Patch "blk-mq: fix blk_mq_hw_ctx active request accounting" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    blk-mq: fix blk_mq_hw_ctx active request accounting

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     blk-mq-fix-blk_mq_hw_ctx-active-request-accounting.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8bfcef9c821771662c7d2951bb3bbcc200debe28
Author: Tian Lan <tian.lan@xxxxxxxxxxxx>
Date:   Sat May 13 18:12:27 2023 -0400

    blk-mq: fix blk_mq_hw_ctx active request accounting
    
    [ Upstream commit ddad59331a4e16088468ca0ad228a9fe32d7955a ]
    
    The nr_active counter continues to increase over time which causes the
    blk_mq_get_tag to hang until the thread is rescheduled to a different
    core despite there are still tags available.
    
    kernel-stack
    
      INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds
      Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11
      "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
      task:inboundIOReacto state:D stack:0  pid:3014879 ppid:4557 flags:0x00000000
        Call Trace:
        <TASK>
        __schedule+0x351/0xa20
        scheduler+0x5d/0xe0
        io_schedule+0x42/0x70
        blk_mq_get_tag+0x11a/0x2a0
        ? dequeue_task_stop+0x70/0x70
        __blk_mq_alloc_requests+0x191/0x2e0
    
    kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before
    __blk_mq_free_request being called.
    
      320    320  kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 in-flight 1
             b'__blk_mq_free_request+0x1 [kernel]'
             b'bt_iter+0x50 [kernel]'
             b'blk_mq_queue_tag_busy_iter+0x318 [kernel]'
             b'blk_mq_timeout_work+0x7c [kernel]'
             b'process_one_work+0x1c4 [kernel]'
             b'worker_thread+0x4d [kernel]'
             b'kthread+0xe6 [kernel]'
             b'ret_from_fork+0x1f [kernel]'
    
    Signed-off-by: Tian Lan <tian.lan@xxxxxxxxxxxx>
    Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
    Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230513221227.497327-1-tilan7663@xxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1ab41fbca0946..add013d5bbdab 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -685,6 +685,10 @@ static void __blk_mq_free_request(struct request *rq)
 	blk_crypto_free_request(rq);
 	blk_pm_mark_last_busy(rq);
 	rq->mq_hctx = NULL;
+
+	if (rq->rq_flags & RQF_MQ_INFLIGHT)
+		__blk_mq_dec_active_requests(hctx);
+
 	if (rq->tag != BLK_MQ_NO_TAG)
 		blk_mq_put_tag(hctx->tags, ctx, rq->tag);
 	if (sched_tag != BLK_MQ_NO_TAG)
@@ -696,15 +700,11 @@ static void __blk_mq_free_request(struct request *rq)
 void blk_mq_free_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;
-	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
 	if ((rq->rq_flags & RQF_ELVPRIV) &&
 	    q->elevator->type->ops.finish_request)
 		q->elevator->type->ops.finish_request(rq);
 
-	if (rq->rq_flags & RQF_MQ_INFLIGHT)
-		__blk_mq_dec_active_requests(hctx);
-
 	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
 		laptop_io_completion(q->disk->bdi);
 



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