block/vpc: set errp in vpc_create

Add more useful error information to failure paths in vpc_create().

Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/vpc.c

@@ -874,6 +874,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         } else if (!strcmp(disk_type_param, "fixed")) {
             disk_type = VHD_FIXED;
         } else {
+            error_setg(errp, "Invalid disk type, %s", disk_type_param);
             ret = -EINVAL;
             goto out;
         }
@@ -924,6 +925,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         total_sectors = total_size / BDRV_SECTOR_SIZE;
         /* Allow a maximum disk size of approximately 2 TB */
         if (total_sectors > VHD_MAX_SECTORS) {
+            error_setg(errp, "Disk size is too large, max size is 2040 GiB");
             ret = -EFBIG;
             goto out;
         }
@@ -974,6 +976,9 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     } else {
         ret = create_fixed_disk(blk, buf, total_size);
     }
+    if (ret < 0) {
+        error_setg(errp, "Unable to create or write VHD header");
+    }
 
 out:
     blk_unref(blk);