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nvmet: fix inline bio check for passthru 

When handling passthru commands, for inline bio allocation we only
consider the transfer size. This works well when req->sg_cnt fits into
the req->inline_bvec, but it will result in the early return from
bio_add_hw_page() when req->sg_cnt > NVMET_MAX_INLINE_BVEC.

Consider an I/O of size 32768 and first buffer is not aligned to the
page boundary, then I/O is split in following manner :-

[ 2206.256140] nvmet: sg->length 3440 sg->offset 656
[ 2206.256144] nvmet: sg->length 4096 sg->offset 0
[ 2206.256148] nvmet: sg->length 4096 sg->offset 0
[ 2206.256152] nvmet: sg->length 4096 sg->offset 0
[ 2206.256155] nvmet: sg->length 4096 sg->offset 0
[ 2206.256159] nvmet: sg->length 4096 sg->offset 0
[ 2206.256163] nvmet: sg->length 4096 sg->offset 0
[ 2206.256166] nvmet: sg->length 4096 sg->offset 0
[ 2206.256170] nvmet: sg->length 656 sg->offset 0

Now the req->transfer_size == NVMET_MAX_INLINE_DATA_LEN i.e. 32768, but
the req->sg_cnt is (9) > NVMET_MAX_INLINE_BIOVEC which is (8).
This will result in early return in the following code path :-

nvmet_bdev_execute_rw()
	bio_add_pc_page()
		bio_add_hw_page()
			if (bio_full(bio, len))
				return 0;

Use previously introduced helper nvmet_use_inline_bvec() to consider
req->sg_cnt when using inline bio. This only affects nvme-loop
transport.

Fixes: dab3902b19 ("nvmet: use inline bio for passthru fast path")
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Chaitanya Kulkarni 2021-05-06 18:51:36 -07:00 committed by Christoph Hellwig
parent 608a969046
commit ab96de5def
1 changed files with 1 additions and 1 deletions
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2
drivers/nvme/target/passthru.c
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@ -194,7 +194,7 @@ static int nvmet_passthru_map_sg(struct nvmet_req *req, struct request *rq)
if (req->sg_cnt > BIO_MAX_VECS)
return -EINVAL;
if (req->transfer_len <= NVMET_MAX_INLINE_DATA_LEN) {
if (nvmet_use_inline_bvec(req)) {
bio = &req->p.inline_bio;
bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
} else {