Merge tag 'md-fixes-2023-03-29' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into block-6.3

Pull MD fix from Song.

* tag 'md-fixes-2023-03-29' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: fix regression for null-ptr-deference in __md_stop()

Author: axboe

drivers/md/md.c

@@ -6260,7 +6260,6 @@ static void __md_stop(struct mddev *mddev)
 	module_put(pers->owner);
 	clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 
-	percpu_ref_exit(&mddev->writes_pending);
 	percpu_ref_exit(&mddev->active_io);
 	bioset_exit(&mddev->bio_set);
 	bioset_exit(&mddev->sync_set);
@@ -6273,6 +6272,7 @@ void md_stop(struct mddev *mddev)
 	 */
 	__md_stop_writes(mddev);
 	__md_stop(mddev);
+	percpu_ref_exit(&mddev->writes_pending);
 }
 
 EXPORT_SYMBOL_GPL(md_stop);
@@ -7843,6 +7843,7 @@ static void md_free_disk(struct gendisk *disk)
 {
 	struct mddev *mddev = disk->private_data;
 
+	percpu_ref_exit(&mddev->writes_pending);
 	mddev_free(mddev);
 }