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Date:   Fri, 12 May 2023 13:21:29 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org,
        Guangwu Zhang <guazhang@redhat.com>,
        Yu Kuai <yukuai1@huaweicloud.com>
Subject: Re: [PATCH] blk-mq: don't queue passthrough request into scheduler
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On Fri, May 12, 2023 at 09:43:32AM -0600, Jens Axboe wrote:
> We really have two types of passthrough - normal kind of IO, and
> potential error recovery etc IO. The former can plug just fine, and I
> don't think we should treat it differently. Might make more sense to
> just bypass plugging for error handling type of IO, or pt that doesn't
> transfer any data to avoid having a NULL bio inserted into the
> scheduler.

I'd suggest we distinguish by ... having a plug or not.  Anything
internal like EH or probing should never come from a context with
a plug.