linux-kernel - [PATCH] nvme: clear nvme request for nonready request

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Message-Id: <20250628064634.3823093-1-yukuai1@huaweicloud.com>
Date: Sat, 28 Jun 2025 14:46:34 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: kbusch@...nel.org,
	axboe@...nel.dk,
	hch@....de,
	sagi@...mberg.me
Cc: yi.zhang@...hat.com,
	linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH] nvme: clear nvme request for nonready request

From: Yu Kuai <yukuai3@...wei.com>

It's found nvme mpath IO inflight counter can be decreased to negtive by
following stack:

CPU: 12 UID: 0 PID: 466 Comm: kworker/12:1H Tainted: G
   6.16.0-rc3.yu+ #2 PREEMPT(voluntary)
Workqueue: kblockd blk_mq_run_work_fn
RIP: 0010:bdev_end_io_acct+0x494/0x5c0
Call Trace:
 <TASK>
 nvme_end_req+0x4d/0x70 [nvme_core]
 nvme_failover_req+0x3bd/0x530 [nvme_core]
 nvme_fail_nonready_command+0x12c/0x170 [nvme_core]
 nvme_fc_queue_rq+0x463/0x720 [nvme_fc]
 blk_mq_dispatch_rq_list+0x358/0x1260
 __blk_mq_sched_dispatch_requests+0x2dd/0x480
 blk_mq_sched_dispatch_requests+0xa6/0x140
 blk_mq_run_work_fn+0x1bb/0x2a0
 process_one_work+0x8ca/0x1950
 worker_thread+0x58d/0xcf0
 kthread+0x3d5/0x7a0
 ret_from_fork+0x403/0x510
 ret_from_fork_asm+0x1a/0x30
 </TASK>

The IO inflight counter is not increased from nvme_fail_nonready_command()
yet, hence decrease it will cause it to be negative.

This is not a problem for blk-mq request because it's already
initialized before issuing, however, nvme request is only initialized from
following nvme_setup_cmd(). Fix the problem by clearing it in
nvme_fail_nonready_command().

Reported-by: Yi Zhang <yi.zhang@...hat.com>
Closes: https://lore.kernel.org/all/CAHj4cs_+dauobyYyP805t33WMJVzOWj=7+51p4_j9rA63D9sog@mail.gmail.com/
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/nvme/host/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 92697f98c601..8caafa25c010 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -764,6 +764,9 @@ blk_status_t nvme_fail_nonready_command(struct nvme_ctrl *ctrl,
 	    !test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags) &&
 	    !blk_noretry_request(rq) && !(rq->cmd_flags & REQ_NVME_MPATH))
 		return BLK_STS_RESOURCE;
+
+	if (!(rq->rq_flags & RQF_DONTPREP))
+		nvme_clear_nvme_request(rq);
 	return nvme_host_path_error(rq);
 }
 EXPORT_SYMBOL_GPL(nvme_fail_nonready_command);
-- 
2.39.2