block: return errors from disk_alloc_events

Prepare for proper error handling in add_disk.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
[hch: split from a larger patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-9-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk.h

@@ -362,7 +362,7 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 
 struct request_queue *blk_alloc_queue(int node_id);
 
-void disk_alloc_events(struct gendisk *disk);
+int disk_alloc_events(struct gendisk *disk);
 void disk_add_events(struct gendisk *disk);
 void disk_del_events(struct gendisk *disk);
 void disk_release_events(struct gendisk *disk);

block/disk-events.c

@@ -444,17 +444,17 @@ module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
 /*
  * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
  */
-void disk_alloc_events(struct gendisk *disk)
+int disk_alloc_events(struct gendisk *disk)
 {
 	struct disk_events *ev;
 
 	if (!disk->fops->check_events || !disk->events)
-		return;
+		return 0;
 
 	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 	if (!ev) {
 		pr_warn("%s: failed to initialize events\n", disk->disk_name);
-		return;
+		return -ENOMEM;
 	}
 
 	INIT_LIST_HEAD(&ev->node);
@@ -466,6 +466,7 @@ void disk_alloc_events(struct gendisk *disk)
 	INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);
 
 	disk->ev = ev;
+	return 0;
 }
 
 void disk_add_events(struct gendisk *disk)