6367 spa_config_tryenter incorrectly handles the multiple-lock case
Reviewed by: Alek Pinchuk <alek.pinchuk@nexenta.com>
Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com>
Reviewed by: Prashanth Sreenivasa <prashksp@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk>
Approved by: Matthew Ahrens <mahrens@delphix.com>

@@ -19,12 +19,13 @@
  * CDDL HEADER END
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
- * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
+ * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  */
 
 #include <sys/zfs_context.h>
 #include <sys/spa_impl.h>
 #include <sys/spa_boot.h>

@@ -383,18 +384,20 @@
                         continue;
                 mutex_enter(&scl->scl_lock);
                 if (rw == RW_READER) {
                         if (scl->scl_writer || scl->scl_write_wanted) {
                                 mutex_exit(&scl->scl_lock);
-                                spa_config_exit(spa, locks ^ (1 << i), tag);
+                                spa_config_exit(spa, locks & ((1 << i) - 1),
+                                    tag);
                                 return (0);
                         }
                 } else {
                         ASSERT(scl->scl_writer != curthread);
                         if (!refcount_is_zero(&scl->scl_count)) {
                                 mutex_exit(&scl->scl_lock);
-                                spa_config_exit(spa, locks ^ (1 << i), tag);
+                                spa_config_exit(spa, locks & ((1 << i) - 1),
+                                    tag);
                                 return (0);
                         }
                         scl->scl_writer = curthread;
                 }
                 (void) refcount_add(&scl->scl_count, tag);