This is a note to let you know that I've just added the patch titled nvme: don't check nvme_req flags for new req to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: nvme-don-t-check-nvme_req-flags-for-new-req.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1372f94d4eda930a943bbcb4303e05479ba1301d Author: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx> Date: Sun Feb 28 18:06:08 2021 -0800 nvme: don't check nvme_req flags for new req [ Upstream commit c03fd85de293a4f65fcb94a795bf4c12a432bb6c ] 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: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx> Signed-off-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index d81b0cff15e0..c42ad0b8247b 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -531,11 +531,9 @@ 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; - } + 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) @@ -854,7 +852,8 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns, struct request *req, struct nvme_ctrl *ctrl = nvme_req(req)->ctrl; blk_status_t ret = BLK_STS_OK; - nvme_clear_nvme_request(req); + if (!(req->rq_flags & RQF_DONTPREP)) + nvme_clear_nvme_request(req); memset(cmd, 0, sizeof(*cmd)); switch (req_op(req)) {