[PATCH] blk-map: provide the bdev to bio if one exists

[PATCH] blk-map: provide the bdev to bio if one exists

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

We can now safely provide a block device when extracting user pages for
driver and user passthrough commands. Set the bdev so the caller doesn't
have to do that later. This has an additional  benefit of being able to
extract P2P pages in the passthrough path.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
Note, this absolutely requires this patch series to be successful:

  https://lore.kernel.org/linux-block/20250827141258.63501-1-kbusch@meta.com/

Otherwise DRV_IN/OUT commands may fail because the interface assumes
logical block size, which is not a valid assumption for passthrough
commands, but we're not relying on the logical block size with the above
patch series, so it's fine.

The ability to test P2P data payloads with the passthrough interface is
the real goal of this path.

 block/blk-map.c           | 5 +++--
 drivers/nvme/host/ioctl.c | 5 -----
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 6d1268aa82715..1098162c09393 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -253,10 +253,11 @@ static void blk_mq_map_bio_put(struct bio *bio)
 static struct bio *blk_rq_map_bio_alloc(struct request *rq,
 		unsigned int nr_vecs, gfp_t gfp_mask)
 {
+	struct block_device *bdev = rq->q->disk ? rq->q->disk->part0 : NULL;
 	struct bio *bio;
 
 	if (rq->cmd_flags & REQ_ALLOC_CACHE && (nr_vecs <= BIO_INLINE_VECS)) {
-		bio = bio_alloc_bioset(NULL, nr_vecs, rq->cmd_flags, gfp_mask,
+		bio = bio_alloc_bioset(bdev, nr_vecs, rq->cmd_flags, gfp_mask,
 					&fs_bio_set);
 		if (!bio)
 			return NULL;
@@ -264,7 +265,7 @@ static struct bio *blk_rq_map_bio_alloc(struct request *rq,
 		bio = bio_kmalloc(nr_vecs, gfp_mask);
 		if (!bio)
 			return NULL;
-		bio_init(bio, NULL, bio->bi_inline_vecs, nr_vecs, req_op(rq));
+		bio_init(bio, bdev, bio->bi_inline_vecs, nr_vecs, req_op(rq));
 	}
 	return bio;
 }
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 6b3ac8ae3f34b..f778f3b5214bd 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -142,14 +142,9 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
 		ret = blk_rq_map_user_io(req, NULL, nvme_to_user_ptr(ubuffer),
 				bufflen, GFP_KERNEL, flags & NVME_IOCTL_VEC, 0,
 				0, rq_data_dir(req));
-
 	if (ret)
 		return ret;
 
-	bio = req->bio;
-	if (bdev)
-		bio_set_dev(bio, bdev);
-
 	if (has_metadata) {
 		ret = blk_rq_integrity_map_user(req, meta_buffer, meta_len);
 		if (ret)
-- 
2.47.3

Re: [PATCH] blk-map: provide the bdev to bio if one exists

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] blk-map: provide the bdev to bio if one exists

[Jens Axboe]

On Wed, 03 Sep 2025 13:27:46 -0700, Keith Busch wrote:
> We can now safely provide a block device when extracting user pages for
> driver and user passthrough commands. Set the bdev so the caller doesn't
> have to do that later. This has an additional  benefit of being able to
> extract P2P pages in the passthrough path.
> 
> 

Applied, thanks!

[1/1] blk-map: provide the bdev to bio if one exists
      commit: d0d1d522316e91f2b935a78bbf962b8e529d8c4f

Best regards,
-- 
Jens Axboe