linux-kernel - Re: [PATCH 1/1] nvme-multipath: Skip nr_active increments in RETRY disposition

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aNR4m9wrO5cgFZIe@kbusch-mbp>
Date: Wed, 24 Sep 2025 17:02:51 -0600
From: Keith Busch <kbusch@...nel.org>
To: Amit Chaudhary <achaudhary@...estorage.com>
Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>, mkhalfella@...estorage.com,
	randyj@...estorage.com, jmeneghi@...hat.com, emilne@...hat.com,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] nvme-multipath: Skip nr_active increments in RETRY
 disposition

On Wed, Sep 24, 2025 at 03:43:18PM -0700, Amit Chaudhary wrote:
>  static inline void nvme_start_request(struct request *rq)
>  {
> -	if (rq->cmd_flags & REQ_NVME_MPATH)
> +	if ((rq->cmd_flags & REQ_NVME_MPATH) && (!nvme_req(rq)->retries))
>  		nvme_mpath_start_request(rq);
>  	blk_mq_start_request(rq);
>  }

Using "retries" is bit indirect as a proxy for multipath active counts.
Could this be moved to the mpath start instead, directly using the flag
that accounts for the path? This also helps to keep track if the command
gets retried across a user toggling the policy to "qd".

---
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 3da980dc60d91..1c630967ddd40 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -182,7 +182,8 @@ 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;
        }
--