From a3a9d320ac8cde96c976378b92dc4fcf553d9287 Mon Sep 17 00:00:00 2001
Message-Id: <a3a9d320ac8cde96c976378b92dc4fcf553d9287@dist-git>
From: Peter Krempa <pkrempa@redhat.com>
Date: Fri, 3 Apr 2020 14:32:55 +0200
Subject: [PATCH] qemuDomainSnapshotDiskPrepareOne: Fix logic of relative
 backing store update
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Commit 2ace7a87a8aced68c250 introduced a logic bug by an improperly
modified condition where we'd skip to the else branch when reusing of
external images was requested and blockdev is available.

The original intentions were to skip the backing store update with
blockdev.

Fix it by only asserting the boolean which was used to track whether we
support update of the backing store only when blockdev is not present
along with the appropriate rename.

https://bugzilla.redhat.com/show_bug.cgi?id=1820016

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
(cherry picked from commit ae64a75a8713cf14b25b40078766c2da93e001ff)
Message-Id: <c4ce185df3fb6d88aa7282d523b0a5c7ccff2aad.1585916255.git.pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/qemu/qemu_driver.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 4701a1905e..26215f8d6a 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15403,7 +15403,7 @@ qemuDomainSnapshotDiskPrepareOne(virQEMUDriverPtr driver,
 {
     virDomainDiskDefPtr persistdisk;
     bool supportsCreate;
-    bool supportsBacking;
+    bool updateRelativeBacking = false;
 
     dd->disk = disk;
 
@@ -15432,19 +15432,22 @@ qemuDomainSnapshotDiskPrepareOne(virQEMUDriverPtr driver,
     }
 
     supportsCreate = virStorageFileSupportsCreate(dd->src);
-    supportsBacking = virStorageFileSupportsBackingChainTraversal(dd->src);
 
-    if (supportsCreate || supportsBacking) {
+    /* relative backing store paths need to be updated so that relative
+     * block commit still works. With blockdev we must update it when doing
+     * commit anyways so it's skipped here */
+    if (!blockdev &&
+        virStorageFileSupportsBackingChainTraversal(dd->src))
+        updateRelativeBacking = true;
+
+    if (supportsCreate || updateRelativeBacking) {
         if (qemuDomainStorageFileInit(driver, vm, dd->src, NULL) < 0)
             return -1;
 
         dd->initialized = true;
 
-        /* relative backing store paths need to be updated so that relative
-         * block commit still works. With blockdev we must update it when doing
-         * commit anyways so it's skipped here */
-        if (reuse && !blockdev) {
-            if (supportsBacking) {
+        if (reuse) {
+            if (updateRelativeBacking) {
                 g_autofree char *backingStoreStr = NULL;
 
                 if (virStorageFileGetBackingStoreStr(dd->src, &backingStoreStr) < 0)
-- 
2.26.0