[PATCH 2/2] nvmet: check sg_cnt for inline bio for passthru

[Chaitanya Kulkarni]

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;

Add a check to consider req->sg_cnt when using inline bio.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
---
 drivers/nvme/target/passthru.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index 2798944899b7..d65d76129000 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -194,7 +194,8 @@ 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 (req->transfer_len <= NVMET_MAX_INLINE_DATA_LEN &&
+	    req->sg_cnt <= NVMET_MAX_INLINE_BIOVEC) {
 		bio = &req->p.inline_bio;
 		bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
 	} else {
-- 
2.22.1