1 files changed, 24 insertions, 16 deletions

diff --git a/fs/locks.c b/fs/locks.c
index 1260c265ba62..f2fa1465046b 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -710,6 +710,20 @@ static void __locks_wake_up_blocks(struct file_lock *blocker)
 
 static void locks_delete_block(struct file_lock *waiter)
 {
+	/*
+	 * If fl_blocker is NULL, it won't be set again as this thread
+	 * "owns" the lock and is the only one that might try to claim
+	 * the lock.  So it is safe to test fl_blocker locklessly.
+	 * Also if fl_blocker is NULL, this waiter is not listed on
+	 * fl_blocked_requests for some lock, so no other request can
+	 * be added to the list of fl_blocked_requests for this
+	 * request.  So if fl_blocker is NULL, it is safe to
+	 * locklessly check if fl_blocked_requests is empty.  If both
+	 * of these checks succeed, there is no need to take the lock.
+	 */
+	if (waiter->fl_blocker == NULL &&
+	    list_empty(&waiter->fl_blocked_requests))
+		return;
 	spin_lock(&blocked_lock_lock);
 	__locks_wake_up_blocks(waiter);
 	__locks_delete_block(waiter);
@@ -1279,12 +1293,10 @@ static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 		if (error != FILE_LOCK_DEFERRED)
 			break;
 		error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
-		if (!error)
-			continue;
-
-		locks_delete_block(fl);
-		break;
+		if (error)
+			break;
 	}
+	locks_delete_block(fl);
 	return error;
 }
 
@@ -1375,9 +1387,9 @@ int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
 				continue;
 		}
 
-		locks_delete_block(&fl);
 		break;
 	}
+	locks_delete_block(&fl);
 
 	return error;
 }
@@ -1973,12 +1985,10 @@ static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 		if (error != FILE_LOCK_DEFERRED)
 			break;
 		error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
-		if (!error)
-			continue;
-
-		locks_delete_block(fl);
-		break;
+		if (error)
+			break;
 	}
+	locks_delete_block(fl);
 	return error;
 }
 
@@ -2252,12 +2262,10 @@ static int do_lock_file_wait(struct file *filp, unsigned int cmd,
 		if (error != FILE_LOCK_DEFERRED)
 			break;
 		error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
-		if (!error)
-			continue;
-
-		locks_delete_block(fl);
-		break;
+		if (error)
+			break;
 	}
+	locks_delete_block(fl);
 
 	return error;
 }