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Date:   Fri, 19 Nov 2021 17:56:27 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Tim Walker <tim.t.walker@seagate.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Ming Lei <ming.lei@redhat.com>,
        Yi Zhang <yi.zhang@redhat.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] blk-mq: don't insert FUA request with data into
 scheduler queue
Message-ID: <20211119165627.GA15266@lst.de>
References: <20211118153041.2163228-1-ming.lei@redhat.com> <163732851304.44181.8545954410705439362.b4-ty@kernel.dk> <BFC93946-13B3-43EC-9E30-8A980CD5234F@seagate.com> <3DEFF083-6C67-4864-81A5-454A7DAC16C0@seagate.com>
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Direct reply without a quote a the formatting of your mail is completely
messed up.  We don't treat a FUA a a flush.  If the device supports
FUA is is just passed on.  But if the device does not support FUA it
is sequenced into doing the write first and then a flush before returning
completion to the caller to guarantee the FUA semantics.  Because of that
the command needs special treatment and be handed over to the flush
state machine, but it won't do anything interesting if FUA is actually
natively supported.