1 files changed, 14 insertions, 2 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index e80c6d96b318..1f9df88afbf6 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -22,6 +22,10 @@
 /* flags for bio submission */
 #define EXTENT_BIO_COMPRESSED 1
 
+/* these are bit numbers for test/set bit */
+#define EXTENT_BUFFER_UPTODATE 0
+#define EXTENT_BUFFER_BLOCKING 1
+
 /*
  * page->private values.  Every page that is controlled by the extent
  * map has page->private set to one.
@@ -95,11 +99,19 @@ struct extent_buffer {
         unsigned long map_start;
         unsigned long map_len;
         struct page *first_page;
+        unsigned long bflags;
         atomic_t refs;
-        int flags;
         struct list_head leak_list;
         struct rb_node rb_node;
-        struct mutex mutex;
+
+        /* the spinlock is used to protect most operations */
+        spinlock_t lock;
+
+        /*
+         * when we keep the lock held while blocking, waiters go onto
+         * the wq
+         */
+        wait_queue_head_t lock_wq;
 };
 
 struct extent_map_tree;