tree ee19a5470211f13d1e53a311cb0d9e2ccc2988fc
parent b6316429af7f365f307dfd2b6a7a42f2563aef19
author Li Zefan <lizf@cn.fujitsu.com> 1318275814 -0400
committer Chris Mason <chris.mason@oracle.com> 1318275814 -0400

Btrfs: fix recursive auto-defrag

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: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>