• Chris Mason's avatar
    Btrfs: make sure not to defrag extents past i_size · f7f43cc8
    Chris Mason authored
    The btrfs file defrag code will loop through the extents and
    force COW on them.  But there is a concurrent truncate in the middle of
    the defrag, it might end up defragging the same range over and over
    again.
    
    The problem is that writepage won't go through and do anything on pages
    past i_size, so the cow won't happen, so the file will appear to still
    be fragmented.  defrag will end up hitting the same extents again and
    again.
    
    In the worst case, the truncate can actually live lock with the defrag
    because the defrag keeps creating new ordered extents which the truncate
    code keeps waiting on.
    
    The fix here is to make defrag check for i_size inside the main loop,
    instead of just once before the looping starts.
    Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
    f7f43cc8
ioctl.c 70.8 KB