linux-kernel - Re: [RFC PATCH 0/4] nvme-tcp: fix hung issues for deleting

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Message-ID: <bd1676d2-4078-4c02-14a9-e2f5ebe2dd29@grimberg.me>
Date:   Tue, 6 Jun 2023 02:09:08 +0300
From:   Sagi Grimberg <sagi@...mberg.me>
To:     "brookxu.cn" <brookxu.cn@...il.com>, kbusch@...nel.org,
        axboe@...nel.dk, hch@....de
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] nvme-tcp: fix hung issues for deleting


> From: Chunguang Xu <chunguang.xu@...pee.com>
> 
> We found that nvme_remove_namespaces() may hang in flush_work(&ctrl->scan_work)
> while removing ctrl. The root cause may due to the state of ctrl changed to
> NVME_CTRL_DELETING while removing ctrl , which intterupt nvme_tcp_error_recovery_work()/
> nvme_reset_ctrl_work()/nvme_tcp_reconnect_or_remove().  At this time, ctrl is
> freezed and queue is quiescing . Since scan_work may continue to issue IOs to
> load partition table, make it blocked, and lead to nvme_tcp_error_recovery_work()
> hang in flush_work(&ctrl->scan_work).
> 
> After analyzation, we found that there are mainly two case:
> 1. Since ctrl is freeze, scan_work hang in __bio_queue_enter() while it issue
>     new IO to load partition table.
> 2. Since queus is quiescing, requeue timeouted IO may hang in hctx->dispatch
>     queue, leading scan_work waiting for IO completion.

Hey, can you please look at the discussion with Mings' proposal in
"nvme: add nvme_delete_dead_ctrl for avoiding io deadlock" ?

Looks the same to me.