1 files changed, 13 insertions, 25 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ef7692381032..029398ff6517 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1132,27 +1132,6 @@ static void __loop_clr_fd(struct loop_device *lo, bool release)
 	struct file *filp;
 	gfp_t gfp = lo->old_gfp_mask;
 
-	/*
-	 * Flush loop_configure() and loop_change_fd(). It is acceptable for
-	 * loop_validate_file() to succeed, for actual clear operation has not
-	 * started yet.
-	 */
-	mutex_lock(&loop_validate_mutex);
-	mutex_unlock(&loop_validate_mutex);
-	/*
-	 * loop_validate_file() now fails because l->lo_state != Lo_bound
-	 * became visible.
-	 */
-
-	/*
-	 * Since this function is called upon "ioctl(LOOP_CLR_FD)" xor "close()
-	 * after ioctl(LOOP_CLR_FD)", it is a sign of something going wrong if
-	 * lo->lo_state has changed while waiting for lo->lo_mutex.
-	 */
-	mutex_lock(&lo->lo_mutex);
-	BUG_ON(lo->lo_state != Lo_rundown);
-	mutex_unlock(&lo->lo_mutex);
-
 	if (test_bit(QUEUE_FLAG_WC, &lo->lo_queue->queue_flags))
 		blk_queue_write_cache(lo->lo_queue, false, false);
 
@@ -1239,11 +1218,20 @@ static int loop_clr_fd(struct loop_device *lo)
 {
 	int err;
 
-	err = mutex_lock_killable(&lo->lo_mutex);
+	/*
+	 * Since lo_ioctl() is called without locks held, it is possible that
+	 * loop_configure()/loop_change_fd() and loop_clr_fd() run in parallel.
+	 *
+	 * Therefore, use global lock when setting Lo_rundown state in order to
+	 * make sure that loop_validate_file() will fail if the "struct file"
+	 * which loop_configure()/loop_change_fd() found via fget() was this
+	 * loop device.
+	 */
+	err = loop_global_lock_killable(lo, true);
 	if (err)
 		return err;
 	if (lo->lo_state != Lo_bound) {
-		mutex_unlock(&lo->lo_mutex);
+		loop_global_unlock(lo, true);
 		return -ENXIO;
 	}
 	/*
@@ -1258,11 +1246,11 @@ static int loop_clr_fd(struct loop_device *lo)
 	 */
 	if (atomic_read(&lo->lo_refcnt) > 1) {
 		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
-		mutex_unlock(&lo->lo_mutex);
+		loop_global_unlock(lo, true);
 		return 0;
 	}
 	lo->lo_state = Lo_rundown;
-	mutex_unlock(&lo->lo_mutex);
+	loop_global_unlock(lo, true);
 
 	__loop_clr_fd(lo, false);
 	return 0;