reiserfs: fix xattr root locking/refcount bug

[linux-2.6] / fs / ntfs / 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 */