1 files changed, 18 insertions, 6 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index b5f120cca916..21a7ca9e7282 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -128,14 +128,26 @@ struct extent_buffer {
         struct rcu_head rcu_head;
         atomic_t refs;
 
-        /* the spinlock is used to protect most operations */
-        spinlock_t lock;
+        /* count of read lock holders on the extent buffer */
+        atomic_t write_locks;
+        atomic_t read_locks;
+        atomic_t blocking_writers;
+        atomic_t blocking_readers;
+        atomic_t spinning_readers;
+        atomic_t spinning_writers;
+
+        /* protects write locks */
+        rwlock_t lock;
+
+        /* readers use lock_wq while they wait for the write
+         * lock holders to unlock
+         */
+        wait_queue_head_t write_lock_wq;
 
-        /*
-         * when we keep the lock held while blocking, waiters go onto
-         * the wq
+        /* writers use read_lock_wq while they wait for readers
+         * to unlock
          */
-        wait_queue_head_t lock_wq;
+        wait_queue_head_t read_lock_wq;
 };
 
 static inline void extent_set_compress_type(unsigned long *bio_flags,