On 5/13/21 12:22 PM, Mikulas Patocka wrote:

We already had problems with too large bios in dm-crypt and we fixed it by 
adding this piece of code:

        /*
         * Check if bio is too large, split as needed.
         */
        if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_VECS << PAGE_SHIFT)) &&
            (bio_data_dir(bio) == WRITE || cc->on_disk_tag_size))
                dm_accept_partial_bio(bio, ((BIO_MAX_VECS << PAGE_SHIFT) >> SECTOR_SHIFT));

It will ask the device mapper to split the bio if it is too large. So, 
crypt_alloc_buffer can't receive a bio that is larger than BIO_MAX_VECS << 
PAGE_SHIFT.

Hi Mikulas,

Are you perhaps referring to commit 4e870e948fba ("dm crypt: fix error
with too large bios")? Did that commit go upstream before multi-page
bvec support? Can larger bios be supported in case of two or more
contiguous pages now that multi-page bvec support is upstream?

Thanks,

Bart.