Btrfs: implement memory reclaim for leaf reference cache

The memory reclaiming issue happens when snapshot exists. In that
case, some cache entries may not be used during old snapshot dropping,
so they will remain in the cache until umount.

The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
the patch makes all dead roots of a given snapshot linked together in order of
create time. After a old snapshot was completely dropped, we check the dead
root list and remove all cache entries created before the oldest dead root in
the list.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index d617c29787f..d43e14c7471 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -56,4 +56,3 @@ int btrfs_tree_locked(struct extent_buffer *eb)
 {
 	return mutex_is_locked(&eb->mutex);
 }
-