       */
      mutex_unlock(&root->log_mutex);

      mutex_lock(&log_root_tree->log_mutex);
      log_root_tree->log_batch++;
      atomic_inc(&log_root_tree->log_writers);
      mutex_unlock(&log_root_tree->log_mutex);

      ret = update_log_root(trans, log);
      BUG_ON(ret);

      mutex_lock(&log_root_tree->log_mutex);
      if (atomic_dec_and_test(&log_root_tree->log_writers)) {
            smp_mb();
            if (waitqueue_active(&log_root_tree->log_writer_wait))
                  wake_up(&log_root_tree->log_writer_wait);
      }

      index2 = log_root_tree->log_transid % 2;
      if (atomic_read(&log_root_tree->log_commit[index2])) {
            wait_log_commit(trans, log_root_tree,
                        log_root_tree->log_transid);
            mutex_unlock(&log_root_tree->log_mutex);
            goto out;
      }
      atomic_set(&log_root_tree->log_commit[index2], 1);

      if (atomic_read(&log_root_tree->log_commit[(index2 + 1) % 2])) {
            wait_log_commit(trans, log_root_tree,
                        log_root_tree->log_transid - 1);
      }

      wait_for_writer(trans, log_root_tree);

      /*
       * now that we've moved on to the tree of log tree roots,
       * check the full commit flag again
       */
      if (root->fs_info->last_trans_log_full_commit == trans->transid) {
            mutex_unlock(&log_root_tree->log_mutex);
            ret = -EAGAIN;
            goto out_wake_log_root;
      }

      ret = btrfs_write_and_wait_marked_extents(log_root_tree,
                        &log_root_tree->dirty_log_pages);
      BUG_ON(ret);

      btrfs_set_super_log_root(&root->fs_info->super_for_commit,
                        log_root_tree->node->start);
      btrfs_set_super_log_root_level(&root->fs_info->super_for_commit,
                        btrfs_header_level(log_root_tree->node));

      log_root_tree->log_batch = 0;
      log_root_tree->log_transid++;
      smp_mb();

      mutex_unlock(&log_root_tree->log_mutex);

      /*
       * nobody else is going to jump in and write the the ctree
       * super here because the log_commit atomic below is protecting
       * us.  We must be called with a transaction handle pinning
       * the running transaction open, so a full commit can't hop
       * in and cause problems either.
       */
      write_ctree_super(trans, root->fs_info->tree_root, 2);
      ret = 0;

out_wake_log_root:
      atomic_set(&log_root_tree->log_commit[index2], 0);
      smp_mb();
      if (waitqueue_active(&log_root_tree->log_commit_wait[index2]))
            wake_up(&log_root_tree->log_commit_wait[index2]);
out:
      atomic_set(&root->log_commit[index1], 0);
      smp_mb();
      if (waitqueue_active(&root->log_commit_wait[index1]))
            wake_up(&root->log_commit_wait[index1]);
      return 0;
}

/*
 * free all the extents used by the tree log.  This should be called
 * at commit time of the full transaction
 */
int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)
{
      int ret;
      struct btrfs_root *log;
      struct key;
      u64 start;
      u64 end;
      struct walk_control wc = {
            .free = 1,
            .process_func = process_one_buffer
      };

      if (!root->log_root || root->fs_info->log_root_recovering)
            return 0;

      log = root->log_root;
      ret = walk_log_tree(trans, log, &wc);
      BUG_ON(ret);

      while (1) {
            ret = find_first_extent_bit(&log->dirty_log_pages,
                            0, &start, &end, EXTENT_DIRTY);
            if (ret)
                  break;

            clear_extent_dirty(&log->dirty_log_pages,
                           start, end, GFP_NOFS);
      }

      if (log->log_transid > 0) {
            ret = btrfs_del_root(trans, root->fs_info->log_root_tree,
                             &log->root_key);
            BUG_ON(ret);
      }
      root->log_root = NULL;
      free_extent_buffer(log->node);
      kfree(log);
      return 0;
}

/*
 * If both a file and directory are logged, and unlinks or renames are
 * mixed in, we have a few interesting corners:
 *
 * create file X in dir Y
 * link file X to X.link in dir Y
 * fsync file X
 * unlink file X but leave X.link
 * fsync dir Y
 *
 * After a crash we would expect only X.link to exist.  But file X
 * didn't get fsync'd again so the log has back refs for X and X.link.
 *
 * We solve this by removing directory entries and inode backrefs from the
 * log when a file that was logged in the current transaction is
 * unlinked.  Any later fsync will include the updated log entries, and
 * we'll be able to reconstruct the proper directory items from backrefs.
 *
 * This optimizations allows us to avoid relogging the entire inode
 * or the entire directory.
 */
int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         const char *name, int name_len,
                         struct inode *dir, u64 index)
{
      struct btrfs_root *log;
      struct btrfs_dir_item *di;
      struct btrfs_path *path;
      int ret;
      int bytes_del = 0;

      if (BTRFS_I(dir)->logged_trans < trans->transid)
            return 0;

      ret = join_running_log_trans(root);
      if (ret)
            return 0;

      mutex_lock(&BTRFS_I(dir)->log_mutex);

      log = root->log_root;
      path = btrfs_alloc_path();
      di = btrfs_lookup_dir_item(trans, log, path, dir->i_ino,
                           name, name_len, -1);
      if (di && !IS_ERR(di)) {
            ret = btrfs_delete_one_dir_name(trans, log, path, di);
            bytes_del += name_len;
            BUG_ON(ret);
      }
      btrfs_release_path(log, path);
      di = btrfs_lookup_dir_index_item(trans, log, path, dir->i_ino,
                               index, name, name_len, -1);
      if (di && !IS_ERR(di)) {
            ret = btrfs_delete_one_dir_name(trans, log, path, di);
            bytes_del += name_len;
            BUG_ON(ret);
      }

      /* update the directory size in the log to reflect the names
       * we have removed
       */
      if (bytes_del) {
            struct btrfs_key key;

            key.objectid = dir->i_ino;
            key.offset = 0;
            key.type = BTRFS_INODE_ITEM_KEY;
            btrfs_release_path(log, path);

            ret = btrfs_search_slot(trans, log, &key, path, 0, 1);
            if (ret == 0) {
                  struct btrfs_inode_item *item;
                  u64 i_size;

                  item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                    struct btrfs_inode_item);
                  i_size = btrfs_inode_size(path->nodes[0], item);
                  if (i_size > bytes_del)
                        i_size -= bytes_del;
                  else
                        i_size = 0;
                  btrfs_set_inode_size(path->nodes[0], item, i_size);
                  btrfs_mark_buffer_dirty(path->nodes[0]);
            } else
                  ret = 0;
            btrfs_release_path(log, path);
      }

      btrfs_free_path(path);
      mutex_unlock(&BTRFS_I(dir)->log_mutex);
      btrfs_end_log_trans(root);

      return 0;
}

/* see comments for btrfs_del_dir_entries_in_log */
int btrfs_del_inode_ref_in_log(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         const char *name, int name_len,
                         struct inode *inode, u64 dirid)
{
      struct btrfs_root *log;
      u64 index;
      int ret;

      if (BTRFS_I(inode)->logged_trans < trans->transid)
            return 0;

      ret = join_running_log_trans(root);
      if (ret)
            return 0;
      log = root->log_root;
      mutex_lock(&BTRFS_I(inode)->log_mutex);

      ret = btrfs_del_inode_ref(trans, log, name, name_len, inode->i_ino,
                          dirid, &index);
      mutex_unlock(&BTRFS_I(inode)->log_mutex);
      btrfs_end_log_trans(root);

      return ret;
}

/*
 * creates a range item in the log for 'dirid'.  first_offset and
 * last_offset tell us which parts of the key space the log should
 * be considered authoritative for.
 */
static noinline int insert_dir_log_key(struct btrfs_trans_handle *trans,
                               struct btrfs_root *log,
                               struct btrfs_path *path,
                               int key_type, u64 dirid,
                               u64 first_offset, u64 last_offset)
{
      int ret;
      struct btrfs_key key;
      struct btrfs_dir_log_item *item;

      key.objectid = dirid;
      key.offset = first_offset;
      if (key_type == BTRFS_DIR_ITEM_KEY)
            key.type = BTRFS_DIR_LOG_ITEM_KEY;
      else
            key.type = BTRFS_DIR_LOG_INDEX_KEY;
      ret = btrfs_insert_empty_item(trans, log, path, &key, sizeof(*item));
      BUG_ON(ret);

      item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                        struct btrfs_dir_log_item);
      btrfs_set_dir_log_end(path->nodes[0], item, last_offset);
      btrfs_mark_buffer_dirty(path->nodes[0]);
      btrfs_release_path(log, path);
      return 0;
}

/*
 * log all the items included in the current transaction for a given
 * directory.  This also creates the range items in the log tree required
 * to replay anything deleted before the fsync
 */
static noinline int log_dir_items(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root, struct inode *inode,
                    struct btrfs_path *path,
                    struct btrfs_path *dst_path, int key_type,
                    u64 min_offset, u64 *last_offset_ret)
{
      struct btrfs_key min_key;
      struct btrfs_key max_key;
      struct btrfs_root *log = root->log_root;
      struct extent_buffer *src;
      int ret;
      int i;
      int nritems;
      u64 first_offset = min_offset;
      u64 last_offset = (u64)-1;

      log = root->log_root;
      max_key.objectid = inode->i_ino;
      max_key.offset = (u64)-1;
      max_key.type = key_type;

      min_key.objectid = inode->i_ino;
      min_key.type = key_type;
      min_key.offset = min_offset;

      path->keep_locks = 1;

      ret = btrfs_search_forward(root, &min_key, &max_key,
                           path, 0, trans->transid);

      /*
       * we didn't find anything from this transaction, see if there
       * is anything at all
       */
      if (ret != 0 || min_key.objectid != inode->i_ino ||
          min_key.type != key_type) {
            min_key.objectid = inode->i_ino;
            min_key.type = key_type;
            min_key.offset = (u64)-1;
            btrfs_release_path(root, path);
            ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
            if (ret < 0) {
                  btrfs_release_path(root, path);
                  return ret;
            }
            ret = btrfs_previous_item(root, path, inode->i_ino, key_type);

            /* if ret == 0 there are items for this type,
             * create a range to tell us the last key of this type.
             * otherwise, there are no items in this directory after
             * *min_offset, and we create a range to indicate that.
             */
            if (ret == 0) {
                  struct btrfs_key tmp;
                  btrfs_item_key_to_cpu(path->nodes[0], &tmp,
                                    path->slots[0]);
                  if (key_type == tmp.type)
                        first_offset = max(min_offset, tmp.offset) + 1;
            }
            goto done;
      }

      /* go backward to find any previous key */
      ret = btrfs_previous_item(root, path, inode->i_ino, key_type);
      if (ret == 0) {
            struct btrfs_key tmp;
            btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
            if (key_type == tmp.type) {
                  first_offset = tmp.offset;
                  ret = overwrite_item(trans, log, dst_path,
                                   path->nodes[0], path->slots[0],
                                   &tmp);
            }
      }
      btrfs_release_path(root, path);

      /* find the first key from this transaction again */
      ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
      if (ret != 0) {
            WARN_ON(1);
            goto done;
      }

      /*
       * we have a block from this transaction, log every item in it
       * from our directory
       */
      while (1) {
            struct btrfs_key tmp;
            src = path->nodes[0];
            nritems = btrfs_header_nritems(src);
            for (i = path->slots[0]; i < nritems; i++) {
                  btrfs_item_key_to_cpu(src, &min_key, i);

                  if (min_key.objectid != inode->i_ino ||
                      min_key.type != key_type)
                        goto done;
                  ret = overwrite_item(trans, log, dst_path, src, i,
                                   &min_key);
                  BUG_ON(ret);
            }
            path->slots[0] = nritems;

            /*
             * look ahead to the next item and see if it is also
             * from this directory and from this transaction
             */
            ret = btrfs_next_leaf(root, path);
            if (ret == 1) {
                  last_offset = (u64)-1;
                  goto done;
            }
            btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
            if (tmp.objectid != inode->i_ino || tmp.type != key_type) {
                  last_offset = (u64)-1;
                  goto done;
            }
            if (btrfs_header_generation(path->nodes[0]) != trans->transid) {
                  ret = overwrite_item(trans, log, dst_path,
                                   path->nodes[0], path->slots[0],
                                   &tmp);

                  BUG_ON(ret);
                  last_offset = tmp.offset;
                  goto done;
            }
      }
done:
      *last_offset_ret = last_offset;
      btrfs_release_path(root, path);
      btrfs_release_path(log, dst_path);

      /* insert the log range keys to indicate where the log is valid */
      ret = insert_dir_log_key(trans, log, path, key_type, inode->i_ino,
                         first_offset, last_offset);
      BUG_ON(ret);
      return 0;
}

/*
 * logging directories is very similar to logging inodes, We find all the items
 * from the current transaction and write them to the log.
 *
 * The recovery code scans the directory in the subvolume, and if it finds a
 * key in the range logged that is not present in the log tree, then it means
 * that dir entry was unlinked during the transaction.
 *
 * In order for that scan to work, we must include one key smaller than
 * the smallest logged by this transaction and one key larger than the largest
 * key logged by this transaction.
 */
static noinline int log_directory_changes(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root, struct inode *inode,
                    struct btrfs_path *path,
                    struct btrfs_path *dst_path)
{
      u64 min_key;
      u64 max_key;
      int ret;
      int key_type = BTRFS_DIR_ITEM_KEY;

again:
      min_key = 0;
      max_key = 0;
      while (1) {
            ret = log_dir_items(trans, root, inode, path,
                            dst_path, key_type, min_key,
                            &max_key);
            BUG_ON(ret);
            if (max_key == (u64)-1)
                  break;
            min_key = max_key + 1;
      }

      if (key_type == BTRFS_DIR_ITEM_KEY) {
            key_type = BTRFS_DIR_INDEX_KEY;
            goto again;
      }
      return 0;
}

/*
 * a helper function to drop items from the log before we relog an
 * inode.  max_key_type indicates the highest item type to remove.
 * This cannot be run for file data extents because it does not
 * free the extents they point to.
 */
static int drop_objectid_items(struct btrfs_trans_handle *trans,
                          struct btrfs_root *log,
                          struct btrfs_path *path,
                          u64 objectid, int max_key_type)
{
      int ret;
      struct btrfs_key key;
      struct btrfs_key found_key;

      key.objectid = objectid;
      key.type = max_key_type;
      key.offset = (u64)-1;

      while (1) {
            ret = btrfs_search_slot(trans, log, &key, path, -1, 1);

            if (ret != 1)
                  break;

            if (path->slots[0] == 0)
                  break;

            path->slots[0]--;
            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                              path->slots[0]);

            if (found_key.objectid != objectid)
                  break;

            ret = btrfs_del_item(trans, log, path);
            BUG_ON(ret);
            btrfs_release_path(log, path);
      }
      btrfs_release_path(log, path);
      return 0;
}

static noinline int copy_items(struct btrfs_trans_handle *trans,
                         struct btrfs_root *log,
                         struct btrfs_path *dst_path,
                         struct extent_buffer *src,
                         int start_slot, int nr, int inode_only)
{
      unsigned long src_offset;
      unsigned long dst_offset;
      struct btrfs_file_extent_item *extent;
      struct btrfs_inode_item *inode_item;
      int ret;
      struct btrfs_key *ins_keys;
      u32 *ins_sizes;
      char *ins_data;
      int i;
      struct list_head ordered_sums;

      INIT_LIST_HEAD(&ordered_sums);

      ins_data = kmalloc(nr * sizeof(struct btrfs_key) +
                     nr * sizeof(u32), GFP_NOFS);
      ins_sizes = (u32 *)ins_data;
      ins_keys = (struct btrfs_key *)(ins_data + nr * sizeof(u32));

      for (i = 0; i < nr; i++) {
            ins_sizes[i] = btrfs_item_size_nr(src, i + start_slot);
            btrfs_item_key_to_cpu(src, ins_keys + i, i + start_slot);
      }
      ret = btrfs_insert_empty_items(trans, log, dst_path,
                               ins_keys, ins_sizes, nr);
      BUG_ON(ret);

      for (i = 0; i < nr; i++, dst_path->slots[0]++) {
            dst_offset = btrfs_item_ptr_offset(dst_path->nodes[0],
                                       dst_path->slots[0]);

            src_offset = btrfs_item_ptr_offset(src, start_slot + i);

            copy_extent_buffer(dst_path->nodes[0], src, dst_offset,
                           src_offset, ins_sizes[i]);

            if (inode_only == LOG_INODE_EXISTS &&
                ins_keys[i].type == BTRFS_INODE_ITEM_KEY) {
                  inode_item = btrfs_item_ptr(dst_path->nodes[0],
                                        dst_path->slots[0],
                                        struct btrfs_inode_item);
                  btrfs_set_inode_size(dst_path->nodes[0], inode_item, 0);

                  /* set the generation to zero so the recover code
                   * can tell the difference between an logging
                   * just to say 'this inode exists' and a logging
                   * to say 'update this inode with these values'
                   */
                  btrfs_set_inode_generation(dst_path->nodes[0],
                                       inode_item, 0);
            }
            /* take a reference on file data extents so that truncates
             * or deletes of this inode don't have to relog the inode
             * again
             */
            if (btrfs_key_type(ins_keys + i) == BTRFS_EXTENT_DATA_KEY) {
                  int found_type;
                  extent = btrfs_item_ptr(src, start_slot + i,
                                    struct btrfs_file_extent_item);

                  found_type = btrfs_file_extent_type(src, extent);
                  if (found_type == BTRFS_FILE_EXTENT_REG ||
                      found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        u64 ds, dl, cs, cl;
                        ds = btrfs_file_extent_disk_bytenr(src,
                                                extent);
                        /* ds == 0 is a hole */
                        if (ds == 0)
                              continue;

                        dl = btrfs_file_extent_disk_num_bytes(src,
                                                extent);
                        cs = btrfs_file_extent_offset(src, extent);
                        cl = btrfs_file_extent_num_bytes(src,
                                                extent);;
                        if (btrfs_file_extent_compression(src,
                                                  extent)) {
                              cs = 0;
                              cl = dl;
                        }

                        ret = btrfs_lookup_csums_range(
                                    log->fs_info->csum_root,
                                    ds + cs, ds + cs + cl - 1,
                                    &ordered_sums);
                        BUG_ON(ret);
                  }
            }
      }

      btrfs_mark_buffer_dirty(dst_path->nodes[0]);
      btrfs_release_path(log, dst_path);
      kfree(ins_data);

      /*
       * we have to do this after the loop above to avoid changing the
       * log tree while trying to change the log tree.
       */
      while (!list_empty(&ordered_sums)) {
            struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
                                       struct btrfs_ordered_sum,
                                       list);
            ret = btrfs_csum_file_blocks(trans, log, sums);
            BUG_ON(ret);
            list_del(&sums->list);
            kfree(sums);
      }
      return 0;
}

/* log a single inode in the tree log.
 * At least one parent directory for this inode must exist in the tree
 * or be logged already.
 *
 * Any items from this inode changed by the current transaction are copied
 * to the log tree.  An extra reference is taken on any extents in this
 * file, allowing us to avoid a whole pile of corner cases around logging
 * blocks that have been removed from the tree.
 *
 * See LOG_INODE_ALL and related defines for a description of what inode_only
 * does.
 *
 * This handles both files and directories.
 */
static int btrfs_log_inode(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root, struct inode *inode,
                       int inode_only)
{
      struct btrfs_path *path;
      struct btrfs_path *dst_path;
      struct btrfs_key min_key;
      struct btrfs_key max_key;
      struct btrfs_root *log = root->log_root;
      struct extent_buffer *src = NULL;
      u32 size;
      int ret;
      int nritems;
      int ins_start_slot = 0;
      int ins_nr;

      log = root->log_root;

      path = btrfs_alloc_path();
      dst_path = btrfs_alloc_path();

      min_key.objectid = inode->i_ino;
      min_key.type = BTRFS_INODE_ITEM_KEY;
      min_key.offset = 0;

      max_key.objectid = inode->i_ino;

      /* today the code can only do partial logging of directories */
      if (!S_ISDIR(inode->i_mode))
          inode_only = LOG_INODE_ALL;

      if (inode_only == LOG_INODE_EXISTS || S_ISDIR(inode->i_mode))
            max_key.type = BTRFS_XATTR_ITEM_KEY;
      else
            max_key.type = (u8)-1;
      max_key.offset = (u64)-1;

      mutex_lock(&BTRFS_I(inode)->log_mutex);

      /*
       * a brute force approach to making sure we get the most uptodate
       * copies of everything.
       */
      if (S_ISDIR(inode->i_mode)) {
            int max_key_type = BTRFS_DIR_LOG_INDEX_KEY;

            if (inode_only == LOG_INODE_EXISTS)
                  max_key_type = BTRFS_XATTR_ITEM_KEY;
            ret = drop_objectid_items(trans, log, path,
                                inode->i_ino, max_key_type);
      } else {
            ret = btrfs_truncate_inode_items(trans, log, inode, 0, 0);
      }
      BUG_ON(ret);
      path->keep_locks = 1;

      while (1) {
            ins_nr = 0;
            ret = btrfs_search_forward(root, &min_key, &max_key,
                                 path, 0, trans->transid);
            if (ret != 0)
                  break;
again:
            /* note, ins_nr might be > 0 here, cleanup outside the loop */
            if (min_key.objectid != inode->i_ino)
                  break;
            if (min_key.type > max_key.type)
                  break;

            src = path->nodes[0];
            size = btrfs_item_size_nr(src, path->slots[0]);
            if (ins_nr && ins_start_slot + ins_nr == path->slots[0]) {
                  ins_nr++;
                  goto next_slot;
            } else if (!ins_nr) {
                  ins_start_slot = path->slots[0];
                  ins_nr = 1;
                  goto next_slot;
            }

            ret = copy_items(trans, log, dst_path, src, ins_start_slot,
                         ins_nr, inode_only);
            BUG_ON(ret);
            ins_nr = 1;
            ins_start_slot = path->slots[0];
next_slot:

            nritems = btrfs_header_nritems(path->nodes[0]);
            path->slots[0]++;
            if (path->slots[0] < nritems) {
                  btrfs_item_key_to_cpu(path->nodes[0], &min_key,
                                    path->slots[0]);
                  goto again;
            }
            if (ins_nr) {
                  ret = copy_items(trans, log, dst_path, src,
                               ins_start_slot,
                               ins_nr, inode_only);
                  BUG_ON(ret);
                  ins_nr = 0;
            }
            btrfs_release_path(root, path);

            if (min_key.offset < (u64)-1)
                  min_key.offset++;
            else if (min_key.type < (u8)-1)
                  min_key.type++;
            else if (min_key.objectid < (u64)-1)
                  min_key.objectid++;
            else
                  break;
      }
      if (ins_nr) {
            ret = copy_items(trans, log, dst_path, src,
                         ins_start_slot,
                         ins_nr, inode_only);
            BUG_ON(ret);
            ins_nr = 0;
      }
      WARN_ON(ins_nr);
      if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {
            btrfs_release_path(root, path);
            btrfs_release_path(log, dst_path);
            ret = log_directory_changes(trans, root, inode, path, dst_path);
            BUG_ON(ret);
      }
      BTRFS_I(inode)->logged_trans = trans->transid;
      mutex_unlock(&BTRFS_I(inode)->log_mutex);

      btrfs_free_path(path);
      btrfs_free_path(dst_path);
      return 0;
}

/*
 * follow the dentry parent pointers up the chain and see if any
 * of the directories in it require a full commit before they can
 * be logged.  Returns zero if nothing special needs to be done or 1 if
 * a full commit is required.
 */
static noinline int check_parent_dirs_for_sync(struct btrfs_trans_handle *trans,
                                     struct inode *inode,
                                     struct dentry *parent,
                                     struct super_block *sb,
                                     u64 last_committed)
{
      int ret = 0;
      struct btrfs_root *root;

      /*
       * for regular files, if its inode is already on disk, we don't
       * have to worry about the parents at all.  This is because
       * we can use the last_unlink_trans field to record renames
       * and other fun in this file.
       */
      if (S_ISREG(inode->i_mode) &&
          BTRFS_I(inode)->generation <= last_committed &&
          BTRFS_I(inode)->last_unlink_trans <= last_committed)
                  goto out;

      if (!S_ISDIR(inode->i_mode)) {
            if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
                  goto out;
            inode = parent->d_inode;
      }

      while (1) {
            BTRFS_I(inode)->logged_trans = trans->transid;
            smp_mb();

            if (BTRFS_I(inode)->last_unlink_trans > last_committed) {
                  root = BTRFS_I(inode)->root;

                  /*
                   * make sure any commits to the log are forced
                   * to be full commits
                   */
                  root->fs_info->last_trans_log_full_commit =
                        trans->transid;
                  ret = 1;
                  break;
            }

            if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
                  break;

            if (parent == sb->s_root)
                  break;

            parent = parent->d_parent;
            inode = parent->d_inode;

      }
out:
      return ret;
}

/*
 * helper function around btrfs_log_inode to make sure newly created
 * parent directories also end up in the log.  A minimal inode and backref
 * only logging is done of any parent directories that are older than
 * the last committed transaction
 */
int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
                struct btrfs_root *root, struct inode *inode,
                struct dentry *parent, int exists_only)
{
      int inode_only = exists_only ? LOG_INODE_EXISTS : LOG_INODE_ALL;
      struct super_block *sb;
      int ret = 0;
      u64 last_committed = root->fs_info->last_trans_committed;

      sb = inode->i_sb;

      if (btrfs_test_opt(root, NOTREELOG)) {
            ret = 1;
            goto end_no_trans;
      }

      if (root->fs_info->last_trans_log_full_commit >
          root->fs_info->last_trans_committed) {
            ret = 1;
            goto end_no_trans;
      }

      ret = check_parent_dirs_for_sync(trans, inode, parent,
                               sb, last_committed);
      if (ret)
            goto end_no_trans;

      start_log_trans(trans, root);

      ret = btrfs_log_inode(trans, root, inode, inode_only);
      BUG_ON(ret);

      /*
       * for regular files, if its inode is already on disk, we don't
       * have to worry about the parents at all.  This is because
       * we can use the last_unlink_trans field to record renames
       * and other fun in this file.
       */
      if (S_ISREG(inode->i_mode) &&
          BTRFS_I(inode)->generation <= last_committed &&
          BTRFS_I(inode)->last_unlink_trans <= last_committed)
                  goto no_parent;

      inode_only = LOG_INODE_EXISTS;
      while (1) {
            if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
                  break;

            inode = parent->d_inode;
            if (BTRFS_I(inode)->generation >
                root->fs_info->last_trans_committed) {
                  ret = btrfs_log_inode(trans, root, inode, inode_only);
                  BUG_ON(ret);
            }
            if (parent == sb->s_root)
                  break;

            parent = parent->d_parent;
      }
no_parent:
      ret = 0;
      btrfs_end_log_trans(root);
end_no_trans:
      return ret;
}

/*
 * it is not safe to log dentry if the chunk root has added new
 * chunks.  This returns 0 if the dentry was logged, and 1 otherwise.
 * If this returns 1, you must commit the transaction to safely get your
 * data on disk.
 */
int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root, struct dentry *dentry)
{
      return btrfs_log_inode_parent(trans, root, dentry->d_inode,
                              dentry->d_parent, 0);
}

/*
 * should be called during mount to recover any replay any log trees
 * from the FS
 */
int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_trans_handle *trans;
      struct btrfs_key key;
      struct btrfs_key found_key;
      struct btrfs_key tmp_key;
      struct btrfs_root *log;
      struct btrfs_fs_info *fs_info = log_root_tree->fs_info;
      u64 highest_inode;
      struct walk_control wc = {
            .process_func = process_one_buffer,
            .stage = 0,
      };

      fs_info->log_root_recovering = 1;
      path = btrfs_alloc_path();
      BUG_ON(!path);

      trans = btrfs_start_transaction(fs_info->tree_root, 1);

      wc.trans = trans;
      wc.pin = 1;

      walk_log_tree(trans, log_root_tree, &wc);

again:
      key.objectid = BTRFS_TREE_LOG_OBJECTID;
      key.offset = (u64)-1;
      btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);

      while (1) {
            ret = btrfs_search_slot(NULL, log_root_tree, &key, path, 0, 0);
            if (ret < 0)
                  break;
            if (ret > 0) {
                  if (path->slots[0] == 0)
                        break;
                  path->slots[0]--;
            }
            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                              path->slots[0]);
            btrfs_release_path(log_root_tree, path);
            if (found_key.objectid != BTRFS_TREE_LOG_OBJECTID)
                  break;

            log = btrfs_read_fs_root_no_radix(log_root_tree,
                                      &found_key);
            BUG_ON(!log);


            tmp_key.objectid = found_key.offset;
            tmp_key.type = BTRFS_ROOT_ITEM_KEY;
            tmp_key.offset = (u64)-1;

            wc.replay_dest = btrfs_read_fs_root_no_name(fs_info, &tmp_key);
            BUG_ON(!wc.replay_dest);

            wc.replay_dest->log_root = log;
            btrfs_record_root_in_trans(trans, wc.replay_dest);
            ret = walk_log_tree(trans, log, &wc);
            BUG_ON(ret);

            if (wc.stage == LOG_WALK_REPLAY_ALL) {
                  ret = fixup_inode_link_counts(trans, wc.replay_dest,
                                          path);
                  BUG_ON(ret);
            }
            ret = btrfs_find_highest_inode(wc.replay_dest, &highest_inode);
            if (ret == 0) {
                  wc.replay_dest->highest_inode = highest_inode;
                  wc.replay_dest->last_inode_alloc = highest_inode;
            }

            key.offset = found_key.offset - 1;
            wc.replay_dest->log_root = NULL;
            free_extent_buffer(log->node);
            free_extent_buffer(log->commit_root);
            kfree(log);

            if (found_key.offset == 0)
                  break;
      }
      btrfs_release_path(log_root_tree, path);

      /* step one is to pin it all, step two is to replay just inodes */
      if (wc.pin) {
            wc.pin = 0;
            wc.process_func = replay_one_buffer;
            wc.stage = LOG_WALK_REPLAY_INODES;
            goto again;
      }
      /* step three is to replay everything */
      if (wc.stage < LOG_WALK_REPLAY_ALL) {
            wc.stage++;
            goto again;
      }

      btrfs_free_path(path);

      free_extent_buffer(log_root_tree->node);
      log_root_tree->log_root = NULL;
      fs_info->log_root_recovering = 0;

      /* step 4: commit the transaction, which also unpins the blocks */
      btrfs_commit_transaction(trans, fs_info->tree_root);

      kfree(log_root_tree);
      return 0;
}

/*
 * there are some corner cases where we want to force a full
 * commit instead of allowing a directory to be logged.
 *
 * They revolve around files there were unlinked from the directory, and
 * this function updates the parent directory so that a full commit is
 * properly done if it is fsync'd later after the unlinks are done.
 */
void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
                       struct inode *dir, struct inode *inode,
                       int for_rename)
{
      /*
       * when we're logging a file, if it hasn't been renamed
       * or unlinked, and its inode is fully committed on disk,
       * we don't have to worry about walking up the directory chain
       * to log its parents.
       *
       * So, we use the last_unlink_trans field to put this transid
       * into the file.  When the file is logged we check it and
       * don't log the parents if the file is fully on disk.
       */
      if (S_ISREG(inode->i_mode))
            BTRFS_I(inode)->last_unlink_trans = trans->transid;

      /*
       * if this directory was already logged any new
       * names for this file/dir will get recorded
       */
      smp_mb();
      if (BTRFS_I(dir)->logged_trans == trans->transid)
            return;

      /*
       * if the inode we're about to unlink was logged,
       * the log will be properly updated for any new names
       */
      if (BTRFS_I(inode)->logged_trans == trans->transid)
            return;

      /*
       * when renaming files across directories, if the directory
       * there we're unlinking from gets fsync'd later on, there's
       * no way to find the destination directory later and fsync it
       * properly.  So, we have to be conservative and force commits
       * so the new name gets discovered.
       */
      if (for_rename)
            goto record;

      /* we can safely do the unlink without any special recording */
      return;

record:
      BTRFS_I(dir)->last_unlink_trans = trans->transid;
}

/*
 * Call this after adding a new name for a file and it will properly
 * update the log to reflect the new name.
 *
 * It will return zero if all goes well, and it will return 1 if a
 * full transaction commit is required.
 */
int btrfs_log_new_name(struct btrfs_trans_handle *trans,
                  struct inode *inode, struct inode *old_dir,
                  struct dentry *parent)
{
      struct btrfs_root * root = BTRFS_I(inode)->root;

      /*
       * this will force the logging code to walk the dentry chain
       * up for the file
       */
      if (S_ISREG(inode->i_mode))
            BTRFS_I(inode)->last_unlink_trans = trans->transid;

      /*
       * if this inode hasn't been logged and directory we're renaming it
       * from hasn't been logged, we don't need to log it
       */
      if (BTRFS_I(inode)->logged_trans <=
          root->fs_info->last_trans_committed &&
          (!old_dir || BTRFS_I(old_dir)->logged_trans <=
                root->fs_info->last_trans_committed))
            return 0;

      return btrfs_log_inode_parent(trans, root, inode, parent, 1);
}


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