UBI: remove redundant mutex

The @mult_mutex does not serve any purpose. We already have
@volumes_mutex and it is enough. The @volume mutex is pushed
down to the 'ubi_rename_volumes()', because we want first
to open all volumes in the exclusive mode, and then lock the
mutex, just like all other ioctl's (remove, re-size, etc) do.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/build.c

@@ -806,7 +806,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 
 	mutex_init(&ubi->buf_mutex);
 	mutex_init(&ubi->ckvol_mutex);
-	mutex_init(&ubi->mult_mutex);
 	mutex_init(&ubi->volumes_mutex);
 	spin_lock_init(&ubi->volumes_lock);
 

drivers/mtd/ubi/cdev.c

@@ -810,9 +810,7 @@ static int rename_volumes(struct ubi_device *ubi,
 			re->desc->vol->vol_id, re->desc->vol->name);
 	}
 
-	mutex_lock(&ubi->volumes_mutex);
 	err = ubi_rename_volumes(ubi, &rename_list);
-	mutex_unlock(&ubi->volumes_mutex);
 
 out_free:
 	list_for_each_entry_safe(re, re1, &rename_list, list) {
@@ -952,9 +950,9 @@ static long ubi_cdev_ioctl(struct file *file, unsigned int cmd,
 			break;
 		}
 
-		mutex_lock(&ubi->mult_mutex);
+		mutex_lock(&ubi->volumes_mutex);
 		err = rename_volumes(ubi, req);
-		mutex_unlock(&ubi->mult_mutex);
+		mutex_unlock(&ubi->volumes_mutex);
 		kfree(req);
 		break;
 	}

drivers/mtd/ubi/ubi.h

@@ -366,7 +366,6 @@ struct ubi_wl_entry;
  * @peb_buf2: another buffer of PEB size used for different purposes
  * @buf_mutex: protects @peb_buf1 and @peb_buf2
  * @ckvol_mutex: serializes static volume checking when opening
- * @mult_mutex: serializes operations on multiple volumes, like re-naming
  * @dbg_peb_buf: buffer of PEB size used for debugging
  * @dbg_buf_mutex: protects @dbg_peb_buf
  */
@@ -444,7 +443,6 @@ struct ubi_device {
 	void *peb_buf2;
 	struct mutex buf_mutex;
 	struct mutex ckvol_mutex;
-	struct mutex mult_mutex;
 #ifdef CONFIG_MTD_UBI_DEBUG
 	void *dbg_peb_buf;
 	struct mutex dbg_buf_mutex;