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Fri, 26 Sep 2025 12:09:55 -0700 (PDT) From: Amit Chaudhary To: achaudhary@purestorage.com, Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg Cc: mkhalfella@purestorage.com, randyj@purestorage.com, jmeneghi@redhat.com, emilne@redhat.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/1] nvme-multipath: Skip nr_active increments in RETRY disposition Date: Fri, 26 Sep 2025 12:08:22 -0700 Message-ID: <20250926190823.5031-1-achaudhary@purestorage.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit For queue-depth I/O policy, this patch fixes unbalanced I/Os across nvme multipaths. Issue Description: The RETRY disposition incorrectly increments ns->ctrl->nr_active counter and reinitializes iostat start-time. In such cases nr_active counter never goes back to zero until that path disconnects and reconnects. Such a path is not chosen for new I/Os if multiple RETRY cases on a given a path cause its queue-depth counter to be artificially higher compared to other paths. This leads to unbalanced I/Os across paths. The patch skips incrementing nr_active if NVME_MPATH_CNT_ACTIVE is already set. And it skips restarting io stats if NVME_MPATH_IO_STATS is already set. base-commit: e989a3da2d371a4b6597ee8dee5c72e407b4db7a Fixes: d4d957b53d91eeb ("nvme-multipath: support io stats on the mpath device") Signed-off-by: Amit Chaudhary Reviewed-by: Randy Jennings --- V1 -> V2: Moved check to mpath start and check relevant path bits drivers/nvme/host/multipath.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index 3da980dc60d9..543e17aead12 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -182,12 +182,14 @@ void nvme_mpath_start_request(struct request *rq) struct nvme_ns *ns = rq->q->queuedata; struct gendisk *disk = ns->head->disk; - if (READ_ONCE(ns->head->subsys->iopolicy) == NVME_IOPOLICY_QD) { + if ((READ_ONCE(ns->head->subsys->iopolicy) == NVME_IOPOLICY_QD) && + !(nvme_req(rq)->flags & NVME_MPATH_CNT_ACTIVE)) { atomic_inc(&ns->ctrl->nr_active); nvme_req(rq)->flags |= NVME_MPATH_CNT_ACTIVE; } - if (!blk_queue_io_stat(disk->queue) || blk_rq_is_passthrough(rq)) + if (!blk_queue_io_stat(disk->queue) || blk_rq_is_passthrough(rq) || + (nvme_req(rq)->flags & NVME_MPATH_IO_STATS)) return; nvme_req(rq)->flags |= NVME_MPATH_IO_STATS; -- 2.43.0