[PATCH 1/2] nvmet: check sg_cnt for inline bio for bdev-ns

[Chaitanya Kulkarni]

When handling rw 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 warning when
req->sg_cnt > NVMET_MAX_INLINE_BVEC.

Consider an I/O 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 the following warning message :-

nvmet_bdev_execute_rw()
	bio_add_page()
		__bio_add_page()
			WARN_ON_ONCE(bio_full(bio, len));

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

diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 9a8b3726a37c..5355956fa4cd 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -258,7 +258,8 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
 
 	sector = nvmet_lba_to_sect(req->ns, req->cmd->rw.slba);
 
-	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->b.inline_bio;
 		bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
 	} else {
-- 
2.22.1