6.6-stable review patch. If anyone has any objections, please let me know.
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From: Christoph Hellwig hch@lst.de
[ Upstream commit beadf0088501d9dcf2454b05d90d5d31ea3ba55f ]
blk_mq_flush_plug_list submits requests in the reverse order that they were submitted, which leads to a rather suboptimal I/O pattern especially in rotational devices. Fix this by rewriting nvme_queue_rqs so that it always pops the requests from the passed in request list, and then adds them to the head of a local submit list. This actually simplifies the code a bit as it removes the complicated list splicing, at the cost of extra updates of the rq_next pointer. As that should be cache hot anyway it should be an easy price to pay.
Fixes: d62cbcf62f2f ("nvme: add support for mq_ops->queue_rqs()") Signed-off-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/20241113152050.157179-2-hch@lst.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/nvme/host/pci.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index e0b502573b427..d525fa1229d79 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -905,9 +905,10 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
static void nvme_submit_cmds(struct nvme_queue *nvmeq, struct request **rqlist) { + struct request *req; + spin_lock(&nvmeq->sq_lock); - while (!rq_list_empty(*rqlist)) { - struct request *req = rq_list_pop(rqlist); + while ((req = rq_list_pop(rqlist))) { struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
nvme_sq_copy_cmd(nvmeq, &iod->cmd); @@ -933,31 +934,25 @@ static bool nvme_prep_rq_batch(struct nvme_queue *nvmeq, struct request *req)
static void nvme_queue_rqs(struct request **rqlist) { - struct request *req, *next, *prev = NULL; + struct request *submit_list = NULL; struct request *requeue_list = NULL; + struct request **requeue_lastp = &requeue_list; + struct nvme_queue *nvmeq = NULL; + struct request *req;
- rq_list_for_each_safe(rqlist, req, next) { - struct nvme_queue *nvmeq = req->mq_hctx->driver_data; - - if (!nvme_prep_rq_batch(nvmeq, req)) { - /* detach 'req' and add to remainder list */ - rq_list_move(rqlist, &requeue_list, req, prev); - - req = prev; - if (!req) - continue; - } + while ((req = rq_list_pop(rqlist))) { + if (nvmeq && nvmeq != req->mq_hctx->driver_data) + nvme_submit_cmds(nvmeq, &submit_list); + nvmeq = req->mq_hctx->driver_data;
- if (!next || req->mq_hctx != next->mq_hctx) { - /* detach rest of list, and submit */ - req->rq_next = NULL; - nvme_submit_cmds(nvmeq, rqlist); - *rqlist = next; - prev = NULL; - } else - prev = req; + if (nvme_prep_rq_batch(nvmeq, req)) + rq_list_add(&submit_list, req); /* reverse order */ + else + rq_list_add_tail(&requeue_lastp, req); }
+ if (nvmeq) + nvme_submit_cmds(nvmeq, &submit_list); *rqlist = requeue_list; }