md: implement ->free_disk

Ensure that all private data is only freed once all accesses are done.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NSong Liu <song@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -5600,12 +5600,6 @@ static void md_free(struct kobject *ko)
 
 	del_gendisk(mddev->gendisk);
 	put_disk(mddev->gendisk);
-
-	percpu_ref_exit(&mddev->writes_pending);
-
-	bioset_exit(&mddev->bio_set);
-	bioset_exit(&mddev->sync_set);
-	kfree(mddev);
 }
 
 static const struct sysfs_ops md_sysfs_ops = {
@@ -7875,6 +7869,17 @@ static unsigned int md_check_events(struct gendisk *disk, unsigned int clearing)
 	return ret;
 }
 
+static void md_free_disk(struct gendisk *disk)
+{
+	struct mddev *mddev = disk->private_data;
+
+	percpu_ref_exit(&mddev->writes_pending);
+	bioset_exit(&mddev->bio_set);
+	bioset_exit(&mddev->sync_set);
+
+	kfree(mddev);
+}
+
 const struct block_device_operations md_fops =
 {
 	.owner		= THIS_MODULE,
@@ -7888,6 +7893,7 @@ const struct block_device_operations md_fops =
 	.getgeo		= md_getgeo,
 	.check_events	= md_check_events,
 	.set_read_only	= md_set_read_only,
+	.free_disk	= md_free_disk,
 };
 
 static int md_thread(void *arg)