From: Hannes Reinecke <hare@suse.de>
Date: Thu, 7 Jun 2018 10:29:44 +0200
Subject: [PATCH] block: always set partition number to '0' in
 blk_partition_remap()
References: bsc#1077989
Git-commit: c04fa44b76b8d9d4f6b577030aa0cbb20359c428
Patch-mainline: v4.18-rc1

blk_partition_remap() will only clear bi_partno if an actual remapping
has happened. But flush request et al don't have an actual size, so
the remapping doesn't happen and bi_partno is never cleared.
So for stacked devices blk_partition_remap() will be called on each level.
If (as is the case for native nvme multipathing) one of the lower-level
devices do _not_support partitioning a spurious I/O error is generated.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 block/blk-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 6d9046da5939..1e2679902da7 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2046,10 +2046,10 @@ static inline int blk_partition_remap(struct bio *bio)
 		if (bio_check_eod(bio, part_nr_sects_read(p)))
 			goto out;
 		bio->bi_iter.bi_sector += p->start_sect;
-		bio->bi_partno = 0;
 		trace_block_bio_remap(bio->bi_disk->queue, bio, part_devt(p),
 				      bio->bi_iter.bi_sector - p->start_sect);
 	}
+	bio->bi_partno = 0;
 	ret = 0;
 out:
 	rcu_read_unlock();
-- 
2.12.3