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Date: Tue, 25 Nov 2025 17:46:04 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Caleb Sander Mateos <csander@purestorage.com>,
	Keith Busch <kbusch@meta.com>, linux-block@vger.kernel.org,
	axboe@kernel.dk, ebiggers@kernel.org,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCHv6] blk-integrity: support arbitrary buffer alignment
Message-ID: <20251125164604.GA29226@lst.de>
References: <20251124161707.3491456-1-kbusch@meta.com> <CADUfDZqrpJXLLU9V3eFJvRgth45-ht-yi4cSpmrBdnbfQGtWYw@mail.gmail.com> <aSTii9KbN6wQCvOt@kbusch-mbp> <CADUfDZogsF53MENLLyd0iCGKUoSqap3bEfSbt72KPifO4tvzfA@mail.gmail.com> <20251125113144.GA22938@lst.de> <aSW8G5C--oIzmfJa@kbusch-mbp>
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On Tue, Nov 25, 2025 at 07:24:27AM -0700, Keith Busch wrote:
> So the solution is to replace mp_bvec_iter_bvec() with bvec_iter_bvec()
> to ensure we don't cross pages? It's a little less efficient, but that's
> not a big deal.

Yes.  At least for CONFIG_HIGHMEM.  Note that in many places I actually
found that open coding these macros leads to nicer code, and with that
CONFIG_HIGHMEM ifdef that would probably also be the case.

> I assumed mapping physically congiguous memory was contiguous in kernel
> address space too,

It is.

> and that seems to work out in testing, but I don't
> have CONFIG_HIGHMEM enable where that might matter.

I keep an x86_32 VM around for that, but I usually only fire it up when
it's too late..