Btrfs: fix the same inode id problem when doing auto defragment

Two files in the different subvolumes may have the same inode id, so
The rb-tree which is used to manage the defragment object must take it
into account. This patch fix this problem.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

diff --cc fs/btrfs/file.c
Simple merge