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To:     Bart Van Assche <bvanassche@acm.org>
Cc:     John Garry <john.g.garry@oracle.com>, axboe@kernel.dk,
        kbusch@kernel.org, hch@lst.de, sagi@grimberg.me,
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Subject: Re: [PATCH 10/21] block: Add fops atomic write support
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
Message-ID: <yq1lecktuoo.fsf@ca-mkp.ca.oracle.com>
References: <20230929102726.2985188-1-john.g.garry@oracle.com>
        <20230929102726.2985188-11-john.g.garry@oracle.com>
        <17ee1669-5830-4ead-888d-a6a4624b638a@acm.org>
        <5d26fa3b-ec34-bc39-ecfe-4616a04977ca@oracle.com>
        <b7a6f380-c6fa-45e0-b727-ba804c6684e4@acm.org>
Date:   Mon, 02 Oct 2023 20:48:06 -0400
In-Reply-To: <b7a6f380-c6fa-45e0-b727-ba804c6684e4@acm.org> (Bart Van Assche's
        message of "Mon, 2 Oct 2023 12:12:49 -0700")
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Bart,

> Are there any SCSI devices that we care about that report an ATOMIC
> TRANSFER LENGTH GRANULARITY that is larger than a single logical
> block?

Yes.

Note that code path used inside a storage device to guarantee atomicity
of an entire I/O may be substantially different from the code path which
only offers an incremental guarantee at a single logical or physical
block level (to the extent that those guarantees are offered at all but
that's a different kettle of fish).

> I'm wondering whether we really have to support such devices.

Yes.

-- 
Martin K. Petersen	Oracle Linux Engineering