• Li Zefan's avatar
    Btrfs: fix recursive auto-defrag · 2a0f7f57
    Li Zefan authored
    Follow those steps:
    
      # mount -o autodefrag /dev/sda7 /mnt
      # dd if=/dev/urandom of=/mnt/tmp bs=200K count=1
      # sync
      # dd if=/dev/urandom of=/mnt/tmp bs=8K count=1 conv=notrunc
    
    and then it'll go into a loop: writeback -> defrag -> writeback ...
    
    It's because writeback writes [8K, 200K] and then writes [0, 8K].
    
    I tried to make writeback know if the pages are dirtied by defrag,
    but the patch was a bit intrusive. Here I simply set writeback_index
    when we defrag a file.
    Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
    Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
    2a0f7f57
ioctl.c 70.8 KB