• Lachlan McIlroy's avatar
    [XFS] Remove xfs_iext_irec_compact_full() · 71a8c87f
    Lachlan McIlroy authored
    Yet another bug was found in xfs_iext_irec_compact_full() and while the
    source of the bug was found it wasn't an easy task to track it down
    because the conditions are very difficult to reproduce.
    A HUGE thank-you goes to Russell Cattelan and Eric Sandeen for their
    significant effort in tracking down the source of this corruption.
    xfs_iext_irec_compact_full() and xfs_iext_irec_compact_pages() are almost
    identical - they both compact indirect extent lists by moving extents from
    subsequent buffers into earlier ones. xfs_iext_irec_compact_pages() only
    moves extents if all of the extents in the next buffer will fit into the
    empty space in the buffer before it. xfs_iext_irec_compact_full() will go
    a step further and move part of the next buffer if all the extents wont
    fit. It will then shift the remaining extents in the next buffer up to the
    start of the buffer. The bug here was that we did not update er_extoff and
    this caused extent list corruption.
    It does not appear that this extra functionality gains us much. Calling
    xfs_iext_irec_compact_pages() instead will do a good enough job at
    compacting the indirect list and will be quicker too.
    For the case in xfs_iext_indirect_to_direct() the total number of extents
    in the indirect list will fit into one buffer so we will never need the
    extra functionality of xfs_iext_irec_compact_full() there.
    Also xfs_iext_irec_compact_pages() doesn't need to do a memmove() (the
    buffers will never overlap) so we don't want the performance hit that can
    SGI-PV: 987159
    SGI-Modid: xfs-linux-melb:xfs-kern:32166a
    Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
    Signed-off-by: default avatarEric Sandeen <sandeen@sandeen.net>
xfs_inode.c 131 KB