qcow2: Add errp to preallocate_co()

We'll add a bdrv_co_truncate() call in the next patch which can return
an Error that we don't want to discard. So add an errp parameter to
preallocate_co().

Cc: qemu-stable@nongnu.org
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

block/qcow2.c

@@ -2721,7 +2721,7 @@ static int qcow2_set_up_encryption(BlockDriverState *bs,
  * Returns: 0 on success, -errno on failure.
  */
 static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
-                                       uint64_t new_length)
+                                       uint64_t new_length, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t bytes;
@@ -2738,6 +2738,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
         ret = qcow2_alloc_cluster_offset(bs, offset, &cur_bytes,
                                          &host_offset, &meta);
         if (ret < 0) {
+            error_setg_errno(errp, -ret, "Allocating clusters failed");
             return ret;
         }
 
@@ -2746,6 +2747,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
 
             ret = qcow2_alloc_cluster_link_l2(bs, meta);
             if (ret < 0) {
+                error_setg_errno(errp, -ret, "Mapping clusters failed");
                 qcow2_free_any_clusters(bs, meta->alloc_offset,
                                         meta->nb_clusters, QCOW2_DISCARD_NEVER);
                 return ret;
@@ -2775,6 +2777,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
         ret = bdrv_pwrite(s->data_file, (host_offset + cur_bytes) - 1,
                           &data, 1);
         if (ret < 0) {
+            error_setg_errno(errp, -ret, "Writing to EOF failed");
             return ret;
         }
     }
@@ -3748,9 +3751,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         break;
 
     case PREALLOC_MODE_METADATA:
-        ret = preallocate_co(bs, old_length, offset);
+        ret = preallocate_co(bs, old_length, offset, errp);
         if (ret < 0) {
-            error_setg_errno(errp, -ret, "Preallocation failed");
             goto fail;
         }
         break;
@@ -3766,9 +3768,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         /* With a data file, preallocation means just allocating the metadata
          * and forwarding the truncate request to the data file */
         if (has_data_file(bs)) {
-            ret = preallocate_co(bs, old_length, offset);
+            ret = preallocate_co(bs, old_length, offset, errp);
             if (ret < 0) {
-                error_setg_errno(errp, -ret, "Preallocation failed");
                 goto fail;
             }
             break;