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mft.c

/**
 * mft.c - NTFS kernel mft record operations. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2006 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/swap.h>

#include "attrib.h"
#include "aops.h"
#include "bitmap.h"
#include "debug.h"
#include "dir.h"
#include "lcnalloc.h"
#include "malloc.h"
#include "mft.h"
#include "ntfs.h"

/**
 * map_mft_record_page - map the page in which a specific mft record resides
 * @ni:           ntfs inode whose mft record page to map
 *
 * This maps the page in which the mft record of the ntfs inode @ni is situated
 * and returns a pointer to the mft record within the mapped page.
 *
 * Return value needs to be checked with IS_ERR() and if that is true PTR_ERR()
 * contains the negative error code returned.
 */
static inline MFT_RECORD *map_mft_record_page(ntfs_inode *ni)
{
      loff_t i_size;
      ntfs_volume *vol = ni->vol;
      struct inode *mft_vi = vol->mft_ino;
      struct page *page;
      unsigned long index, end_index;
      unsigned ofs;

      BUG_ON(ni->page);
      /*
       * The index into the page cache and the offset within the page cache
       * page of the wanted mft record. FIXME: We need to check for
       * overflowing the unsigned long, but I don't think we would ever get
       * here if the volume was that big...
       */
      index = (u64)ni->mft_no << vol->mft_record_size_bits >>
                  PAGE_CACHE_SHIFT;
      ofs = (ni->mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;

      i_size = i_size_read(mft_vi);
      /* The maximum valid index into the page cache for $MFT's data. */
      end_index = i_size >> PAGE_CACHE_SHIFT;

      /* If the wanted index is out of bounds the mft record doesn't exist. */
      if (unlikely(index >= end_index)) {
            if (index > end_index || (i_size & ~PAGE_CACHE_MASK) < ofs +
                        vol->mft_record_size) {
                  page = ERR_PTR(-ENOENT);
                  ntfs_error(vol->sb, "Attemt to read mft record 0x%lx, "
                              "which is beyond the end of the mft.  "
                              "This is probably a bug in the ntfs "
                              "driver.", ni->mft_no);
                  goto err_out;
            }
      }
      /* Read, map, and pin the page. */
      page = ntfs_map_page(mft_vi->i_mapping, index);
      if (likely(!IS_ERR(page))) {
            /* Catch multi sector transfer fixup errors. */
            if (likely(ntfs_is_mft_recordp((le32*)(page_address(page) +
                        ofs)))) {
                  ni->page = page;
                  ni->page_ofs = ofs;
                  return page_address(page) + ofs;
            }
            ntfs_error(vol->sb, "Mft record 0x%lx is corrupt.  "
                        "Run chkdsk.", ni->mft_no);
            ntfs_unmap_page(page);
            page = ERR_PTR(-EIO);
            NVolSetErrors(vol);
      }
err_out:
      ni->page = NULL;
      ni->page_ofs = 0;
      return (void*)page;
}

/**
 * map_mft_record - map, pin and lock an mft record
 * @ni:           ntfs inode whose MFT record to map
 *
 * First, take the mrec_lock mutex.  We might now be sleeping, while waiting
 * for the mutex if it was already locked by someone else.
 *
 * The page of the record is mapped using map_mft_record_page() before being
 * returned to the caller.
 *
 * This in turn uses ntfs_map_page() to get the page containing the wanted mft
 * record (it in turn calls read_cache_page() which reads it in from disk if
 * necessary, increments the use count on the page so that it cannot disappear
 * under us and returns a reference to the page cache page).
 *
 * If read_cache_page() invokes ntfs_readpage() to load the page from disk, it
 * sets PG_locked and clears PG_uptodate on the page. Once I/O has completed
 * and the post-read mst fixups on each mft record in the page have been
 * performed, the page gets PG_uptodate set and PG_locked cleared (this is done
 * in our asynchronous I/O completion handler end_buffer_read_mft_async()).
 * ntfs_map_page() waits for PG_locked to become clear and checks if
 * PG_uptodate is set and returns an error code if not. This provides
 * sufficient protection against races when reading/using the page.
 *
 * However there is the write mapping to think about. Doing the above described
 * checking here will be fine, because when initiating the write we will set
 * PG_locked and clear PG_uptodate making sure nobody is touching the page
 * contents. Doing the locking this way means that the commit to disk code in
 * the page cache code paths is automatically sufficiently locked with us as
 * we will not touch a page that has been locked or is not uptodate. The only
 * locking problem then is them locking the page while we are accessing it.
 *
 * So that code will end up having to own the mrec_lock of all mft
 * records/inodes present in the page before I/O can proceed. In that case we
 * wouldn't need to bother with PG_locked and PG_uptodate as nobody will be
 * accessing anything without owning the mrec_lock mutex.  But we do need to
 * use them because of the read_cache_page() invocation and the code becomes so
 * much simpler this way that it is well worth it.
 *
 * The mft record is now ours and we return a pointer to it. You need to check
 * the returned pointer with IS_ERR() and if that is true, PTR_ERR() will return
 * the error code.
 *
 * NOTE: Caller is responsible for setting the mft record dirty before calling
 * unmap_mft_record(). This is obviously only necessary if the caller really
 * modified the mft record...
 * Q: Do we want to recycle one of the VFS inode state bits instead?
 * A: No, the inode ones mean we want to change the mft record, not we want to
 * write it out.
 */
MFT_RECORD *map_mft_record(ntfs_inode *ni)
{
      MFT_RECORD *m;

      ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

      /* Make sure the ntfs inode doesn't go away. */
      atomic_inc(&ni->count);

      /* Serialize access to this mft record. */
      mutex_lock(&ni->mrec_lock);

      m = map_mft_record_page(ni);
      if (likely(!IS_ERR(m)))
            return m;

      mutex_unlock(&ni->mrec_lock);
      atomic_dec(&ni->count);
      ntfs_error(ni->vol->sb, "Failed with error code %lu.", -PTR_ERR(m));
      return m;
}

/**
 * unmap_mft_record_page - unmap the page in which a specific mft record resides
 * @ni:           ntfs inode whose mft record page to unmap
 *
 * This unmaps the page in which the mft record of the ntfs inode @ni is
 * situated and returns. This is a NOOP if highmem is not configured.
 *
 * The unmap happens via ntfs_unmap_page() which in turn decrements the use
 * count on the page thus releasing it from the pinned state.
 *
 * We do not actually unmap the page from memory of course, as that will be
 * done by the page cache code itself when memory pressure increases or
 * whatever.
 */
static inline void unmap_mft_record_page(ntfs_inode *ni)
{
      BUG_ON(!ni->page);

      // TODO: If dirty, blah...
      ntfs_unmap_page(ni->page);
      ni->page = NULL;
      ni->page_ofs = 0;
      return;
}

/**
 * unmap_mft_record - release a mapped mft record
 * @ni:           ntfs inode whose MFT record to unmap
 *
 * We release the page mapping and the mrec_lock mutex which unmaps the mft
 * record and releases it for others to get hold of. We also release the ntfs
 * inode by decrementing the ntfs inode reference count.
 *
 * NOTE: If caller has modified the mft record, it is imperative to set the mft
 * record dirty BEFORE calling unmap_mft_record().
 */
void unmap_mft_record(ntfs_inode *ni)
{
      struct page *page = ni->page;

      BUG_ON(!page);

      ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

      unmap_mft_record_page(ni);
      mutex_unlock(&ni->mrec_lock);
      atomic_dec(&ni->count);
      /*
       * If pure ntfs_inode, i.e. no vfs inode attached, we leave it to
       * ntfs_clear_extent_inode() in the extent inode case, and to the
       * caller in the non-extent, yet pure ntfs inode case, to do the actual
       * tear down of all structures and freeing of all allocated memory.
       */
      return;
}

/**
 * map_extent_mft_record - load an extent inode and attach it to its base
 * @base_ni:      base ntfs inode
 * @mref:   mft reference of the extent inode to load
 * @ntfs_ino:     on successful return, pointer to the ntfs_inode structure
 *
 * Load the extent mft record @mref and attach it to its base inode @base_ni.
 * Return the mapped extent mft record if IS_ERR(result) is false.  Otherwise
 * PTR_ERR(result) gives the negative error code.
 *
 * On successful return, @ntfs_ino contains a pointer to the ntfs_inode
 * structure of the mapped extent inode.
 */
MFT_RECORD *map_extent_mft_record(ntfs_inode *base_ni, MFT_REF mref,
            ntfs_inode **ntfs_ino)
{
      MFT_RECORD *m;
      ntfs_inode *ni = NULL;
      ntfs_inode **extent_nis = NULL;
      int i;
      unsigned long mft_no = MREF(mref);
      u16 seq_no = MSEQNO(mref);
      bool destroy_ni = false;

      ntfs_debug("Mapping extent mft record 0x%lx (base mft record 0x%lx).",
                  mft_no, base_ni->mft_no);
      /* Make sure the base ntfs inode doesn't go away. */
      atomic_inc(&base_ni->count);
      /*
       * Check if this extent inode has already been added to the base inode,
       * in which case just return it. If not found, add it to the base
       * inode before returning it.
       */
      mutex_lock(&base_ni->extent_lock);
      if (base_ni->nr_extents > 0) {
            extent_nis = base_ni->ext.extent_ntfs_inos;
            for (i = 0; i < base_ni->nr_extents; i++) {
                  if (mft_no != extent_nis[i]->mft_no)
                        continue;
                  ni = extent_nis[i];
                  /* Make sure the ntfs inode doesn't go away. */
                  atomic_inc(&ni->count);
                  break;
            }
      }
      if (likely(ni != NULL)) {
            mutex_unlock(&base_ni->extent_lock);
            atomic_dec(&base_ni->count);
            /* We found the record; just have to map and return it. */
            m = map_mft_record(ni);
            /* map_mft_record() has incremented this on success. */
            atomic_dec(&ni->count);
            if (likely(!IS_ERR(m))) {
                  /* Verify the sequence number. */
                  if (likely(le16_to_cpu(m->sequence_number) == seq_no)) {
                        ntfs_debug("Done 1.");
                        *ntfs_ino = ni;
                        return m;
                  }
                  unmap_mft_record(ni);
                  ntfs_error(base_ni->vol->sb, "Found stale extent mft "
                              "reference! Corrupt filesystem. "
                              "Run chkdsk.");
                  return ERR_PTR(-EIO);
            }
map_err_out:
            ntfs_error(base_ni->vol->sb, "Failed to map extent "
                        "mft record, error code %ld.", -PTR_ERR(m));
            return m;
      }
      /* Record wasn't there. Get a new ntfs inode and initialize it. */
      ni = ntfs_new_extent_inode(base_ni->vol->sb, mft_no);
      if (unlikely(!ni)) {
            mutex_unlock(&base_ni->extent_lock);
            atomic_dec(&base_ni->count);
            return ERR_PTR(-ENOMEM);
      }
      ni->vol = base_ni->vol;
      ni->seq_no = seq_no;
      ni->nr_extents = -1;
      ni->ext.base_ntfs_ino = base_ni;
      /* Now map the record. */
      m = map_mft_record(ni);
      if (IS_ERR(m)) {
            mutex_unlock(&base_ni->extent_lock);
            atomic_dec(&base_ni->count);
            ntfs_clear_extent_inode(ni);
            goto map_err_out;
      }
      /* Verify the sequence number if it is present. */
      if (seq_no && (le16_to_cpu(m->sequence_number) != seq_no)) {
            ntfs_error(base_ni->vol->sb, "Found stale extent mft "
                        "reference! Corrupt filesystem. Run chkdsk.");
            destroy_ni = true;
            m = ERR_PTR(-EIO);
            goto unm_err_out;
      }
      /* Attach extent inode to base inode, reallocating memory if needed. */
      if (!(base_ni->nr_extents & 3)) {
            ntfs_inode **tmp;
            int new_size = (base_ni->nr_extents + 4) * sizeof(ntfs_inode *);

            tmp = kmalloc(new_size, GFP_NOFS);
            if (unlikely(!tmp)) {
                  ntfs_error(base_ni->vol->sb, "Failed to allocate "
                              "internal buffer.");
                  destroy_ni = true;
                  m = ERR_PTR(-ENOMEM);
                  goto unm_err_out;
            }
            if (base_ni->nr_extents) {
                  BUG_ON(!base_ni->ext.extent_ntfs_inos);
                  memcpy(tmp, base_ni->ext.extent_ntfs_inos, new_size -
                              4 * sizeof(ntfs_inode *));
                  kfree(base_ni->ext.extent_ntfs_inos);
            }
            base_ni->ext.extent_ntfs_inos = tmp;
      }
      base_ni->ext.extent_ntfs_inos[base_ni->nr_extents++] = ni;
      mutex_unlock(&base_ni->extent_lock);
      atomic_dec(&base_ni->count);
      ntfs_debug("Done 2.");
      *ntfs_ino = ni;
      return m;
unm_err_out:
      unmap_mft_record(ni);
      mutex_unlock(&base_ni->extent_lock);
      atomic_dec(&base_ni->count);
      /*
       * If the extent inode was not attached to the base inode we need to
       * release it or we will leak memory.
       */
      if (destroy_ni)
            ntfs_clear_extent_inode(ni);
      return m;
}

#ifdef NTFS_RW

/**
 * __mark_mft_record_dirty - set the mft record and the page containing it dirty
 * @ni:           ntfs inode describing the mapped mft record
 *
 * Internal function.  Users should call mark_mft_record_dirty() instead.
 *
 * Set the mapped (extent) mft record of the (base or extent) ntfs inode @ni,
 * as well as the page containing the mft record, dirty.  Also, mark the base
 * vfs inode dirty.  This ensures that any changes to the mft record are
 * written out to disk.
 *
 * NOTE:  We only set I_DIRTY_SYNC and I_DIRTY_DATASYNC (and not I_DIRTY_PAGES)
 * on the base vfs inode, because even though file data may have been modified,
 * it is dirty in the inode meta data rather than the data page cache of the
 * inode, and thus there are no data pages that need writing out.  Therefore, a
 * full mark_inode_dirty() is overkill.  A mark_inode_dirty_sync(), on the
 * other hand, is not sufficient, because I_DIRTY_DATASYNC needs to be set to
 * ensure ->write_inode is called from generic_osync_inode() and this needs to
 * happen or the file data would not necessarily hit the device synchronously,
 * even though the vfs inode has the O_SYNC flag set.  Also, I_DIRTY_DATASYNC
 * simply "feels" better than just I_DIRTY_SYNC, since the file data has not
 * actually hit the block device yet, which is not what I_DIRTY_SYNC on its own
 * would suggest.
 */
void __mark_mft_record_dirty(ntfs_inode *ni)
{
      ntfs_inode *base_ni;

      ntfs_debug("Entering for inode 0x%lx.", ni->mft_no);
      BUG_ON(NInoAttr(ni));
      mark_ntfs_record_dirty(ni->page, ni->page_ofs);
      /* Determine the base vfs inode and mark it dirty, too. */
      mutex_lock(&ni->extent_lock);
      if (likely(ni->nr_extents >= 0))
            base_ni = ni;
      else
            base_ni = ni->ext.base_ntfs_ino;
      mutex_unlock(&ni->extent_lock);
      __mark_inode_dirty(VFS_I(base_ni), I_DIRTY_SYNC | I_DIRTY_DATASYNC);
}

static const char *ntfs_please_email = "Please email "
            "linux-ntfs-dev@lists.sourceforge.net and say that you saw "
            "this message.  Thank you.";

/**
 * ntfs_sync_mft_mirror_umount - synchronise an mft record to the mft mirror
 * @vol:    ntfs volume on which the mft record to synchronize resides
 * @mft_no: mft record number of mft record to synchronize
 * @m:            mapped, mst protected (extent) mft record to synchronize
 *
 * Write the mapped, mst protected (extent) mft record @m with mft record
 * number @mft_no to the mft mirror ($MFTMirr) of the ntfs volume @vol,
 * bypassing the page cache and the $MFTMirr inode itself.
 *
 * This function is only for use at umount time when the mft mirror inode has
 * already been disposed off.  We BUG() if we are called while the mft mirror
 * inode is still attached to the volume.
 *
 * On success return 0.  On error return -errno.
 *
 * NOTE:  This function is not implemented yet as I am not convinced it can
 * actually be triggered considering the sequence of commits we do in super.c::
 * ntfs_put_super().  But just in case we provide this place holder as the
 * alternative would be either to BUG() or to get a NULL pointer dereference
 * and Oops.
 */
static int ntfs_sync_mft_mirror_umount(ntfs_volume *vol,
            const unsigned long mft_no, MFT_RECORD *m)
{
      BUG_ON(vol->mftmirr_ino);
      ntfs_error(vol->sb, "Umount time mft mirror syncing is not "
                  "implemented yet.  %s", ntfs_please_email);
      return -EOPNOTSUPP;
}

/**
 * ntfs_sync_mft_mirror - synchronize an mft record to the mft mirror
 * @vol:    ntfs volume on which the mft record to synchronize resides
 * @mft_no: mft record number of mft record to synchronize
 * @m:            mapped, mst protected (extent) mft record to synchronize
 * @sync:   if true, wait for i/o completion
 *
 * Write the mapped, mst protected (extent) mft record @m with mft record
 * number @mft_no to the mft mirror ($MFTMirr) of the ntfs volume @vol.
 *
 * On success return 0.  On error return -errno and set the volume errors flag
 * in the ntfs volume @vol.
 *
 * NOTE:  We always perform synchronous i/o and ignore the @sync parameter.
 *
 * TODO:  If @sync is false, want to do truly asynchronous i/o, i.e. just
 * schedule i/o via ->writepage or do it via kntfsd or whatever.
 */
int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no,
            MFT_RECORD *m, int sync)
{
      struct page *page;
      unsigned int blocksize = vol->sb->s_blocksize;
      int max_bhs = vol->mft_record_size / blocksize;
      struct buffer_head *bhs[max_bhs];
      struct buffer_head *bh, *head;
      u8 *kmirr;
      runlist_element *rl;
      unsigned int block_start, block_end, m_start, m_end, page_ofs;
      int i_bhs, nr_bhs, err = 0;
      unsigned char blocksize_bits = vol->sb->s_blocksize_bits;

      ntfs_debug("Entering for inode 0x%lx.", mft_no);
      BUG_ON(!max_bhs);
      if (unlikely(!vol->mftmirr_ino)) {
            /* This could happen during umount... */
            err = ntfs_sync_mft_mirror_umount(vol, mft_no, m);
            if (likely(!err))
                  return err;
            goto err_out;
      }
      /* Get the page containing the mirror copy of the mft record @m. */
      page = ntfs_map_page(vol->mftmirr_ino->i_mapping, mft_no >>
                  (PAGE_CACHE_SHIFT - vol->mft_record_size_bits));
      if (IS_ERR(page)) {
            ntfs_error(vol->sb, "Failed to map mft mirror page.");
            err = PTR_ERR(page);
            goto err_out;
      }
      lock_page(page);
      BUG_ON(!PageUptodate(page));
      ClearPageUptodate(page);
      /* Offset of the mft mirror record inside the page. */
      page_ofs = (mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
      /* The address in the page of the mirror copy of the mft record @m. */
      kmirr = page_address(page) + page_ofs;
      /* Copy the mst protected mft record to the mirror. */
      memcpy(kmirr, m, vol->mft_record_size);
      /* Create uptodate buffers if not present. */
      if (unlikely(!page_has_buffers(page))) {
            struct buffer_head *tail;

            bh = head = alloc_page_buffers(page, blocksize, 1);
            do {
                  set_buffer_uptodate(bh);
                  tail = bh;
                  bh = bh->b_this_page;
            } while (bh);
            tail->b_this_page = head;
            attach_page_buffers(page, head);
      }
      bh = head = page_buffers(page);
      BUG_ON(!bh);
      rl = NULL;
      nr_bhs = 0;
      block_start = 0;
      m_start = kmirr - (u8*)page_address(page);
      m_end = m_start + vol->mft_record_size;
      do {
            block_end = block_start + blocksize;
            /* If the buffer is outside the mft record, skip it. */
            if (block_end <= m_start)
                  continue;
            if (unlikely(block_start >= m_end))
                  break;
            /* Need to map the buffer if it is not mapped already. */
            if (unlikely(!buffer_mapped(bh))) {
                  VCN vcn;
                  LCN lcn;
                  unsigned int vcn_ofs;

                  bh->b_bdev = vol->sb->s_bdev;
                  /* Obtain the vcn and offset of the current block. */
                  vcn = ((VCN)mft_no << vol->mft_record_size_bits) +
                              (block_start - m_start);
                  vcn_ofs = vcn & vol->cluster_size_mask;
                  vcn >>= vol->cluster_size_bits;
                  if (!rl) {
                        down_read(&NTFS_I(vol->mftmirr_ino)->
                                    runlist.lock);
                        rl = NTFS_I(vol->mftmirr_ino)->runlist.rl;
                        /*
                         * $MFTMirr always has the whole of its runlist
                         * in memory.
                         */
                        BUG_ON(!rl);
                  }
                  /* Seek to element containing target vcn. */
                  while (rl->length && rl[1].vcn <= vcn)
                        rl++;
                  lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
                  /* For $MFTMirr, only lcn >= 0 is a successful remap. */
                  if (likely(lcn >= 0)) {
                        /* Setup buffer head to correct block. */
                        bh->b_blocknr = ((lcn <<
                                    vol->cluster_size_bits) +
                                    vcn_ofs) >> blocksize_bits;
                        set_buffer_mapped(bh);
                  } else {
                        bh->b_blocknr = -1;
                        ntfs_error(vol->sb, "Cannot write mft mirror "
                                    "record 0x%lx because its "
                                    "location on disk could not "
                                    "be determined (error code "
                                    "%lli).", mft_no,
                                    (long long)lcn);
                        err = -EIO;
                  }
            }
            BUG_ON(!buffer_uptodate(bh));
            BUG_ON(!nr_bhs && (m_start != block_start));
            BUG_ON(nr_bhs >= max_bhs);
            bhs[nr_bhs++] = bh;
            BUG_ON((nr_bhs >= max_bhs) && (m_end != block_end));
      } while (block_start = block_end, (bh = bh->b_this_page) != head);
      if (unlikely(rl))
            up_read(&NTFS_I(vol->mftmirr_ino)->runlist.lock);
      if (likely(!err)) {
            /* Lock buffers and start synchronous write i/o on them. */
            for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
                  struct buffer_head *tbh = bhs[i_bhs];

                  if (unlikely(test_set_buffer_locked(tbh)))
                        BUG();
                  BUG_ON(!buffer_uptodate(tbh));
                  clear_buffer_dirty(tbh);
                  get_bh(tbh);
                  tbh->b_end_io = end_buffer_write_sync;
                  submit_bh(WRITE, tbh);
            }
            /* Wait on i/o completion of buffers. */
            for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
                  struct buffer_head *tbh = bhs[i_bhs];

                  wait_on_buffer(tbh);
                  if (unlikely(!buffer_uptodate(tbh))) {
                        err = -EIO;
                        /*
                         * Set the buffer uptodate so the page and
                         * buffer states do not become out of sync.
                         */
                        set_buffer_uptodate(tbh);
                  }
            }
      } else /* if (unlikely(err)) */ {
            /* Clean the buffers. */
            for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++)
                  clear_buffer_dirty(bhs[i_bhs]);
      }
      /* Current state: all buffers are clean, unlocked, and uptodate. */
      /* Remove the mst protection fixups again. */
      post_write_mst_fixup((NTFS_RECORD*)kmirr);
      flush_dcache_page(page);
      SetPageUptodate(page);
      unlock_page(page);
      ntfs_unmap_page(page);
      if (likely(!err)) {
            ntfs_debug("Done.");
      } else {
            ntfs_error(vol->sb, "I/O error while writing mft mirror "
                        "record 0x%lx!", mft_no);
err_out:
            ntfs_error(vol->sb, "Failed to synchronize $MFTMirr (error "
                        "code %i).  Volume will be left marked dirty "
                        "on umount.  Run ntfsfix on the partition "
                        "after umounting to correct this.", -err);
            NVolSetErrors(vol);
      }
      return err;
}

/**
 * write_mft_record_nolock - write out a mapped (extent) mft record
 * @ni:           ntfs inode describing the mapped (extent) mft record
 * @m:            mapped (extent) mft record to write
 * @sync:   if true, wait for i/o completion
 *
 * Write the mapped (extent) mft record @m described by the (regular or extent)
 * ntfs inode @ni to backing store.  If the mft record @m has a counterpart in
 * the mft mirror, that is also updated.
 *
 * We only write the mft record if the ntfs inode @ni is dirty and the first
 * buffer belonging to its mft record is dirty, too.  We ignore the dirty state
 * of subsequent buffers because we could have raced with
 * fs/ntfs/aops.c::mark_ntfs_record_dirty().
 *
 * On success, clean the mft record and return 0.  On error, leave the mft
 * record dirty and return -errno.
 *
 * NOTE:  We always perform synchronous i/o and ignore the @sync parameter.
 * However, if the mft record has a counterpart in the mft mirror and @sync is
 * true, we write the mft record, wait for i/o completion, and only then write
 * the mft mirror copy.  This ensures that if the system crashes either the mft
 * or the mft mirror will contain a self-consistent mft record @m.  If @sync is
 * false on the other hand, we start i/o on both and then wait for completion
 * on them.  This provides a speedup but no longer guarantees that you will end
 * up with a self-consistent mft record in the case of a crash but if you asked
 * for asynchronous writing you probably do not care about that anyway.
 *
 * TODO:  If @sync is false, want to do truly asynchronous i/o, i.e. just
 * schedule i/o via ->writepage or do it via kntfsd or whatever.
 */
int write_mft_record_nolock(ntfs_inode *ni, MFT_RECORD *m, int sync)
{
      ntfs_volume *vol = ni->vol;
      struct page *page = ni->page;
      unsigned int blocksize = vol->sb->s_blocksize;
      unsigned char blocksize_bits = vol->sb->s_blocksize_bits;
      int max_bhs = vol->mft_record_size / blocksize;
      struct buffer_head *bhs[max_bhs];
      struct buffer_head *bh, *head;
      runlist_element *rl;
      unsigned int block_start, block_end, m_start, m_end;
      int i_bhs, nr_bhs, err = 0;

      ntfs_debug("Entering for inode 0x%lx.", ni->mft_no);
      BUG_ON(NInoAttr(ni));
      BUG_ON(!max_bhs);
      BUG_ON(!PageLocked(page));
      /*
       * If the ntfs_inode is clean no need to do anything.  If it is dirty,
       * mark it as clean now so that it can be redirtied later on if needed.
       * There is no danger of races since the caller is holding the locks
       * for the mft record @m and the page it is in.
       */
      if (!NInoTestClearDirty(ni))
            goto done;
      bh = head = page_buffers(page);
      BUG_ON(!bh);
      rl = NULL;
      nr_bhs = 0;
      block_start = 0;
      m_start = ni->page_ofs;
      m_end = m_start + vol->mft_record_size;
      do {
            block_end = block_start + blocksize;
            /* If the buffer is outside the mft record, skip it. */
            if (block_end <= m_start)
                  continue;
            if (unlikely(block_start >= m_end))
                  break;
            /*
             * If this block is not the first one in the record, we ignore
             * the buffer's dirty state because we could have raced with a
             * parallel mark_ntfs_record_dirty().
             */
            if (block_start == m_start) {
                  /* This block is the first one in the record. */
                  if (!buffer_dirty(bh)) {
                        BUG_ON(nr_bhs);
                        /* Clean records are not written out. */
                        break;
                  }
            }
            /* Need to map the buffer if it is not mapped already. */
            if (unlikely(!buffer_mapped(bh))) {
                  VCN vcn;
                  LCN lcn;
                  unsigned int vcn_ofs;

                  bh->b_bdev = vol->sb->s_bdev;
                  /* Obtain the vcn and offset of the current block. */
                  vcn = ((VCN)ni->mft_no << vol->mft_record_size_bits) +
                              (block_start - m_start);
                  vcn_ofs = vcn & vol->cluster_size_mask;
                  vcn >>= vol->cluster_size_bits;
                  if (!rl) {
                        down_read(&NTFS_I(vol->mft_ino)->runlist.lock);
                        rl = NTFS_I(vol->mft_ino)->runlist.rl;
                        BUG_ON(!rl);
                  }
                  /* Seek to element containing target vcn. */
                  while (rl->length && rl[1].vcn <= vcn)
                        rl++;
                  lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
                  /* For $MFT, only lcn >= 0 is a successful remap. */
                  if (likely(lcn >= 0)) {
                        /* Setup buffer head to correct block. */
                        bh->b_blocknr = ((lcn <<
                                    vol->cluster_size_bits) +
                                    vcn_ofs) >> blocksize_bits;
                        set_buffer_mapped(bh);
                  } else {
                        bh->b_blocknr = -1;
                        ntfs_error(vol->sb, "Cannot write mft record "
                                    "0x%lx because its location "
                                    "on disk could not be "
                                    "determined (error code %lli).",
                                    ni->mft_no, (long long)lcn);
                        err = -EIO;
                  }
            }
            BUG_ON(!buffer_uptodate(bh));
            BUG_ON(!nr_bhs && (m_start != block_start));
            BUG_ON(nr_bhs >= max_bhs);
            bhs[nr_bhs++] = bh;
            BUG_ON((nr_bhs >= max_bhs) && (m_end != block_end));
      } while (block_start = block_end, (bh = bh->b_this_page) != head);
      if (unlikely(rl))
            up_read(&NTFS_I(vol->mft_ino)->runlist.lock);
      if (!nr_bhs)
            goto done;
      if (unlikely(err))
            goto cleanup_out;
      /* Apply the mst protection fixups. */
      err = pre_write_mst_fixup((NTFS_RECORD*)m, vol->mft_record_size);
      if (err) {
            ntfs_error(vol->sb, "Failed to apply mst fixups!");
            goto cleanup_out;
      }
      flush_dcache_mft_record_page(ni);
      /* Lock buffers and start synchronous write i/o on them. */
      for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
            struct buffer_head *tbh = bhs[i_bhs];

            if (unlikely(test_set_buffer_locked(tbh)))
                  BUG();
            BUG_ON(!buffer_uptodate(tbh));
            clear_buffer_dirty(tbh);
            get_bh(tbh);
            tbh->b_end_io = end_buffer_write_sync;
            submit_bh(WRITE, tbh);
      }
      /* Synchronize the mft mirror now if not @sync. */
      if (!sync && ni->mft_no < vol->mftmirr_size)
            ntfs_sync_mft_mirror(vol, ni->mft_no, m, sync);
      /* Wait on i/o completion of buffers. */
      for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
            struct buffer_head *tbh = bhs[i_bhs];

            wait_on_buffer(tbh);
            if (unlikely(!buffer_uptodate(tbh))) {
                  err = -EIO;
                  /*
                   * Set the buffer uptodate so the page and buffer
                   * states do not become out of sync.
                   */
                  if (PageUptodate(page))
                        set_buffer_uptodate(tbh);
            }
      }
      /* If @sync, now synchronize the mft mirror. */
      if (sync && ni->mft_no < vol->mftmirr_size)
            ntfs_sync_mft_mirror(vol, ni->mft_no, m, sync);
      /* Remove the mst protection fixups again. */
      post_write_mst_fixup((NTFS_RECORD*)m);
      flush_dcache_mft_record_page(ni);
      if (unlikely(err)) {
            /* I/O error during writing.  This is really bad! */
            ntfs_error(vol->sb, "I/O error while writing mft record "
                        "0x%lx!  Marking base inode as bad.  You "
                        "should unmount the volume and run chkdsk.",
                        ni->mft_no);
            goto err_out;
      }
done:
      ntfs_debug("Done.");
      return 0;
cleanup_out:
      /* Clean the buffers. */
      for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++)
            clear_buffer_dirty(bhs[i_bhs]);
err_out:
      /*
       * Current state: all buffers are clean, unlocked, and uptodate.
       * The caller should mark the base inode as bad so that no more i/o
       * happens.  ->clear_inode() will still be invoked so all extent inodes
       * and other allocated memory will be freed.
       */
      if (err == -ENOMEM) {
            ntfs_error(vol->sb, "Not enough memory to write mft record.  "
                        "Redirtying so the write is retried later.");
            mark_mft_record_dirty(ni);
            err = 0;
      } else
            NVolSetErrors(vol);
      return err;
}

/**
 * ntfs_may_write_mft_record - check if an mft record may be written out
 * @vol:    [IN]  ntfs volume on which the mft record to check resides
 * @mft_no: [IN]  mft record number of the mft record to check
 * @m:            [IN]  mapped mft record to check
 * @locked_ni:    [OUT] caller has to unlock this ntfs inode if one is returned
 *
 * Check if the mapped (base or extent) mft record @m with mft record number
 * @mft_no belonging to the ntfs volume @vol may be written out.  If necessary
 * and possible the ntfs inode of the mft record is locked and the base vfs
 * inode is pinned.  The locked ntfs inode is then returned in @locked_ni.  The
 * caller is responsible for unlocking the ntfs inode and unpinning the base
 * vfs inode.
 *
 * Return 'true' if the mft record may be written out and 'false' if not.
 *
 * The caller has locked the page and cleared the uptodate flag on it which
 * means that we can safely write out any dirty mft records that do not have
 * their inodes in icache as determined by ilookup5() as anyone
 * opening/creating such an inode would block when attempting to map the mft
 * record in read_cache_page() until we are finished with the write out.
 *
 * Here is a description of the tests we perform:
 *
 * If the inode is found in icache we know the mft record must be a base mft
 * record.  If it is dirty, we do not write it and return 'false' as the vfs
 * inode write paths will result in the access times being updated which would
 * cause the base mft record to be redirtied and written out again.  (We know
 * the access time update will modify the base mft record because Windows
 * chkdsk complains if the standard information attribute is not in the base
 * mft record.)
 *
 * If the inode is in icache and not dirty, we attempt to lock the mft record
 * and if we find the lock was already taken, it is not safe to write the mft
 * record and we return 'false'.
 *
 * If we manage to obtain the lock we have exclusive access to the mft record,
 * which also allows us safe writeout of the mft record.  We then set
 * @locked_ni to the locked ntfs inode and return 'true'.
 *
 * Note we cannot just lock the mft record and sleep while waiting for the lock
 * because this would deadlock due to lock reversal (normally the mft record is
 * locked before the page is locked but we already have the page locked here
 * when we try to lock the mft record).
 *
 * If the inode is not in icache we need to perform further checks.
 *
 * If the mft record is not a FILE record or it is a base mft record, we can
 * safely write it and return 'true'.
 *
 * We now know the mft record is an extent mft record.  We check if the inode
 * corresponding to its base mft record is in icache and obtain a reference to
 * it if it is.  If it is not, we can safely write it and return 'true'.
 *
 * We now have the base inode for the extent mft record.  We check if it has an
 * ntfs inode for the extent mft record attached and if not it is safe to write
 * the extent mft record and we return 'true'.
 *
 * The ntfs inode for the extent mft record is attached to the base inode so we
 * attempt to lock the extent mft record and if we find the lock was already
 * taken, it is not safe to write the extent mft record and we return 'false'.
 *
 * If we manage to obtain the lock we have exclusive access to the extent mft
 * record, which also allows us safe writeout of the extent mft record.  We
 * set the ntfs inode of the extent mft record clean and then set @locked_ni to
 * the now locked ntfs inode and return 'true'.
 *
 * Note, the reason for actually writing dirty mft records here and not just
 * relying on the vfs inode dirty code paths is that we can have mft records
 * modified without them ever having actual inodes in memory.  Also we can have
 * dirty mft records with clean ntfs inodes in memory.  None of the described
 * cases would result in the dirty mft records being written out if we only
 * relied on the vfs inode dirty code paths.  And these cases can really occur
 * during allocation of new mft records and in particular when the
 * initialized_size of the $MFT/$DATA attribute is extended and the new space
 * is initialized using ntfs_mft_record_format().  The clean inode can then
 * appear if the mft record is reused for a new inode before it got written
 * out.
 */
bool ntfs_may_write_mft_record(ntfs_volume *vol, const unsigned long mft_no,
            const MFT_RECORD *m, ntfs_inode **locked_ni)
{
      struct super_block *sb = vol->sb;
      struct inode *mft_vi = vol->mft_ino;
      struct inode *vi;
      ntfs_inode *ni, *eni, **extent_nis;
      int i;
      ntfs_attr na;

      ntfs_debug("Entering for inode 0x%lx.", mft_no);
      /*
       * Normally we do not return a locked inode so set @locked_ni to NULL.
       */
      BUG_ON(!locked_ni);
      *locked_ni = NULL;
      /*
       * Check if the inode corresponding to this mft record is in the VFS
       * inode cache and obtain a reference to it if it is.
       */
      ntfs_debug("Looking for inode 0x%lx in icache.", mft_no);
      na.mft_no = mft_no;
      na.name = NULL;
      na.name_len = 0;
      na.type = AT_UNUSED;
      /*
       * Optimize inode 0, i.e. $MFT itself, since we have it in memory and
       * we get here for it rather often.
       */
      if (!mft_no) {
            /* Balance the below iput(). */
            vi = igrab(mft_vi);
            BUG_ON(vi != mft_vi);
      } else {
            /*
             * Have to use ilookup5_nowait() since ilookup5() waits for the
             * inode lock which causes ntfs to deadlock when a concurrent
             * inode write via the inode dirty code paths and the page
             * dirty code path of the inode dirty code path when writing
             * $MFT occurs.
             */
            vi = ilookup5_nowait(sb, mft_no, (test_t)ntfs_test_inode, &na);
      }
      if (vi) {
            ntfs_debug("Base inode 0x%lx is in icache.", mft_no);
            /* The inode is in icache. */
            ni = NTFS_I(vi);
            /* Take a reference to the ntfs inode. */
            atomic_inc(&ni->count);
            /* If the inode is dirty, do not write this record. */
            if (NInoDirty(ni)) {
                  ntfs_debug("Inode 0x%lx is dirty, do not write it.",
                              mft_no);
                  atomic_dec(&ni->count);
                  iput(vi);
                  return false;
            }
            ntfs_debug("Inode 0x%lx is not dirty.", mft_no);
            /* The inode is not dirty, try to take the mft record lock. */
            if (unlikely(!mutex_trylock(&ni->mrec_lock))) {
                  ntfs_debug("Mft record 0x%lx is already locked, do "
                              "not write it.", mft_no);
                  atomic_dec(&ni->count);
                  iput(vi);
                  return false;
            }
            ntfs_debug("Managed to lock mft record 0x%lx, write it.",
                        mft_no);
            /*
             * The write has to occur while we hold the mft record lock so
             * return the locked ntfs inode.
             */
            *locked_ni = ni;
            return true;
      }
      ntfs_debug("Inode 0x%lx is not in icache.", mft_no);
      /* The inode is not in icache. */
      /* Write the record if it is not a mft record (type "FILE"). */
      if (!ntfs_is_mft_record(m->magic)) {
            ntfs_debug("Mft record 0x%lx is not a FILE record, write it.",
                        mft_no);
            return true;
      }
      /* Write the mft record if it is a base inode. */
      if (!m->base_mft_record) {
            ntfs_debug("Mft record 0x%lx is a base record, write it.",
                        mft_no);
            return true;
      }
      /*
       * This is an extent mft record.  Check if the inode corresponding to
       * its base mft record is in icache and obtain a reference to it if it
       * is.
       */
      na.mft_no = MREF_LE(m->base_mft_record);
      ntfs_debug("Mft record 0x%lx is an extent record.  Looking for base "
                  "inode 0x%lx in icache.", mft_no, na.mft_no);
      if (!na.mft_no) {
            /* Balance the below iput(). */
            vi = igrab(mft_vi);
            BUG_ON(vi != mft_vi);
      } else
            vi = ilookup5_nowait(sb, na.mft_no, (test_t)ntfs_test_inode,
                        &na);
      if (!vi) {
            /*
             * The base inode is not in icache, write this extent mft
             * record.
             */
            ntfs_debug("Base inode 0x%lx is not in icache, write the "
                        "extent record.", na.mft_no);
            return true;
      }
      ntfs_debug("Base inode 0x%lx is in icache.", na.mft_no);
      /*
       * The base inode is in icache.  Check if it has the extent inode
       * corresponding to this extent mft record attached.
       */
      ni = NTFS_I(vi);
      mutex_lock(&ni->extent_lock);
      if (ni->nr_extents <= 0) {
            /*
             * The base inode has no attached extent inodes, write this
             * extent mft record.
             */
            mutex_unlock(&ni->extent_lock);
            iput(vi);
            ntfs_debug("Base inode 0x%lx has no attached extent inodes, "
                        "write the extent record.", na.mft_no);
            return true;
      }
      /* Iterate over the attached extent inodes. */
      extent_nis = ni->ext.extent_ntfs_inos;
      for (eni = NULL, i = 0; i < ni->nr_extents; ++i) {
            if (mft_no == extent_nis[i]->mft_no) {
                  /*
                   * Found the extent inode corresponding to this extent
                   * mft record.
                   */
                  eni = extent_nis[i];
                  break;
            }
      }
      /*
       * If the extent inode was not attached to the base inode, write this
       * extent mft record.
       */
      if (!eni) {
            mutex_unlock(&ni->extent_lock);
            iput(vi);
            ntfs_debug("Extent inode 0x%lx is not attached to its base "
                        "inode 0x%lx, write the extent record.",
                        mft_no, na.mft_no);
            return true;
      }
      ntfs_debug("Extent inode 0x%lx is attached to its base inode 0x%lx.",
                  mft_no, na.mft_no);
      /* Take a reference to the extent ntfs inode. */
      atomic_inc(&eni->count);
      mutex_unlock(&ni->extent_lock);
      /*
       * Found the extent inode coresponding to this extent mft record.
       * Try to take the mft record lock.
       */
      if (unlikely(!mutex_trylock(&eni->mrec_lock))) {
            atomic_dec(&eni->count);
            iput(vi);
            ntfs_debug("Extent mft record 0x%lx is already locked, do "
                        "not write it.", mft_no);
            return false;
      }
      ntfs_debug("Managed to lock extent mft record 0x%lx, write it.",
                  mft_no);
      if (NInoTestClearDirty(eni))
            ntfs_debug("Extent inode 0x%lx is dirty, marking it clean.",
                        mft_no);
      /*
       * The write has to occur while we hold the mft record lock so return
       * the locked extent ntfs inode.
       */
      *locked_ni = eni;
      return true;
}

static const char *es = "  Leaving inconsistent metadata.  Unmount and run "
            "chkdsk.";

/**
 * ntfs_mft_bitmap_find_and_alloc_free_rec_nolock - see name
 * @vol:    volume on which to search for a free mft record
 * @base_ni:      open base inode if allocating an extent mft record or NULL
 *
 * Search for a free mft record in the mft bitmap attribute on the ntfs volume
 * @vol.
 *
 * If @base_ni is NULL start the search at the default allocator position.
 *
 * If @base_ni is not NULL start the search at the mft record after the base
 * mft record @base_ni.
 *
 * Return the free mft record on success and -errno on error.  An error code of
 * -ENOSPC means that there are no free mft records in the currently
 * initialized mft bitmap.
 *
 * Locking: Caller must hold vol->mftbmp_lock for writing.
 */
static int ntfs_mft_bitmap_find_and_alloc_free_rec_nolock(ntfs_volume *vol,
            ntfs_inode *base_ni)
{
      s64 pass_end, ll, data_pos, pass_start, ofs, bit;
      unsigned long flags;
      struct address_space *mftbmp_mapping;
      u8 *buf, *byte;
      struct page *page;
      unsigned int page_ofs, size;
      u8 pass, b;

      ntfs_debug("Searching for free mft record in the currently "
                  "initialized mft bitmap.");
      mftbmp_mapping = vol->mftbmp_ino->i_mapping;
      /*
       * Set the end of the pass making sure we do not overflow the mft
       * bitmap.
       */
      read_lock_irqsave(&NTFS_I(vol->mft_ino)->size_lock, flags);
      pass_end = NTFS_I(vol->mft_ino)->allocated_size >>
                  vol->mft_record_size_bits;
      read_unlock_irqrestore(&NTFS_I(vol->mft_ino)->size_lock, flags);
      read_lock_irqsave(&NTFS_I(vol->mftbmp_ino)->size_lock, flags);
      ll = NTFS_I(vol->mftbmp_ino)->initialized_size << 3;
      read_unlock_irqrestore(&NTFS_I(vol->mftbmp_ino)->size_lock, flags);
      if (pass_end > ll)
            pass_end = ll;
      pass = 1;
      if (!base_ni)
            data_pos = vol->mft_data_pos;
      else
            data_pos = base_ni->mft_no + 1;
      if (data_pos < 24)
            data_pos = 24;
      if (data_pos >= pass_end) {
            data_pos = 24;
            pass = 2;
            /* This happens on a freshly formatted volume. */
            if (data_pos >= pass_end)
                  return -ENOSPC;
      }
      pass_start = data_pos;
      ntfs_debug("Starting bitmap search: pass %u, pass_start 0x%llx, "
                  "pass_end 0x%llx, data_pos 0x%llx.", pass,
                  (long long)pass_start, (long long)pass_end,
                  (long long)data_pos);
      /* Loop until a free mft record is found. */
      for (; pass <= 2;) {
            /* Cap size to pass_end. */
            ofs = data_pos >> 3;
            page_ofs = ofs & ~PAGE_CACHE_MASK;
            size = PAGE_CACHE_SIZE - page_ofs;
            ll = ((pass_end + 7) >> 3) - ofs;
            if (size > ll)
                  size = ll;
            size <<= 3;
            /*
             * If we are still within the active pass, search the next page
             * for a zero bit.
             */
            if (size) {
                  page = ntfs_map_page(mftbmp_mapping,
                              ofs >> PAGE_CACHE_SHIFT);
                  if (unlikely(IS_ERR(page))) {
                        ntfs_error(vol->sb, "Failed to read mft "
                                    "bitmap, aborting.");
                        return PTR_ERR(page);
                  }
                  buf = (u8*)page_address(page) + page_ofs;
                  bit = data_pos & 7;
                  data_pos &= ~7ull;
                  ntfs_debug("Before inner for loop: size 0x%x, "
                              "data_pos 0x%llx, bit 0x%llx", size,
                              (long long)data_pos, (long long)bit);
                  for (; bit < size && data_pos + bit < pass_end;
                              bit &= ~7ull, bit += 8) {
                        byte = buf + (bit >> 3);
                        if (*byte == 0xff)
                              continue;
                        b = ffz((unsigned long)*byte);
                        if (b < 8 && b >= (bit & 7)) {
                              ll = data_pos + (bit & ~7ull) + b;
                              if (unlikely(ll > (1ll << 32))) {
                                    ntfs_unmap_page(page);
                                    return -ENOSPC;
                              }
                              *byte |= 1 << b;
                              flush_dcache_page(page);
                              set_page_dirty(page);
                              ntfs_unmap_page(page);
                              ntfs_debug("Done.  (Found and "
                                          "allocated mft record "
                                          "0x%llx.)",
                                          (long long)ll);
                              return ll;
                        }
                  }
                  ntfs_debug("After inner for loop: size 0x%x, "
                              "data_pos 0x%llx, bit 0x%llx", size,
                              (long long)data_pos, (long long)bit);
                  data_pos += size;
                  ntfs_unmap_page(page);
                  /*
                   * If the end of the pass has not been reached yet,
                   * continue searching the mft bitmap for a zero bit.
                   */
                  if (data_pos < pass_end)
                        continue;
            }
            /* Do the next pass. */
            if (++pass == 2) {
                  /*
                   * Starting the second pass, in which we scan the first
                   * part of the zone which we omitted earlier.
                   */
                  pass_end = pass_start;
                  data_pos = pass_start = 24;
                  ntfs_debug("pass %i, pass_start 0x%llx, pass_end "
                              "0x%llx.", pass, (long long)pass_start,
                              (long long)pass_end);
                  if (data_pos >= pass_end)
                        break;
            }
      }
      /* No free mft records in currently initialized mft bitmap. */
      ntfs_debug("Done.  (No free mft records left in currently initialized "
                  "mft bitmap.)");
      return -ENOSPC;
}

/**
 * ntfs_mft_bitmap_extend_allocation_nolock - extend mft bitmap by a cluster
 * @vol:    volume on which to extend the mft bitmap attribute
 *
 * Extend the mft bitmap attribute on the ntfs volume @vol by one cluster.
 *
 * Note: Only changes allocated_size, i.e. does not touch initialized_size or
 * data_size.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - Caller must hold vol->mftbmp_lock for writing.
 *        - This function takes NTFS_I(vol->mftbmp_ino)->runlist.lock for
 *          writing and releases it before returning.
 *        - This function takes vol->lcnbmp_lock for writing and releases it
 *          before returning.
 */
static int ntfs_mft_bitmap_extend_allocation_nolock(ntfs_volume *vol)
{
      LCN lcn;
      s64 ll;
      unsigned long flags;
      struct page *page;
      ntfs_inode *mft_ni, *mftbmp_ni;
      runlist_element *rl, *rl2 = NULL;
      ntfs_attr_search_ctx *ctx = NULL;
      MFT_RECORD *mrec;
      ATTR_RECORD *a = NULL;
      int ret, mp_size;
      u32 old_alen = 0;
      u8 *b, tb;
      struct {
            u8 added_cluster:1;
            u8 added_run:1;
            u8 mp_rebuilt:1;
      } status = { 0, 0, 0 };

      ntfs_debug("Extending mft bitmap allocation.");
      mft_ni = NTFS_I(vol->mft_ino);
      mftbmp_ni = NTFS_I(vol->mftbmp_ino);
      /*
       * Determine the last lcn of the mft bitmap.  The allocated size of the
       * mft bitmap cannot be zero so we are ok to do this.
       */
      down_write(&mftbmp_ni->runlist.lock);
      read_lock_irqsave(&mftbmp_ni->size_lock, flags);
      ll = mftbmp_ni->allocated_size;
      read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      rl = ntfs_attr_find_vcn_nolock(mftbmp_ni,
                  (ll - 1) >> vol->cluster_size_bits, NULL);
      if (unlikely(IS_ERR(rl) || !rl->length || rl->lcn < 0)) {
            up_write(&mftbmp_ni->runlist.lock);
            ntfs_error(vol->sb, "Failed to determine last allocated "
                        "cluster of mft bitmap attribute.");
            if (!IS_ERR(rl))
                  ret = -EIO;
            else
                  ret = PTR_ERR(rl);
            return ret;
      }
      lcn = rl->lcn + rl->length;
      ntfs_debug("Last lcn of mft bitmap attribute is 0x%llx.",
                  (long long)lcn);
      /*
       * Attempt to get the cluster following the last allocated cluster by
       * hand as it may be in the MFT zone so the allocator would not give it
       * to us.
       */
      ll = lcn >> 3;
      page = ntfs_map_page(vol->lcnbmp_ino->i_mapping,
                  ll >> PAGE_CACHE_SHIFT);
      if (IS_ERR(page)) {
            up_write(&mftbmp_ni->runlist.lock);
            ntfs_error(vol->sb, "Failed to read from lcn bitmap.");
            return PTR_ERR(page);
      }
      b = (u8*)page_address(page) + (ll & ~PAGE_CACHE_MASK);
      tb = 1 << (lcn & 7ull);
      down_write(&vol->lcnbmp_lock);
      if (*b != 0xff && !(*b & tb)) {
            /* Next cluster is free, allocate it. */
            *b |= tb;
            flush_dcache_page(page);
            set_page_dirty(page);
            up_write(&vol->lcnbmp_lock);
            ntfs_unmap_page(page);
            /* Update the mft bitmap runlist. */
            rl->length++;
            rl[1].vcn++;
            status.added_cluster = 1;
            ntfs_debug("Appending one cluster to mft bitmap.");
      } else {
            up_write(&vol->lcnbmp_lock);
            ntfs_unmap_page(page);
            /* Allocate a cluster from the DATA_ZONE. */
            rl2 = ntfs_cluster_alloc(vol, rl[1].vcn, 1, lcn, DATA_ZONE,
                        true);
            if (IS_ERR(rl2)) {
                  up_write(&mftbmp_ni->runlist.lock);
                  ntfs_error(vol->sb, "Failed to allocate a cluster for "
                              "the mft bitmap.");
                  return PTR_ERR(rl2);
            }
            rl = ntfs_runlists_merge(mftbmp_ni->runlist.rl, rl2);
            if (IS_ERR(rl)) {
                  up_write(&mftbmp_ni->runlist.lock);
                  ntfs_error(vol->sb, "Failed to merge runlists for mft "
                              "bitmap.");
                  if (ntfs_cluster_free_from_rl(vol, rl2)) {
                        ntfs_error(vol->sb, "Failed to dealocate "
                                    "allocated cluster.%s", es);
                        NVolSetErrors(vol);
                  }
                  ntfs_free(rl2);
                  return PTR_ERR(rl);
            }
            mftbmp_ni->runlist.rl = rl;
            status.added_run = 1;
            ntfs_debug("Adding one run to mft bitmap.");
            /* Find the last run in the new runlist. */
            for (; rl[1].length; rl++)
                  ;
      }
      /*
       * Update the attribute record as well.  Note: @rl is the last
       * (non-terminator) runlist element of mft bitmap.
       */
      mrec = map_mft_record(mft_ni);
      if (IS_ERR(mrec)) {
            ntfs_error(vol->sb, "Failed to map mft record.");
            ret = PTR_ERR(mrec);
            goto undo_alloc;
      }
      ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
      if (unlikely(!ctx)) {
            ntfs_error(vol->sb, "Failed to get search context.");
            ret = -ENOMEM;
            goto undo_alloc;
      }
      ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
                  mftbmp_ni->name_len, CASE_SENSITIVE, rl[1].vcn, NULL,
                  0, ctx);
      if (unlikely(ret)) {
            ntfs_error(vol->sb, "Failed to find last attribute extent of "
                        "mft bitmap attribute.");
            if (ret == -ENOENT)
                  ret = -EIO;
            goto undo_alloc;
      }
      a = ctx->attr;
      ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
      /* Search back for the previous last allocated cluster of mft bitmap. */
      for (rl2 = rl; rl2 > mftbmp_ni->runlist.rl; rl2--) {
            if (ll >= rl2->vcn)
                  break;
      }
      BUG_ON(ll < rl2->vcn);
      BUG_ON(ll >= rl2->vcn + rl2->length);
      /* 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)) {
            ntfs_error(vol->sb, "Get size for mapping pairs failed for "
                        "mft bitmap attribute extent.");
            ret = mp_size;
            if (!ret)
                  ret = -EIO;
            goto undo_alloc;
      }
      /* Expand the attribute record if necessary. */
      old_alen = le32_to_cpu(a->length);
      ret = ntfs_attr_record_resize(ctx->mrec, a, mp_size +
                  le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
      if (unlikely(ret)) {
            if (ret != -ENOSPC) {
                  ntfs_error(vol->sb, "Failed to resize attribute "
                              "record for mft bitmap attribute.");
                  goto undo_alloc;
            }
            // TODO: Deal with this by moving this extent to a new mft
            // record or by starting a new extent in a new mft record or by
            // moving other attributes out of this mft record.
            // Note: It will need to be a special mft record and if none of
            // those are available it gets rather complicated...
            ntfs_error(vol->sb, "Not enough space in this mft record to "
                        "accomodate extended mft bitmap attribute "
                        "extent.  Cannot handle this yet.");
            ret = -EOPNOTSUPP;
            goto undo_alloc;
      }
      status.mp_rebuilt = 1;
      /* Generate the mapping pairs array directly into the attr record. */
      ret = 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(ret)) {
            ntfs_error(vol->sb, "Failed to build mapping pairs array for "
                        "mft bitmap attribute.");
            goto undo_alloc;
      }
      /* Update the highest_vcn. */
      a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 1);
      /*
       * We now have extended the mft bitmap allocated_size by one cluster.
       * 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);
            ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
                        mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL,
                        0, ctx);
            if (unlikely(ret)) {
                  ntfs_error(vol->sb, "Failed to find first attribute "
                              "extent of mft bitmap attribute.");
                  goto restore_undo_alloc;
            }
            a = ctx->attr;
      }
      write_lock_irqsave(&mftbmp_ni->size_lock, flags);
      mftbmp_ni->allocated_size += vol->cluster_size;
      a->data.non_resident.allocated_size =
                  cpu_to_sle64(mftbmp_ni->allocated_size);
      write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      /* Ensure the changes make it to disk. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(mft_ni);
      up_write(&mftbmp_ni->runlist.lock);
      ntfs_debug("Done.");
      return 0;
restore_undo_alloc:
      ntfs_attr_reinit_search_ctx(ctx);
      if (ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
                  mftbmp_ni->name_len, CASE_SENSITIVE, rl[1].vcn, NULL,
                  0, ctx)) {
            ntfs_error(vol->sb, "Failed to find last attribute extent of "
                        "mft bitmap attribute.%s", es);
            write_lock_irqsave(&mftbmp_ni->size_lock, flags);
            mftbmp_ni->allocated_size += vol->cluster_size;
            write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
            ntfs_attr_put_search_ctx(ctx);
            unmap_mft_record(mft_ni);
            up_write(&mftbmp_ni->runlist.lock);
            /*
             * The only thing that is now wrong is ->allocated_size of the
             * base attribute extent which chkdsk should be able to fix.
             */
            NVolSetErrors(vol);
            return ret;
      }
      a = ctx->attr;
      a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 2);
undo_alloc:
      if (status.added_cluster) {
            /* Truncate the last run in the runlist by one cluster. */
            rl->length--;
            rl[1].vcn--;
      } else if (status.added_run) {
            lcn = rl->lcn;
            /* Remove the last run from the runlist. */
            rl->lcn = rl[1].lcn;
            rl->length = 0;
      }
      /* Deallocate the cluster. */
      down_write(&vol->lcnbmp_lock);
      if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
            ntfs_error(vol->sb, "Failed to free allocated cluster.%s", es);
            NVolSetErrors(vol);
      }
      up_write(&vol->lcnbmp_lock);
      if (status.mp_rebuilt) {
            if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                        a->data.non_resident.mapping_pairs_offset),
                        old_alen - le16_to_cpu(
                        a->data.non_resident.mapping_pairs_offset),
                        rl2, ll, -1, NULL)) {
                  ntfs_error(vol->sb, "Failed to restore mapping pairs "
                              "array.%s", es);
                  NVolSetErrors(vol);
            }
            if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
                  ntfs_error(vol->sb, "Failed to restore attribute "
                              "record.%s", es);
                  NVolSetErrors(vol);
            }
            flush_dcache_mft_record_page(ctx->ntfs_ino);
            mark_mft_record_dirty(ctx->ntfs_ino);
      }
      if (ctx)
            ntfs_attr_put_search_ctx(ctx);
      if (!IS_ERR(mrec))
            unmap_mft_record(mft_ni);
      up_write(&mftbmp_ni->runlist.lock);
      return ret;
}

/**
 * ntfs_mft_bitmap_extend_initialized_nolock - extend mftbmp initialized data
 * @vol:    volume on which to extend the mft bitmap attribute
 *
 * Extend the initialized portion of the mft bitmap attribute on the ntfs
 * volume @vol by 8 bytes.
 *
 * Note:  Only changes initialized_size and data_size, i.e. requires that
 * allocated_size is big enough to fit the new initialized_size.
 *
 * Return 0 on success and -error on error.
 *
 * Locking: Caller must hold vol->mftbmp_lock for writing.
 */
static int ntfs_mft_bitmap_extend_initialized_nolock(ntfs_volume *vol)
{
      s64 old_data_size, old_initialized_size;
      unsigned long flags;
      struct inode *mftbmp_vi;
      ntfs_inode *mft_ni, *mftbmp_ni;
      ntfs_attr_search_ctx *ctx;
      MFT_RECORD *mrec;
      ATTR_RECORD *a;
      int ret;

      ntfs_debug("Extending mft bitmap initiailized (and data) size.");
      mft_ni = NTFS_I(vol->mft_ino);
      mftbmp_vi = vol->mftbmp_ino;
      mftbmp_ni = NTFS_I(mftbmp_vi);
      /* Get the attribute record. */
      mrec = map_mft_record(mft_ni);
      if (IS_ERR(mrec)) {
            ntfs_error(vol->sb, "Failed to map mft record.");
            return PTR_ERR(mrec);
      }
      ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
      if (unlikely(!ctx)) {
            ntfs_error(vol->sb, "Failed to get search context.");
            ret = -ENOMEM;
            goto unm_err_out;
      }
      ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
                  mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL, 0, ctx);
      if (unlikely(ret)) {
            ntfs_error(vol->sb, "Failed to find first attribute extent of "
                        "mft bitmap attribute.");
            if (ret == -ENOENT)
                  ret = -EIO;
            goto put_err_out;
      }
      a = ctx->attr;
      write_lock_irqsave(&mftbmp_ni->size_lock, flags);
      old_data_size = i_size_read(mftbmp_vi);
      old_initialized_size = mftbmp_ni->initialized_size;
      /*
       * We can simply update the initialized_size before filling the space
       * with zeroes because the caller is holding the mft bitmap lock for
       * writing which ensures that no one else is trying to access the data.
       */
      mftbmp_ni->initialized_size += 8;
      a->data.non_resident.initialized_size =
                  cpu_to_sle64(mftbmp_ni->initialized_size);
      if (mftbmp_ni->initialized_size > old_data_size) {
            i_size_write(mftbmp_vi, mftbmp_ni->initialized_size);
            a->data.non_resident.data_size =
                        cpu_to_sle64(mftbmp_ni->initialized_size);
      }
      write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      /* Ensure the changes make it to disk. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(mft_ni);
      /* Initialize the mft bitmap attribute value with zeroes. */
      ret = ntfs_attr_set(mftbmp_ni, old_initialized_size, 8, 0);
      if (likely(!ret)) {
            ntfs_debug("Done.  (Wrote eight initialized bytes to mft "
                        "bitmap.");
            return 0;
      }
      ntfs_error(vol->sb, "Failed to write to mft bitmap.");
      /* Try to recover from the error. */
      mrec = map_mft_record(mft_ni);
      if (IS_ERR(mrec)) {
            ntfs_error(vol->sb, "Failed to map mft record.%s", es);
            NVolSetErrors(vol);
            return ret;
      }
      ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
      if (unlikely(!ctx)) {
            ntfs_error(vol->sb, "Failed to get search context.%s", es);
            NVolSetErrors(vol);
            goto unm_err_out;
      }
      if (ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
                  mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL, 0, ctx)) {
            ntfs_error(vol->sb, "Failed to find first attribute extent of "
                        "mft bitmap attribute.%s", es);
            NVolSetErrors(vol);
put_err_out:
            ntfs_attr_put_search_ctx(ctx);
unm_err_out:
            unmap_mft_record(mft_ni);
            goto err_out;
      }
      a = ctx->attr;
      write_lock_irqsave(&mftbmp_ni->size_lock, flags);
      mftbmp_ni->initialized_size = old_initialized_size;
      a->data.non_resident.initialized_size =
                  cpu_to_sle64(old_initialized_size);
      if (i_size_read(mftbmp_vi) != old_data_size) {
            i_size_write(mftbmp_vi, old_data_size);
            a->data.non_resident.data_size = cpu_to_sle64(old_data_size);
      }
      write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(mft_ni);
#ifdef DEBUG
      read_lock_irqsave(&mftbmp_ni->size_lock, flags);
      ntfs_debug("Restored status of mftbmp: allocated_size 0x%llx, "
                  "data_size 0x%llx, initialized_size 0x%llx.",
                  (long long)mftbmp_ni->allocated_size,
                  (long long)i_size_read(mftbmp_vi),
                  (long long)mftbmp_ni->initialized_size);
      read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
err_out:
      return ret;
}

/**
 * ntfs_mft_data_extend_allocation_nolock - extend mft data attribute
 * @vol:    volume on which to extend the mft data attribute
 *
 * Extend the mft data attribute on the ntfs volume @vol by 16 mft records
 * worth of clusters or if not enough space for this by one mft record worth
 * of clusters.
 *
 * Note:  Only changes allocated_size, i.e. does not touch initialized_size or
 * data_size.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - Caller must hold vol->mftbmp_lock for writing.
 *        - This function takes NTFS_I(vol->mft_ino)->runlist.lock for
 *          writing and releases it before returning.
 *        - This function calls functions which take vol->lcnbmp_lock for
 *          writing and release it before returning.
 */
static int ntfs_mft_data_extend_allocation_nolock(ntfs_volume *vol)
{
      LCN lcn;
      VCN old_last_vcn;
      s64 min_nr, nr, ll;
      unsigned long flags;
      ntfs_inode *mft_ni;
      runlist_element *rl, *rl2;
      ntfs_attr_search_ctx *ctx = NULL;
      MFT_RECORD *mrec;
      ATTR_RECORD *a = NULL;
      int ret, mp_size;
      u32 old_alen = 0;
      bool mp_rebuilt = false;

      ntfs_debug("Extending mft data allocation.");
      mft_ni = NTFS_I(vol->mft_ino);
      /*
       * Determine the preferred allocation location, i.e. the last lcn of
       * the mft data attribute.  The allocated size of the mft data
       * attribute cannot be zero so we are ok to do this.
       */
      down_write(&mft_ni->runlist.lock);
      read_lock_irqsave(&mft_ni->size_lock, flags);
      ll = mft_ni->allocated_size;
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      rl = ntfs_attr_find_vcn_nolock(mft_ni,
                  (ll - 1) >> vol->cluster_size_bits, NULL);
      if (unlikely(IS_ERR(rl) || !rl->length || rl->lcn < 0)) {
            up_write(&mft_ni->runlist.lock);
            ntfs_error(vol->sb, "Failed to determine last allocated "
                        "cluster of mft data attribute.");
            if (!IS_ERR(rl))
                  ret = -EIO;
            else
                  ret = PTR_ERR(rl);
            return ret;
      }
      lcn = rl->lcn + rl->length;
      ntfs_debug("Last lcn of mft data attribute is 0x%llx.", (long long)lcn);
      /* Minimum allocation is one mft record worth of clusters. */
      min_nr = vol->mft_record_size >> vol->cluster_size_bits;
      if (!min_nr)
            min_nr = 1;
      /* Want to allocate 16 mft records worth of clusters. */
      nr = vol->mft_record_size << 4 >> vol->cluster_size_bits;
      if (!nr)
            nr = min_nr;
      /* Ensure we do not go above 2^32-1 mft records. */
      read_lock_irqsave(&mft_ni->size_lock, flags);
      ll = mft_ni->allocated_size;
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      if (unlikely((ll + (nr << vol->cluster_size_bits)) >>
                  vol->mft_record_size_bits >= (1ll << 32))) {
            nr = min_nr;
            if (unlikely((ll + (nr << vol->cluster_size_bits)) >>
                        vol->mft_record_size_bits >= (1ll << 32))) {
                  ntfs_warning(vol->sb, "Cannot allocate mft record "
                              "because the maximum number of inodes "
                              "(2^32) has already been reached.");
                  up_write(&mft_ni->runlist.lock);
                  return -ENOSPC;
            }
      }
      ntfs_debug("Trying mft data allocation with %s cluster count %lli.",
                  nr > min_nr ? "default" : "minimal", (long long)nr);
      old_last_vcn = rl[1].vcn;
      do {
            rl2 = ntfs_cluster_alloc(vol, old_last_vcn, nr, lcn, MFT_ZONE,
                        true);
            if (likely(!IS_ERR(rl2)))
                  break;
            if (PTR_ERR(rl2) != -ENOSPC || nr == min_nr) {
                  ntfs_error(vol->sb, "Failed to allocate the minimal "
                              "number of clusters (%lli) for the "
                              "mft data attribute.", (long long)nr);
                  up_write(&mft_ni->runlist.lock);
                  return PTR_ERR(rl2);
            }
            /*
             * There is not enough space to do the allocation, but there
             * might be enough space to do a minimal allocation so try that
             * before failing.
             */
            nr = min_nr;
            ntfs_debug("Retrying mft data allocation with minimal cluster "
                        "count %lli.", (long long)nr);
      } while (1);
      rl = ntfs_runlists_merge(mft_ni->runlist.rl, rl2);
      if (IS_ERR(rl)) {
            up_write(&mft_ni->runlist.lock);
            ntfs_error(vol->sb, "Failed to merge runlists for mft data "
                        "attribute.");
            if (ntfs_cluster_free_from_rl(vol, rl2)) {
                  ntfs_error(vol->sb, "Failed to dealocate clusters "
                              "from the mft data attribute.%s", es);
                  NVolSetErrors(vol);
            }
            ntfs_free(rl2);
            return PTR_ERR(rl);
      }
      mft_ni->runlist.rl = rl;
      ntfs_debug("Allocated %lli clusters.", (long long)nr);
      /* Find the last run in the new runlist. */
      for (; rl[1].length; rl++)
            ;
      /* Update the attribute record as well. */
      mrec = map_mft_record(mft_ni);
      if (IS_ERR(mrec)) {
            ntfs_error(vol->sb, "Failed to map mft record.");
            ret = PTR_ERR(mrec);
            goto undo_alloc;
      }
      ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
      if (unlikely(!ctx)) {
            ntfs_error(vol->sb, "Failed to get search context.");
            ret = -ENOMEM;
            goto undo_alloc;
      }
      ret = ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
                  CASE_SENSITIVE, rl[1].vcn, NULL, 0, ctx);
      if (unlikely(ret)) {
            ntfs_error(vol->sb, "Failed to find last attribute extent of "
                        "mft data attribute.");
            if (ret == -ENOENT)
                  ret = -EIO;
            goto undo_alloc;
      }
      a = ctx->attr;
      ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
      /* Search back for the previous last allocated cluster of mft bitmap. */
      for (rl2 = rl; rl2 > mft_ni->runlist.rl; rl2--) {
            if (ll >= rl2->vcn)
                  break;
      }
      BUG_ON(ll < rl2->vcn);
      BUG_ON(ll >= rl2->vcn + rl2->length);
      /* 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)) {
            ntfs_error(vol->sb, "Get size for mapping pairs failed for "
                        "mft data attribute extent.");
            ret = mp_size;
            if (!ret)
                  ret = -EIO;
            goto undo_alloc;
      }
      /* Expand the attribute record if necessary. */
      old_alen = le32_to_cpu(a->length);
      ret = ntfs_attr_record_resize(ctx->mrec, a, mp_size +
                  le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
      if (unlikely(ret)) {
            if (ret != -ENOSPC) {
                  ntfs_error(vol->sb, "Failed to resize attribute "
                              "record for mft data attribute.");
                  goto undo_alloc;
            }
            // TODO: Deal with this by moving this extent to a new mft
            // record or by starting a new extent in a new mft record or by
            // moving other attributes out of this mft record.
            // Note: Use the special reserved mft records and ensure that
            // this extent is not required to find the mft record in
            // question.  If no free special records left we would need to
            // move an existing record away, insert ours in its place, and
            // then place the moved record into the newly allocated space
            // and we would then need to update all references to this mft
            // record appropriately.  This is rather complicated...
            ntfs_error(vol->sb, "Not enough space in this mft record to "
                        "accomodate extended mft data attribute "
                        "extent.  Cannot handle this yet.");
            ret = -EOPNOTSUPP;
            goto undo_alloc;
      }
      mp_rebuilt = true;
      /* Generate the mapping pairs array directly into the attr record. */
      ret = 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(ret)) {
            ntfs_error(vol->sb, "Failed to build mapping pairs array of "
                        "mft data attribute.");
            goto undo_alloc;
      }
      /* Update the highest_vcn. */
      a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 1);
      /*
       * We now have extended the mft data allocated_size by nr clusters.
       * Reflect this in the ntfs_inode structure and the attribute record.
       * @rl is the last (non-terminator) runlist element of mft data
       * attribute.
       */
      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);
            ret = ntfs_attr_lookup(mft_ni->type, mft_ni->name,
                        mft_ni->name_len, CASE_SENSITIVE, 0, NULL, 0,
                        ctx);
            if (unlikely(ret)) {
                  ntfs_error(vol->sb, "Failed to find first attribute "
                              "extent of mft data attribute.");
                  goto restore_undo_alloc;
            }
            a = ctx->attr;
      }
      write_lock_irqsave(&mft_ni->size_lock, flags);
      mft_ni->allocated_size += nr << vol->cluster_size_bits;
      a->data.non_resident.allocated_size =
                  cpu_to_sle64(mft_ni->allocated_size);
      write_unlock_irqrestore(&mft_ni->size_lock, flags);
      /* Ensure the changes make it to disk. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(mft_ni);
      up_write(&mft_ni->runlist.lock);
      ntfs_debug("Done.");
      return 0;
restore_undo_alloc:
      ntfs_attr_reinit_search_ctx(ctx);
      if (ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
                  CASE_SENSITIVE, rl[1].vcn, NULL, 0, ctx)) {
            ntfs_error(vol->sb, "Failed to find last attribute extent of "
                        "mft data attribute.%s", es);
            write_lock_irqsave(&mft_ni->size_lock, flags);
            mft_ni->allocated_size += nr << vol->cluster_size_bits;
            write_unlock_irqrestore(&mft_ni->size_lock, flags);
            ntfs_attr_put_search_ctx(ctx);
            unmap_mft_record(mft_ni);
            up_write(&mft_ni->runlist.lock);
            /*
             * The only thing that is now wrong is ->allocated_size of the
             * base attribute extent which chkdsk should be able to fix.
             */
            NVolSetErrors(vol);
            return ret;
      }
      ctx->attr->data.non_resident.highest_vcn =
                  cpu_to_sle64(old_last_vcn - 1);
undo_alloc:
      if (ntfs_cluster_free(mft_ni, old_last_vcn, -1, ctx) < 0) {
            ntfs_error(vol->sb, "Failed to free clusters from mft data "
                        "attribute.%s", es);
            NVolSetErrors(vol);
      }
      a = ctx->attr;
      if (ntfs_rl_truncate_nolock(vol, &mft_ni->runlist, old_last_vcn)) {
            ntfs_error(vol->sb, "Failed to truncate mft data attribute "
                        "runlist.%s", es);
            NVolSetErrors(vol);
      }
      if (mp_rebuilt && !IS_ERR(ctx->mrec)) {
            if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                        a->data.non_resident.mapping_pairs_offset),
                        old_alen - le16_to_cpu(
                        a->data.non_resident.mapping_pairs_offset),
                        rl2, ll, -1, NULL)) {
                  ntfs_error(vol->sb, "Failed to restore mapping pairs "
                              "array.%s", es);
                  NVolSetErrors(vol);
            }
            if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
                  ntfs_error(vol->sb, "Failed to restore attribute "
                              "record.%s", es);
                  NVolSetErrors(vol);
            }
            flush_dcache_mft_record_page(ctx->ntfs_ino);
            mark_mft_record_dirty(ctx->ntfs_ino);
      } else if (IS_ERR(ctx->mrec)) {
            ntfs_error(vol->sb, "Failed to restore attribute search "
                        "context.%s", es);
            NVolSetErrors(vol);
      }
      if (ctx)
            ntfs_attr_put_search_ctx(ctx);
      if (!IS_ERR(mrec))
            unmap_mft_record(mft_ni);
      up_write(&mft_ni->runlist.lock);
      return ret;
}

/**
 * ntfs_mft_record_layout - layout an mft record into a memory buffer
 * @vol:    volume to which the mft record will belong
 * @mft_no: mft reference specifying the mft record number
 * @m:            destination buffer of size >= @vol->mft_record_size bytes
 *
 * Layout an empty, unused mft record with the mft record number @mft_no into
 * the buffer @m.  The volume @vol is needed because the mft record structure
 * was modified in NTFS 3.1 so we need to know which volume version this mft
 * record will be used on.
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_mft_record_layout(const ntfs_volume *vol, const s64 mft_no,
            MFT_RECORD *m)
{
      ATTR_RECORD *a;

      ntfs_debug("Entering for mft record 0x%llx.", (long long)mft_no);
      if (mft_no >= (1ll << 32)) {
            ntfs_error(vol->sb, "Mft record number 0x%llx exceeds "
                        "maximum of 2^32.", (long long)mft_no);
            return -ERANGE;
      }
      /* Start by clearing the whole mft record to gives us a clean slate. */
      memset(m, 0, vol->mft_record_size);
      /* Aligned to 2-byte boundary. */
      if (vol->major_ver < 3 || (vol->major_ver == 3 && !vol->minor_ver))
            m->usa_ofs = cpu_to_le16((sizeof(MFT_RECORD_OLD) + 1) & ~1);
      else {
            m->usa_ofs = cpu_to_le16((sizeof(MFT_RECORD) + 1) & ~1);
            /*
             * Set the NTFS 3.1+ specific fields while we know that the
             * volume version is 3.1+.
             */
            m->reserved = 0;
            m->mft_record_number = cpu_to_le32((u32)mft_no);
      }
      m->magic = magic_FILE;
      if (vol->mft_record_size >= NTFS_BLOCK_SIZE)
            m->usa_count = cpu_to_le16(vol->mft_record_size /
                        NTFS_BLOCK_SIZE + 1);
      else {
            m->usa_count = cpu_to_le16(1);
            ntfs_warning(vol->sb, "Sector size is bigger than mft record "
                        "size.  Setting usa_count to 1.  If chkdsk "
                        "reports this as corruption, please email "
                        "linux-ntfs-dev@lists.sourceforge.net stating "
                        "that you saw this message and that the "
                        "modified filesystem created was corrupt.  "
                        "Thank you.");
      }
      /* Set the update sequence number to 1. */
      *(le16*)((u8*)m + le16_to_cpu(m->usa_ofs)) = cpu_to_le16(1);
      m->lsn = 0;
      m->sequence_number = cpu_to_le16(1);
      m->link_count = 0;
      /*
       * Place the attributes straight after the update sequence array,
       * aligned to 8-byte boundary.
       */
      m->attrs_offset = cpu_to_le16((le16_to_cpu(m->usa_ofs) +
                  (le16_to_cpu(m->usa_count) << 1) + 7) & ~7);
      m->flags = 0;
      /*
       * Using attrs_offset plus eight bytes (for the termination attribute).
       * attrs_offset is already aligned to 8-byte boundary, so no need to
       * align again.
       */
      m->bytes_in_use = cpu_to_le32(le16_to_cpu(m->attrs_offset) + 8);
      m->bytes_allocated = cpu_to_le32(vol->mft_record_size);
      m->base_mft_record = 0;
      m->next_attr_instance = 0;
      /* Add the termination attribute. */
      a = (ATTR_RECORD*)((u8*)m + le16_to_cpu(m->attrs_offset));
      a->type = AT_END;
      a->length = 0;
      ntfs_debug("Done.");
      return 0;
}

/**
 * ntfs_mft_record_format - format an mft record on an ntfs volume
 * @vol:    volume on which to format the mft record
 * @mft_no: mft record number to format
 *
 * Format the mft record @mft_no in $MFT/$DATA, i.e. lay out an empty, unused
 * mft record into the appropriate place of the mft data attribute.  This is
 * used when extending the mft data attribute.
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_mft_record_format(const ntfs_volume *vol, const s64 mft_no)
{
      loff_t i_size;
      struct inode *mft_vi = vol->mft_ino;
      struct page *page;
      MFT_RECORD *m;
      pgoff_t index, end_index;
      unsigned int ofs;
      int err;

      ntfs_debug("Entering for mft record 0x%llx.", (long long)mft_no);
      /*
       * The index into the page cache and the offset within the page cache
       * page of the wanted mft record.
       */
      index = mft_no << vol->mft_record_size_bits >> PAGE_CACHE_SHIFT;
      ofs = (mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
      /* The maximum valid index into the page cache for $MFT's data. */
      i_size = i_size_read(mft_vi);
      end_index = i_size >> PAGE_CACHE_SHIFT;
      if (unlikely(index >= end_index)) {
            if (unlikely(index > end_index || ofs + vol->mft_record_size >=
                        (i_size & ~PAGE_CACHE_MASK))) {
                  ntfs_error(vol->sb, "Tried to format non-existing mft "
                              "record 0x%llx.", (long long)mft_no);
                  return -ENOENT;
            }
      }
      /* Read, map, and pin the page containing the mft record. */
      page = ntfs_map_page(mft_vi->i_mapping, index);
      if (unlikely(IS_ERR(page))) {
            ntfs_error(vol->sb, "Failed to map page containing mft record "
                        "to format 0x%llx.", (long long)mft_no);
            return PTR_ERR(page);
      }
      lock_page(page);
      BUG_ON(!PageUptodate(page));
      ClearPageUptodate(page);
      m = (MFT_RECORD*)((u8*)page_address(page) + ofs);
      err = ntfs_mft_record_layout(vol, mft_no, m);
      if (unlikely(err)) {
            ntfs_error(vol->sb, "Failed to layout mft record 0x%llx.",
                        (long long)mft_no);
            SetPageUptodate(page);
            unlock_page(page);
            ntfs_unmap_page(page);
            return err;
      }
      flush_dcache_page(page);
      SetPageUptodate(page);
      unlock_page(page);
      /*
       * Make sure the mft record is written out to disk.  We could use
       * ilookup5() to check if an inode is in icache and so on but this is
       * unnecessary as ntfs_writepage() will write the dirty record anyway.
       */
      mark_ntfs_record_dirty(page, ofs);
      ntfs_unmap_page(page);
      ntfs_debug("Done.");
      return 0;
}

/**
 * ntfs_mft_record_alloc - allocate an mft record on an ntfs volume
 * @vol:    [IN]  volume on which to allocate the mft record
 * @mode:   [IN]  mode if want a file or directory, i.e. base inode or 0
 * @base_ni:      [IN]  open base inode if allocating an extent mft record or NULL
 * @mrec:   [OUT] on successful return this is the mapped mft record
 *
 * Allocate an mft record in $MFT/$DATA of an open ntfs volume @vol.
 *
 * If @base_ni is NULL make the mft record a base mft record, i.e. a file or
 * direvctory inode, and allocate it at the default allocator position.  In
 * this case @mode is the file mode as given to us by the caller.  We in
 * particular use @mode to distinguish whether a file or a directory is being
 * created (S_IFDIR(mode) and S_IFREG(mode), respectively).
 *
 * If @base_ni is not NULL make the allocated mft record an extent record,
 * allocate it starting at the mft record after the base mft record and attach
 * the allocated and opened ntfs inode to the base inode @base_ni.  In this
 * case @mode must be 0 as it is meaningless for extent inodes.
 *
 * You need to check the return value with IS_ERR().  If false, the function
 * was successful and the return value is the now opened ntfs inode of the
 * allocated mft record.  *@mrec is then set to the allocated, mapped, pinned,
 * and locked mft record.  If IS_ERR() is true, the function failed and the
 * error code is obtained from PTR_ERR(return value).  *@mrec is undefined in
 * this case.
 *
 * Allocation strategy:
 *
 * To find a free mft record, we scan the mft bitmap for a zero bit.  To
 * optimize this we start scanning at the place specified by @base_ni or if
 * @base_ni is NULL we start where we last stopped and we perform wrap around
 * when we reach the end.  Note, we do not try to allocate mft records below
 * number 24 because numbers 0 to 15 are the defined system files anyway and 16
 * to 24 are special in that they are used for storing extension mft records
 * for the $DATA attribute of $MFT.  This is required to avoid the possibility
 * of creating a runlist with a circular dependency which once written to disk
 * can never be read in again.  Windows will only use records 16 to 24 for
 * normal files if the volume is completely out of space.  We never use them
 * which means that when the volume is really out of space we cannot create any
 * more files while Windows can still create up to 8 small files.  We can start
 * doing this at some later time, it does not matter much for now.
 *
 * When scanning the mft bitmap, we only search up to the last allocated mft
 * record.  If there are no free records left in the range 24 to number of
 * allocated mft records, then we extend the $MFT/$DATA attribute in order to
 * create free mft records.  We extend the allocated size of $MFT/$DATA by 16
 * records at a time or one cluster, if cluster size is above 16kiB.  If there
 * is not sufficient space to do this, we try to extend by a single mft record
 * or one cluster, if cluster size is above the mft record size.
 *
 * No matter how many mft records we allocate, we initialize only the first
 * allocated mft record, incrementing mft data size and initialized size
 * accordingly, open an ntfs_inode for it and return it to the caller, unless
 * there are less than 24 mft records, in which case we allocate and initialize
 * mft records until we reach record 24 which we consider as the first free mft
 * record for use by normal files.
 *
 * If during any stage we overflow the initialized data in the mft bitmap, we
 * extend the initialized size (and data size) by 8 bytes, allocating another
 * cluster if required.  The bitmap data size has to be at least equal to the
 * number of mft records in the mft, but it can be bigger, in which case the
 * superflous bits are padded with zeroes.
 *
 * Thus, when we return successfully (IS_ERR() is false), we will have:
 *    - initialized / extended the mft bitmap if necessary,
 *    - initialized / extended the mft data if necessary,
 *    - set the bit corresponding to the mft record being allocated in the
 *      mft bitmap,
 *    - opened an ntfs_inode for the allocated mft record, and we will have
 *    - returned the ntfs_inode as well as the allocated mapped, pinned, and
 *      locked mft record.
 *
 * On error, the volume will be left in a consistent state and no record will
 * be allocated.  If rolling back a partial operation fails, we may leave some
 * inconsistent metadata in which case we set NVolErrors() so the volume is
 * left dirty when unmounted.
 *
 * Note, this function cannot make use of most of the normal functions, like
 * for example for attribute resizing, etc, because when the run list overflows
 * the base mft record and an attribute list is used, it is very important that
 * the extension mft records used to store the $DATA attribute of $MFT can be
 * reached without having to read the information contained inside them, as
 * this would make it impossible to find them in the first place after the
 * volume is unmounted.  $MFT/$BITMAP probably does not need to follow this
 * rule because the bitmap is not essential for finding the mft records, but on
 * the other hand, handling the bitmap in this special way would make life
 * easier because otherwise there might be circular invocations of functions
 * when reading the bitmap.
 */
ntfs_inode *ntfs_mft_record_alloc(ntfs_volume *vol, const int mode,
            ntfs_inode *base_ni, MFT_RECORD **mrec)
{
      s64 ll, bit, old_data_initialized, old_data_size;
      unsigned long flags;
      struct inode *vi;
      struct page *page;
      ntfs_inode *mft_ni, *mftbmp_ni, *ni;
      ntfs_attr_search_ctx *ctx;
      MFT_RECORD *m;
      ATTR_RECORD *a;
      pgoff_t index;
      unsigned int ofs;
      int err;
      le16 seq_no, usn;
      bool record_formatted = false;

      if (base_ni) {
            ntfs_debug("Entering (allocating an extent mft record for "
                        "base mft record 0x%llx).",
                        (long long)base_ni->mft_no);
            /* @mode and @base_ni are mutually exclusive. */
            BUG_ON(mode);
      } else
            ntfs_debug("Entering (allocating a base mft record).");
      if (mode) {
            /* @mode and @base_ni are mutually exclusive. */
            BUG_ON(base_ni);
            /* We only support creation of normal files and directories. */
            if (!S_ISREG(mode) && !S_ISDIR(mode))
                  return ERR_PTR(-EOPNOTSUPP);
      }
      BUG_ON(!mrec);
      mft_ni = NTFS_I(vol->mft_ino);
      mftbmp_ni = NTFS_I(vol->mftbmp_ino);
      down_write(&vol->mftbmp_lock);
      bit = ntfs_mft_bitmap_find_and_alloc_free_rec_nolock(vol, base_ni);
      if (bit >= 0) {
            ntfs_debug("Found and allocated free record (#1), bit 0x%llx.",
                        (long long)bit);
            goto have_alloc_rec;
      }
      if (bit != -ENOSPC) {
            up_write(&vol->mftbmp_lock);
            return ERR_PTR(bit);
      }
      /*
       * No free mft records left.  If the mft bitmap already covers more
       * than the currently used mft records, the next records are all free,
       * so we can simply allocate the first unused mft record.
       * Note: We also have to make sure that the mft bitmap at least covers
       * the first 24 mft records as they are special and whilst they may not
       * be in use, we do not allocate from them.
       */
      read_lock_irqsave(&mft_ni->size_lock, flags);
      ll = mft_ni->initialized_size >> vol->mft_record_size_bits;
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      read_lock_irqsave(&mftbmp_ni->size_lock, flags);
      old_data_initialized = mftbmp_ni->initialized_size;
      read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      if (old_data_initialized << 3 > ll && old_data_initialized > 3) {
            bit = ll;
            if (bit < 24)
                  bit = 24;
            if (unlikely(bit >= (1ll << 32)))
                  goto max_err_out;
            ntfs_debug("Found free record (#2), bit 0x%llx.",
                        (long long)bit);
            goto found_free_rec;
      }
      /*
       * The mft bitmap needs to be expanded until it covers the first unused
       * mft record that we can allocate.
       * Note: The smallest mft record we allocate is mft record 24.
       */
      bit = old_data_initialized << 3;
      if (unlikely(bit >= (1ll << 32)))
            goto max_err_out;
      read_lock_irqsave(&mftbmp_ni->size_lock, flags);
      old_data_size = mftbmp_ni->allocated_size;
      ntfs_debug("Status of mftbmp before extension: allocated_size 0x%llx, "
                  "data_size 0x%llx, initialized_size 0x%llx.",
                  (long long)old_data_size,
                  (long long)i_size_read(vol->mftbmp_ino),
                  (long long)old_data_initialized);
      read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
      if (old_data_initialized + 8 > old_data_size) {
            /* Need to extend bitmap by one more cluster. */
            ntfs_debug("mftbmp: initialized_size + 8 > allocated_size.");
            err = ntfs_mft_bitmap_extend_allocation_nolock(vol);
            if (unlikely(err)) {
                  up_write(&vol->mftbmp_lock);
                  goto err_out;
            }
#ifdef DEBUG
            read_lock_irqsave(&mftbmp_ni->size_lock, flags);
            ntfs_debug("Status of mftbmp after allocation extension: "
                        "allocated_size 0x%llx, data_size 0x%llx, "
                        "initialized_size 0x%llx.",
                        (long long)mftbmp_ni->allocated_size,
                        (long long)i_size_read(vol->mftbmp_ino),
                        (long long)mftbmp_ni->initialized_size);
            read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
      }
      /*
       * We now have sufficient allocated space, extend the initialized_size
       * as well as the data_size if necessary and fill the new space with
       * zeroes.
       */
      err = ntfs_mft_bitmap_extend_initialized_nolock(vol);
      if (unlikely(err)) {
            up_write(&vol->mftbmp_lock);
            goto err_out;
      }
#ifdef DEBUG
      read_lock_irqsave(&mftbmp_ni->size_lock, flags);
      ntfs_debug("Status of mftbmp after initialized extention: "
                  "allocated_size 0x%llx, data_size 0x%llx, "
                  "initialized_size 0x%llx.",
                  (long long)mftbmp_ni->allocated_size,
                  (long long)i_size_read(vol->mftbmp_ino),
                  (long long)mftbmp_ni->initialized_size);
      read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
      ntfs_debug("Found free record (#3), bit 0x%llx.", (long long)bit);
found_free_rec:
      /* @bit is the found free mft record, allocate it in the mft bitmap. */
      ntfs_debug("At found_free_rec.");
      err = ntfs_bitmap_set_bit(vol->mftbmp_ino, bit);
      if (unlikely(err)) {
            ntfs_error(vol->sb, "Failed to allocate bit in mft bitmap.");
            up_write(&vol->mftbmp_lock);
            goto err_out;
      }
      ntfs_debug("Set bit 0x%llx in mft bitmap.", (long long)bit);
have_alloc_rec:
      /*
       * The mft bitmap is now uptodate.  Deal with mft data attribute now.
       * Note, we keep hold of the mft bitmap lock for writing until all
       * modifications to the mft data attribute are complete, too, as they
       * will impact decisions for mft bitmap and mft record allocation done
       * by a parallel allocation and if the lock is not maintained a
       * parallel allocation could allocate the same mft record as this one.
       */
      ll = (bit + 1) << vol->mft_record_size_bits;
      read_lock_irqsave(&mft_ni->size_lock, flags);
      old_data_initialized = mft_ni->initialized_size;
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      if (ll <= old_data_initialized) {
            ntfs_debug("Allocated mft record already initialized.");
            goto mft_rec_already_initialized;
      }
      ntfs_debug("Initializing allocated mft record.");
      /*
       * The mft record is outside the initialized data.  Extend the mft data
       * attribute until it covers the allocated record.  The loop is only
       * actually traversed more than once when a freshly formatted volume is
       * first written to so it optimizes away nicely in the common case.
       */
      read_lock_irqsave(&mft_ni->size_lock, flags);
      ntfs_debug("Status of mft data before extension: "
                  "allocated_size 0x%llx, data_size 0x%llx, "
                  "initialized_size 0x%llx.",
                  (long long)mft_ni->allocated_size,
                  (long long)i_size_read(vol->mft_ino),
                  (long long)mft_ni->initialized_size);
      while (ll > mft_ni->allocated_size) {
            read_unlock_irqrestore(&mft_ni->size_lock, flags);
            err = ntfs_mft_data_extend_allocation_nolock(vol);
            if (unlikely(err)) {
                  ntfs_error(vol->sb, "Failed to extend mft data "
                              "allocation.");
                  goto undo_mftbmp_alloc_nolock;
            }
            read_lock_irqsave(&mft_ni->size_lock, flags);
            ntfs_debug("Status of mft data after allocation extension: "
                        "allocated_size 0x%llx, data_size 0x%llx, "
                        "initialized_size 0x%llx.",
                        (long long)mft_ni->allocated_size,
                        (long long)i_size_read(vol->mft_ino),
                        (long long)mft_ni->initialized_size);
      }
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      /*
       * Extend mft data initialized size (and data size of course) to reach
       * the allocated mft record, formatting the mft records allong the way.
       * Note: We only modify the ntfs_inode structure as that is all that is
       * needed by ntfs_mft_record_format().  We will update the attribute
       * record itself in one fell swoop later on.
       */
      write_lock_irqsave(&mft_ni->size_lock, flags);
      old_data_initialized = mft_ni->initialized_size;
      old_data_size = vol->mft_ino->i_size;
      while (ll > mft_ni->initialized_size) {
            s64 new_initialized_size, mft_no;
            
            new_initialized_size = mft_ni->initialized_size +
                        vol->mft_record_size;
            mft_no = mft_ni->initialized_size >> vol->mft_record_size_bits;
            if (new_initialized_size > i_size_read(vol->mft_ino))
                  i_size_write(vol->mft_ino, new_initialized_size);
            write_unlock_irqrestore(&mft_ni->size_lock, flags);
            ntfs_debug("Initializing mft record 0x%llx.",
                        (long long)mft_no);
            err = ntfs_mft_record_format(vol, mft_no);
            if (unlikely(err)) {
                  ntfs_error(vol->sb, "Failed to format mft record.");
                  goto undo_data_init;
            }
            write_lock_irqsave(&mft_ni->size_lock, flags);
            mft_ni->initialized_size = new_initialized_size;
      }
      write_unlock_irqrestore(&mft_ni->size_lock, flags);
      record_formatted = true;
      /* Update the mft data attribute record to reflect the new sizes. */
      m = map_mft_record(mft_ni);
      if (IS_ERR(m)) {
            ntfs_error(vol->sb, "Failed to map mft record.");
            err = PTR_ERR(m);
            goto undo_data_init;
      }
      ctx = ntfs_attr_get_search_ctx(mft_ni, m);
      if (unlikely(!ctx)) {
            ntfs_error(vol->sb, "Failed to get search context.");
            err = -ENOMEM;
            unmap_mft_record(mft_ni);
            goto undo_data_init;
      }
      err = ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
                  CASE_SENSITIVE, 0, NULL, 0, ctx);
      if (unlikely(err)) {
            ntfs_error(vol->sb, "Failed to find first attribute extent of "
                        "mft data attribute.");
            ntfs_attr_put_search_ctx(ctx);
            unmap_mft_record(mft_ni);
            goto undo_data_init;
      }
      a = ctx->attr;
      read_lock_irqsave(&mft_ni->size_lock, flags);
      a->data.non_resident.initialized_size =
                  cpu_to_sle64(mft_ni->initialized_size);
      a->data.non_resident.data_size =
                  cpu_to_sle64(i_size_read(vol->mft_ino));
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
      /* Ensure the changes make it to disk. */
      flush_dcache_mft_record_page(ctx->ntfs_ino);
      mark_mft_record_dirty(ctx->ntfs_ino);
      ntfs_attr_put_search_ctx(ctx);
      unmap_mft_record(mft_ni);
      read_lock_irqsave(&mft_ni->size_lock, flags);
      ntfs_debug("Status of mft data after mft record initialization: "
                  "allocated_size 0x%llx, data_size 0x%llx, "
                  "initialized_size 0x%llx.",
                  (long long)mft_ni->allocated_size,
                  (long long)i_size_read(vol->mft_ino),
                  (long long)mft_ni->initialized_size);
      BUG_ON(i_size_read(vol->mft_ino) > mft_ni->allocated_size);
      BUG_ON(mft_ni->initialized_size > i_size_read(vol->mft_ino));
      read_unlock_irqrestore(&mft_ni->size_lock, flags);
mft_rec_already_initialized:
      /*
       * We can finally drop the mft bitmap lock as the mft data attribute
       * has been fully updated.  The only disparity left is that the
       * allocated mft record still needs to be marked as in use to match the
       * set bit in the mft bitmap but this is actually not a problem since
       * this mft record is not referenced from anywhere yet and the fact
       * that it is allocated in the mft bitmap means that no-one will try to
       * allocate it either.
       */
      up_write(&vol->mftbmp_lock);
      /*
       * We now have allocated and initialized the mft record.  Calculate the
       * index of and the offset within the page cache page the record is in.
       */
      index = bit << vol->mft_record_size_bits >> PAGE_CACHE_SHIFT;
      ofs = (bit << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
      /* Read, map, and pin the page containing the mft record. */
      page = ntfs_map_page(vol->mft_ino->i_mapping, index);
      if (unlikely(IS_ERR(page))) {
            ntfs_error(vol->sb, "Failed to map page containing allocated "
                        "mft record 0x%llx.", (long long)bit);
            err = PTR_ERR(page);
            goto undo_mftbmp_alloc;
      }
      lock_page(page);
      BUG_ON(!PageUptodate(page));
      ClearPageUptodate(page);
      m = (MFT_RECORD*)((u8*)page_address(page) + ofs);
      /* If we just formatted the mft record no need to do it again. */
      if (!record_formatted) {
            /* Sanity check that the mft record is really not in use. */
            if (ntfs_is_file_record(m->magic) &&
                        (m->flags & MFT_RECORD_IN_USE)) {
                  ntfs_error(vol->sb, "Mft record 0x%llx was marked "
                              "free in mft bitmap but is marked "
                              "used itself.  Corrupt filesystem.  "
                              "Unmount and run chkdsk.",
                              (long long)bit);
                  err = -EIO;
                  SetPageUptodate(page);
                  unlock_page(page);
                  ntfs_unmap_page(page);
                  NVolSetErrors(vol);
                  goto undo_mftbmp_alloc;
            }
            /*
             * We need to (re-)format the mft record, preserving the
             * sequence number if it is not zero as well as the update
             * sequence number if it is not zero or -1 (0xffff).  This
             * means we do not need to care whether or not something went
             * wrong with the previous mft record.
             */
            seq_no = m->sequence_number;
            usn = *(le16*)((u8*)m + le16_to_cpu(m->usa_ofs));
            err = ntfs_mft_record_layout(vol, bit, m);
            if (unlikely(err)) {
                  ntfs_error(vol->sb, "Failed to layout allocated mft "
                              "record 0x%llx.", (long long)bit);
                  SetPageUptodate(page);
                  unlock_page(page);
                  ntfs_unmap_page(page);
                  goto undo_mftbmp_alloc;
            }
            if (seq_no)
                  m->sequence_number = seq_no;
            if (usn && le16_to_cpu(usn) != 0xffff)
                  *(le16*)((u8*)m + le16_to_cpu(m->usa_ofs)) = usn;
      }
      /* Set the mft record itself in use. */
      m->flags |= MFT_RECORD_IN_USE;
      if (S_ISDIR(mode))
            m->flags |= MFT_RECORD_IS_DIRECTORY;
      flush_dcache_page(page);
      SetPageUptodate(page);
      if (base_ni) {
            /*
             * Setup the base mft record in the extent mft record.  This
             * completes initialization of the allocated extent mft record
             * and we can simply use it with map_extent_mft_record().
             */
            m->base_mft_record = MK_LE_MREF(base_ni->mft_no,
                        base_ni->seq_no);
            /*
             * Allocate an extent inode structure for the new mft record,
             * attach it to the base inode @base_ni and map, pin, and lock
             * its, i.e. the allocated, mft record.
             */
            m = map_extent_mft_record(base_ni, bit, &ni);
            if (IS_ERR(m)) {
                  ntfs_error(vol->sb, "Failed to map allocated extent "
                              "mft record 0x%llx.", (long long)bit);
                  err = PTR_ERR(m);
                  /* Set the mft record itself not in use. */
                  m->flags &= cpu_to_le16(
                              ~le16_to_cpu(MFT_RECORD_IN_USE));
                  flush_dcache_page(page);
                  /* Make sure the mft record is written out to disk. */
                  mark_ntfs_record_dirty(page, ofs);
                  unlock_page(page);
                  ntfs_unmap_page(page);
                  goto undo_mftbmp_alloc;
            }
            /*
             * Make sure the allocated mft record is written out to disk.
             * No need to set the inode dirty because the caller is going
             * to do that anyway after finishing with the new extent mft
             * record (e.g. at a minimum a new attribute will be added to
             * the mft record.
             */
            mark_ntfs_record_dirty(page, ofs);
            unlock_page(page);
            /*
             * Need to unmap the page since map_extent_mft_record() mapped
             * it as well so we have it mapped twice at the moment.
             */
            ntfs_unmap_page(page);
      } else {
            /*
             * Allocate a new VFS inode and set it up.  NOTE: @vi->i_nlink
             * is set to 1 but the mft record->link_count is 0.  The caller
             * needs to bear this in mind.
             */
            vi = new_inode(vol->sb);
            if (unlikely(!vi)) {
                  err = -ENOMEM;
                  /* Set the mft record itself not in use. */
                  m->flags &= cpu_to_le16(
                              ~le16_to_cpu(MFT_RECORD_IN_USE));
                  flush_dcache_page(page);
                  /* Make sure the mft record is written out to disk. */
                  mark_ntfs_record_dirty(page, ofs);
                  unlock_page(page);
                  ntfs_unmap_page(page);
                  goto undo_mftbmp_alloc;
            }
            vi->i_ino = bit;
            /*
             * This is for checking whether an inode has changed w.r.t. a
             * file so that the file can be updated if necessary (compare
             * with f_version).
             */
            vi->i_version = 1;

            /* The owner and group come from the ntfs volume. */
            vi->i_uid = vol->uid;
            vi->i_gid = vol->gid;

            /* Initialize the ntfs specific part of @vi. */
            ntfs_init_big_inode(vi);
            ni = NTFS_I(vi);
            /*
             * Set the appropriate mode, attribute type, and name.  For
             * directories, also setup the index values to the defaults.
             */
            if (S_ISDIR(mode)) {
                  vi->i_mode = S_IFDIR | S_IRWXUGO;
                  vi->i_mode &= ~vol->dmask;

                  NInoSetMstProtected(ni);
                  ni->type = AT_INDEX_ALLOCATION;
                  ni->name = I30;
                  ni->name_len = 4;

                  ni->itype.index.block_size = 4096;
                  ni->itype.index.block_size_bits = ntfs_ffs(4096) - 1;
                  ni->itype.index.collation_rule = COLLATION_FILE_NAME;
                  if (vol->cluster_size <= ni->itype.index.block_size) {
                        ni->itype.index.vcn_size = vol->cluster_size;
                        ni->itype.index.vcn_size_bits =
                                    vol->cluster_size_bits;
                  } else {
                        ni->itype.index.vcn_size = vol->sector_size;
                        ni->itype.index.vcn_size_bits =
                                    vol->sector_size_bits;
                  }
            } else {
                  vi->i_mode = S_IFREG | S_IRWXUGO;
                  vi->i_mode &= ~vol->fmask;

                  ni->type = AT_DATA;
                  ni->name = NULL;
                  ni->name_len = 0;
            }
            if (IS_RDONLY(vi))
                  vi->i_mode &= ~S_IWUGO;

            /* Set the inode times to the current time. */
            vi->i_atime = vi->i_mtime = vi->i_ctime =
                  current_fs_time(vi->i_sb);
            /*
             * Set the file size to 0, the ntfs inode sizes are set to 0 by
             * the call to ntfs_init_big_inode() below.
             */
            vi->i_size = 0;
            vi->i_blocks = 0;

            /* Set the sequence number. */
            vi->i_generation = ni->seq_no = le16_to_cpu(m->sequence_number);
            /*
             * Manually map, pin, and lock the mft record as we already
             * have its page mapped and it is very easy to do.
             */
            atomic_inc(&ni->count);
            mutex_lock(&ni->mrec_lock);
            ni->page = page;
            ni->page_ofs = ofs;
            /*
             * Make sure the allocated mft record is written out to disk.
             * NOTE: We do not set the ntfs inode dirty because this would
             * fail in ntfs_write_inode() because the inode does not have a
             * standard information attribute yet.  Also, there is no need
             * to set the inode dirty because the caller is going to do
             * that anyway after finishing with the new mft record (e.g. at
             * a minimum some new attributes will be added to the mft
             * record.
             */
            mark_ntfs_record_dirty(page, ofs);
            unlock_page(page);

            /* Add the inode to the inode hash for the superblock. */
            insert_inode_hash(vi);

            /* Update the default mft allocation position. */
            vol->mft_data_pos = bit + 1;
      }
      /*
       * Return the opened, allocated inode of the allocated mft record as
       * well as the mapped, pinned, and locked mft record.
       */
      ntfs_debug("Returning opened, allocated %sinode 0x%llx.",
                  base_ni ? "extent " : "", (long long)bit);
      *mrec = m;
      return ni;
undo_data_init:
      write_lock_irqsave(&mft_ni->size_lock, flags);
      mft_ni->initialized_size = old_data_initialized;
      i_size_write(vol->mft_ino, old_data_size);
      write_unlock_irqrestore(&mft_ni->size_lock, flags);
      goto undo_mftbmp_alloc_nolock;
undo_mftbmp_alloc:
      down_write(&vol->mftbmp_lock);
undo_mftbmp_alloc_nolock:
      if (ntfs_bitmap_clear_bit(vol->mftbmp_ino, bit)) {
            ntfs_error(vol->sb, "Failed to clear bit in mft bitmap.%s", es);
            NVolSetErrors(vol);
      }
      up_write(&vol->mftbmp_lock);
err_out:
      return ERR_PTR(err);
max_err_out:
      ntfs_warning(vol->sb, "Cannot allocate mft record because the maximum "
                  "number of inodes (2^32) has already been reached.");
      up_write(&vol->mftbmp_lock);
      return ERR_PTR(-ENOSPC);
}

/**
 * ntfs_extent_mft_record_free - free an extent mft record on an ntfs volume
 * @ni:           ntfs inode of the mapped extent mft record to free
 * @m:            mapped extent mft record of the ntfs inode @ni
 *
 * Free the mapped extent mft record @m of the extent ntfs inode @ni.
 *
 * Note that this function unmaps the mft record and closes and destroys @ni
 * internally and hence you cannot use either @ni nor @m any more after this
 * function returns success.
 *
 * On success return 0 and on error return -errno.  @ni and @m are still valid
 * in this case and have not been freed.
 *
 * For some errors an error message is displayed and the success code 0 is
 * returned and the volume is then left dirty on umount.  This makes sense in
 * case we could not rollback the changes that were already done since the
 * caller no longer wants to reference this mft record so it does not matter to
 * the caller if something is wrong with it as long as it is properly detached
 * from the base inode.
 */
int ntfs_extent_mft_record_free(ntfs_inode *ni, MFT_RECORD *m)
{
      unsigned long mft_no = ni->mft_no;
      ntfs_volume *vol = ni->vol;
      ntfs_inode *base_ni;
      ntfs_inode **extent_nis;
      int i, err;
      le16 old_seq_no;
      u16 seq_no;
      
      BUG_ON(NInoAttr(ni));
      BUG_ON(ni->nr_extents != -1);

      mutex_lock(&ni->extent_lock);
      base_ni = ni->ext.base_ntfs_ino;
      mutex_unlock(&ni->extent_lock);

      BUG_ON(base_ni->nr_extents <= 0);

      ntfs_debug("Entering for extent inode 0x%lx, base inode 0x%lx.\n",
                  mft_no, base_ni->mft_no);

      mutex_lock(&base_ni->extent_lock);

      /* Make sure we are holding the only reference to the extent inode. */
      if (atomic_read(&ni->count) > 2) {
            ntfs_error(vol->sb, "Tried to free busy extent inode 0x%lx, "
                        "not freeing.", base_ni->mft_no);
            mutex_unlock(&base_ni->extent_lock);
            return -EBUSY;
      }

      /* Dissociate the ntfs inode from the base inode. */
      extent_nis = base_ni->ext.extent_ntfs_inos;
      err = -ENOENT;
      for (i = 0; i < base_ni->nr_extents; i++) {
            if (ni != extent_nis[i])
                  continue;
            extent_nis += i;
            base_ni->nr_extents--;
            memmove(extent_nis, extent_nis + 1, (base_ni->nr_extents - i) *
                        sizeof(ntfs_inode*));
            err = 0;
            break;
      }

      mutex_unlock(&base_ni->extent_lock);

      if (unlikely(err)) {
            ntfs_error(vol->sb, "Extent inode 0x%lx is not attached to "
                        "its base inode 0x%lx.", mft_no,
                        base_ni->mft_no);
            BUG();
      }

      /*
       * The extent inode is no longer attached to the base inode so no one
       * can get a reference to it any more.
       */

      /* Mark the mft record as not in use. */
      m->flags &= const_cpu_to_le16(~const_le16_to_cpu(MFT_RECORD_IN_USE));

      /* Increment the sequence number, skipping zero, if it is not zero. */
      old_seq_no = m->sequence_number;
      seq_no = le16_to_cpu(old_seq_no);
      if (seq_no == 0xffff)
            seq_no = 1;
      else if (seq_no)
            seq_no++;
      m->sequence_number = cpu_to_le16(seq_no);

      /*
       * Set the ntfs inode dirty and write it out.  We do not need to worry
       * about the base inode here since whatever caused the extent mft
       * record to be freed is guaranteed to do it already.
       */
      NInoSetDirty(ni);
      err = write_mft_record(ni, m, 0);
      if (unlikely(err)) {
            ntfs_error(vol->sb, "Failed to write mft record 0x%lx, not "
                        "freeing.", mft_no);
            goto rollback;
      }
rollback_error:
      /* Unmap and throw away the now freed extent inode. */
      unmap_extent_mft_record(ni);
      ntfs_clear_extent_inode(ni);

      /* Clear the bit in the $MFT/$BITMAP corresponding to this record. */
      down_write(&vol->mftbmp_lock);
      err = ntfs_bitmap_clear_bit(vol->mftbmp_ino, mft_no);
      up_write(&vol->mftbmp_lock);
      if (unlikely(err)) {
            /*
             * The extent inode is gone but we failed to deallocate it in
             * the mft bitmap.  Just emit a warning and leave the volume
             * dirty on umount.
             */
            ntfs_error(vol->sb, "Failed to clear bit in mft bitmap.%s", es);
            NVolSetErrors(vol);
      }
      return 0;
rollback:
      /* Rollback what we did... */
      mutex_lock(&base_ni->extent_lock);
      extent_nis = base_ni->ext.extent_ntfs_inos;
      if (!(base_ni->nr_extents & 3)) {
            int new_size = (base_ni->nr_extents + 4) * sizeof(ntfs_inode*);

            extent_nis = kmalloc(new_size, GFP_NOFS);
            if (unlikely(!extent_nis)) {
                  ntfs_error(vol->sb, "Failed to allocate internal "
                              "buffer during rollback.%s", es);
                  mutex_unlock(&base_ni->extent_lock);
                  NVolSetErrors(vol);
                  goto rollback_error;
            }
            if (base_ni->nr_extents) {
                  BUG_ON(!base_ni->ext.extent_ntfs_inos);
                  memcpy(extent_nis, base_ni->ext.extent_ntfs_inos,
                              new_size - 4 * sizeof(ntfs_inode*));
                  kfree(base_ni->ext.extent_ntfs_inos);
            }
            base_ni->ext.extent_ntfs_inos = extent_nis;
      }
      m->flags |= MFT_RECORD_IN_USE;
      m->sequence_number = old_seq_no;
      extent_nis[base_ni->nr_extents++] = ni;
      mutex_unlock(&base_ni->extent_lock);
      mark_mft_record_dirty(ni);
      return err;
}
#endif /* NTFS_RW */

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