Commit c03fd85d authored by Chaitanya Kulkarni's avatar Chaitanya Kulkarni Committed by Christoph Hellwig
Browse files

nvme: don't check nvme_req flags for new req 



nvme_clear_request() has a check for flag REQ_DONTPREP and it is called
from nvme_init_request() and nvme_setuo_cmd().

The function nvme_init_request() is called from nvme_alloc_request()
and nvme_alloc_request_qid(). From these two callers new request is
allocated everytime. For newly allocated request RQF_DONTPREP is never
set. Since after getting a tag, block layer sets the req->rq_flags == 0
and never sets the REQ_DONTPREP when returning the request :-

nvme_alloc_request()
	blk_mq_alloc_request()
		blk_mq_rq_ctx_init()
			rq->rq_flags = 0 <----

nvme_alloc_request_qid()
	blk_mq_alloc_request_hctx()
		blk_mq_rq_ctx_init()
			rq->rq_flags = 0 <----

The block layer does set req->rq_flags but REQ_DONTPREP is not one of
them and that is set by the driver.

That means we can unconditinally set the REQ_DONTPREP value to the
rq->rq_flags when nvme_init_request()->nvme_clear_request() is called
from above two callers.

Move the check for REQ_DONTPREP from nvme_clear_nvme_request() into
nvme_setup_cmd().

This is needed since nvme_alloc_request() now gets called from fast
path when NVMeOF target is configured with passthru backend to avoid
unnecessary checks in the fast path.

Signed-off-by: default avatarChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 7a366046

drivers/nvme/host/core.c

+5 −6
Original line number Diff line number Diff line
@@ -575,12 +575,10 @@ EXPORT_SYMBOL_NS_GPL(nvme_put_ns, NVME_TARGET_PASSTHRU); 


static inline void nvme_clear_nvme_request(struct request *req)

{

	if (!(req->rq_flags & RQF_DONTPREP)) {

	nvme_req(req)->retries = 0;

	nvme_req(req)->flags = 0;

	req->rq_flags |= RQF_DONTPREP;

}

}



static inline unsigned int nvme_req_op(struct nvme_command *cmd)

{
@@ -893,6 +891,7 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns, struct request *req, 
{

	blk_status_t ret = BLK_STS_OK;



	if (!(req->rq_flags & RQF_DONTPREP))

		nvme_clear_nvme_request(req);



	memset(cmd, 0, sizeof(*cmd));