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Date: Tue, 23 Jun 2026 17:10:21 +0200
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@meta.com>
Cc: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	dm-devel@lists.linux.dev, hch@lst.de, axboe@kernel.dk,
	brauner@kernel.org, djwong@kernel.org, viro@zeniv.linux.org.uk,
	Keith Busch <kbusch@kernel.org>, stable@vger.kernel.org
Subject: Re: [PATCHv2 6/6] block: validate user space vectors during
 extraction
Message-ID: <20260623151021.GA14919@lst.de>
References: <20260622174241.2299563-1-kbusch@meta.com> <20260622174241.2299563-7-kbusch@meta.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

> +#ifdef CONFIG_DEBUG_KERNEL

That's a pretty broad option.  Not that I have any better idea off the
bat.

> +static inline bool bio_iov_bvec_aligned(const struct bio *bio,
> +					unsigned mem_align_mask)
> +{
> +	/*
> +	 * The vectors are owned and laid out by the caller; we only forward
> +	 * them. Most callers are already aligned, but io_uring can place a
> +	 * user chosen offset through a registered buffer, where only the first
> +	 * vector may be unaligned.
> +	 */
> +	return !(mp_bvec_iter_offset(bio->bi_io_vec, bio->bi_iter) &
> +							mem_align_mask);

I don't fully understand the comment.  I guess this is to say ITER_BVEC
users better don't create any alignment gaps?  Maybe we should also
clearly document that in uio.h?

>  	return bio_iov_iter_get_pages(bio, iter,
> +			bdev_dma_alignment(bdev),

Nit: this easily fits onto the previous line.

Otherwise this looks good.