From: Li Zefan Date: Mon, 10 Oct 2011 19:43:34 +0000 (-0400) Subject: Btrfs: fix recursive auto-defrag X-Git-Tag: v3.12-rc1~4691^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2a0f7f5769992bae5b3f97157fd80b2b943be485;p=kernel%2Fkernel-generic.git 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 Signed-off-by: Chris Mason --- diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 6f89bcc..df40b7c 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1055,6 +1055,13 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, if (!max_to_defrag) max_to_defrag = last_index - 1; + /* + * make writeback starts from i, so the defrag range can be + * written sequentially. + */ + if (i < inode->i_mapping->writeback_index) + inode->i_mapping->writeback_index = i; + while (i <= last_index && defrag_count < max_to_defrag) { /* * make sure we stop running if someone unmounts