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Date:   Tue, 13 Jun 2023 08:41:46 -0600
From:   Keith Busch <kbusch@kernel.org>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
        linux-nvme@lists.infradead.org, Yi Zhang <yi.zhang@redhat.com>,
        linux-block@vger.kernel.org, Chunguang Xu <brookxu.cn@gmail.com>
Subject: Re: [PATCH 2/2] nvme: don't freeze/unfreeze queues from different
 contexts
Message-ID: <ZIiAKhi5Vmc0Fc9W@kbusch-mbp.dhcp.thefacebook.com>
References: <20230613005847.1762378-1-ming.lei@redhat.com>
 <20230613005847.1762378-3-ming.lei@redhat.com>
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On Tue, Jun 13, 2023 at 08:58:47AM +0800, Ming Lei wrote:
> And this way is correct because quiesce is enough for driver to handle
> error recovery. The only difference is where to wait during error recovery.
> With this way, IO is just queued in block layer queue instead of
> __bio_queue_enter(), finally waiting for completion is done in upper
> layer. Either way, IO can't move on during error recovery.

The point was to contain the fallout from modifying the hctx mappings.
If you allow IO to queue in the blk-mq layer while a reset is in
progress, they may be entering a context that won't be as expected on
the other side of the reset.