Btrfs: Add a leaf reference cache

Much of the IO done while dropping snapshots is done looking up
leaves in the filesystem trees to see if they point to any extents and
to drop the references on any extents found.

This creates a cache so that IO isn't required.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 5a0fd7b0e3e7..a4b38177abdb 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -6,7 +6,8 @@ btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
            hash.o file-item.o inode-item.o inode-map.o disk-io.o \
            transaction.o bit-radix.o inode.o file.o tree-defrag.o \
            extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
-           extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o
+           extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
+           ref-cache.o
 
 btrfs-$(CONFIG_FS_POSIX_ACL)    += acl.o
 else