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

[Eric Biggers]

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);
 }