Btrfs: alloc_mutex latency reduction

This releases the alloc_mutex in a few places that hold it for over long
operations.  btrfs_lookup_block_group is changed so that it doesn't need
the mutex at all.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index eeb5afa6e9b1..90504ba7f838 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -483,6 +483,7 @@ struct btrfs_block_group_cache {
         struct btrfs_key key;
         struct btrfs_block_group_item item;
         struct btrfs_space_info *space_info;
+        spinlock_t lock;
         u64 pinned;
         u64 flags;
         int cached;