6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Amit Chaudhary achaudhary@purestorage.com
[ Upstream commit bb642e2d300ee27dcede65cda7ffc47a7047bd69 ]
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 achaudhary@purestorage.com Reviewed-by: Randy Jennings randyj@purestorage.com Signed-off-by: Keith Busch kbusch@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 119afdfe4b91e..57416bbf9344f 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -131,12 +131,14 @@ 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;