[PATCH 1/2] qemu: Don't try to start NBD server twice

Michal Privoznik mprivozn at redhat.com
Mon Oct 26 10:41:35 UTC 2020

In one of recent patches the way that we start NBD server for
incoming migration was reworked (v6.8.0-rc1~298). A new boolean
was introduced that tracks whether the NBD server was started so
that we don't start it twice nor record in the port in the port
allocator twice. Well, this idea is good, but in the
implementation the boolean is never set, so we are reserving the
port twice and would be starting the NBD server twice too if it
wasn't for port reservation fail.

Fixes: e74d627bb3bc2684cbe3edc1e2f7cc745b4e1ff3
Reported-by: Vjaceslavs Klimovs <vklimovs at gmail.com>
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
 src/qemu/qemu_migration.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 2f5d61f8e7..6f764b0c73 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -479,9 +479,11 @@ qemuMigrationDstStartNBDServer(virQEMUDriverPtr driver,
                                            QEMU_ASYNC_JOB_MIGRATION_IN) < 0)
             goto cleanup;
-        if (!server_started &&
-            qemuMonitorNBDServerStart(priv->mon, &server, tls_alias) < 0)
-            goto exit_monitor;
+        if (!server_started) {
+            if (qemuMonitorNBDServerStart(priv->mon, &server, tls_alias) < 0)
+                goto exit_monitor;
+            server_started = true;
+        }
         if (qemuBlockExportAddNBD(vm, diskAlias, disk->src, diskAlias, true, NULL) < 0)
             goto exit_monitor;

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