block: bdrv_has_zero_init

This fixes the problem that qemu-img's use of no_zero_init only considered the
no_zero_init flag of the format driver, but not of the underlying protocols.

Between the raw/file split and this fix, converting to host devices is broken.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/block.c b/block.c
index eb1d5621b..56835afc5 100644
--- a/block.c
+++ b/block.c
@@ -1282,6 +1282,19 @@ void bdrv_flush_all(void)
     }
 }
 
+int bdrv_has_zero_init(BlockDriverState *bs)
+{
+    assert(bs->drv);
+
+    if (bs->drv->no_zero_init) {
+        return 0;
+    } else if (bs->file) {
+        return bdrv_has_zero_init(bs->file);
+    }
+
+    return 1;
+}
+
 /*
  * Returns true iff the specified sector is present in the disk image. Drivers
  * not implementing the functionality are assumed to not support backing files,