Commit 9ac85f4cc7 for qemu.org

commit 9ac85f4cc7995217db8f736733b990d6addcb036
Author: Fiona Ebner <f.ebner@proxmox.com>
Date:   Wed Mar 11 15:54:25 2026 +0100

    block/mirror: fix assertion failure upon duplicate complete for job using 'replaces'

    If s->replace_blocker was already set by an earlier invocation of
    mirror_complete(), then there will be an assertion failure when
    error_setg() is called for it a second time. The bdrv_op_block_all()
    and bdrv_ref() operations should only be done a single time too.

    Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
    Message-Id: <20260311145717.668492-2-f.ebner@proxmox.com>
    Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
    Signed-off-by: Hanna Czenczek <hreitz@redhat.com>

diff --git a/block/mirror.c b/block/mirror.c
index fa1d975eb9..2fcded9e93 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1276,23 +1276,25 @@ static void mirror_complete(Job *job, Error **errp)
         return;
     }

-    /* block all operations on to_replace bs */
-    if (s->replaces) {
-        s->to_replace = bdrv_find_node(s->replaces);
-        if (!s->to_replace) {
-            error_setg(errp, "Node name '%s' not found", s->replaces);
-            return;
+    if (!s->should_complete) {
+        /* block all operations on to_replace bs */
+        if (s->replaces) {
+            s->to_replace = bdrv_find_node(s->replaces);
+            if (!s->to_replace) {
+                error_setg(errp, "Node name '%s' not found", s->replaces);
+                return;
+            }
+
+            /* TODO Translate this into child freeze system. */
+            error_setg(&s->replace_blocker,
+                       "block device is in use by block-job-complete");
+            bdrv_op_block_all(s->to_replace, s->replace_blocker);
+            bdrv_ref(s->to_replace);
         }

-        /* TODO Translate this into child freeze system. */
-        error_setg(&s->replace_blocker,
-                   "block device is in use by block-job-complete");
-        bdrv_op_block_all(s->to_replace, s->replace_blocker);
-        bdrv_ref(s->to_replace);
+        s->should_complete = true;
     }

-    s->should_complete = true;
-
     /* If the job is paused, it will be re-entered when it is resumed */
     WITH_JOB_LOCK_GUARD() {
         if (!job->paused) {