qemu_ns: Allow /dev/mapper/control for PR

If qemu-pr-helper is compiled with multipath support the first
thing it does is open /dev/mapper/control. Since we're going
to be running it inside qemu namespace we need to create it
there. Unfortunately, we don't know if it was compiled with or
without multipath so we have to create it anyway.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/qemu/qemu_domain.c

@@ -109,6 +109,7 @@ VIR_ENUM_IMPL(qemuDomainNamespace, QEMU_DOMAIN_NS_LAST,
 #define PROC_MOUNTS "/proc/mounts"
 #define DEVPREFIX "/dev/"
 #define DEV_VFIO "/dev/vfio/vfio"
+#define DEVICE_MAPPER_CONTROL_PATH "/dev/mapper/control"
 
 
 struct _qemuDomainLogContext {
@@ -10213,6 +10214,11 @@ qemuDomainSetupDisk(virQEMUDriverConfigPtr cfg ATTRIBUTE_UNUSED,
             goto cleanup;
     }
 
+    /* qemu-pr-helper might require access to /dev/mapper/control. */
+    if (virStoragePRDefIsEnabled(disk->src->pr) &&
+        qemuDomainCreateDevice(DEVICE_MAPPER_CONTROL_PATH, data, true) < 0)
+        goto cleanup;
+
     ret = 0;
  cleanup:
     VIR_FREE(dst);
@@ -11224,6 +11230,7 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
     virStorageSourcePtr next;
     const char **paths = NULL;
     size_t npaths = 0;
+    char *dmPath = NULL;
     int ret = -1;
 
     if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
@@ -11240,11 +11247,18 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
             goto cleanup;
     }
 
+    /* qemu-pr-helper might require access to /dev/mapper/control. */
+    if (virStoragePRDefIsEnabled(src->pr) &&
+        (VIR_STRDUP(dmPath, DEVICE_MAPPER_CONTROL_PATH) < 0 ||
+         VIR_APPEND_ELEMENT_COPY(paths, npaths, dmPath) < 0))
+        goto cleanup;
+
     if (qemuDomainNamespaceMknodPaths(vm, paths, npaths) < 0)
         goto cleanup;
 
     ret = 0;
  cleanup:
+    VIR_FREE(dmPath);
     VIR_FREE(paths);
     return ret;
 }