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Date: Tue, 26 Aug 2025 17:11:24 -0600
From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <kbusch@meta.com>, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	snitzer@kernel.org, axboe@kernel.dk, dw@davidwei.uk,
	brauner@kernel.org, martin.petersen@oracle.com, djwong@kernel.org,
	linux-xfs@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: [PATCHv3 3/8] block: align the bio after building it
Message-ID: <aK4_HMksxi1HEMZF@kbusch-mbp>
References: <20250819164922.640964-1-kbusch@meta.com>
 <20250819164922.640964-4-kbusch@meta.com>
 <20250825074744.GF20853@lst.de>
 <aK0Bsf6AKL8a0wFy@kbusch-mbp>
 <20250826080200.GA23095@lst.de>
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In-Reply-To: <20250826080200.GA23095@lst.de>

On Tue, Aug 26, 2025 at 10:02:00AM +0200, Christoph Hellwig wrote:
> On Mon, Aug 25, 2025 at 06:37:05PM -0600, Keith Busch wrote:
> > bio_iov_iter_get_pages() might submit the segments as separate IO's
> > anyway for other reasons. I am not sure why the alignment conditions are
> > handled specifically here.
> 
> I'll take another look.  Basically what this wants to prevent is
> bio_iov_iter_get_pages creating bios not aligned to file system
> block size.

Got it, I think we're okay in that case. You should only need to
consider the ki_pos and the iov_iter_count to align to the filesystem
block size. This patch will dispatch appropriately sized IO as long as
the hw limits allow it, and you'll get an error (same as before) if it
doesn't.