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Date:   Mon, 7 Nov 2022 13:16:27 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc:     Christoph Hellwig <hch@lst.de>, linux-ide@vger.kernel.org,
        linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        "Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
        Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH v5 5/7] ata: libata: Fix FUA handling in
 ata_build_rw_tf()
Message-ID: <20221107121627.GA17441@lst.de>
References: <20221107005021.1327692-1-damien.lemoal@opensource.wdc.com> <20221107005021.1327692-6-damien.lemoal@opensource.wdc.com> <20221107055000.GD28873@lst.de> <ca10f501-0d3e-fcae-2b98-d39ca1822a67@opensource.wdc.com>
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On Mon, Nov 07, 2022 at 09:12:57PM +0900, Damien Le Moal wrote:
> On 11/7/22 14:50, Christoph Hellwig wrote:
> > On Mon, Nov 07, 2022 at 09:50:19AM +0900, Damien Le Moal wrote:
> >> Finally, since the block layer should never issue a FUA read
> >> request, warn in ata_build_rw_tf() if we see such request.
> > 
> > Couldn't this be triggered using SG_IO passthrough with a SCSI 
> > WRITE* command that has the FUA bit set?
> 
> Yes indeed. Should I drop the warn ?

I think the warn needs to go.  But don't we also need to handle the
non-NCQ fua case if we don't want to break pure passthrough appliations?
Or do we simply not care?  In the latter case we'll at least need a
comment documenting that tradeoff.