block/qcow2: refactor encryption code

* Change the qcow2_co_{encrypt|decrypt} to just receive full host and
  guest offsets and use this function directly instead of calling
  do_perform_cow_encrypt (which is removed by that patch).

* Adjust qcow2_co_encdec to take full host and guest offsets as well.

* Document the qcow2_co_{encrypt|decrypt} arguments
  to prevent the bug fixed in former commit from hopefully
  happening again.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-id: 20190915203655.21638-3-mlevitsk@redhat.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[mreitz: Let perform_cow() return the error value returned by
         qcow2_co_encrypt(), as proposed by Vladimir]
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 13 insertions, 28 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index cac0b6c7ba..8d5fa1539c 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -462,28 +462,6 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
     return 0;
 }
 
-static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
-                                                uint64_t src_cluster_offset,
-                                                uint64_t cluster_offset,
-                                                unsigned offset_in_cluster,
-                                                uint8_t *buffer,
-                                                unsigned bytes)
-{
-    if (bytes && bs->encrypted) {
-        BDRVQcow2State *s = bs->opaque;
-        assert(QEMU_IS_ALIGNED(offset_in_cluster, BDRV_SECTOR_SIZE));
-        assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
-        assert(s->crypto);
-        if (qcow2_co_encrypt(bs,
-                start_of_cluster(s, cluster_offset + offset_in_cluster),
-                src_cluster_offset + offset_in_cluster,
-                buffer, bytes) < 0) {
-            return false;
-        }
-    }
-    return true;
-}
-
 static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
                                              uint64_t cluster_offset,
                                              unsigned offset_in_cluster,
@@ -891,12 +869,19 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
 
     /* Encrypt the data if necessary before writing it */
     if (bs->encrypted) {
-        if (!do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
-                                    start->offset, start_buffer,
-                                    start->nb_bytes) ||
-            !do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
-                                    end->offset, end_buffer, end->nb_bytes)) {
-            ret = -EIO;
+        ret = qcow2_co_encrypt(bs,
+                               m->alloc_offset + start->offset,
+                               m->offset + start->offset,
+                               start_buffer, start->nb_bytes);
+        if (ret < 0) {
+            goto fail;
+        }
+
+        ret = qcow2_co_encrypt(bs,
+                               m->alloc_offset + end->offset,
+                               m->offset + end->offset,
+                               end_buffer, end->nb_bytes);
+        if (ret < 0) {
             goto fail;
         }
     }