Re: [bug report] blktests nvme/tcp triggered WARNING at kernel/workqueue.c:2628 check_flush_dependency+0x110/0x14c

From: Sagi Grimberg <sagi@grimberg.me>
To: Christoph Hellwig <hch@infradead.org>
Cc: Yi Zhang <yi.zhang@redhat.com>,
	linux-block <linux-block@vger.kernel.org>,
	"open list:NVM EXPRESS DRIVER" <linux-nvme@lists.infradead.org>
Subject: Re: [bug report] blktests nvme/tcp triggered WARNING at kernel/workqueue.c:2628 check_flush_dependency+0x110/0x14c
Date: Sun, 24 Jul 2022 11:21:18 +0300	[thread overview]
Message-ID: <472156f4-ff58-aeba-64eb-b8e5815e9c29@grimberg.me> (raw)
In-Reply-To: <YtoriAQGW8+p4pFe@infradead.org>


>> The problem is that nvme_wq is MEM_RECLAIM, and nvme_tcp_wq is
>> for the socket threads, that does not need to be MEM_RECLAIM workqueue.
> 
> Why don't we need MEM_RECLAIM for the socket threads?
> 
>> But reset/error-recovery that take place on nvme_wq, stop nvme-tcp
>> queues, and that must involve flushing queue->io_work in order to
>> fence concurrent execution.
>>
>> So what is the solution? make nvme_tcp_wq MEM_RECLAIM?
> 
> I think so.

OK.

Yi, does this patch makes the issue go away?
--

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 0a9542599ad1..dc3b4dc8fe08 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -1839,7 +1839,8 @@ static int __init nvmet_tcp_init(void)
  {
         int ret;

-       nvmet_tcp_wq = alloc_workqueue("nvmet_tcp_wq", WQ_HIGHPRI, 0);
+       nvmet_tcp_wq = alloc_workqueue("nvmet_tcp_wq",
+                               WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
         if (!nvmet_tcp_wq)
                 return -ENOMEM;
--
