tree c1654f1b2f029c8cfd5385568b37f90a0b47f3c4
parent 1f12bd063285b059cb63315d1424dae1ddd87a64
author Liu Bo <liubo2009@cn.fujitsu.com> 1333029465 -0400
committer Chris Mason <chris.mason@oracle.com> 1333029465 -0400

Btrfs: fix recursive defragment with autodefrag option

$ mkfs.btrfs disk
$ mount disk /mnt -o autodefrag
$ dd if=/dev/zero of=/mnt/foobar bs=4k count=10 2>/dev/null && sync
$ for i in `seq 9 -2 0`; do dd if=/dev/zero of=/mnt/foobar bs=4k count=1 \
  seek=$i conv=notrunc 2> /dev/null; done && sync

then we'll get to defrag "foobar" again and again.
So does option "-o autodefrag,compress".

Reasons:
When the cleaner kthread gets to fetch inodes from the defrag tree and defrag
them, it will dirty pages and submit them, this will comes to another DATA COW
where the processing inode will be inserted to the defrag tree again.

This patch sets a rule for COW code, i.e. insert an inode when we're really
going to make some defragments.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>