Btrfs: avoid taking the chunk_mutex in do_chunk_alloc

Everytime we try to allocate disk space we try and see if we can pre-emptively
allocate a chunk, but in the common case we don't allocate anything, so there is
no sense in taking the chunk_mutex at all.  So instead if we are allocating a
chunk, mark it in the space_info so we don't get two people trying to allocate
at the same time.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Reviewed-by: Liu Bo <liubo2009@cn.fujitsu.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0d00a07b5b29..2e61fe1b6b8c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -740,8 +740,10 @@ struct btrfs_space_info {
          */
         unsigned long reservation_progress;
 
-        int full;               /* indicates that we cannot allocate any more
+        int full:1;             /* indicates that we cannot allocate any more
                                    chunks for this space */
+        int chunk_alloc:1;      /* set if we are allocating a chunk */
+
         int force_alloc;        /* set if we need to force a chunk alloc for
                                    this space */