From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@meta.com>,
dm-devel@lists.linux.dev, linux-block@vger.kernel.org,
snitzer@kernel.org, axboe@kernel.dk, ebiggers@kernel.org
Subject: Re: [PATCHv2 1/3] block: remove stacking default dma_alignment
Date: Tue, 25 Nov 2025 07:35:40 +0100 [thread overview]
Message-ID: <20251125063540.GA14873@lst.de> (raw)
In-Reply-To: <aSUZP6yP8mvi-q7v@kbusch-mbp>
On Mon, Nov 24, 2025 at 07:49:35PM -0700, Keith Busch wrote:
> On Mon, Nov 24, 2025 at 06:12:30PM +0100, Christoph Hellwig wrote:
> > On Mon, Nov 24, 2025 at 09:09:01AM -0800, Keith Busch wrote:
> > > From: Keith Busch <kbusch@kernel.org>
> > >
> > > The dma_alignment becomes 511 anyway if the caller doesn't explicitly
> > > set it. But setting this default prevents the stacked device from
> > > requesting a lower value even if it can handle lower alignments.
> >
> > Given how much trouble we had with drivers doing software processing
> > and unaligned buffers I'd feel more comfortable keeping this default
> > limitation. Drivers that want to relax it can still trivially do
> > that right after calling blk_set_stacking_limits.
>
> That should have the same result, but it's totally fine with me if you
> prefer the caller overwrite the default instead.
I think it's much safer if we require the opt-in.
next prev parent reply other threads:[~2025-11-25 6:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-24 17:09 [PATCHv2 0/2] dm-crypt: support relaxed memory alignment Keith Busch
2025-11-24 17:09 ` [PATCHv2 1/3] block: remove stacking default dma_alignment Keith Busch
2025-11-24 17:12 ` Christoph Hellwig
2025-11-25 2:49 ` Keith Busch
2025-11-25 6:35 ` Christoph Hellwig [this message]
2025-11-24 17:09 ` [PATCHv2 2/3] dm-crypt: allow unaligned bio_vecs for direct io Keith Busch
2025-11-24 17:09 ` [PATCHv2 3/3] dm-crypt: dynamic scatterlist for many segments Keith Busch
-- strict thread matches above, loose matches on Subject: below --
2025-11-28 3:22 kernel test robot
2025-11-28 6:15 ` Dan Carpenter
2026-01-14 15:41 [PATCHv2 0/2] dm-crypt: support relaxed memory alignment Keith Busch
2026-01-14 15:41 ` [PATCHv2 1/3] block: remove stacking default dma_alignment Keith Busch
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