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Date: Mon, 29 Apr 2024 19:07:29 +0200
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Kanchan Joshi <joshi.k@samsung.com>, Christoph Hellwig <hch@lst.de>,
	axboe@kernel.dk, martin.petersen@oracle.com, brauner@kernel.org,
	asml.silence@gmail.com, dw@davidwei.uk, io-uring@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	gost.dev@samsung.com, Anuj Gupta <anuj20.g@samsung.com>
Subject: Re: [PATCH 02/10] block: copy bip_max_vcnt vecs instead of
 bip_vcnt during clone
Message-ID: <20240429170728.GA31337@lst.de>
References: <20240425183943.6319-1-joshi.k@samsung.com> <CGME20240425184653epcas5p28de1473090e0141ae74f8b0a6eb921a7@epcas5p2.samsung.com> <20240425183943.6319-3-joshi.k@samsung.com> <20240427070331.GB3873@lst.de> <73cc82c3-fbf6-ea3e-94ec-3bdce55af541@samsung.com> <Zi-MvOZ_bYVuiuBb@kbusch-mbp.mynextlight.net>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Mon, Apr 29, 2024 at 01:04:12PM +0100, Keith Busch wrote:
> An earlier version added a field in the bip to point to the original
> bvec from the user address. That extra field wouldn't be used in the far
> majority of cases, so moving the user bvec to the end of the existing
> bip_vec is a spatial optimization. The code may look a little more
> confusing that way, but I think it's better than making the bip bigger.

I think we need to do something like that - just hiding the bounce
buffer is not really maintainable once we get multiple levels of stacking
and other creative bio cloning.