Add support for hotplugging (adding disks) to the libvirt attach-method.

When libvirt is used, we can allow disks to be hotplugged.
guestfs_add_drive can be called after launch to hot-add a disk.

When a disk is hot-added, we first ask libvirt to add the disk to the
appliance, then we make an internal call into the appliance to get it
to wait for the disk to appear (ie. udev_settle ()).

Hot-added disks are tracked in the g->drives array.

This also adds a test.

1 files changed, 67 insertions, 0 deletions

diff --git a/daemon/hotplug.c b/daemon/hotplug.c
new file mode 100644
index 00000000..aae638e7
--- /dev/null
+++ b/daemon/hotplug.c
@@ -0,0 +1,67 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2012 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <time.h>
+
+#include "guestfs_protocol.h"
+#include "daemon.h"
+#include "actions.h"
+
+#define HOT_ADD_TIMEOUT 30 /* seconds */
+
+/* Wait for /dev/disk/guestfs/<label> to appear.  Timeout (and error)
+ * if it doesn't appear after a reasonable length of time.
+ */
+int
+do_internal_hot_add_drive (const char *label)
+{
+  time_t start_t, now_t;
+  size_t len = strlen (label);
+  char path[len+64];
+  int r;
+
+  snprintf (path, len+64, "/dev/disk/guestfs/%s", label);
+
+  time (&start_t);
+
+  while (time (&now_t) - start_t <= HOT_ADD_TIMEOUT) {
+    udev_settle ();
+
+    r = access (path, F_OK);
+    if (r == -1 && errno != ENOENT) {
+      reply_with_perror ("%s", path);
+      return -1;
+    }
+    if (r == 0)
+      return 0;
+
+    sleep (1);
+  }
+
+  reply_with_error ("hot-add drive: '%s' did not appear after %d seconds: "
+                    "this could mean that virtio-scsi (in qemu or kernel) "
+                    "or udev is not working",
+                    path, HOT_ADD_TIMEOUT);
+  return -1;
+}