[PATCH] md: clear the congested_fn when stopping a raid5

If this mddev and queue got reused for another array that doesn't register a
congested_fn, this function would get called incorretly.
Signed-off-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/md/md.c

@@ -3325,6 +3325,7 @@ static int do_md_stop(mddev_t * mddev, int mode)
 			mddev->queue->merge_bvec_fn = NULL;
 			mddev->queue->unplug_fn = NULL;
 			mddev->queue->issue_flush_fn = NULL;
+			mddev->queue->backing_dev_info.congested_fn = NULL;
 			if (mddev->pers->sync_request)
 				sysfs_remove_group(&mddev->kobj, &md_redundancy_group);
 

drivers/md/raid5.c

@@ -3646,8 +3646,8 @@ static int run(mddev_t *mddev)
 
 	mddev->queue->unplug_fn = raid5_unplug_device;
 	mddev->queue->issue_flush_fn = raid5_issue_flush;
-	mddev->queue->backing_dev_info.congested_fn = raid5_congested;
 	mddev->queue->backing_dev_info.congested_data = mddev;
+	mddev->queue->backing_dev_info.congested_fn = raid5_congested;
 
 	mddev->array_size =  mddev->size * (conf->previous_raid_disks -
 					    conf->max_degraded);
@@ -3678,6 +3678,7 @@ static int stop(mddev_t *mddev)
 	mddev->thread = NULL;
 	shrink_stripes(conf);
 	kfree(conf->stripe_hashtbl);
+	mddev->queue->backing_dev_info.congested_fn = NULL;
 	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 	sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
 	kfree(conf->disks);