Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c	2021-03-02 19:24:13.000000000 +0100
+++ linux-2.6/drivers/md/dm.c	2021-03-02 19:25:54.000000000 +0100
@@ -72,6 +72,8 @@ struct clone_info {
 	struct dm_io *io;
 	sector_t sector;
 	unsigned sector_count;
+	blk_qc_t poll_cookie;
+	struct request_queue *poll_queue;
 };
 
 /*
@@ -1294,14 +1296,13 @@ static noinline void __set_swap_bios_lim
 	mutex_unlock(&md->swap_bios_lock);
 }
 
-static blk_qc_t __map_bio(struct dm_target_io *tio)
+static void __map_bio(struct clone_info *ci, struct dm_target_io *tio)
 {
 	int r;
 	sector_t sector;
 	struct bio *clone = &tio->clone;
 	struct dm_io *io = tio->io;
 	struct dm_target *ti = tio->ti;
-	blk_qc_t ret = BLK_QC_T_NONE;
 
 	clone->bi_end_io = clone_endio;
 
@@ -1328,7 +1329,14 @@ static blk_qc_t __map_bio(struct dm_targ
 	case DM_MAPIO_REMAPPED:
 		/* the bio has been remapped so dispatch it */
 		trace_block_bio_remap(clone, bio_dev(io->orig_bio), sector);
-		ret = submit_bio_noacct(clone);
+		if (clone->bi_opf & REQ_HIPRI &&
+		    test_bit(QUEUE_FLAG_POLL, &clone->bi_bdev->bd_disk->queue->queue_flags)) {
+			ci->poll_queue = clone->bi_bdev->bd_disk->queue;
+			ci->poll_cookie = submit_bio_noacct_mq_direct(clone);
+		} else {
+			ci->poll_cookie = BLK_QC_T_NONE;
+			submit_bio_noacct(clone);
+		}
 		break;
 	case DM_MAPIO_KILL:
 		if (unlikely(swap_bios_limit(ti, clone))) {
@@ -1350,8 +1358,6 @@ static blk_qc_t __map_bio(struct dm_targ
 		DMWARN("unimplemented target map return value: %d", r);
 		BUG();
 	}
-
-	return ret;
 }
 
 static void bio_setup_sector(struct bio *bio, sector_t sector, unsigned len)
@@ -1438,8 +1444,8 @@ static void alloc_multiple_bios(struct b
 	}
 }
 
-static blk_qc_t __clone_and_map_simple_bio(struct clone_info *ci,
-					   struct dm_target_io *tio, unsigned *len)
+static void __clone_and_map_simple_bio(struct clone_info *ci,
+				       struct dm_target_io *tio, unsigned *len)
 {
 	struct bio *clone = &tio->clone;
 
@@ -1449,7 +1455,7 @@ static blk_qc_t __clone_and_map_simple_b
 	if (len)
 		bio_setup_sector(clone, ci->sector, *len);
 
-	return __map_bio(tio);
+	__map_bio(ci, tio);
 }
 
 static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
@@ -1463,7 +1469,7 @@ static void __send_duplicate_bios(struct
 
 	while ((bio = bio_list_pop(&blist))) {
 		tio = container_of(bio, struct dm_target_io, clone);
-		(void) __clone_and_map_simple_bio(ci, tio, len);
+		__clone_and_map_simple_bio(ci, tio, len);
 	}
 }
 
@@ -1507,7 +1513,7 @@ static int __clone_and_map_data_bio(stru
 		free_tio(tio);
 		return r;
 	}
-	(void) __map_bio(tio);
+	__map_bio(ci, tio);
 
 	return 0;
 }
@@ -1614,6 +1620,7 @@ static void init_clone_info(struct clone
 	ci->map = map;
 	ci->io = alloc_io(md, bio);
 	ci->sector = bio->bi_iter.bi_sector;
+	ci->poll_cookie = BLK_QC_T_NONE;
 }
 
 #define __dm_part_stat_sub(part, field, subnd)	\
@@ -1622,11 +1629,10 @@ static void init_clone_info(struct clone
 /*
  * Entry point to split a bio into clones and submit them to the targets.
  */
-static blk_qc_t __split_and_process_bio(struct mapped_device *md,
-					struct dm_table *map, struct bio *bio)
+static void __split_and_process_bio(struct mapped_device *md,
+				    struct dm_table *map, struct bio *bio)
 {
 	struct clone_info ci;
-	blk_qc_t ret = BLK_QC_T_NONE;
 	int error = 0;
 
 	init_clone_info(&ci, md, map, bio);
@@ -1643,7 +1649,7 @@ static blk_qc_t __split_and_process_bio(
 		ci.sector_count = bio_sectors(bio);
 		while (ci.sector_count && !error) {
 			error = __split_and_process_non_flush(&ci);
-			if (ci.sector_count && !error) {
+			if (ci.sector_count && !error && ci.poll_cookie == BLK_QC_T_NONE) {
 				/*
 				 * Remainder must be passed to submit_bio_noacct()
 				 * so that it gets handled *after* bios already submitted
@@ -1670,7 +1676,7 @@ static blk_qc_t __split_and_process_bio(
 
 				bio_chain(b, bio);
 				trace_block_split(b, bio->bi_iter.bi_sector);
-				ret = submit_bio_noacct(bio);
+				submit_bio_noacct(bio);
 				break;
 			}
 		}
@@ -1678,13 +1684,11 @@ static blk_qc_t __split_and_process_bio(
 
 	/* drop the extra reference count */
 	dec_pending(ci.io, errno_to_blk_status(error));
-	return ret;
 }
 
 static blk_qc_t dm_submit_bio(struct bio *bio)
 {
 	struct mapped_device *md = bio->bi_bdev->bd_disk->private_data;
-	blk_qc_t ret = BLK_QC_T_NONE;
 	int srcu_idx;
 	struct dm_table *map;
 
@@ -1714,10 +1718,10 @@ static blk_qc_t dm_submit_bio(struct bio
 	if (is_abnormal_io(bio))
 		blk_queue_split(&bio);
 
-	ret = __split_and_process_bio(md, map, bio);
+	__split_and_process_bio(md, map, bio);
 out:
 	dm_put_live_table(md, srcu_idx);
-	return ret;
+	return BLK_QC_T_NONE;
 }
 
 /*-----------------------------------------------------------------
