block: Formats don't need CONSISTENT_READ with NO_IO

Commit 1f4ad7d fixed 'qemu-img info' for raw images that are currently
in use as a mirror target. It is not enough for image formats, though,
as these still unconditionally request BLK_PERM_CONSISTENT_READ.

As this permission is geared towards whether the guest-visible data is
consistent, and has no impact on whether the metadata is sane, and
'qemu-img info' does not read guest-visible data (except for the raw
format), it makes sense to not require BLK_PERM_CONSISTENT_READ if there
is not going to be any guest I/O performed, regardless of image format.

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

diff --git a/block.c b/block.c
index 1c37ce4554b03ed2e914159013118531431cbfbd..db0be7ef36aedb03532ca77411a8c01c26614aad 100644 (file)
--- a/block.c
+++ b/block.c
@@ -1924,6 +1924,8 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
     assert(role == &child_backing || role == &child_file);
 
     if (!backing) {
+        int flags = bdrv_reopen_get_flags(reopen_queue, bs);
+
         /* Apart from the modifications below, the same permissions are
          * forwarded and left alone as for filters */
         bdrv_filter_default_perms(bs, c, role, reopen_queue, perm, shared,
@@ -1936,7 +1938,9 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
 
         /* bs->file always needs to be consistent because of the metadata. We
          * can never allow other users to resize or write to it. */
-        perm |= BLK_PERM_CONSISTENT_READ;
+        if (!(flags & BDRV_O_NO_IO)) {
+            perm |= BLK_PERM_CONSISTENT_READ;
+        }
         shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
     } else {
         /* We want consistent read from backing files if the parent needs it.