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    Subject[PATCH 3.18 20/67] ext4: fix interaction between i_size, fallocate, and delalloc after a crash
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: Theodore Ts'o <tytso@mit.edu>

    commit 51e3ae81ec58e95f10a98ef3dd6d7bce5d8e35a2 upstream.

    If there are pending writes subject to delayed allocation, then i_size
    will show size after the writes have completed, while i_disksize
    contains the value of i_size on the disk (since the writes have not
    been persisted to disk).

    If fallocate(2) is called with the FALLOC_FL_KEEP_SIZE flag, either
    with or without the FALLOC_FL_ZERO_RANGE flag set, and the new size
    after the fallocate(2) is between i_size and i_disksize, then after a
    crash, if a journal commit has resulted in the changes made by the
    fallocate() call to be persisted after a crash, but the delayed
    allocation write has not resolved itself, i_size would not be updated,
    and this would cause the following e2fsck complaint:

    Inode 12, end of extent exceeds allowed value
    (logical block 33, physical block 33441, len 7)

    This can only take place on a sparse file, where the fallocate(2) call
    is allocating blocks in a range which is before a pending delayed
    allocation write which is extending i_size. Since this situation is
    quite rare, and the window in which the crash must take place is
    typically < 30 seconds, in practice this condition will rarely happen.

    Nevertheless, it can be triggered in testing, and in particular by
    xfstests generic/456.

    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Reported-by: Amir Goldstein <amir73il@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ext4/extents.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/fs/ext4/extents.c
    +++ b/fs/ext4/extents.c
    @@ -4807,7 +4807,8 @@ static long ext4_zero_range(struct file
    }

    if (!(mode & FALLOC_FL_KEEP_SIZE) &&
    - offset + len > i_size_read(inode)) {
    + (offset + len > i_size_read(inode) ||
    + offset + len > EXT4_I(inode)->i_disksize)) {
    new_size = offset + len;
    ret = inode_newsize_ok(inode, new_size);
    if (ret)
    @@ -4951,7 +4952,8 @@ long ext4_fallocate(struct file *file, i
    }

    if (!(mode & FALLOC_FL_KEEP_SIZE) &&
    - offset + len > i_size_read(inode)) {
    + (offset + len > i_size_read(inode) ||
    + offset + len > EXT4_I(inode)->i_disksize)) {
    new_size = offset + len;
    ret = inode_newsize_ok(inode, new_size);
    if (ret)

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