The same change as commit 2b23f28639 ('block/copy-on-read: Fix
permissions for inactive node') made for the copy-on-read driver can be
made for bdrv_filter_default_perms(): Retaining the old permissions from
the BdrvChild if it is given complicates things unnecessary when in the
end this only means that the options set in the c == NULL case (i.e.
during child creation) are retained.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index cbd8da5f3b..6db8ecd62b 100644
--- a/block.c
+++ b/block.c
@@ -2168,16 +2168,8 @@ void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c,
                                uint64_t perm, uint64_t shared,
                                uint64_t *nperm, uint64_t *nshared)
 {
-    if (c == NULL) {
-        *nperm = perm & DEFAULT_PERM_PASSTHROUGH;
-        *nshared = (shared & DEFAULT_PERM_PASSTHROUGH) | DEFAULT_PERM_UNCHANGED;
-        return;
-    }
-
-    *nperm = (perm & DEFAULT_PERM_PASSTHROUGH) |
-             (c->perm & DEFAULT_PERM_UNCHANGED);
-    *nshared = (shared & DEFAULT_PERM_PASSTHROUGH) |
-               (c->shared_perm & DEFAULT_PERM_UNCHANGED);
+    *nperm = perm & DEFAULT_PERM_PASSTHROUGH;
+    *nshared = (shared & DEFAULT_PERM_PASSTHROUGH) | DEFAULT_PERM_UNCHANGED;
 }
 
 void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
-- 
2.20.1

On 8/2/19 9:03 AM, Kevin Wolf wrote:
> The same change as commit 2b23f28639 ('block/copy-on-read: Fix
> permissions for inactive node') made for the copy-on-read driver can be
> made for bdrv_filter_default_perms(): Retaining the old permissions from
> the BdrvChild if it is given complicates things unnecessary when in the

unnecessarily

> end this only means that the options set in the c == NULL case (i.e.
> during child creation) are retained.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On 02.08.19 16:03, Kevin Wolf wrote:
> The same change as commit 2b23f28639 ('block/copy-on-read: Fix
> permissions for inactive node') made for the copy-on-read driver can be
> made for bdrv_filter_default_perms(): Retaining the old permissions from
> the BdrvChild if it is given complicates things unnecessary when in the
> end this only means that the options set in the c == NULL case (i.e.
> during child creation) are retained.

My best guess is that we had this code because this way any party could
set or remove the GRAPH_MOD permission and it would be kept through
.bdrv_child_perm() invocations.  (But I think that’s kaputt.)

> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>