Re: [PATCH 9/9] blk-crypto: use mempool_alloc_bulk for encrypted bio page allocation

[Vlastimil Babka <vbabka@suse.cz>]

On 10/31/25 10:34, Christoph Hellwig wrote:
> @@ -192,6 +205,29 @@ static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,
>  	bio->bi_write_stream	= bio_src->bi_write_stream;
>  	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
>  	bio_clone_blkg_association(bio, bio_src);
> +
> +	/*
> +	 * Move page array up in the allocated memory for the bio vecs as far as
> +	 * possible so that we can start filling biovecs from the beginning
> +	 * without overwriting the temporary page array.
> +	 */
> +	static_assert(PAGE_PTRS_PER_BVEC > 1);
> +	pages = (struct page **)bio->bi_io_vec;
> +	pages += nr_segs * (PAGE_PTRS_PER_BVEC - 1);
> +
> +	/*
> +	 * Try a bulk allocation first.  This could leave random pages in the
> +	 * array unallocated, but we'll fix that up later in mempool_alloc_bulk.
> +	 *
> +	 * Note: alloc_pages_bulk needs the array to be zeroed, as it assumes
> +	 * any non-zero slot already contains a valid allocation.
> +	 */
> +	memset(pages, 0, sizeof(struct page *) * nr_segs);
> +	if (alloc_pages_bulk(GFP_NOFS, nr_segs, pages) < nr_segs) {
> +		mempool_alloc_bulk(blk_crypto_bounce_page_pool, (void **)pages,
> +				nr_segs, GFP_NOIO);

Why do the GFP flags differ?

> +	}
> +	*pages_ret = pages;
>  	return bio;
>  }
>  
> @@ -234,6 +270,7 @@ static blk_status_t __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
>  	struct scatterlist src, dst;
>  	union blk_crypto_iv iv;
>  	struct bio *enc_bio = NULL;
> +	struct page **enc_pages;
>  	unsigned int nr_segs;
>  	unsigned int enc_idx = 0;
>  	unsigned int j;
> @@ -259,11 +296,10 @@ static blk_status_t __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
>  
>  		if (!enc_bio) {
>  			enc_bio = blk_crypto_alloc_enc_bio(src_bio,
> -					min(nr_segs, BIO_MAX_VECS));
> +					min(nr_segs, BIO_MAX_VECS), &enc_pages);
>  		}
>  
> -		enc_page = mempool_alloc(blk_crypto_bounce_page_pool,
> -				GFP_NOIO);
> +		enc_page = enc_pages[enc_idx];
>  		__bio_add_page(enc_bio, enc_page, src_bv.bv_len,
>  				src_bv.bv_offset);
>