block: handle bio_split_to_limits() NULL return

This can't happen right now, but in preparation for allowing
bio_split_to_limits() returning NULL if it ended the bio, check for it
in all the callers.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -358,11 +358,13 @@ struct bio *__bio_split_to_limits(struct bio *bio,
 	default:
 		split = bio_split_rw(bio, lim, nr_segs, bs,
 				get_max_io_size(bio, lim) << SECTOR_SHIFT);
+		if (IS_ERR(split))
+			return NULL;
 		break;
 	}
 
 	if (split) {
-		/* there isn't chance to merge the splitted bio */
+		/* there isn't chance to merge the split bio */
 		split->bi_opf |= REQ_NOMERGE;
 
 		blkcg_bio_issue_init(split);

block/blk-mq.c

@@ -2951,8 +2951,11 @@ void blk_mq_submit_bio(struct bio *bio)
 	blk_status_t ret;
 
 	bio = blk_queue_bounce(bio, q);
-	if (bio_may_exceed_limits(bio, &q->limits))
+	if (bio_may_exceed_limits(bio, &q->limits)) {
 		bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
+		if (!bio)
+			return;
+	}
 
 	if (!bio_integrity_prep(bio))
 		return;

drivers/block/drbd/drbd_req.c

@@ -1607,6 +1607,8 @@ void drbd_submit_bio(struct bio *bio)
 	struct drbd_device *device = bio->bi_bdev->bd_disk->private_data;
 
 	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
 
 	/*
 	 * what we "blindly" assume:

drivers/block/ps3vram.c

@@ -587,6 +587,8 @@ static void ps3vram_submit_bio(struct bio *bio)
 	dev_dbg(&dev->core, "%s\n", __func__);
 
 	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
 
 	spin_lock_irq(&priv->lock);
 	busy = !bio_list_empty(&priv->list);

drivers/md/dm.c

@@ -1742,6 +1742,8 @@ static void dm_split_and_process_bio(struct mapped_device *md,
 		 * otherwise associated queue_limits won't be imposed.
 		 */
 		bio = bio_split_to_limits(bio);
+		if (!bio)
+			return;
 	}
 
 	init_clone_info(&ci, md, map, bio, is_abnormal);

drivers/md/md.c

@@ -455,6 +455,8 @@ static void md_submit_bio(struct bio *bio)
 	}
 
 	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
 
 	if (mddev->ro == MD_RDONLY && unlikely(rw == WRITE)) {
 		if (bio_sectors(bio) != 0)

drivers/nvme/host/multipath.c

@@ -376,6 +376,8 @@ static void nvme_ns_head_submit_bio(struct bio *bio)
 	 * pool from the original queue to allocate the bvecs from.
 	 */
 	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
 
 	srcu_idx = srcu_read_lock(&head->srcu);
 	ns = nvme_find_path(head);

drivers/s390/block/dcssblk.c

@@ -865,6 +865,8 @@ dcssblk_submit_bio(struct bio *bio)
 	unsigned long bytes_done;
 
 	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
 
 	bytes_done = 0;
 	dev_info = bio->bi_bdev->bd_disk->private_data;