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attrib.c

/**
 * attrib.c - NTFS attribute operations.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2007 Anton Altaparmakov
 * Copyright (c) 2002 Richard Russon
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file 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 (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/buffer_head.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/writeback.h>

#include "attrib.h"
#include "debug.h"
#include "layout.h"
#include "lcnalloc.h"
#include "malloc.h"
#include "mft.h"
#include "ntfs.h"
#include "types.h"

/**
 * ntfs_map_runlist_nolock - map (a part of) a runlist of an ntfs inode
 * @ni:           ntfs inode for which to map (part of) a runlist
 * @vcn:    map runlist part containing this vcn
 * @ctx:    active attribute search context if present or NULL if not
 *
 * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
 *
 * If @ctx is specified, it is an active search context of @ni and its base mft
 * record.  This is needed when ntfs_map_runlist_nolock() encounters unmapped
 * runlist fragments and allows their mapping.  If you do not have the mft
 * record mapped, you can specify @ctx as NULL and ntfs_map_runlist_nolock()
 * will perform the necessary mapping and unmapping.
 *
 * Note, ntfs_map_runlist_nolock() saves the state of @ctx on entry and
 * restores it before returning.  Thus, @ctx will be left pointing to the same
 * attribute on return as on entry.  However, the actual pointers in @ctx may
 * point to different memory locations on return, so you must remember to reset
 * any cached pointers from the @ctx, i.e. after the call to
 * ntfs_map_runlist_nolock(), you will probably want to do:
 *    m = ctx->mrec;
 *    a = ctx->attr;
 * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
 * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
 *
 * Return 0 on success and -errno on error.  There is one special error code
 * which is not an error as such.  This is -ENOENT.  It means that @vcn is out
 * of bounds of the runlist.
 *
 * Note the runlist can be NULL after this function returns if @vcn is zero and
 * the attribute has zero allocated size, i.e. there simply is no runlist.
 *
 * WARNING: If @ctx is supplied, regardless of whether success or failure is
 *        returned, you need to check IS_ERR(@ctx->mrec) and if 'true' the @ctx
 *        is no longer valid, i.e. you need to either call
 *        ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
 *        In that case PTR_ERR(@ctx->mrec) will give you the error code for
 *        why the mapping of the old inode failed.
 *
 * Locking: - The runlist described by @ni must be locked for writing on entry
 *          and is locked on return.  Note the runlist will be modified.
 *        - If @ctx is NULL, the base mft record of @ni must not be mapped on
 *          entry and it will be left unmapped on return.
 *        - If @ctx is not NULL, the base mft record must be mapped on entry
 *          and it will be left mapped on return.
 */
int ntfs_map_runlist_nolock(ntfs_inode *ni, VCN vcn, ntfs_attr_search_ctx *ctx)
{
      VCN end_vcn;
      unsigned long flags;
      ntfs_inode *base_ni;
      MFT_RECORD *m;
      ATTR_RECORD *a;
      runlist_element *rl;
      struct page *put_this_page = NULL;
      int err = 0;
      bool ctx_is_temporary, ctx_needs_reset;
      ntfs_attr_search_ctx old_ctx = { NULL, };

      ntfs_debug("Mapping runlist part containing vcn 0x%llx.",
                  (unsigned long long)vcn);
      if (!NInoAttr(ni))
            base_ni = ni;
      else
            base_ni = ni->ext.base_ntfs_ino;
      if (!ctx) {
            ctx_is_temporary = ctx_needs_reset = true;
            m = map_mft_record(base_ni);
            if (IS_ERR(m))
                  return PTR_ERR(m);
            ctx = ntfs_attr_get_search_ctx(base_ni, m);
            if (unlikely(!ctx)) {
                  err = -ENOMEM;
                  goto err_out;
            }
      } else {
            VCN allocated_size_vcn;

            BUG_ON(IS_ERR(ctx->mrec));
            a = ctx->attr;
            BUG_ON(!a->non_resident);
            ctx_is_temporary = false;
            end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
            read_lock_irqsave(&ni->size_lock, flags);
            allocated_size_vcn = ni->allocated_size >>
                        ni->vol->cluster_size_bits;
            read_unlock_irqrestore(&ni->size_lock, flags);
            if (!a->data.non_resident.lowest_vcn && end_vcn <= 0)
                  end_vcn = allocated_size_vcn - 1;
            /*
             * If we already have the attribute extent containing @vcn in
             * @ctx, no need to look it up again.  We slightly cheat in
             * that if vcn exceeds the allocated size, we will refuse to
             * map the runlist below, so there is definitely no need to get
             * the right attribute extent.
             */
            if (vcn >= allocated_size_vcn || (a->type == ni->type &&
                        a->name_length == ni->name_len &&
                        !memcmp((u8*)a + le16_to_cpu(a->name_offset),
                        ni->name, ni->name_len) &&
                        sle64_to_cpu(a->data.non_resident.lowest_vcn)
                        <= vcn && end_vcn >= vcn))
                  ctx_needs_reset = false;
            else {
                  /* Save the old search context. */
                  old_ctx = *ctx;
                  /*
                   * If the currently mapped (extent) inode is not the
                   * base inode we will unmap it when we reinitialize the
                   * search context which means we need to get a
                   * reference to the page containing the mapped mft
                   * record so we do not accidentally drop changes to the
                   * mft record when it has not been marked dirty yet.
                   */
                  if (old_ctx.base_ntfs_ino && old_ctx.ntfs_ino !=
                              old_ctx.base_ntfs_ino) {
                        put_this_page = old_ctx.ntfs_ino->page;
                        page_cache_get(put_this_page);
                  }
                  /*
                   * Reinitialize the search context so we can lookup the
                   * needed attribute extent.
                   */
                  ntfs_attr_reinit_search_ctx(ctx);
                  ctx_needs_reset = true;
            }
      }
      if (ctx_needs_reset) {
            err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                        CASE_SENSITIVE, vcn, NULL, 0, ctx);
            if (unlikely(err)) {
                  if (err == -ENOENT)
                        err = -EIO;
                  goto err_out;
            }
            BUG_ON(!ctx->attr->non_resident);
      }
      a = ctx->attr;
      /*
       * Only decompress the mapping pairs if @vcn is inside it.  Otherwise
       * we get into problems when we try to map an out of bounds vcn because
       * we then try to map the already mapped runlist fragment and
       * ntfs_mapping_pairs_decompress() fails.
       */
      end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn) + 1;
      if (unlikely(vcn && vcn >= end_vcn)) {
            err = -ENOENT;
            goto err_out;
      }
      rl = ntfs_mapping_pairs_decompress(ni->vol, a, ni->runlist.rl);
      if (IS_ERR(rl))
            err = PTR_ERR(rl);
      else
            ni->runlist.rl = rl;
err_out:
      if (ctx_is_temporary) {
            if (likely(ctx))
                  ntfs_attr_put_search_ctx(ctx);
            unmap_mft_record(base_ni);
      } else if (ctx_needs_reset) {
            /*
             * If there is no attribute list, restoring the search context
             * is acomplished simply by copying the saved context back over
             * the caller supplied context.  If there is an attribute list,
             * things are more complicated as we need to deal with mapping
             * of mft records and resulting potential changes in pointers.
             */
            if (NInoAttrList(base_ni)) {
                  /*
                   * If the currently mapped (extent) inode is not the
                   * one we had before, we need to unmap it and map the
                   * old one.
                   */
                  if (ctx->ntfs_ino != old_ctx.ntfs_ino) {
                        /*
                         * If the currently mapped inode is not the
                         * base inode, unmap it.
                         */
                        if (ctx->base_ntfs_ino && ctx->ntfs_ino !=
                                    ctx->base_ntfs_ino) {
                              unmap_extent_mft_record(ctx->ntfs_ino);
                              ctx->mrec = ctx->base_mrec;
                              BUG_ON(!ctx->mrec);
                        }
                        /*
                         * If the old mapped inode is not the base
                         * inode, map it.
                         */
                        if (old_ctx.base_ntfs_ino &&
                                    old_ctx.ntfs_ino !=
                                    old_ctx.base_ntfs_ino) {
retry_map:
                              ctx->mrec = map_mft_record(
                                          old_ctx.ntfs_ino);
                              /*
                               * Something bad has happened.  If out
                               * of memory retry till it succeeds.
                               * Any other errors are fatal and we
                               * return the error code in ctx->mrec.
                               * Let the caller deal with it...  We
                               * just need to fudge things so the
                               * caller can reinit and/or put the
                               * search context safely.
                               */
                              if (IS_ERR(ctx->mrec)) {
                                    if (PTR_ERR(ctx->mrec) ==
                                                -ENOMEM) {
                                          schedule();
                                          goto retry_map;
                                    } else
                                          old_ctx.ntfs_ino =
                                                old_ctx.
                                                base_ntfs_ino;
                              }
                        }
                  }
                  /* Update the changed pointers in the saved context. */
                  if (ctx->mrec != old_ctx.mrec) {
                        if (!IS_ERR(ctx->mrec))
                              old_ctx.attr = (ATTR_RECORD*)(
                                          (u8*)ctx->mrec +
                                          ((u8*)old_ctx.attr -
                                          (u8*)old_ctx.mrec));
                        old_ctx.mrec = ctx->mrec;
                  }
            }
            /* Restore the search context to the saved one. */
            *ctx = old_ctx;
            /*
             * We drop the reference on the page we took earlier.  In the
             * case that IS_ERR(ctx->mrec) is true this means we might lose
             * some changes to the mft record that had been made between
             * the last time it was marked dirty/written out and now.  This
             * at this stage is not a problem as the mapping error is fatal
             * enough that the mft record cannot be written out anyway and
             * the caller is very likely to shutdown the whole inode
             * immediately and mark the volume dirty for chkdsk to pick up
             * the pieces anyway.
             */
            if (put_this_page)
                  page_cache_release(put_this_page);
      }
      return err;
}

/**
 * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
 * @ni:           ntfs inode for which to map (part of) a runlist
 * @vcn:    map runlist part containing this vcn
 *
 * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
 *
 * Return 0 on success and -errno on error.  There is one special error code
 * which is not an error as such.  This is -ENOENT.  It means that @vcn is out
 * of bounds of the runlist.
 *
 * Locking: - The runlist must be unlocked on entry and is unlocked on return.
 *        - This function takes the runlist lock for writing and may modify
 *          the runlist.
 */
int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
{
      int err = 0;

      down_write(&ni->runlist.lock);
      /* Make sure someone else didn't do the work while we were sleeping. */
      if (likely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) <=
                  LCN_RL_NOT_MAPPED))
            err = ntfs_map_runlist_nolock(ni, vcn, NULL);
      up_write(&ni->runlist.lock);
      return err;
}

/**
 * ntfs_attr_vcn_to_lcn_nolock - convert a vcn into a lcn given an ntfs inode
 * @ni:                 ntfs inode of the attribute whose runlist to search
 * @vcn:          vcn to convert
 * @write_locked: true if the runlist is locked for writing
 *
 * Find the virtual cluster number @vcn in the runlist of the ntfs attribute
 * described by the ntfs inode @ni and return the corresponding logical cluster
 * number (lcn).
 *
 * If the @vcn is not mapped yet, the attempt is made to map the attribute
 * extent containing the @vcn and the vcn to lcn conversion is retried.
 *
 * If @write_locked is true the caller has locked the runlist for writing and
 * if false for reading.
 *
 * Since lcns must be >= 0, we use negative return codes with special meaning:
 *
 * Return code    Meaning / Description
 * ==========================================
 *  LCN_HOLE      Hole / not allocated on disk.
 *  LCN_ENOENT    There is no such vcn in the runlist, i.e. @vcn is out of bounds.
 *  LCN_ENOMEM    Not enough memory to map runlist.
 *  LCN_EIO Critical error (runlist/file is corrupt, i/o error, etc).
 *
 * Locking: - The runlist must be locked on entry and is left locked on return.
 *        - If @write_locked is 'false', i.e. the runlist is locked for reading,
 *          the lock may be dropped inside the function so you cannot rely on
 *          the runlist still being the same when this function returns.
 */
LCN ntfs_attr_vcn_to_lcn_nolock(ntfs_inode *ni, const VCN vcn,
            const bool write_locked)
{
      LCN lcn;
      unsigned long flags;
      bool is_retry = false;

      ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, %s_locked.",
                  ni->mft_no, (unsigned long long)vcn,
                  write_locked ? "write" : "read");
      BUG_ON(!ni);
      BUG_ON(!NInoNonResident(ni));
      BUG_ON(vcn < 0);
      if (!ni->runlist.rl) {
            read_lock_irqsave(&ni->size_lock, flags);
            if (!ni->allocated_size) {
                  read_unlock_irqrestore(&ni->size_lock, flags);
                  return LCN_ENOENT;
            }
            read_unlock_irqrestore(&ni->size_lock, flags);
      }
retry_remap:
      /* Convert vcn to lcn.  If that fails map the runlist and retry once. */
      lcn = ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn);
      if (likely(lcn >= LCN_HOLE)) {
            ntfs_debug("Done, lcn 0x%llx.", (long long)lcn);
            return lcn;
      }
      if (lcn != LCN_RL_NOT_MAPPED) {
            if (lcn != LCN_ENOENT)
                  lcn = LCN_EIO;
      } else if (!is_retry) {
            int err;

            if (!write_locked) {
                  up_read(&ni->runlist.lock);
                  down_write(&ni->runlist.lock);
                  if (unlikely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) !=
                              LCN_RL_NOT_MAPPED)) {
                        up_write(&ni->runlist.lock);
                        down_read(&ni->runlist.lock);
                        goto retry_remap;
                  }
            }
            err = ntfs_map_runlist_nolock(ni, vcn, NULL);
            if (!write_locked) {
                  up_write(&ni->runlist.lock);
                  down_read(&ni->runlist.lock);
            }
            if (likely(!err)) {
                  is_retry = true;
                  goto retry_remap;
            }
            if (err == -ENOENT)
                  lcn = LCN_ENOENT;
            else if (err == -ENOMEM)
                  lcn = LCN_ENOMEM;
            else
                  lcn = LCN_EIO;
      }
      if (lcn != LCN_ENOENT)
            ntfs_error(ni->vol->sb, "Failed with error code %lli.",
                        (long long)lcn);
      return lcn;
}

/**
 * ntfs_attr_find_vcn_nolock - find a vcn in the runlist of an ntfs inode
 * @ni:           ntfs inode describing the runlist to search
 * @vcn:    vcn to find
 * @ctx:    active attribute search context if present or NULL if not
 *
 * Find the virtual cluster number @vcn in the runlist described by the ntfs
 * inode @ni and return the address of the runlist element containing the @vcn.
 *
 * If the @vcn is not mapped yet, the attempt is made to map the attribute
 * extent containing the @vcn and the vcn to lcn conversion is retried.
 *
 * If @ctx is specified, it is an active search context of @ni and its base mft
 * record.  This is needed when ntfs_attr_find_vcn_nolock() encounters unmapped
 * runlist fragments and allows their mapping.  If you do not have the mft
 * record mapped, you can specify @ctx as NULL and ntfs_attr_find_vcn_nolock()
 * will perform the necessary mapping and unmapping.
 *
 * Note, ntfs_attr_find_vcn_nolock() saves the state of @ctx on entry and
 * restores it before returning.  Thus, @ctx will be left pointing to the same
 * attribute on return as on entry.  However, the actual pointers in @ctx may
 * point to different memory locations on return, so you must remember to reset
 * any cached pointers from the @ctx, i.e. after the call to
 * ntfs_attr_find_vcn_nolock(), you will probably want to do:
 *    m = ctx->mrec;
 *    a = ctx->attr;
 * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
 * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
 * Note you need to distinguish between the lcn of the returned runlist element
 * being >= 0 and LCN_HOLE.  In the later case you have to return zeroes on
 * read and allocate clusters on write.
 *
 * Return the runlist element containing the @vcn on success and
 * ERR_PTR(-errno) on error.  You need to test the return value with IS_ERR()
 * to decide if the return is success or failure and PTR_ERR() to get to the
 * error code if IS_ERR() is true.
 *
 * The possible error return codes are:
 *    -ENOENT - No such vcn in the runlist, i.e. @vcn is out of bounds.
 *    -ENOMEM - Not enough memory to map runlist.
 *    -EIO  - Critical error (runlist/file is corrupt, i/o error, etc).
 *
 * WARNING: If @ctx is supplied, regardless of whether success or failure is
 *        returned, you need to check IS_ERR(@ctx->mrec) and if 'true' the @ctx
 *        is no longer valid, i.e. you need to either call
 *        ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
 *        In that case PTR_ERR(@ctx->mrec) will give you the error code for
 *        why the mapping of the old inode failed.
 *
 * Locking: - The runlist described by @ni must be locked for writing on entry
 *          and is locked on return.  Note the runlist may be modified when
 *          needed runlist fragments need to be mapped.
 *        - If @ctx is NULL, the base mft record of @ni must not be mapped on
 *          entry and it will be left unmapped on return.
 *        - If @ctx is not NULL, the base mft record must be mapped on entry
 *          and it will be left mapped on return.
 */
runlist_element *ntfs_attr_find_vcn_nolock(ntfs_inode *ni, const VCN vcn,
            ntfs_attr_search_ctx *ctx)
{
      unsigned long flags;
      runlist_element *rl;
      int err = 0;
      bool is_retry = false;

      ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, with%s ctx.",
                  ni->mft_no, (unsigned long long)vcn, ctx ? "" : "out");
      BUG_ON(!ni);
      BUG_ON(!NInoNonResident(ni));
      BUG_ON(vcn < 0);
      if (!ni->runlist.rl) {
            read_lock_irqsave(&ni->size_lock, flags);
            if (!ni->allocated_size) {
                  read_unlock_irqrestore(&ni->size_lock, flags);
                  return ERR_PTR(-ENOENT);
            }
            read_unlock_irqrestore(&ni->size_lock, flags);
      }
retry_remap:
      rl = ni->runlist.rl;
      if (likely(rl && vcn >= rl[0].vcn)) {
            while (likely(rl->length)) {
                  if (unlikely(vcn < rl[1].vcn)) {
                        if (likely(rl->lcn >= LCN_HOLE)) {
                              ntfs_debug("Done.");
                              return rl;
                        }
                        break;
                  }
                  rl++;
            }
            if (likely(rl->lcn != LCN_RL_NOT_MAPPED)) {
                  if (likely(rl->lcn == LCN_ENOENT))
                        err = -ENOENT;
                  else
                        err = -EIO;
            }
      }
      if (!err && !is_retry) {
            /*
             * If the search context is invalid we cannot map the unmapped
             * region.
             */
            if (IS_ERR(ctx->mrec))
                  err = PTR_ERR(ctx->mrec);
            else {
                  /*
                   * The @vcn is in an unmapped region, map the runlist
                   * and retry.
                   */
                  err = ntfs_map_runlist_nolock(ni, vcn, ctx);
                  if (likely(!err)) {
                        is_retry = true;
                        goto retry_remap;
                  }
            }
            if (err == -EINVAL)
                  err = -EIO;
      } else if (!err)
            err = -EIO;
      if (err != -ENOENT)
            ntfs_error(ni->vol->sb, "Failed with error code %i.", err);
      return ERR_PTR(err);
}

/**
 * ntfs_attr_find - find (next) attribute in mft record
 * @type:   attribute type to find
 * @name:   attribute name to find (optional, i.e. NULL means don't care)
 * @name_len:     attribute name length (only needed if @name present)
 * @ic:           IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
 * @val:    attribute value to find (optional, resident attributes only)
 * @val_len:      attribute value length
 * @ctx:    search context with mft record and attribute to search from
 *
 * You should not need to call this function directly.  Use ntfs_attr_lookup()
 * instead.
 *
 * ntfs_attr_find() takes a search context @ctx as parameter and searches the
 * mft record specified by @ctx->mrec, beginning at @ctx->attr, for an
 * attribute of @type, optionally @name and @val.
 *
 * If the attribute is found, ntfs_attr_find() returns 0 and @ctx->attr will
 * point to the found attribute.
 *
 * If the attribute is not found, ntfs_attr_find() returns -ENOENT and
 * @ctx->attr will point to the attribute before which the attribute being
 * searched for would need to be inserted if such an action were to be desired.
 *
 * On actual error, ntfs_attr_find() returns -EIO.  In this case @ctx->attr is
 * undefined and in particular do not rely on it not changing.
 *
 * If @ctx->is_first is 'true', the search begins with @ctx->attr itself.  If it
 * is 'false', the search begins after @ctx->attr.
 *
 * If @ic is IGNORE_CASE, the @name comparisson is not case sensitive and
 * @ctx->ntfs_ino must be set to the ntfs inode to which the mft record
 * @ctx->mrec belongs.  This is so we can get at the ntfs volume and hence at
 * the upcase table.  If @ic is CASE_SENSITIVE, the comparison is case
 * sensitive.  When @name is present, @name_len is the @name length in Unicode
 * characters.
 *
 * If @name is not present (NULL), we assume that the unnamed attribute is
 * being searched for.
 *
 * Finally, the resident attribute value @val is looked for, if present.  If
 * @val is not present (NULL), @val_len is ignored.
 *
 * ntfs_attr_find() only searches the specified mft record and it ignores the
 * presence of an attribute list attribute (unless it is the one being searched
 * for, obviously).  If you need to take attribute lists into consideration,
 * use ntfs_attr_lookup() instead (see below).  This also means that you cannot
 * use ntfs_attr_find() to search for extent records of non-resident
 * attributes, as extents with lowest_vcn != 0 are usually described by the
 * attribute list attribute only. - Note that it is possible that the first
 * extent is only in the attribute list while the last extent is in the base
 * mft record, so do not rely on being able to find the first extent in the
 * base mft record.
 *
 * Warning: Never use @val when looking for attribute types which can be
 *        non-resident as this most likely will result in a crash!
 */
static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name,
            const u32 name_len, const IGNORE_CASE_BOOL ic,
            const u8 *val, const u32 val_len, ntfs_attr_search_ctx *ctx)
{
      ATTR_RECORD *a;
      ntfs_volume *vol = ctx->ntfs_ino->vol;
      ntfschar *upcase = vol->upcase;
      u32 upcase_len = vol->upcase_len;

      /*
       * Iterate over attributes in mft record starting at @ctx->attr, or the
       * attribute following that, if @ctx->is_first is 'true'.
       */
      if (ctx->is_first) {
            a = ctx->attr;
            ctx->is_first = false;
      } else
            a = (ATTR_RECORD*)((u8*)ctx->attr +
                        le32_to_cpu(ctx->attr->length));
      for (;;     a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) {
            if ((u8*)a < (u8*)ctx->mrec || (u8*)a > (u8*)ctx->mrec +
                        le32_to_cpu(ctx->mrec->bytes_allocated))
                  break;
            ctx->attr = a;
            if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) ||
                        a->type == AT_END))
                  return -ENOENT;
            if (unlikely(!a->length))
                  break;
            if (a->type != type)
                  continue;
            /*
             * If @name is present, compare the two names.  If @name is
             * missing, assume we want an unnamed attribute.
             */
            if (!name) {
                  /* The search failed if the found attribute is named. */
                  if (a->name_length)
                        return -ENOENT;
            } else if (!ntfs_are_names_equal(name, name_len,
                      (ntfschar*)((u8*)a + le16_to_cpu(a->name_offset)),
                      a->name_length, ic, upcase, upcase_len)) {
                  register int rc;

                  rc = ntfs_collate_names(name, name_len,
                              (ntfschar*)((u8*)a +
                              le16_to_cpu(a->name_offset)),
                              a->name_length, 1, IGNORE_CASE,
                              upcase, upcase_len);
                  /*
                   * If @name collates before a->name, there is no
                   * matching attribute.
                   */
                  if (rc == -1)
                        return -ENOENT;
                  /* If the strings are not equal, continue search. */
                  if (rc)
                        continue;
                  rc = ntfs_collate_names(name, name_len,
                              (ntfschar*)((u8*)a +
                              le16_to_cpu(a->name_offset)),
                              a->name_length, 1, CASE_SENSITIVE,
                              upcase, upcase_len);
                  if (rc == -1)
                        return -ENOENT;
                  if (rc)
                        continue;
            }
            /*
             * The names match or @name not present and attribute is
             * unnamed.  If no @val specified, we have found the attribute
             * and are done.
             */
            if (!val)
                  return 0;
            /* @val is present; compare values. */
            else {
                  register int rc;

                  rc = memcmp(val, (u8*)a + le16_to_cpu(
                              a->data.resident.value_offset),
                              min_t(u32, val_len, le32_to_cpu(
                              a->data.resident.value_length)));
                  /*
                   * If @val collates before the current attribute's
                   * value, there is no matching attribute.
                   */
                  if (!rc) {
                        register u32 avl;

                        avl = le32_to_cpu(
                                    a->data.resident.value_length);
                        if (val_len == avl)
                              return 0;
                        if (val_len < avl)
                              return -ENOENT;
                  } else if (rc < 0)
                        return -ENOENT;
            }
      }
      ntfs_error(vol->sb, "Inode is corrupt.  Run chkdsk.");
      NVolSetErrors(vol);
      return -EIO;
}

/**
 * load_attribute_list - load an attribute list into memory
 * @vol:          ntfs volume from which to read
 * @runlist:            runlist of the attribute list
 * @al_start:           destination buffer
 * @size:         size of the destination buffer in bytes
 * @initialized_size:   initialized size of the attribute list
 *
 * Walk the runlist @runlist and load all clusters from it copying them into
 * the linear buffer @al. The maximum number of bytes copied to @al is @size
 * bytes. Note, @size does not need to be a multiple of the cluster size. If
 * @initialized_size is less than @size, the region in @al between
 * @initialized_size and @size will be zeroed and not read from disk.
 *
 * Return 0 on success or -errno on error.
 */
int load_attribute_list(ntfs_volume *vol, runlist *runlist, u8 *al_start,
            const s64 size, const s64 initialized_size)
{
      LCN lcn;
      u8 *al = al_start;
      u8 *al_end = al + initialized_size;
      runlist_element *rl;
      struct buffer_head *bh;
      struct super_block *sb;
      unsigned long block_size;
      unsigned long block, max_block;
      int err = 0;
      unsigned char block_size_bits;

      ntfs_debug("Entering.");
      if (!vol || !runlist || !al || size <= 0 || initialized_size < 0 ||
                  initialized_size > size)
            return -EINVAL;
      if (!initialized_size) {
            memset(al, 0, size);
            return 0;
      }
      sb = vol->sb;
      block_size = sb->s_blocksize;
      block_size_bits = sb->s_blocksize_bits;
      down_read(&runlist->lock);
      rl = runlist->rl;
      if (!rl) {
            ntfs_error(sb, "Cannot read attribute list since runlist is "
                        "missing.");
            goto err_out;     
      }
      /* Read all clusters specified by the runlist one run at a time. */
      while (rl->length) {
            lcn = ntfs_rl_vcn_to_lcn(rl, rl->vcn);
            ntfs_debug("Reading vcn = 0x%llx, lcn = 0x%llx.",
                        (unsigned long long)rl->vcn,
                        (unsigned long long)lcn);
            /* The attribute list cannot be sparse. */
            if (lcn < 0) {
                  ntfs_error(sb, "ntfs_rl_vcn_to_lcn() failed.  Cannot "
                              "read attribute list.");
                  goto err_out;
            }
            block = lcn << vol->cluster_size_bits >> block_size_bits;
            /* Read the run from device in chunks of block_size bytes. */
            max_block = block + (rl->length << vol->cluster_size_bits >>
                        block_size_bits);
            ntfs_debug("max_block = 0x%lx.", max_block);
            do {
                  ntfs_debug("Reading block = 0x%lx.", block);
                  bh = sb_bread(sb, block);
                  if (!bh) {
                        ntfs_error(sb, "sb_bread() failed. Cannot "
                                    "read attribute list.");
                        goto err_out;
                  }
                  if (al + block_size >= al_end)
                        goto do_final;
                  memcpy(al, bh->b_data, block_size);
                  brelse(bh);
                  al += block_size;
            } while (++block < max_block);
            rl++;
      }
      if (initialized_size < size) {
initialize:
            memset(al_start + initialized_size, 0, size - initialized_size);
      }
done:
      up_read(&runlist->lock);
      return err;
do_final:
      if (al < al_end) {
            /*
             * Partial block.
             *
             * Note: The attribute list can be smaller than its allocation
             * by multiple clusters.  This has been encountered by at least
             * two people running Windows XP, thus we cannot do any
             * truncation sanity checking here. (AIA)
             */
            memcpy(al, bh->b_data, al_end - al);
            brelse(bh);
            if (initialized_size < size)
                  goto initialize;
            goto done;
      }
      brelse(bh);
      /* Real overflow! */
      ntfs_error(sb, "Attribute list buffer overflow. Read attribute list "
                  "is truncated.");
err_out:
      err = -EIO;
      goto done;
}

/**
 * ntfs_external_attr_find - find an attribute in the attribute list of an inode
 * @type:   attribute type to find
 * @name:   attribute name to find (optional, i.e. NULL means don't care)
 * @name_len:     attribute name length (only needed if @name present)
 * @ic:           IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
 * @lowest_vcn:   lowest vcn to find (optional, non-resident attributes only)
 * @val:    attribute value to find (optional, resident attributes only)
 * @val_len:      attribute value length
 * @ctx:    search context with mft record and attribute to search from
 *
 * You should not need to call this function directly.  Use ntfs_attr_lookup()
 * instead.
 *
 * Find an attribute by searching the attribute list for the corresponding
 * attribute list entry.  Having found the entry, map the mft record if the
 * attribute is in a different mft record/inode, ntfs_attr_find() the attribute
 * in there and return it.
 *
 * On first search @ctx->ntfs_ino must be the base mft record and @ctx must
 * have been obtained from a call to ntfs_attr_get_search_ctx().  On subsequent
 * calls @ctx->ntfs_ino can be any extent inode, too (@ctx->base_ntfs_ino is
 * then the base inode).
 *
 * After finishing with the attribute/mft record you need to call
 * ntfs_attr_put_search_ctx() to cleanup the search context (unmapping any
 * mapped inodes, etc).
 *
 * If the attribute is found, ntfs_external_attr_find() returns 0 and
 * @ctx->attr will point to the found attribute.  @ctx->mrec will point to the
 * mft record in which @ctx->attr is located and @ctx->al_entry will point to
 * the attribute list entry for the attribute.
 *
 * If the attribute is not found, ntfs_external_attr_find() returns -ENOENT and
 * @ctx->attr will point to the attribute in the base mft record before which
 * the attribute being searched for would need to be inserted if such an action
 * were to be desired.  @ctx->mrec will point to the mft record in which
 * @ctx->attr is located and @ctx->al_entry will point to the attribute list
 * entry of the attribute before which the attribute being searched for would
 * need to be inserted if such an action were to be desired.
 *
 * Thus to insert the not found attribute, one wants to add the attribute to
 * @ctx->mrec (the base mft record) and if there is not enough space, the
 * attribute should be placed in a newly allocated extent mft record.  The
 * attribute list entry for the inserted attribute should be inserted in the
 * attribute list attribute at @ctx->al_entry.
 *
 * On actual error, ntfs_external_attr_find() returns -EIO.  In this case
 * @ctx->attr is undefined and in particular do not rely on it not changing.
 */
static int ntfs_external_attr_find(const ATTR_TYPE type,
            const ntfschar *name, const u32 name_len,
            const IGNORE_CASE_BOOL ic, const VCN lowest_vcn,
            const u8 *val, const u32 val_len, ntfs_attr_search_ctx *ctx)
{
      ntfs_inode *base_ni, *ni;
      ntfs_volume *vol;
      ATTR_LIST_ENTRY *al_entry, *next_al_entry;
      u8 *al_start, *al_end;
      ATTR_RECORD *a;
      ntfschar *al_name;
      u32 al_name_len;
      int err = 0;
      static const char *es = " Unmount and run chkdsk.";

      ni = ctx->ntfs_ino;
      base_ni = ctx->base_ntfs_ino;
      ntfs_debug("Entering for inode 0x%lx, type 0x%x.", ni->mft_no, type);
      if (!base_ni) {
            /* First call happens with the base mft record. */
            base_ni = ctx->base_ntfs_ino = ctx->ntfs_ino;
            ctx->base_mrec = ctx->mrec;
      }
      if (ni == base_ni)
            ctx->base_attr = ctx->attr;
      if (type == AT_END)
            goto not_found;
      vol = base_ni->vol;
      al_start = base_ni->attr_list;
      al_end = al_start + base_ni->attr_list_size;
      if (!ctx->al_entry)
            ctx->al_entry = (ATTR_LIST_ENTRY*)al_start;
      /*
       * Iterate over entries in attribute list starting at @ctx->al_entry,
       * or the entry following that, if @ctx->is_first is 'true'.
       */
      if (ctx->is_first) {
            al_entry = ctx->al_entry;
            ctx->is_first = false;
      } else
            al_entry = (ATTR_LIST_ENTRY*)((u8*)ctx->al_entry +
                        le16_to_cpu(ctx->al_entry->length));
      for (;; al_entry = next_al_entry) {
            /* Out of bounds check. */
            if ((u8*)al_entry < base_ni->attr_list ||
                        (u8*)al_entry > al_end)
                  break;      /* Inode is corrupt. */
            ctx->al_entry = al_entry;
            /* Catch the end of the attribute list. */
            if ((u8*)al_entry == al_end)
                  goto not_found;
            if (!al_entry->length)
                  break;
            if ((u8*)al_entry + 6 > al_end || (u8*)al_entry +
                        le16_to_cpu(al_entry->length) > al_end)
                  break;
            next_al_entry = (ATTR_LIST_ENTRY*)((u8*)al_entry +
                        le16_to_cpu(al_entry->length));
            if (le32_to_cpu(al_entry->type) > le32_to_cpu(type))
                  goto not_found;
            if (type != al_entry->type)
                  continue;
            /*
             * If @name is present, compare the two names.  If @name is
             * missing, assume we want an unnamed attribute.
             */
            al_name_len = al_entry->name_length;
            al_name = (ntfschar*)((u8*)al_entry + al_entry->name_offset);
            if (!name) {
                  if (al_name_len)
                        goto not_found;
            } else if (!ntfs_are_names_equal(al_name, al_name_len, name,
                        name_len, ic, vol->upcase, vol->upcase_len)) {
                  register int rc;

                  rc = ntfs_collate_names(name, name_len, al_name,
                              al_name_len, 1, IGNORE_CASE,
                              vol->upcase, vol->upcase_len);
                  /*
                   * If @name collates before al_name, there is no
                   * matching attribute.
                   */
                  if (rc == -1)
                        goto not_found;
                  /* If the strings are not equal, continue search. */
                  if (rc)
                        continue;
                  /*
                   * FIXME: Reverse engineering showed 0, IGNORE_CASE but
                   * that is inconsistent with ntfs_attr_find().  The
                   * subsequent rc checks were also different.  Perhaps I
                   * made a mistake in one of the two.  Need to recheck
                   * which is correct or at least see what is going on...
                   * (AIA)
                   */
                  rc = ntfs_collate_names(name, name_len, al_name,
                              al_name_len, 1, CASE_SENSITIVE,
                              vol->upcase, vol->upcase_len);
                  if (rc == -1)
                        goto not_found;
                  if (rc)
                        continue;
            }
            /*
             * The names match or @name not present and attribute is
             * unnamed.  Now check @lowest_vcn.  Continue search if the
             * next attribute list entry still fits @lowest_vcn.  Otherwise
             * we have reached the right one or the search has failed.
             */
            if (lowest_vcn && (u8*)next_al_entry >= al_start          &&
                        (u8*)next_al_entry + 6 < al_end               &&
                        (u8*)next_al_entry + le16_to_cpu(
                              next_al_entry->length) <= al_end    &&
                        sle64_to_cpu(next_al_entry->lowest_vcn) <=
                              lowest_vcn                  &&
                        next_al_entry->type == al_entry->type         &&
                        next_al_entry->name_length == al_name_len   &&
                        ntfs_are_names_equal((ntfschar*)((u8*)
                              next_al_entry +
                              next_al_entry->name_offset),
                              next_al_entry->name_length,
                              al_name, al_name_len, CASE_SENSITIVE,
                              vol->upcase, vol->upcase_len))
                  continue;
            if (MREF_LE(al_entry->mft_reference) == ni->mft_no) {
                  if (MSEQNO_LE(al_entry->mft_reference) != ni->seq_no) {
                        ntfs_error(vol->sb, "Found stale mft "
                                    "reference in attribute list "
                                    "of base inode 0x%lx.%s",
                                    base_ni->mft_no, es);
                        err = -EIO;
                        break;
                  }
            } else { /* Mft references do not match. */
                  /* If there is a mapped record unmap it first. */
                  if (ni != base_ni)
                        unmap_extent_mft_record(ni);
                  /* Do we want the base record back? */
                  if (MREF_LE(al_entry->mft_reference) ==
                              base_ni->mft_no) {
                        ni = ctx->ntfs_ino = base_ni;
                        ctx->mrec = ctx->base_mrec;
                  } else {
                        /* We want an extent record. */
                        ctx->mrec = map_extent_mft_record(base_ni,
                                    le64_to_cpu(
                                    al_entry->mft_reference), &ni);
                        if (IS_ERR(ctx->mrec)) {
                              ntfs_error(vol->sb, "Failed to map "
                                          "extent mft record "
                                          "0x%lx of base inode "
                                          "0x%lx.%s",
                                          MREF_LE(al_entry->
                                          mft_reference),
                                          base_ni->mft_no, es);
                              err = PTR_ERR(ctx->mrec);
                              if (err == -ENOENT)
                                    err = -EIO;
                              /* Cause @ctx to be sanitized below. */
                              ni = NULL;
                              break;
                        }
                        ctx->ntfs_ino = ni;
                  }
                  ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
                              le16_to_cpu(ctx->mrec->attrs_offset));
            }
            /*
             * ctx->vfs_ino, ctx->mrec, and ctx->attr now point to the
             * mft record containing the attribute represented by the
             * current al_entry.
             */
            /*
             * We could call into ntfs_attr_find() to find the right
             * attribute in this mft record but this would be less
             * efficient and not quite accurate as ntfs_attr_find() ignores
             * the attribute instance numbers for example which become
             * important when one plays with attribute lists.  Also,
             * because a proper match has been found in the attribute list
             * entry above, the comparison can now be optimized.  So it is
             * worth re-implementing a simplified ntfs_attr_find() here.
             */
            a = ctx->attr;
            /*
             * Use a manual loop so we can still use break and continue
             * with the same meanings as above.
             */
do_next_attr_loop:
            if ((u8*)a < (u8*)ctx->mrec || (u8*)a > (u8*)ctx->mrec +
                        le32_to_cpu(ctx->mrec->bytes_allocated))
                  break;
            if (a->type == AT_END)
                  break;
            if (!a->length)
                  break;
            if (al_entry->instance != a->instance)
                  goto do_next_attr;
            /*
             * If the type and/or the name are mismatched between the
             * attribute list entry and the attribute record, there is
             * corruption so we break and return error EIO.
             */
            if (al_entry->type != a->type)
                  break;
            if (!ntfs_are_names_equal((ntfschar*)((u8*)a +
                        le16_to_cpu(a->name_offset)), a->name_length,
                        al_name, al_name_len, CASE_SENSITIVE,
                        vol->upcase, vol->upcase_len))
                  break;
            ctx->attr = a;
            /*
             * If no @val specified or @val specified and it matches, we
             * have found it!
             */
            if (!val || (!a->non_resident && le32_to_cpu(
                        a->data.resident.value_length) == val_len &&
                        !memcmp((u8*)a +
                        le16_to_cpu(a->data.resident.value_offset),
                        val, val_len))) {
                  ntfs_debug("Done, found.");
                  return 0;
            }
do_next_attr:
            /* Proceed to the next attribute in the current mft record. */
            a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length));
            goto do_next_attr_loop;
      }
      if (!err) {
            ntfs_error(vol->sb, "Base inode 0x%lx contains corrupt "
                        "attribute list attribute.%s", base_ni->mft_no,
                        es);
            err = -EIO;
      }
      if (ni != base_ni) {
            if (ni)
                  unmap_extent_mft_record(ni);
            ctx->ntfs_ino = base_ni;
            ctx->mrec = ctx->base_mrec;
            ctx->attr = ctx->base_attr;
      }
      if (err != -ENOMEM)
            NVolSetErrors(vol);
      return err;
not_found:
      /*
       * If we were looking for AT_END, we reset the search context @ctx and
       * use ntfs_attr_find() to seek to the end of the base mft record.
       */
      if (type == AT_END) {
            ntfs_attr_reinit_search_ctx(ctx);
            return ntfs_attr_find(AT_END, name, name_len, ic, val, val_len,
                        ctx);
      }
      /*
       * The attribute was not found.  Before we return, we want to ensure
       * @ctx->mrec and @ctx->attr indicate the position at which the
       * attribute should be inserted in the base mft record.  Since we also
       * want to preserve @ctx->al_entry we cannot reinitialize the search
       * context using ntfs_attr_reinit_search_ctx() as this would set
       * @ctx->al_entry to NULL.  Thus we do the necessary bits manually (see
       * ntfs_attr_init_search_ctx() below).  Note, we _only_ preserve
       * @ctx->al_entry as the remaining fields (base_*) are identical to
       * their non base_ counterparts and we cannot set @ctx->base_attr
       * correctly yet as we do not know what @ctx->attr will be set to by
       * the call to ntfs_attr_find() below.
       */
      if (ni != base_ni)
            unmap_extent_mft_record(ni);
      ctx->mrec = ctx->base_mrec;
      ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
                  le16_to_cpu(ctx->mrec->attrs_offset));
      ctx->is_first = true;
      ctx->ntfs_ino = base_ni;
      ctx->base_ntfs_ino = NULL;
      ctx->base_mrec = NULL;
      ctx->base_attr = NULL;
      /*
       * In case there are multiple matches in the base mft record, need to
       * keep enumerating until we get an attribute not found response (or
       * another error), otherwise we would keep returning the same attribute
       * over and over again and all programs using us for enumeration would
       * lock up in a tight loop.
       */
      do {
            err = ntfs_attr_find(type, name, name_len, ic, val, val_len,
                        ctx);
      } while (!err);
      ntfs_debug("Done, not found.");
      return err;
}

/**
 * ntfs_attr_lookup - find an attribute in an ntfs inode
 * @type:   attribute type to find
 * @name:   attribute name to find (optional, i.e. NULL means don't care)
 * @name_len:     attribute name length (only needed if @name present)
 * @ic:           IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
 * @lowest_vcn:   lowest vcn to find (optional, non-resident attributes only)
 * @val:    attribute value to find (optional, resident attributes only)
 * @val_len:      attribute value length
 * @ctx:    search context with mft record and attribute to search from
 *
 * Find an attribute in an ntfs inode.  On first search @ctx->ntfs_ino must
 * be the base mft record and @ctx must have been obtained from a call to
 * ntfs_attr_get_search_ctx().
 *
 * This function transparently handles attribute lists and @ctx is used to
 * continue searches where they were left off at.
 *
 * After finishing with the attribute/mft record you need to call
 * ntfs_attr_put_search_ctx() to cleanup the search context (unmapping any
 * mapped inodes, etc).
 *
 * Return 0 if the search was successful and -errno if not.
 *
 * When 0, @ctx->attr is the found attribute and it is in mft record
 * @ctx->mrec.  If an attribute list attribute is present, @ctx->al_entry is
 * the attribute list entry of the found attribute.
 *
 * When -ENOENT, @ctx->attr is the attribute which collates just after the
 * attribute being searched for, i.e. if one wants to add the attribute to the
 * mft record this is the correct place to insert it into.  If an attribute
 * list attribute is present, @ctx->al_entry is the attribute list entry which
 * collates just after the attribute list entry of the attribute being searched
 * for, i.e. if one wants to add the attribute to the mft record this is the
 * correct place to insert its attribute list entry into.
 *
 * When -errno != -ENOENT, an error occured during the lookup.  @ctx->attr is
 * then undefined and in particular you should not rely on it not changing.
 */
int ntfs_attr_lookup(const ATTR_TYPE type, const ntfschar *name,
            const u32 name_len, const IGNORE_CASE_BOOL ic,
            const VCN lowest_vcn, const u8 *val, const u32 val_len,
            ntfs_attr_search_ctx *ctx)
{
      ntfs_inode *base_ni;

      ntfs_debug("Entering.");
      BUG_ON(IS_ERR(ctx->mrec));
      if (ctx->base_ntfs_ino)
            base_ni = ctx->base_ntfs_ino;
      else
            base_ni = ctx->ntfs_ino;
      /* Sanity check, just for debugging really. */
      BUG_ON(!base_ni);
      if (!NInoAttrList(base_ni) || type == AT_ATTRIBUTE_LIST)
            return ntfs_attr_find(type, name, name_len, ic, val, val_len,
                        ctx);
      return ntfs_external_attr_find(type, name, name_len, ic, lowest_vcn,
                  val, val_len, ctx);
}

/**
 * ntfs_attr_init_search_ctx - initialize an attribute search context
 * @ctx:    attribute search context to initialize
 * @ni:           ntfs inode with which to initialize the search context
 * @mrec:   mft record with which to initialize the search context
 *
 * Initialize the attribute search context @ctx with @ni and @mrec.
 */
static inline void ntfs_attr_init_search_ctx(ntfs_attr_search_ctx *ctx,
            ntfs_inode *ni, MFT_RECORD *mrec)
{
      *ctx = (ntfs_attr_search_ctx) {
            .mrec = mrec,
            /* Sanity checks are performed elsewhere. */
            .attr = (ATTR_RECORD*)((u8*)mrec +
                        le16_to_cpu(mrec->attrs_offset)),
            .is_first = true,
            .ntfs_ino = ni,
      };
}

/**
 * ntfs_attr_reinit_search_ctx - reinitialize an attribute search context
 * @ctx:    attribute search context to reinitialize
 *
 * Reinitialize the attribute search context @ctx, unmapping an associated
 * extent mft record if present, and initialize the search context again.
 *
 * This is used when a search for a new attribute is being started to reset
 * the search context to the beginning.
 */
void ntfs_attr_reinit_search_ctx(ntfs_attr_search_ctx *ctx)
{
      if (likely(!ctx->base_ntfs_ino)) {
            /* No attribute list. */
            ctx->is_first = true;
            /* Sanity checks are performed elsewhere. */
            ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
                        le16_to_cpu(ctx->mrec->attrs_offset));
            /*
             * This needs resetting due to ntfs_external_attr_find() which
             * can leave it set despite having zeroed ctx->base_ntfs_ino.
             */
            ctx->al_entry = NULL;
            return;
      } /* Attribute list. */
      if (ctx->ntfs_ino != ctx->base_ntfs_ino)
            unmap_extent_mft_record(ctx->ntfs_ino);
      ntfs_attr_init_search_ctx(ctx, ctx->base_ntfs_ino, ctx->base_mrec);
      return;
}

/**
 * ntfs_attr_get_search_ctx - allocate/initialize a new attribute search context
 * @ni:           ntfs inode with which to initialize the search context
 * @mrec:   mft record with which to initialize the search context
 *
 * Allocate a new attribute search context, initialize it with @ni and @mrec,
 * and return it. Return NULL if allocation failed.
 */
ntfs_attr_search_ctx *ntfs_attr_get_search_ctx(ntfs_inode *ni, MFT_RECORD *mrec)
{
      ntfs_attr_search_ctx *ctx;

      ctx = kmem_cache_alloc(ntfs_attr_ctx_cache, GFP_NOFS);
      if (ctx)
            ntfs_attr_init_search_ctx(ctx, ni, mrec);
      return ctx;
}

/**
 * ntfs_attr_put_search_ctx - release an attribute search context
 * @ctx:    attribute search context to free
 *
 * Release the attribute search context @ctx, unmapping an associated extent
 * mft record if present.
 */
void ntfs_attr_put_search_ctx(ntfs_attr_search_ctx *ctx)
{
      if (ctx->base_ntfs_ino && ctx->ntfs_ino != ctx->base_ntfs_ino)
            unmap_extent_mft_record(ctx->ntfs_ino);
      kmem_cache_free(ntfs_attr_ctx_cache, ctx);
      return;
}

#ifdef NTFS_RW

/**
 * ntfs_attr_find_in_attrdef - find an attribute in the $AttrDef system file
 * @vol:    ntfs volume to which the attribute belongs
 * @type:   attribute type which to find
 *
 * Search for the attribute definition record corresponding to the attribute
 * @type in the $AttrDef system file.
 *
 * Return the attribute type definition record if found and NULL if not found.
 */
static ATTR_DEF *ntfs_attr_find_in_attrdef(const ntfs_volume *vol,
            const ATTR_TYPE type)
{
      ATTR_DEF *ad;

      BUG_ON(!vol->attrdef);
      BUG_ON(!type);
      for (ad = vol->attrdef; (u8*)ad - (u8*)vol->attrdef <
                  vol->attrdef_size && ad->type; ++ad) {
            /* We have not found it yet, carry on searching. */
            if (likely(le32_to_cpu(ad->type) < le32_to_cpu(type)))
                  continue;
            /* We found the attribute; return it. */
            if (likely(ad->type == type))
                  return ad;
            /* We have gone too far already.  No point in continuing. */
            break;
      }
      /* Attribute not found. */
      ntfs_debug("Attribute type 0x%x not found in $AttrDef.",
                  le32_to_cpu(type));
      return NULL;
}

/**
 * ntfs_attr_size_bounds_check - check a size of an attribute type for validity
 * @vol:    ntfs volume to which the attribute belongs
 * @type:   attribute type which to check
 * @size:   size which to check
 *
 * Check whether the @size in bytes is valid for an attribute of @type on the
 * ntfs volume @vol.  This information is obtained from $AttrDef system file.
 *
 * Return 0 if valid, -ERANGE if not valid, or -ENOENT if the attribute is not
 * listed in $AttrDef.
 */
int ntfs_attr_size_bounds_check(const ntfs_volume *vol, const ATTR_TYPE type,
            const s64 size)
{
      ATTR_DEF *ad;

      BUG_ON(size < 0);
      /*
       * $ATTRIBUTE_LIST has a maximum size of 256kiB, but this is not
       * listed in $AttrDef.
       */
      if (unlikely(type == AT_ATTRIBUTE_LIST && size > 256 * 1024))
            return -ERANGE;
      /* Get the $AttrDef entry for the attribute @type. */
      ad = ntfs_attr_find_in_attrdef(vol, type);
      if (unlikely(!ad))
            return -ENOENT;
      /* Do the bounds check. */
      if (((sle64_to_cpu(ad->min_size) > 0) &&
                  size < sle64_to_cpu(ad->min_size)) ||
                  ((sle64_to_cpu(ad->max_size) > 0) && size >
                  sle64_to_cpu(ad->max_size)))
            return -ERANGE;
      return 0;
}

/**
 * ntfs_attr_can_be_non_resident - check if an attribute can be non-resident
 * @vol:    ntfs volume to which the attribute belongs
 * @type:   attribute type which to check
 *
 * Check whether the attribute of @type on the ntfs volume @vol is allowed to
 * be non-resident.  This information is obtained from $AttrDef system file.
 *
 * Return 0 if the attribute is allowed to be non-resident, -EPERM if not, and
 * -ENOENT if the attribute is not listed in $AttrDef.
 */
int ntfs_attr_can_be_non_resident(const ntfs_volume *vol, const ATTR_TYPE type)
{
      ATTR_DEF *ad;

      /* Find the attribute definition record in $AttrDef. */
      ad = ntfs_attr_find_in_attrdef(vol, type);
      if (unlikely(!ad))
            return -ENOENT;
      /* Check the flags and return the result. */
      if (ad->flags & ATTR_DEF_RESIDENT)
            return -EPERM;
      return 0;
}

/**
 * ntfs_attr_can_be_resident - check if an attribute can be resident
 * @vol:    ntfs volume to which the attribute belongs
 * @type:   attribute type which to check
 *
 * Check whether the attribute of @type on the ntfs volume @vol is allowed to
 * be resident.  This information is derived from our ntfs knowledge and may
 * not be completely accurate, especially when user defined attributes are
 * present.  Basically we allow everything to be resident except for index
 * allocation and $EA attributes.
 *
 * Return 0 if the attribute is allowed to be non-resident and -EPERM if not.
 *
 * Warning: In the system file $MFT the attribute $Bitmap must be non-resident
 *        otherwise windows will not boot (blue screen of death)!  We cannot
 *        check for this here as we do not know which inode's $Bitmap is
 *        being asked about so the caller needs to special case this.
 */
int ntfs_attr_can_be_resident(const ntfs_volume *vol, const ATTR_TYPE type)
{
      if (type == AT_INDEX_ALLOCATION)
            return -EPERM;
      return 0;
}

/**
 * ntfs_attr_record_resize - resize an attribute record
 * @m:            mft record containing attribute record
 * @a:            attribute record to resize
 * @new_size:     new size in bytes to which to resize the attribute record @a
 *
 * Resize the attribute record @a, i.e. the resident part of the attribute, in
 * the mft record @m to @new_size bytes.
 *
 * Return 0 on success and -errno on error.  The following error codes are
 * defined:
 *    -ENOSPC     - Not enough space in the mft record @m to perform the resize.
 *
 * Note: On error, no modifications have been performed whatsoever.
 *
 * Warning: If you make a record smaller without having copied all the data you
 *        are interested in the data may be overwritten.
 */
int ntfs_attr_record_resize(MFT_RECORD *m, ATTR_RECORD *a, u32 new_size)
{
      ntfs_debug("Entering for new_size %u.", new_size);
      /* Align to 8 bytes if it is not already done. */
      if (new_size & 7)
            new_size = (new_size + 7) & ~7;
      /* If the actual attribute length has changed, move things around. */
      if (new_size != le32_to_cpu(a->length)) {
            u32 new_muse = le32_to_cpu(m->bytes_in_use) -
                        le32_to_cpu(a->length) + new_size;
            /* Not enough space in this mft record. */
            if (new_muse > le32_to_cpu(m->bytes_allocated))
                  return -ENOSPC;
            /* Move attributes following @a to their new location. */
            memmove((u8*)a + new_size, (u8*)a + le32_to_cpu(a->length),
                        le32_to_cpu(m->bytes_in_use) - ((u8*)a -
                        (u8*)m) - le32_to_cpu(a->length));
            /* Adjust @m to reflect the change in used space. */
            m->bytes_in_use = cpu_to_le32(new_muse);
            /* Adjust @a to reflect the new size. */
            if (new_size >= offsetof(ATTR_REC, length) + sizeof(a->length))
                  a->length = cpu_to_le32(new_size);
      }
      return 0;
}

/**
 * ntfs_resident_attr_value_resize - resize the value of a resident attribute
 * @m:            mft record containing attribute record
 * @a:            attribute record whose value to resize
 * @new_size:     new size in bytes to which to resize the attribute value of @a
 *
 * Resize the value of the attribute @a in the mft record @m to @new_size bytes.
 * If the value is made bigger, the newly allocated space is cleared.
 *
 * Return 0 on success and -errno on error.  The following error codes are
 * defined:
 *    -ENOSPC     - Not enough space in the mft record @m to perform the resize.
 *
 * Note: On error, no modifications have been performed whatsoever.
 *
 * Warning: If you make a record smaller without having copied all the data you
 *        are interested in the data may be overwritten.
 */
int ntfs_resident_attr_value_resize(MFT_RECORD *m, ATTR_RECORD *a,
            const u32 new_size)
{
      u32 old_size;

      /* Resize the resident part of the attribute record. */
      if (ntfs_attr_record_resize(m, a,
                  le16_to_cpu(a->data.resident.value_offset) + new_size))
            return -ENOSPC;
      /*
       * The resize succeeded!  If we made the attribute value bigger, clear
       * the area between the old size and @new_size.
       */
      old_size = le32_to_cpu(a->data.resident.value_length);
      if (new_size > old_size)
            memset((u8*)a + le16_to_cpu(a->data.resident.value_offset) +
                        old_size, 0, new_size - old_size);
      /* Finally update the length of the attribute value. */
      a->data.resident.value_length = cpu_to_le32(new_size);
      return 0;
}

/**
 * ntfs_attr_make_non_resident - convert a resident to a non-resident attribute
 * @ni:           ntfs inode describing the attribute to convert
 * @data_size:    size of the resident data to copy to the non-resident attribute
 *
 * Convert the resident ntfs attribute described by the ntfs inode @ni to a
 * non-resident one.
 *
 * @data_size must be equal to the attribute value size.  This is needed since
 * we need to know the size before we can map the mft record and our callers
 * always know it.  The reason we cannot simply read the size from the vfs
 * inode i_size is that this is not necessarily uptodate.  This happens when
 * ntfs_attr_make_non_resident() is called in the ->truncate call path(s).
 *
 * Return 0 on success and -errno on error.  The following error return codes
 * are defined:
 *    -EPERM      - The attribute is not allowed to be non-resident.
 *    -ENOMEM     - Not enough memory.
 *    -ENOSPC     - Not enough disk space.
 *    -EINVAL     - Attribute not defined on the volume.
 *    -EIO  - I/o error or other error.
 * Note that -ENOSPC is also returned in the case that there is not enough
 * space in the mft record to do the conversion.  This can happen when the mft
 * record is already very full.  The caller is responsible for trying to make
 * space in the mft record and trying again.  FIXME: Do we need a separate
 * error return code for this kind of -ENOSPC or is it always worth trying
 * again in case the attribute may then fit in a resident state so no need to
 * make it non-resident at all?  Ho-hum...  (AIA)
 *
 * NOTE to self: No changes in the attribute list are required to move from
 *           a resident to a non-resident attribute.
 *
 * Locking: - The caller must hold i_mutex on the inode.
 */
int ntfs_attr_make_non_resident(ntfs_inode *ni, const u32 data_size)
{
      s64 new_size;
      struct inode *vi = VFS_I(ni);
      ntfs_volume *vol = ni->vol;
      ntfs_inode *base_ni;
      MFT_RECORD *m;
      ATTR_RECORD *a;
      ntfs_attr_search_ctx *ctx;
      struct page *page;
      runlist_element *rl;
      u8 *kaddr;
      unsigned long flags;
      int mp_size, mp_ofs, name_ofs, arec_size, err, err2;
      u32 attr_size;
      u8 old_res_attr_flags;

      /* Check that the attribute is allowed to be non-resident. */
      err = ntfs_attr_can_be_non_resident(vol, ni->type);
      if (unlikely(err)) {
            if (err == -EPERM)
                  ntfs_debug("Attribute is not allowed to be "
                              "non-resident.");
            else
                  ntfs_debug("Attribute not defined on the NTFS "
                              "volume!");
            return err;
      }
      /*
       * FIXME: Compressed and encrypted attributes are not supported when
       * writing and we should never have gotten here for them.
       */
      BUG_ON(NInoCompressed(ni));
      BUG_ON(NInoEncrypted(ni));
      /*
       * The size needs to be aligned to a cluster boundary for allocation
       * purposes.
       */
      new_size = (data_size + vol->cluster_size - 1) &
                  ~(vol->cluster_size - 1);
      if (new_size > 0) {
            /*
             * Will need the page later and since the page lock nests
             * outside all ntfs locks, we need to get the page now.
             */
            page = find_or_create_page(vi->i_mapping, 0,
                        mapping_gfp_mask(vi->i_mapping));
            if (unlikely(!page))
                  return -ENOMEM;
            /* Start by allocating clusters to hold the attribute value. */
            rl = ntfs_cluster_alloc(vol, 0, new_size >>
                        vol->cluster_size_bits, -1, DATA_ZONE, true);
            if (IS_ERR(rl)) {
                  err = PTR_ERR(rl);
                  ntfs_debug("Failed to allocate cluster%s, error code "
                              "%i.", (new_size >>
                              vol->cluster_size_bits) > 1 ? "s" : "",
                              err);
                  goto page_err_out;
            }
      } else {
            rl = NULL;
            page = NULL;
      }
      /* Determine the size of the mapping pairs array. */
      mp_size = ntfs_get_size_for_mapping_pairs(vol, rl, 0, -1);
      if (unlikely(mp_size < 0)) {
            err = mp_size;
            ntfs_debug("Failed to get size for mapping pairs array, error "
                        "code %i.", err);
            goto rl_err_out;
      }
      down_write(&ni->runlist.lock);
      if (!NInoAttr(ni))
            base_ni = ni;
      else
            base_ni = ni->ext.base_ntfs_ino;
      m = map_mft_record(base_ni);
      if (IS_ERR(m)) {
            err = PTR_ERR(m);
            m = NULL;
            ctx = NULL;
            goto err_out;
      }
      ctx = ntfs_attr_get_search_ctx(base_ni, m);
      if (unlikely(!ctx)) {
            err = -ENOMEM;
            goto err_out;
      }
      err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                  CASE_SENSITIVE, 0, NULL, 0, ctx);
      if (unlikely(err)) {
            if (err == -ENOENT)
                  err = -EIO;
            goto err_out;
      }
      m = ctx->mrec;
      a = ctx->attr;
      BUG_ON(NInoNonResident(ni));
      BUG_ON(a->non_resident);
      /*
       * Calculate new offsets for the name and the mapping pairs array.
       */
      if (NInoSparse(ni) || NInoCompressed(ni))
            name_ofs = (offsetof(ATTR_REC,
                        data.non_resident.compressed_size) +
                        sizeof(a->data.non_resident.compressed_size) +
                        7) & ~7;
      else
            name_ofs = (offsetof(ATTR_REC,
                        data.non_resident.compressed_size) + 7) & ~7;
      mp_ofs = (name_ofs + a->name_length * sizeof(ntfschar) + 7) & ~7;
      /*
       * Determine the size of the resident part of the now non-resident
       * attribute record.
       */
      arec_size = (mp_ofs + mp_size + 7) & ~7;
      /*
       * If the page is not uptodate bring it uptodate by copying from the
       * attribute value.
       */
      attr_size = le32_to_cpu(a->data.resident.value_length);
      BUG_ON(attr_size != data_size);
      if (page && !PageUptodate(page)) {
            kaddr = kmap_atomic(page, KM_USER0);
            memcpy(kaddr, (u8*)a +
                        le16_to_cpu(a->data.resident.value_offset),
                        attr_size);
            memset(kaddr + attr_size, 0, PAGE_CACHE_SIZE - attr_size);
            kunmap_atomic(kaddr, KM_USER0);
            flush_dcache_page(page);
            SetPageUptodate(page);
      }
      /* Backup the attribute flag. */
      old_res_attr_flags = a->data.resident.flags;
      /* Resize the resident part of the attribute record. */
      err = ntfs_attr_record_resize(m, a, arec_size);
      if (unlikely(err))
            goto err_out;
      /*
       * Convert the resident part of the attribute record to describe a
       * non-resident attribute.
       */
      a->non_resident = 1;
      /* Move the attribute name if it exists and update the offset. */
      if (a->name_length)
            memmove((u8*)a + name_ofs, (u8*)a + le16_to_cpu(a->name_offset),
                        a->name_length * sizeof(ntfschar));
      a->name_offset = cpu_to_le16(name_ofs);
      /* Setup the fields specific to non-resident attributes. */
      a->data.non_resident.lowest_vcn = 0;
      a->data.non_resident.highest_vcn = cpu_to_sle64((new_size - 1) >>
                  vol->cluster_size_bits);
      a->data.non_resident.mapping_pairs_offset = cpu_to_le16(mp_ofs);
      memset(&a->data.non_resident.reserved, 0,
                  sizeof(a->data.non_resident.reserved));
      a->data.non_resident.allocated_size = cpu_to_sle64(new_size);
      a->data.non_resident.data_size =
                  a->data.non_resident.initialized_size =
                  cpu_to_sle64(attr_size);
      if (NInoSparse(ni) || NInoCompressed(ni)) {
            a->data.non_resident.compression_unit = 0;
            if (NInoCompressed(ni) || vol->major_ver < 3)
                  a->data.non_resident.compression_unit = 4;
            a->data.non_resident.compressed_size =
                        a->data.non_resident.allocated_size;
      } else
            a->data.non_resident.compression_unit = 0;
      /* Generate the mapping pairs array into the attribute record. */
      err = ntfs_mapping_pairs_build(vol, (u8*)a + mp_ofs,
                  arec_size - mp_ofs, rl, 0, -1, NULL);
      if (unlikely(err)) {
            ntfs_debug("Failed to build mapping pairs, error code %i.",
                        err);
            goto undo_err_out;
      }
      /* Setup the in-memory attribute structure to be non-resident. */
      ni->runlist.rl = rl;
      write_lock_irqsave(&ni->size_lock, flags);
      ni->allocated_size = new_size;
      if (NInoSparse(ni) || NInoCompressed(ni)) {
            ni->itype.compressed.size = ni->allocated_size;
            if (a->data.non_resident.compression_unit) {
                  ni->itype.compressed.block_size = 1U << (a->data.
                              non_resident.compression_unit +
                              vol->cluster_size_bits);
                  ni->itype.compressed.block_size_bits =
                              ffs(ni->itype.compressed.block_size) -
                              1;
                  ni->itype.compressed.block_clusters = 1U <<
                              a->data.non_resident.compression_unit;
            } else {
                  ni->itype.compressed.block_size = 0;
                  ni->itype.compressed.block_size_bits = 0;
                  ni->itype.compressed.block_clusters = 0;
            }
            vi->i_blocks = ni->itype.compressed.size >> 9;
      } else
            vi->i_blocks = ni->allocated_size >> 9;
      write_unlock_irqrestore(&ni->size_lock, flags);
      /*
       * This needs to be last since the address space operations ->readpage
       * and ->writepage can run concurrently with us as they are not
       * serialized on i_mutex.  Note, we are not allowed to fail once we flip
       * this switch, which is another reason to do this last.
       */
      NInoSetNonResident(ni);
      /* Mark the mft record dirty, so it gets written back. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(base_ni);
      up_write(&ni->runlist.lock);
      if (page) {
            set_page_dirty(page);
            unlock_page(page);
            mark_page_accessed(page);
            page_cache_release(page);
      }
      ntfs_debug("Done.");
      return 0;
undo_err_out:
      /* Convert the attribute back into a resident attribute. */
      a->non_resident = 0;
      /* Move the attribute name if it exists and update the offset. */
      name_ofs = (offsetof(ATTR_RECORD, data.resident.reserved) +
                  sizeof(a->data.resident.reserved) + 7) & ~7;
      if (a->name_length)
            memmove((u8*)a + name_ofs, (u8*)a + le16_to_cpu(a->name_offset),
                        a->name_length * sizeof(ntfschar));
      mp_ofs = (name_ofs + a->name_length * sizeof(ntfschar) + 7) & ~7;
      a->name_offset = cpu_to_le16(name_ofs);
      arec_size = (mp_ofs + attr_size + 7) & ~7;
      /* Resize the resident part of the attribute record. */
      err2 = ntfs_attr_record_resize(m, a, arec_size);
      if (unlikely(err2)) {
            /*
             * This cannot happen (well if memory corruption is at work it
             * could happen in theory), but deal with it as well as we can.
             * If the old size is too small, truncate the attribute,
             * otherwise simply give it a larger allocated size.
             * FIXME: Should check whether chkdsk complains when the
             * allocated size is much bigger than the resident value size.
             */
            arec_size = le32_to_cpu(a->length);
            if ((mp_ofs + attr_size) > arec_size) {
                  err2 = attr_size;
                  attr_size = arec_size - mp_ofs;
                  ntfs_error(vol->sb, "Failed to undo partial resident "
                              "to non-resident attribute "
                              "conversion.  Truncating inode 0x%lx, "
                              "attribute type 0x%x from %i bytes to "
                              "%i bytes to maintain metadata "
                              "consistency.  THIS MEANS YOU ARE "
                              "LOSING %i BYTES DATA FROM THIS %s.",
                              vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type),
                              err2, attr_size, err2 - attr_size,
                              ((ni->type == AT_DATA) &&
                              !ni->name_len) ? "FILE": "ATTRIBUTE");
                  write_lock_irqsave(&ni->size_lock, flags);
                  ni->initialized_size = attr_size;
                  i_size_write(vi, attr_size);
                  write_unlock_irqrestore(&ni->size_lock, flags);
            }
      }
      /* Setup the fields specific to resident attributes. */
      a->data.resident.value_length = cpu_to_le32(attr_size);
      a->data.resident.value_offset = cpu_to_le16(mp_ofs);
      a->data.resident.flags = old_res_attr_flags;
      memset(&a->data.resident.reserved, 0,
                  sizeof(a->data.resident.reserved));
      /* Copy the data from the page back to the attribute value. */
      if (page) {
            kaddr = kmap_atomic(page, KM_USER0);
            memcpy((u8*)a + mp_ofs, kaddr, attr_size);
            kunmap_atomic(kaddr, KM_USER0);
      }
      /* Setup the allocated size in the ntfs inode in case it changed. */
      write_lock_irqsave(&ni->size_lock, flags);
      ni->allocated_size = arec_size - mp_ofs;
      write_unlock_irqrestore(&ni->size_lock, flags);
      /* Mark the mft record dirty, so it gets written back. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
err_out:
      if (ctx)
            ntfs_attr_put_search_ctx(ctx);
      if (m)
            unmap_mft_record(base_ni);
      ni->runlist.rl = NULL;
      up_write(&ni->runlist.lock);
rl_err_out:
      if (rl) {
            if (ntfs_cluster_free_from_rl(vol, rl) < 0) {
                  ntfs_error(vol->sb, "Failed to release allocated "
                              "cluster(s) in error code path.  Run "
                              "chkdsk to recover the lost "
                              "cluster(s).");
                  NVolSetErrors(vol);
            }
            ntfs_free(rl);
page_err_out:
            unlock_page(page);
            page_cache_release(page);
      }
      if (err == -EINVAL)
            err = -EIO;
      return err;
}

/**
 * ntfs_attr_extend_allocation - extend the allocated space of an attribute
 * @ni:                 ntfs inode of the attribute whose allocation to extend
 * @new_alloc_size:     new size in bytes to which to extend the allocation to
 * @new_data_size:      new size in bytes to which to extend the data to
 * @data_start:         beginning of region which is required to be non-sparse
 *
 * Extend the allocated space of an attribute described by the ntfs inode @ni
 * to @new_alloc_size bytes.  If @data_start is -1, the whole extension may be
 * implemented as a hole in the file (as long as both the volume and the ntfs
 * inode @ni have sparse support enabled).  If @data_start is >= 0, then the
 * region between the old allocated size and @data_start - 1 may be made sparse
 * but the regions between @data_start and @new_alloc_size must be backed by
 * actual clusters.
 *
 * If @new_data_size is -1, it is ignored.  If it is >= 0, then the data size
 * of the attribute is extended to @new_data_size.  Note that the i_size of the
 * vfs inode is not updated.  Only the data size in the base attribute record
 * is updated.  The caller has to update i_size separately if this is required.
 * WARNING: It is a BUG() for @new_data_size to be smaller than the old data
 * size as well as for @new_data_size to be greater than @new_alloc_size.
 *
 * For resident attributes this involves resizing the attribute record and if
 * necessary moving it and/or other attributes into extent mft records and/or
 * converting the attribute to a non-resident attribute which in turn involves
 * extending the allocation of a non-resident attribute as described below.
 *
 * For non-resident attributes this involves allocating clusters in the data
 * zone on the volume (except for regions that are being made sparse) and
 * extending the run list to describe the allocated clusters as well as
 * updating the mapping pairs array of the attribute.  This in turn involves
 * resizing the attribute record and if necessary moving it and/or other
 * attributes into extent mft records and/or splitting the attribute record
 * into multiple extent attribute records.
 *
 * Also, the attribute list attribute is updated if present and in some of the
 * above cases (the ones where extent mft records/attributes come into play),
 * an attribute list attribute is created if not already present.
 *
 * Return the new allocated size on success and -errno on error.  In the case
 * that an error is encountered but a partial extension at least up to
 * @data_start (if present) is possible, the allocation is partially extended
 * and this is returned.  This means the caller must check the returned size to
 * determine if the extension was partial.  If @data_start is -1 then partial
 * allocations are not performed.
 *
 * WARNING: Do not call ntfs_attr_extend_allocation() for $MFT/$DATA.
 *
 * Locking: This function takes the runlist lock of @ni for writing as well as
 * locking the mft record of the base ntfs inode.  These locks are maintained
 * throughout execution of the function.  These locks are required so that the
 * attribute can be resized safely and so that it can for example be converted
 * from resident to non-resident safely.
 *
 * TODO: At present attribute list attribute handling is not implemented.
 *
 * TODO: At present it is not safe to call this function for anything other
 * than the $DATA attribute(s) of an uncompressed and unencrypted file.
 */
s64 ntfs_attr_extend_allocation(ntfs_inode *ni, s64 new_alloc_size,
            const s64 new_data_size, const s64 data_start)
{
      VCN vcn;
      s64 ll, allocated_size, start = data_start;
      struct inode *vi = VFS_I(ni);
      ntfs_volume *vol = ni->vol;
      ntfs_inode *base_ni;
      MFT_RECORD *m;
      ATTR_RECORD *a;
      ntfs_attr_search_ctx *ctx;
      runlist_element *rl, *rl2;
      unsigned long flags;
      int err, mp_size;
      u32 attr_len = 0; /* Silence stupid gcc warning. */
      bool mp_rebuilt;

#ifdef DEBUG
      read_lock_irqsave(&ni->size_lock, flags);
      allocated_size = ni->allocated_size;
      read_unlock_irqrestore(&ni->size_lock, flags);
      ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
                  "old_allocated_size 0x%llx, "
                  "new_allocated_size 0x%llx, new_data_size 0x%llx, "
                  "data_start 0x%llx.", vi->i_ino,
                  (unsigned)le32_to_cpu(ni->type),
                  (unsigned long long)allocated_size,
                  (unsigned long long)new_alloc_size,
                  (unsigned long long)new_data_size,
                  (unsigned long long)start);
#endif
retry_extend:
      /*
       * For non-resident attributes, @start and @new_size need to be aligned
       * to cluster boundaries for allocation purposes.
       */
      if (NInoNonResident(ni)) {
            if (start > 0)
                  start &= ~(s64)vol->cluster_size_mask;
            new_alloc_size = (new_alloc_size + vol->cluster_size - 1) &
                        ~(s64)vol->cluster_size_mask;
      }
      BUG_ON(new_data_size >= 0 && new_data_size > new_alloc_size);
      /* Check if new size is allowed in $AttrDef. */
      err = ntfs_attr_size_bounds_check(vol, ni->type, new_alloc_size);
      if (unlikely(err)) {
            /* Only emit errors when the write will fail completely. */
            read_lock_irqsave(&ni->size_lock, flags);
            allocated_size = ni->allocated_size;
            read_unlock_irqrestore(&ni->size_lock, flags);
            if (start < 0 || start >= allocated_size) {
                  if (err == -ERANGE) {
                        ntfs_error(vol->sb, "Cannot extend allocation "
                                    "of inode 0x%lx, attribute "
                                    "type 0x%x, because the new "
                                    "allocation would exceed the "
                                    "maximum allowed size for "
                                    "this attribute type.",
                                    vi->i_ino, (unsigned)
                                    le32_to_cpu(ni->type));
                  } else {
                        ntfs_error(vol->sb, "Cannot extend allocation "
                                    "of inode 0x%lx, attribute "
                                    "type 0x%x, because this "
                                    "attribute type is not "
                                    "defined on the NTFS volume.  "
                                    "Possible corruption!  You "
                                    "should run chkdsk!",
                                    vi->i_ino, (unsigned)
                                    le32_to_cpu(ni->type));
                  }
            }
            /* Translate error code to be POSIX conformant for write(2). */
            if (err == -ERANGE)
                  err = -EFBIG;
            else
                  err = -EIO;
            return err;
      }
      if (!NInoAttr(ni))
            base_ni = ni;
      else
            base_ni = ni->ext.base_ntfs_ino;
      /*
       * We will be modifying both the runlist (if non-resident) and the mft
       * record so lock them both down.
       */
      down_write(&ni->runlist.lock);
      m = map_mft_record(base_ni);
      if (IS_ERR(m)) {
            err = PTR_ERR(m);
            m = NULL;
            ctx = NULL;
            goto err_out;
      }
      ctx = ntfs_attr_get_search_ctx(base_ni, m);
      if (unlikely(!ctx)) {
            err = -ENOMEM;
            goto err_out;
      }
      read_lock_irqsave(&ni->size_lock, flags);
      allocated_size = ni->allocated_size;
      read_unlock_irqrestore(&ni->size_lock, flags);
      /*
       * If non-resident, seek to the last extent.  If resident, there is
       * only one extent, so seek to that.
       */
      vcn = NInoNonResident(ni) ? allocated_size >> vol->cluster_size_bits :
                  0;
      /*
       * Abort if someone did the work whilst we waited for the locks.  If we
       * just converted the attribute from resident to non-resident it is
       * likely that exactly this has happened already.  We cannot quite
       * abort if we need to update the data size.
       */
      if (unlikely(new_alloc_size <= allocated_size)) {
            ntfs_debug("Allocated size already exceeds requested size.");
            new_alloc_size = allocated_size;
            if (new_data_size < 0)
                  goto done;
            /*
             * We want the first attribute extent so that we can update the
             * data size.
             */
            vcn = 0;
      }
      err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                  CASE_SENSITIVE, vcn, NULL, 0, ctx);
      if (unlikely(err)) {
            if (err == -ENOENT)
                  err = -EIO;
            goto err_out;
      }
      m = ctx->mrec;
      a = ctx->attr;
      /* Use goto to reduce indentation. */
      if (a->non_resident)
            goto do_non_resident_extend;
      BUG_ON(NInoNonResident(ni));
      /* The total length of the attribute value. */
      attr_len = le32_to_cpu(a->data.resident.value_length);
      /*
       * Extend the attribute record to be able to store the new attribute
       * size.  ntfs_attr_record_resize() will not do anything if the size is
       * not changing.
       */
      if (new_alloc_size < vol->mft_record_size &&
                  !ntfs_attr_record_resize(m, a,
                  le16_to_cpu(a->data.resident.value_offset) +
                  new_alloc_size)) {
            /* The resize succeeded! */
            write_lock_irqsave(&ni->size_lock, flags);
            ni->allocated_size = le32_to_cpu(a->length) -
                        le16_to_cpu(a->data.resident.value_offset);
            write_unlock_irqrestore(&ni->size_lock, flags);
            if (new_data_size >= 0) {
                  BUG_ON(new_data_size < attr_len);
                  a->data.resident.value_length =
                              cpu_to_le32((u32)new_data_size);
            }
            goto flush_done;
      }
      /*
       * We have to drop all the locks so we can call
       * ntfs_attr_make_non_resident().  This could be optimised by try-
       * locking the first page cache page and only if that fails dropping
       * the locks, locking the page, and redoing all the locking and
       * lookups.  While this would be a huge optimisation, it is not worth
       * it as this is definitely a slow code path.
       */
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(base_ni);
      up_write(&ni->runlist.lock);
      /*
       * Not enough space in the mft record, try to make the attribute
       * non-resident and if successful restart the extension process.
       */
      err = ntfs_attr_make_non_resident(ni, attr_len);
      if (likely(!err))
            goto retry_extend;
      /*
       * Could not make non-resident.  If this is due to this not being
       * permitted for this attribute type or there not being enough space,
       * try to make other attributes non-resident.  Otherwise fail.
       */
      if (unlikely(err != -EPERM && err != -ENOSPC)) {
            /* Only emit errors when the write will fail completely. */
            read_lock_irqsave(&ni->size_lock, flags);
            allocated_size = ni->allocated_size;
            read_unlock_irqrestore(&ni->size_lock, flags);
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Cannot extend allocation of "
                              "inode 0x%lx, attribute type 0x%x, "
                              "because the conversion from resident "
                              "to non-resident attribute failed "
                              "with error code %i.", vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type), err);
            if (err != -ENOMEM)
                  err = -EIO;
            goto conv_err_out;
      }
      /* TODO: Not implemented from here, abort. */
      read_lock_irqsave(&ni->size_lock, flags);
      allocated_size = ni->allocated_size;
      read_unlock_irqrestore(&ni->size_lock, flags);
      if (start < 0 || start >= allocated_size) {
            if (err == -ENOSPC)
                  ntfs_error(vol->sb, "Not enough space in the mft "
                              "record/on disk for the non-resident "
                              "attribute value.  This case is not "
                              "implemented yet.");
            else /* if (err == -EPERM) */
                  ntfs_error(vol->sb, "This attribute type may not be "
                              "non-resident.  This case is not "
                              "implemented yet.");
      }
      err = -EOPNOTSUPP;
      goto conv_err_out;
#if 0
      // TODO: Attempt to make other attributes non-resident.
      if (!err)
            goto do_resident_extend;
      /*
       * Both the attribute list attribute and the standard information
       * attribute must remain in the base inode.  Thus, if this is one of
       * these attributes, we have to try to move other attributes out into
       * extent mft records instead.
       */
      if (ni->type == AT_ATTRIBUTE_LIST ||
                  ni->type == AT_STANDARD_INFORMATION) {
            // TODO: Attempt to move other attributes into extent mft
            // records.
            err = -EOPNOTSUPP;
            if (!err)
                  goto do_resident_extend;
            goto err_out;
      }
      // TODO: Attempt to move this attribute to an extent mft record, but
      // only if it is not already the only attribute in an mft record in
      // which case there would be nothing to gain.
      err = -EOPNOTSUPP;
      if (!err)
            goto do_resident_extend;
      /* There is nothing we can do to make enough space. )-: */
      goto err_out;
#endif
do_non_resident_extend:
      BUG_ON(!NInoNonResident(ni));
      if (new_alloc_size == allocated_size) {
            BUG_ON(vcn);
            goto alloc_done;
      }
      /*
       * If the data starts after the end of the old allocation, this is a
       * $DATA attribute and sparse attributes are enabled on the volume and
       * for this inode, then create a sparse region between the old
       * allocated size and the start of the data.  Otherwise simply proceed
       * with filling the whole space between the old allocated size and the
       * new allocated size with clusters.
       */
      if ((start >= 0 && start <= allocated_size) || ni->type != AT_DATA ||
                  !NVolSparseEnabled(vol) || NInoSparseDisabled(ni))
            goto skip_sparse;
      // TODO: This is not implemented yet.  We just fill in with real
      // clusters for now...
      ntfs_debug("Inserting holes is not-implemented yet.  Falling back to "
                  "allocating real clusters instead.");
skip_sparse:
      rl = ni->runlist.rl;
      if (likely(rl)) {
            /* Seek to the end of the runlist. */
            while (rl->length)
                  rl++;
      }
      /* If this attribute extent is not mapped, map it now. */
      if (unlikely(!rl || rl->lcn == LCN_RL_NOT_MAPPED ||
                  (rl->lcn == LCN_ENOENT && rl > ni->runlist.rl &&
                  (rl-1)->lcn == LCN_RL_NOT_MAPPED))) {
            if (!rl && !allocated_size)
                  goto first_alloc;
            rl = ntfs_mapping_pairs_decompress(vol, a, ni->runlist.rl);
            if (IS_ERR(rl)) {
                  err = PTR_ERR(rl);
                  if (start < 0 || start >= allocated_size)
                        ntfs_error(vol->sb, "Cannot extend allocation "
                                    "of inode 0x%lx, attribute "
                                    "type 0x%x, because the "
                                    "mapping of a runlist "
                                    "fragment failed with error "
                                    "code %i.", vi->i_ino,
                                    (unsigned)le32_to_cpu(ni->type),
                                    err);
                  if (err != -ENOMEM)
                        err = -EIO;
                  goto err_out;
            }
            ni->runlist.rl = rl;
            /* Seek to the end of the runlist. */
            while (rl->length)
                  rl++;
      }
      /*
       * We now know the runlist of the last extent is mapped and @rl is at
       * the end of the runlist.  We want to begin allocating clusters
       * starting at the last allocated cluster to reduce fragmentation.  If
       * there are no valid LCNs in the attribute we let the cluster
       * allocator choose the starting cluster.
       */
      /* If the last LCN is a hole or simillar seek back to last real LCN. */
      while (rl->lcn < 0 && rl > ni->runlist.rl)
            rl--;
first_alloc:
      // FIXME: Need to implement partial allocations so at least part of the
      // write can be performed when start >= 0.  (Needed for POSIX write(2)
      // conformance.)
      rl2 = ntfs_cluster_alloc(vol, allocated_size >> vol->cluster_size_bits,
                  (new_alloc_size - allocated_size) >>
                  vol->cluster_size_bits, (rl && (rl->lcn >= 0)) ?
                  rl->lcn + rl->length : -1, DATA_ZONE, true);
      if (IS_ERR(rl2)) {
            err = PTR_ERR(rl2);
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Cannot extend allocation of "
                              "inode 0x%lx, attribute type 0x%x, "
                              "because the allocation of clusters "
                              "failed with error code %i.", vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type), err);
            if (err != -ENOMEM && err != -ENOSPC)
                  err = -EIO;
            goto err_out;
      }
      rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
      if (IS_ERR(rl)) {
            err = PTR_ERR(rl);
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Cannot extend allocation of "
                              "inode 0x%lx, attribute type 0x%x, "
                              "because the runlist merge failed "
                              "with error code %i.", vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type), err);
            if (err != -ENOMEM)
                  err = -EIO;
            if (ntfs_cluster_free_from_rl(vol, rl2)) {
                  ntfs_error(vol->sb, "Failed to release allocated "
                              "cluster(s) in error code path.  Run "
                              "chkdsk to recover the lost "
                              "cluster(s).");
                  NVolSetErrors(vol);
            }
            ntfs_free(rl2);
            goto err_out;
      }
      ni->runlist.rl = rl;
      ntfs_debug("Allocated 0x%llx clusters.", (long long)(new_alloc_size -
                  allocated_size) >> vol->cluster_size_bits);
      /* Find the runlist element with which the attribute extent starts. */
      ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
      rl2 = ntfs_rl_find_vcn_nolock(rl, ll);
      BUG_ON(!rl2);
      BUG_ON(!rl2->length);
      BUG_ON(rl2->lcn < LCN_HOLE);
      mp_rebuilt = false;
      /* Get the size for the new mapping pairs array for this extent. */
      mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, ll, -1);
      if (unlikely(mp_size <= 0)) {
            err = mp_size;
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Cannot extend allocation of "
                              "inode 0x%lx, attribute type 0x%x, "
                              "because determining the size for the "
                              "mapping pairs failed with error code "
                              "%i.", vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type), err);
            err = -EIO;
            goto undo_alloc;
      }
      /* Extend the attribute record to fit the bigger mapping pairs array. */
      attr_len = le32_to_cpu(a->length);
      err = ntfs_attr_record_resize(m, a, mp_size +
                  le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
      if (unlikely(err)) {
            BUG_ON(err != -ENOSPC);
            // TODO: Deal with this by moving this extent to a new mft
            // record or by starting a new extent in a new mft record,
            // possibly by extending this extent partially and filling it
            // and creating a new extent for the remainder, or by making
            // other attributes non-resident and/or by moving other
            // attributes out of this mft record.
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Not enough space in the mft "
                              "record for the extended attribute "
                              "record.  This case is not "
                              "implemented yet.");
            err = -EOPNOTSUPP;
            goto undo_alloc;
      }
      mp_rebuilt = true;
      /* Generate the mapping pairs array directly into the attr record. */
      err = ntfs_mapping_pairs_build(vol, (u8*)a +
                  le16_to_cpu(a->data.non_resident.mapping_pairs_offset),
                  mp_size, rl2, ll, -1, NULL);
      if (unlikely(err)) {
            if (start < 0 || start >= allocated_size)
                  ntfs_error(vol->sb, "Cannot extend allocation of "
                              "inode 0x%lx, attribute type 0x%x, "
                              "because building the mapping pairs "
                              "failed with error code %i.", vi->i_ino,
                              (unsigned)le32_to_cpu(ni->type), err);
            err = -EIO;
            goto undo_alloc;
      }
      /* Update the highest_vcn. */
      a->data.non_resident.highest_vcn = cpu_to_sle64((new_alloc_size >>
                  vol->cluster_size_bits) - 1);
      /*
       * We now have extended the allocated size of the attribute.  Reflect
       * this in the ntfs_inode structure and the attribute record.
       */
      if (a->data.non_resident.lowest_vcn) {
            /*
             * We are not in the first attribute extent, switch to it, but
             * first ensure the changes will make it to disk later.
             */
            flush_dcache_mft_record_page(ctx->ntfs_ino);
            mark_mft_record_dirty(ctx->ntfs_ino);
            ntfs_attr_reinit_search_ctx(ctx);
            err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                        CASE_SENSITIVE, 0, NULL, 0, ctx);
            if (unlikely(err))
                  goto restore_undo_alloc;
            /* @m is not used any more so no need to set it. */
            a = ctx->attr;
      }
      write_lock_irqsave(&ni->size_lock, flags);
      ni->allocated_size = new_alloc_size;
      a->data.non_resident.allocated_size = cpu_to_sle64(new_alloc_size);
      /*
       * FIXME: This would fail if @ni is a directory, $MFT, or an index,
       * since those can have sparse/compressed set.  For example can be
       * set compressed even though it is not compressed itself and in that
       * case the bit means that files are to be created compressed in the
       * directory...  At present this is ok as this code is only called for
       * regular files, and only for their $DATA attribute(s).
       * FIXME: The calculation is wrong if we created a hole above.  For now
       * it does not matter as we never create holes.
       */
      if (NInoSparse(ni) || NInoCompressed(ni)) {
            ni->itype.compressed.size += new_alloc_size - allocated_size;
            a->data.non_resident.compressed_size =
                        cpu_to_sle64(ni->itype.compressed.size);
            vi->i_blocks = ni->itype.compressed.size >> 9;
      } else
            vi->i_blocks = new_alloc_size >> 9;
      write_unlock_irqrestore(&ni->size_lock, flags);
alloc_done:
      if (new_data_size >= 0) {
            BUG_ON(new_data_size <
                        sle64_to_cpu(a->data.non_resident.data_size));
            a->data.non_resident.data_size = cpu_to_sle64(new_data_size);
      }
flush_done:
      /* Ensure the changes make it to disk. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
done:
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(base_ni);
      up_write(&ni->runlist.lock);
      ntfs_debug("Done, new_allocated_size 0x%llx.",
                  (unsigned long long)new_alloc_size);
      return new_alloc_size;
restore_undo_alloc:
      if (start < 0 || start >= allocated_size)
            ntfs_error(vol->sb, "Cannot complete extension of allocation "
                        "of inode 0x%lx, attribute type 0x%x, because "
                        "lookup of first attribute extent failed with "
                        "error code %i.", vi->i_ino,
                        (unsigned)le32_to_cpu(ni->type), err);
      if (err == -ENOENT)
            err = -EIO;
      ntfs_attr_reinit_search_ctx(ctx);
      if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len, CASE_SENSITIVE,
                  allocated_size >> vol->cluster_size_bits, NULL, 0,
                  ctx)) {
            ntfs_error(vol->sb, "Failed to find last attribute extent of "
                        "attribute in error code path.  Run chkdsk to "
                        "recover.");
            write_lock_irqsave(&ni->size_lock, flags);
            ni->allocated_size = new_alloc_size;
            /*
             * FIXME: This would fail if @ni is a directory...  See above.
             * FIXME: The calculation is wrong if we created a hole above.
             * For now it does not matter as we never create holes.
             */
            if (NInoSparse(ni) || NInoCompressed(ni)) {
                  ni->itype.compressed.size += new_alloc_size -
                              allocated_size;
                  vi->i_blocks = ni->itype.compressed.size >> 9;
            } else
                  vi->i_blocks = new_alloc_size >> 9;
            write_unlock_irqrestore(&ni->size_lock, flags);
            ntfs_attr_put_search_ctx(ctx);
            unmap_mft_record(base_ni);
            up_write(&ni->runlist.lock);
            /*
             * The only thing that is now wrong is the allocated size of the
             * base attribute extent which chkdsk should be able to fix.
             */
            NVolSetErrors(vol);
            return err;
      }
      ctx->attr->data.non_resident.highest_vcn = cpu_to_sle64(
                  (allocated_size >> vol->cluster_size_bits) - 1);
undo_alloc:
      ll = allocated_size >> vol->cluster_size_bits;
      if (ntfs_cluster_free(ni, ll, -1, ctx) < 0) {
            ntfs_error(vol->sb, "Failed to release allocated cluster(s) "
                        "in error code path.  Run chkdsk to recover "
                        "the lost cluster(s).");
            NVolSetErrors(vol);
      }
      m = ctx->mrec;
      a = ctx->attr;
      /*
       * If the runlist truncation fails and/or the search context is no
       * longer valid, we cannot resize the attribute record or build the
       * mapping pairs array thus we mark the inode bad so that no access to
       * the freed clusters can happen.
       */
      if (ntfs_rl_truncate_nolock(vol, &ni->runlist, ll) || IS_ERR(m)) {
            ntfs_error(vol->sb, "Failed to %s in error code path.  Run "
                        "chkdsk to recover.", IS_ERR(m) ?
                        "restore attribute search context" :
                        "truncate attribute runlist");
            NVolSetErrors(vol);
      } else if (mp_rebuilt) {
            if (ntfs_attr_record_resize(m, a, attr_len)) {
                  ntfs_error(vol->sb, "Failed to restore attribute "
                              "record in error code path.  Run "
                              "chkdsk to recover.");
                  NVolSetErrors(vol);
            } else /* if (success) */ {
                  if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                              a->data.non_resident.
                              mapping_pairs_offset), attr_len -
                              le16_to_cpu(a->data.non_resident.
                              mapping_pairs_offset), rl2, ll, -1,
                              NULL)) {
                        ntfs_error(vol->sb, "Failed to restore "
                                    "mapping pairs array in error "
                                    "code path.  Run chkdsk to "
                                    "recover.");
                        NVolSetErrors(vol);
                  }
                  flush_dcache_mft_record_page(ctx->ntfs_ino);
                  mark_mft_record_dirty(ctx->ntfs_ino);
            }
      }
err_out:
      if (ctx)
            ntfs_attr_put_search_ctx(ctx);
      if (m)
            unmap_mft_record(base_ni);
      up_write(&ni->runlist.lock);
conv_err_out:
      ntfs_debug("Failed.  Returning error code %i.", err);
      return err;
}

/**
 * ntfs_attr_set - fill (a part of) an attribute with a byte
 * @ni:           ntfs inode describing the attribute to fill
 * @ofs:    offset inside the attribute at which to start to fill
 * @cnt:    number of bytes to fill
 * @val:    the unsigned 8-bit value with which to fill the attribute
 *
 * Fill @cnt bytes of the attribute described by the ntfs inode @ni starting at
 * byte offset @ofs inside the attribute with the constant byte @val.
 *
 * This function is effectively like memset() applied to an ntfs attribute.
 * Note thie function actually only operates on the page cache pages belonging
 * to the ntfs attribute and it marks them dirty after doing the memset().
 * Thus it relies on the vm dirty page write code paths to cause the modified
 * pages to be written to the mft record/disk.
 *
 * Return 0 on success and -errno on error.  An error code of -ESPIPE means
 * that @ofs + @cnt were outside the end of the attribute and no write was
 * performed.
 */
int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
{
      ntfs_volume *vol = ni->vol;
      struct address_space *mapping;
      struct page *page;
      u8 *kaddr;
      pgoff_t idx, end;
      unsigned start_ofs, end_ofs, size;

      ntfs_debug("Entering for ofs 0x%llx, cnt 0x%llx, val 0x%hx.",
                  (long long)ofs, (long long)cnt, val);
      BUG_ON(ofs < 0);
      BUG_ON(cnt < 0);
      if (!cnt)
            goto done;
      /*
       * FIXME: Compressed and encrypted attributes are not supported when
       * writing and we should never have gotten here for them.
       */
      BUG_ON(NInoCompressed(ni));
      BUG_ON(NInoEncrypted(ni));
      mapping = VFS_I(ni)->i_mapping;
      /* Work out the starting index and page offset. */
      idx = ofs >> PAGE_CACHE_SHIFT;
      start_ofs = ofs & ~PAGE_CACHE_MASK;
      /* Work out the ending index and page offset. */
      end = ofs + cnt;
      end_ofs = end & ~PAGE_CACHE_MASK;
      /* If the end is outside the inode size return -ESPIPE. */
      if (unlikely(end > i_size_read(VFS_I(ni)))) {
            ntfs_error(vol->sb, "Request exceeds end of attribute.");
            return -ESPIPE;
      }
      end >>= PAGE_CACHE_SHIFT;
      /* If there is a first partial page, need to do it the slow way. */
      if (start_ofs) {
            page = read_mapping_page(mapping, idx, NULL);
            if (IS_ERR(page)) {
                  ntfs_error(vol->sb, "Failed to read first partial "
                              "page (error, index 0x%lx).", idx);
                  return PTR_ERR(page);
            }
            /*
             * If the last page is the same as the first page, need to
             * limit the write to the end offset.
             */
            size = PAGE_CACHE_SIZE;
            if (idx == end)
                  size = end_ofs;
            kaddr = kmap_atomic(page, KM_USER0);
            memset(kaddr + start_ofs, val, size - start_ofs);
            flush_dcache_page(page);
            kunmap_atomic(kaddr, KM_USER0);
            set_page_dirty(page);
            page_cache_release(page);
            balance_dirty_pages_ratelimited(mapping);
            cond_resched();
            if (idx == end)
                  goto done;
            idx++;
      }
      /* Do the whole pages the fast way. */
      for (; idx < end; idx++) {
            /* Find or create the current page.  (The page is locked.) */
            page = grab_cache_page(mapping, idx);
            if (unlikely(!page)) {
                  ntfs_error(vol->sb, "Insufficient memory to grab "
                              "page (index 0x%lx).", idx);
                  return -ENOMEM;
            }
            kaddr = kmap_atomic(page, KM_USER0);
            memset(kaddr, val, PAGE_CACHE_SIZE);
            flush_dcache_page(page);
            kunmap_atomic(kaddr, KM_USER0);
            /*
             * If the page has buffers, mark them uptodate since buffer
             * state and not page state is definitive in 2.6 kernels.
             */
            if (page_has_buffers(page)) {
                  struct buffer_head *bh, *head;

                  bh = head = page_buffers(page);
                  do {
                        set_buffer_uptodate(bh);
                  } while ((bh = bh->b_this_page) != head);
            }
            /* Now that buffers are uptodate, set the page uptodate, too. */
            SetPageUptodate(page);
            /*
             * Set the page and all its buffers dirty and mark the inode
             * dirty, too.  The VM will write the page later on.
             */
            set_page_dirty(page);
            /* Finally unlock and release the page. */
            unlock_page(page);
            page_cache_release(page);
            balance_dirty_pages_ratelimited(mapping);
            cond_resched();
      }
      /* If there is a last partial page, need to do it the slow way. */
      if (end_ofs) {
            page = read_mapping_page(mapping, idx, NULL);
            if (IS_ERR(page)) {
                  ntfs_error(vol->sb, "Failed to read last partial page "
                              "(error, index 0x%lx).", idx);
                  return PTR_ERR(page);
            }
            kaddr = kmap_atomic(page, KM_USER0);
            memset(kaddr, val, end_ofs);
            flush_dcache_page(page);
            kunmap_atomic(kaddr, KM_USER0);
            set_page_dirty(page);
            page_cache_release(page);
            balance_dirty_pages_ratelimited(mapping);
            cond_resched();
      }
done:
      ntfs_debug("Done.");
      return 0;
}

#endif /* NTFS_RW */

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