linux-kernel - Re: [PATCHv2 1/7] block: check for valid bio while splitting

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Message-ID: <yq11ppf2bnf.fsf@ca-mkp.ca.oracle.com>
Date: Wed, 13 Aug 2025 17:23:47 -0400
From: "Martin K. Petersen" <martin.petersen@...cle.com>
To: Keith Busch <kbusch@...nel.org>
Cc: Keith Busch <kbusch@...a.com>, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        snitzer@...nel.org, axboe@...nel.dk, dw@...idwei.uk,
        brauner@...nel.org, Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCHv2 1/7] block: check for valid bio while splitting


Hi Keith!

> NVMe wants this check to actually be this:
>
> 		if ((bv.bv_offset | bv.bv_len) & lim->dma_alignment)
>
> because the dma alignment defines not only the starting address offset,
> but also the length. NVMe's default alignment is 4 bytes.

dma_alignment defines the alignment of the DMA starting address. We
don't have a dedicated queue limit for the transfer length granularity
described by NVMe.

-- 
Martin K. Petersen