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Date:   Wed, 24 May 2023 08:13:56 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org, Mike Snitzer <snitzer@kernel.org>,
        Damien Le Moal <dlemoal@kernel.org>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH v3 4/7] block: Make it easier to debug zoned write
 reordering
Message-ID: <20230524061356.GE19611@lst.de>
References: <20230522183845.354920-1-bvanassche@acm.org> <20230522183845.354920-5-bvanassche@acm.org> <20230523071957.GD8758@lst.de> <41dd1a93-2491-a094-dc61-f424b51af6cb@acm.org>
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On Tue, May 23, 2023 at 12:34:38PM -0700, Bart Van Assche wrote:
>> What makes sequential writes here special vs other requests that are
>> supposed to be using the scheduler and not a bypass?
>
> Hi Christoph,
>
> If some REQ_OP_WRITE or REQ_OP_WRITE_ZEROES requests are submitted to the 
> I/O scheduler and others bypass the I/O scheduler this may lead to 
> reordering. Hence this patch that triggers a kernel warning if any 
> REQ_OP_WRITE or REQ_OP_WRITE_ZEROES requests bypass the I/O scheduler.

But why would we ever do a direct insert when using a scheduler for
write (an read for that matter) commands when not on a zoned device?