Re: [PATCHv2 6/6] block: validate user space vectors during extraction

[Christoph Hellwig <hch@lst.de>]

> +#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.