qcow2: Get the request alignment for encrypted images from QCryptoBlock

This doesn't have any practical effect at the moment because the
values of BDRV_SECTOR_SIZE, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE and
QCRYPTO_BLOCK_QCOW_SECTOR_SIZE are all the same (512 bytes), but
future encryption methods could have different requirements.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -1677,7 +1677,7 @@ static void qcow2_refresh_limits(BlockDriverState *bs, Error **errp)
 
     if (bs->encrypted) {
         /* Encryption works on a sector granularity */
-        bs->bl.request_alignment = BDRV_SECTOR_SIZE;
+        bs->bl.request_alignment = qcrypto_block_get_sector_size(s->crypto);
     }
     bs->bl.pwrite_zeroes_alignment = s->cluster_size;
     bs->bl.pdiscard_alignment = s->cluster_size;