From a80280654277c361714ec5f3925d2d6b077eca7b Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Mon, 15 Jan 2018 11:23:37 +0100
Subject: [PATCH 12/12] block: Formats don't need CONSISTENT_READ with NO_IO

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20180115112337.20885-4-kwolf@redhat.com>
Patchwork-id: 78574
O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH 3/3] block: Formats don't need CONSISTENT_READ with NO_IO
Bugzilla: 1515604
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>

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>
(cherry picked from commit 5fbfabd313b77e1cc7038ae8c4481c4b9f8b650a)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index 90a60bc..ca8a46b 100644
--- a/block.c
+++ b/block.c
@@ -1885,6 +1885,8 @@ 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,
@@ -1897,7 +1899,9 @@ 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.
-- 
1.8.3.1