block: Make bdrv_img_create() size selection easier to read

All callers of bdrv_img_create() pass in a size, or -1 to read the
size from the backing file.  We then set that size as the QemuOpt
default, which means we will reuse that default rather than the
final parameter to qemu_opt_get_size() several lines later.  But
it is rather confusing to read subsequent checks of 'size == -1'
when it looks (without seeing the full context) like size defaults
to 0; it also doesn't help that a size of 0 is valid (for some
formats).

Rework the logic to make things more legible.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/block.c b/block.c
index 5c65fac672..528cda7b2c 100644
--- a/block.c
+++ b/block.c
@@ -4488,7 +4488,7 @@ void bdrv_img_create(const char *filename, const char *fmt,
 
     /* The size for the image must always be specified, unless we have a backing
      * file and we have not been forbidden from opening it. */
-    size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 0);
+    size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, img_size);
     if (backing_file && !(flags & BDRV_O_NO_BACKING)) {
         BlockDriverState *bs;
         char *full_backing = g_new0(char, PATH_MAX);