vgscan: add --notifydbus to send a notification

This command option can be used to trigger a D-Bus
notification independent of the usual notifications
that are sent from other commands as an effect of
changes to PV/VG/LV state.  If lvm is not built with
dbus notification support or if notify_dbus is disabled
in the config, this command will exit with an error.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.146 - 
 =================================
+  Add vgscan --notifydbus to send a dbus notification.
   Add dbus notification from commands after a PV/VG/LV changes state.
 
 Version 2.02.145 - 4th March 2016

lib/notify/lvmnotify.c

@@ -20,6 +20,11 @@
 #ifdef NOTIFYDBUS_SUPPORT
 #include <systemd/sd-bus.h>
 
+int lvmnotify_is_supported(void)
+{
+	return 1;
+}
+
 void lvmnotify_send(struct cmd_context *cmd)
 {
 	sd_bus *bus = NULL;
@@ -89,6 +94,11 @@ void set_pv_notify(struct cmd_context *cmd)
 
 #else
 
+int lvmnotify_is_supported(void)
+{
+	return 0;
+}
+
 void lvmnotify_send(struct cmd_context *cmd)
 {
 }

lib/notify/lvmnotify.h

@@ -11,6 +11,7 @@
 #ifndef _LVMNOTIFY_H
 #define _LVMNOTIFY_H
 
+int lvmnotify_is_supported(void);
 void lvmnotify_send(struct cmd_context *cmd);
 void set_vg_notify(struct cmd_context *cmd);
 void set_lv_notify(struct cmd_context *cmd);

man/vgscan.8.in

@@ -9,6 +9,7 @@ vgscan \(em scan all disks for volume groups and rebuild caches
 .RB [ \-h | \-? | \-\-help ]
 .RB [ \-\-ignorelockingfailure ]
 .RB [ \-\-mknodes ]
+.RB [ \-\-notifydbus ]
 .RB [ \-P | \-\-partial ]
 .RB [ \-v | \-\-verbose ]
 .SH DESCRIPTION
@@ -26,6 +27,11 @@ See \fBlvm\fP(8) for common options.
 Also checks the LVM special files in /dev that are needed for active 
 logical volumes and creates any missing ones and removes unused ones.
 .TP
+.B \-\-notifydbus
+Send a notification to D-Bus. The command will exit with an error
+if LVM is not built with support for D-Bus notification, or if the
+notify_dbus config setting is disabled.
+.TP
 .B \-\-cache
 Scan devices for LVM physical volumes and volume groups and instruct
 the lvmetad daemon to update its cached state accordingly.

tools/args.h

@@ -74,6 +74,7 @@ arg(nolocking_ARG, '\0', "nolocking", NULL, 0)
 arg(norestorefile_ARG, '\0', "norestorefile", NULL, 0)
 arg(nosuffix_ARG, '\0', "nosuffix", NULL, 0)
 arg(nosync_ARG, '\0', "nosync", NULL, 0)
+arg(notifydbus_ARG, '\0', "notifydbus", NULL, 0)
 arg(noudevsync_ARG, '\0', "noudevsync", NULL, 0)
 arg(originname_ARG, '\0', "originname", string_arg, 0)
 arg(physicalvolumesize_ARG, '\0', "setphysicalvolumesize", size_mb_arg, 0)

tools/commands.h

@@ -1390,11 +1390,12 @@ xx(vgscan,
    "\t[-h|--help]\n"
    "\t[--ignorelockingfailure]\n"
    "\t[--mknodes]\n"
+   "\t[--notifydbus]\n"
    "\t[-P|--partial]\n"
    "\t[-v|--verbose]\n"
    "\t[--version]\n",
 
-   cache_long_ARG, ignorelockingfailure_ARG, mknodes_ARG, partial_ARG)
+   cache_long_ARG, ignorelockingfailure_ARG, mknodes_ARG, notifydbus_ARG, partial_ARG)
 
 xx(vgsplit,
    "Move physical volumes into a new or existing volume group",

tools/vgscan.c

@@ -37,6 +37,21 @@ int vgscan(struct cmd_context *cmd, int argc, char **argv)
 		return EINVALID_CMD_LINE;
 	}
 
+	if (arg_is_set(cmd, notifydbus_ARG)) {
+		if (!lvmnotify_is_supported()) {
+			log_error("Cannot notify dbus: lvm is not built with dbus support.");
+			return ECMD_FAILED;
+		}
+		if (!find_config_tree_bool(cmd, global_notify_dbus_CFG, NULL)) {
+			log_error("Cannot notify dbus: notify_dbus is disabled in lvm config.");
+			return ECMD_FAILED;
+		}
+		set_pv_notify(cmd);
+		set_vg_notify(cmd);
+		set_lv_notify(cmd);
+		return ECMD_PROCESSED;
+	}
+
 	if (!lock_vol(cmd, VG_GLOBAL, LCK_VG_WRITE, NULL)) {
 		log_error("Unable to obtain global lock.");
 		return ECMD_FAILED;