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    Subject[070/102] ext4: fix i_blocks/quota accounting when extent insertion fails
    3.0-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Maxim Patlasov <maxim.patlasov@gmail.com>

    commit 7132de744ba76930d13033061018ddd7e3e8cd91 upstream.

    The current implementation of ext4_free_blocks() always calls
    dquot_free_block This looks quite sensible in the most cases: blocks
    to be freed are associated with inode and were accounted in quota and
    i_blocks some time ago.

    However, there is a case when blocks to free were not accounted by the
    time calling ext4_free_blocks() yet:

    1. delalloc is on, write_begin pre-allocated some space in quota
    2. write-back happens, ext4 allocates some blocks in ext4_ext_map_blocks()
    3. then ext4_ext_map_blocks() gets an error (e.g. ENOSPC) from
    ext4_ext_insert_extent() and calls ext4_free_blocks().

    In this scenario, ext4_free_blocks() calls dquot_free_block() who, in
    turn, decrements i_blocks for blocks which were not accounted yet (due
    to delalloc) After clean umount, e2fsck reports something like:

    > Inode 21, i_blocks is 5080, should be 5128. Fix<y>?
    because i_blocks was erroneously decremented as explained above.

    The patch fixes the problem by passing the new flag
    EXT4_FREE_BLOCKS_NO_QUOT_UPDATE to ext4_free_blocks(), to request
    that the dquot_free_block() call be skipped.

    Signed-off-by: Maxim Patlasov <maxim.patlasov@gmail.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/ext4/ext4.h | 1 +
    fs/ext4/extents.c | 4 +++-
    fs/ext4/mballoc.c | 2 +-
    3 files changed, 5 insertions(+), 2 deletions(-)

    --- a/fs/ext4/ext4.h
    +++ b/fs/ext4/ext4.h
    @@ -526,6 +526,7 @@ struct ext4_new_group_data {
    #define EXT4_FREE_BLOCKS_METADATA 0x0001
    #define EXT4_FREE_BLOCKS_FORGET 0x0002
    #define EXT4_FREE_BLOCKS_VALIDATED 0x0004
    +#define EXT4_FREE_BLOCKS_NO_QUOT_UPDATE 0x0008

    /*
    * ioctl commands
    --- a/fs/ext4/extents.c
    +++ b/fs/ext4/extents.c
    @@ -3601,12 +3601,14 @@ int ext4_ext_map_blocks(handle_t *handle

    err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
    if (err) {
    + int fb_flags = flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE ?
    + EXT4_FREE_BLOCKS_NO_QUOT_UPDATE : 0;
    /* free data blocks we just allocated */
    /* not a good idea to call discard here directly,
    * but otherwise we'd need to call it every free() */
    ext4_discard_preallocations(inode);
    ext4_free_blocks(handle, inode, NULL, ext4_ext_pblock(&newex),
    - ext4_ext_get_actual_len(&newex), 0);
    + ext4_ext_get_actual_len(&newex), fb_flags);
    goto out2;
    }

    --- a/fs/ext4/mballoc.c
    +++ b/fs/ext4/mballoc.c
    @@ -4637,7 +4637,7 @@ do_more:
    }
    ext4_mark_super_dirty(sb);
    error_return:
    - if (freed)
    + if (freed && !(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
    dquot_free_block(inode, freed);
    brelse(bitmap_bh);
    ext4_std_error(sb, err);



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