Re: [PATCH 7/9] blk-crypto: use mempool_alloc_bulk for encrypted bio page allocation

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Dec 17, 2025 at 07:06:50AM +0100, Christoph Hellwig wrote:
>  new_bio:
> -	enc_bio = blk_crypto_alloc_enc_bio(src_bio, nr_segs);
> +	enc_bio = blk_crypto_alloc_enc_bio(src_bio, nr_segs, &enc_pages);
>  	enc_idx = 0;
>  	for (;;) {
>  		struct bio_vec src_bv =
>  			bio_iter_iovec(src_bio, src_bio->bi_iter);
> -		struct page *enc_page;
> +		struct page *enc_page = enc_pages[enc_idx];
>  
> -		enc_page = mempool_alloc(blk_crypto_bounce_page_pool,
> -				GFP_NOIO);
>  		__bio_add_page(enc_bio, enc_page, src_bv.bv_len,
>  				src_bv.bv_offset);
>  
> @@ -246,10 +284,8 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
>  		/* Encrypt each data unit in this page */
>  		for (j = 0; j < src_bv.bv_len; j += data_unit_size) {
>  			blk_crypto_dun_to_iv(curr_dun, &iv);
> -			if (crypto_skcipher_encrypt(ciph_req)) {
> -				enc_idx++;
> -				goto out_free_bounce_pages;
> -			}
> +			if (crypto_skcipher_encrypt(ciph_req))
> +				goto out_free_enc_bio;
>  			bio_crypt_dun_increment(curr_dun, 1);
>  			src.offset += data_unit_size;
>  			dst.offset += data_unit_size;
> @@ -278,9 +314,9 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
>  	submit_bio(enc_bio);
>  	return;
>  
> -out_free_bounce_pages:
> -	while (enc_idx > 0)
> -		mempool_free(enc_bio->bi_io_vec[--enc_idx].bv_page,
> +out_free_enc_bio:
> +	for (enc_idx = 0; enc_idx < enc_bio->bi_max_vecs; enc_idx++)
> +		mempool_free(enc_bio->bi_io_vec[enc_idx].bv_page,
>  			     blk_crypto_bounce_page_pool);
>  	bio_put(enc_bio);
>  	cmpxchg(&src_bio->bi_status, 0, BLK_STS_IOERR);

The error handling at out_free_enc_bio is still broken, I'm afraid.
It's not taking into account that some of the pages may have been moved
into bvecs and some have not.

I think it needs something like the following:

diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
index 23e097197450..d6760404b76c 100644
--- a/block/blk-crypto-fallback.c
+++ b/block/blk-crypto-fallback.c
@@ -272,7 +272,7 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
 	for (;;) {
 		struct bio_vec src_bv =
 			bio_iter_iovec(src_bio, src_bio->bi_iter);
-		struct page *enc_page = enc_pages[enc_idx];
+		struct page *enc_page;
 
 		if (!IS_ALIGNED(src_bv.bv_len | src_bv.bv_offset,
 				data_unit_size)) {
@@ -280,6 +280,7 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
 			goto out_free_enc_bio;
 		}
 
+		enc_page = enc_pages[enc_idx++];
 		__bio_add_page(enc_bio, enc_page, src_bv.bv_len,
 				src_bv.bv_offset);
 
@@ -305,7 +306,7 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
 			break;
 
 		nr_segs--;
-		if (++enc_idx == enc_bio->bi_max_vecs) {
+		if (enc_idx == enc_bio->bi_max_vecs) {
 			/*
 			 * For each additional encrypted bio submitted,
 			 * increment the source bio's remaining count.  Each
@@ -323,9 +324,11 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
 	return;
 
 out_free_enc_bio:
-	for (enc_idx = 0; enc_idx < enc_bio->bi_max_vecs; enc_idx++)
+	for (j = 0; j < enc_idx; j++)
 		mempool_free(enc_bio->bi_io_vec[j].bv_page,
 			     blk_crypto_bounce_page_pool);
+	for (; j < enc_bio->bi_max_vecs; j++)
+		mempool_free(enc_pages[j], blk_crypto_bounce_page_pool);
 	bio_put(enc_bio);
 	bio_endio(src_bio);
 }