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Date: Wed, 19 Aug 2026 16:27:23 +0200
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@meta.com>,
	linux-block@vger.kernel.org, axboe@kernel.dk,
	Eric Auger <eauger@redhat.com>
Subject: Re: [PATCH] block: save page offset gaps in cloned bio
Message-ID: <20260819142723.GB825@lst.de>
References: <20260817165908.137682-1-kbusch@meta.com> <20260819052306.GA32364@lst.de> <aoW3-6U0XkrHudpy@kbusch-mbp>
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On Wed, Aug 19, 2026 at 08:04:43AM -0600, Keith Busch wrote:
> > > The split remainder meanwhile can reset its gaps to 0
> > > since it advanced beyond it and will start accounting from there.
> > 
> > I don't really understand this part, though.  As in I don't even
> > understand what you mean here..
> 
> The accounting for the vector gaps happens at the same time we consider
> a bio for splitting. When we do split, the gap value applies only to the
> front bio because that's as far as been processed. The remaining split
> bio should reset its gap value to 0, and it will be recalculated when it
> continues through the split consideration.

Ḣ. but bio_split is used for a lot of different thing.  Then again the
bi_bvec_gap_bit is only used by the low-level blk-mq code, so it might
not matter.  But this for sure warrants a big fat comment explaining
the rationale for the clearing.