• Omar Sandoval's avatar
    xfs: fix inobt inode allocation search optimization · c44245b3
    Omar Sandoval authored
    When we try to allocate a free inode by searching the inobt, we try to
    find the inode nearest the parent inode by searching chunks both left
    and right of the chunk containing the parent. As an optimization, we
    cache the leftmost and rightmost records that we previously searched; if
    we do another allocation with the same parent inode, we'll pick up the
    search where it last left off.
    
    There's a bug in the case where we found a free inode to the left of the
    parent's chunk: we need to update the cached left and right records, but
    because we already reassigned the right record to point to the left, we
    end up assigning the left record to both the cached left and right
    records.
    
    This isn't a correctness problem strictly, but it can result in the next
    allocation rechecking chunks unnecessarily or allocating inodes further
    away from the parent than it needs to. Fix it by swapping the record
    pointer after we update the cached left and right records.
    
    Fixes: bd169565 ("xfs: speed up free inode search")
    Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    c44245b3
xfs_ialloc.c 72.2 KB