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Date:   Thu, 19 May 2022 10:35:23 -0600
From:   Keith Busch <kbusch@kernel.org>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Eric Biggers <ebiggers@kernel.org>, Keith Busch <kbusch@fb.com>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        axboe@kernel.dk, Kernel Team <Kernel-team@fb.com>,
        bvanassche@acm.org, damien.lemoal@opensource.wdc.com
Subject: Re: [PATCHv2 3/3] block: relax direct io memory alignment
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On Thu, May 19, 2022 at 09:41:14AM +0200, Christoph Hellwig wrote:
> On Wed, May 18, 2022 at 10:56:04PM -0600, Keith Busch wrote:
> > I'm surely missing something here. I know the bvecs are not necessarily lbs
> > aligned, but why does that matter? Is there some driver that can only take
> > exactly 1 bvec, but allows it to be unaligned? If so, we could take the segment
> > queue limit into account, but I am not sure that we need to.
> 
> At least stacking drivers had all kinds of interesting limitations in
> this area.  How much testing did this series get with all kinds of
> interesting dm targets and md pesonalities?

The dma limit doesn't stack (should it?). It gets the default, sector size - 1,
so their constraints are effectively unchanged.