systemd: add lvm2 activation generator

The lvm2 activation generator generates systemd units conditionally
based on the global/use_lvmetad lvm.conf setting.

If use_lvmetad=0, the lvm2-activation-early.service and lvm2-activation.service
units will be generated. These units are responsible for direct volume activation
by calling "vgchange -aay --sysinit" (this is actually the original on-boot
activation as it was used before). If use_lvmetad=1, no units will be generated
as we're relying on autoactivation.

Important thing to note is that the lvm2-activation units normally bring
in the udev-settle ("storage-wait") service that waits for udev to settle
(with block devices). We don't need this if lvmetad is used in conjunction
with autoactivation feature... but systemd units can't be enabled or disabled
(or dependencies added/removed) dynamically based on external configuration.

Therefore, we need the unit generator which adds support for such situations:
the units as a whole either exist or not based on the external configuration.

1 files changed, 169 insertions, 0 deletions

diff --git a/scripts/lvm2_activation_generator_systemd_red_hat.c b/scripts/lvm2_activation_generator_systemd_red_hat.c
new file mode 100644
index 00000000..99210049
--- /dev/null
+++ b/scripts/lvm2_activation_generator_systemd_red_hat.c
@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc. All rights reserved.
+ *
+ * This file is part of the device-mapper userspace tools.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License v.2.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "lvm2app.h"
+
+#define KMSG_DEV_PATH        "/dev/kmsg"
+#define LVM_CONF_USE_LVMETAD "global/use_lvmetad"
+
+#define DEFAULT_UNIT_DIR     "/tmp"
+#define UNIT_NAME_EARLY      "lvm2-activation-early.service"
+#define UNIT_NAME            "lvm2-activation.service"
+#define UNIT_TARGET          "local-fs.target"
+
+static char unit_path[PATH_MAX];
+static char target_path[PATH_MAX];
+static char message[PATH_MAX];
+static int kmsg_fd = -1;
+
+static void kmsg(const char *format, ...)
+{
+	va_list ap;
+	int n;
+
+	va_start(ap, format);
+	n = vsnprintf(message, sizeof(message), format, ap);
+	va_end(ap);
+
+	if (kmsg_fd < 0 || (n < 0 || ((unsigned) n + 1 > sizeof(message))))
+		return;
+
+	write(kmsg_fd, message, n + 1);
+}
+
+static int lvm_uses_lvmetad(void)
+{
+	lvm_t lvm;
+	int r;
+
+	if (!(lvm = lvm_init(NULL))) {
+		kmsg("LVM: Failed to initialize library context for activation generator.\n");
+		return 0;
+	}
+	r = lvm_config_find_bool(lvm, LVM_CONF_USE_LVMETAD, 0);
+	lvm_quit(lvm);
+
+	return r;
+}
+
+static int register_unit_with_target(const char *dir, const char *unit, const char *target)
+{
+	int r = 1;
+
+	if (dm_snprintf(target_path, PATH_MAX, "%s/%s.wants", dir, target) < 0) {
+		r = 0; goto out;
+	}
+	(void) dm_prepare_selinux_context(target_path, S_IFDIR);
+	if (mkdir(target_path, 0755) < 0 && errno != EEXIST) {
+		kmsg("LVM: Failed to create target directory %s: %m.\n", target_path);
+		r = 0; goto out;
+	}
+
+	if (dm_snprintf(target_path, PATH_MAX, "%s/%s.wants/%s", dir, target, unit) < 0) {
+		r = 0; goto out;
+	}
+	(void) dm_prepare_selinux_context(target_path, S_IFLNK);
+	if (symlink(unit_path, target_path) < 0) {
+		kmsg("LVM: Failed to create symlink for unit %s: %m.\n", unit);
+		r = 0;
+	}
+out:
+	dm_prepare_selinux_context(NULL, 0);
+	return r;
+}
+
+static int generate_unit(const char *dir, int early)
+{
+	FILE *f;
+	const char *unit = early ? UNIT_NAME_EARLY : UNIT_NAME;
+
+	if (dm_snprintf(unit_path, PATH_MAX, "%s/%s", dir, unit) < 0)
+		return 0;
+
+	if (!(f = fopen(unit_path, "wxe"))) {
+		kmsg("LVM: Failed to create unit file %s: %m.\n", unit);
+		return 0;
+	}
+
+	fputs("# Automatically generated by lvm2-activation-generator.\n"
+	      "#\n"
+	      "# This unit is responsible for direct activation of LVM2 logical volumes\n"
+	      "# if lvmetad daemon is not used (global/use_lvmetad=0 lvm.conf setting),\n"
+	      "# hence volume autoactivation is not applicable.\n"
+	      "# Direct LVM2 activation requires udev to be settled!\n\n"
+	      "[Unit]\n"
+	      "Description=Activation of LVM2 logical volumes\n"
+	      "Documentation=man:lvm(8) man:vgchange(8)\n"
+	      "SourcePath=/etc/lvm/lvm.conf\n"
+	      "DefaultDependencies=no\n", f);
+
+	if (early)
+		fputs("After=fedora-wait-storage.service\n", f);
+	else
+		fputs("After=lvm2-activation-early.service cryptsetup.target\n", f);
+
+	fputs("Before=local-fs.target shutdown.target\n"
+	      "Wants=fedora-wait-storage.service\n\n"
+	      "[Service]\n"
+	      "ExecStart=/usr/sbin/lvm vgchange -aay --sysinit\n"
+	      "Type=oneshot\n", f);
+
+	if (fclose(f) < 0) {
+		kmsg("LVM: Failed to write unit file %s: %m.\n", unit);
+		return 0;
+	}
+
+	if (!register_unit_with_target(dir, unit, UNIT_TARGET)) {
+		kmsg("LVM: Failed to register unit %s with target %s.\n", unit, UNIT_TARGET);
+		return 0;
+	}
+
+	return 1;
+}
+
+int main(int argc, char *argv[])
+{
+	const char *dir;
+	int r = EXIT_SUCCESS;
+
+	kmsg_fd = open(KMSG_DEV_PATH, O_WRONLY|O_NOCTTY|O_CLOEXEC);
+
+	if (argc > 1 && argc != 4) {
+		kmsg("LVM: Activation generator takes three or no arguments.\n");
+		r = EXIT_FAILURE; goto out;
+	}
+
+	/* If lvmetad used, rely on autoactivation instead of direct activation. */
+	if (lvm_uses_lvmetad()) {
+		kmsg("LVM: Logical Volume autoactivation enabled.\n");
+		goto out;
+	}
+
+	dir = argc > 1 ? argv[1] : DEFAULT_UNIT_DIR;
+
+	if (!generate_unit(dir, 1) || !generate_unit(dir, 0))
+		r = EXIT_FAILURE;
+out:
+	kmsg("LVM: Activation generator %s.\n", r ? "failed" : "successfully completed");
+	if (kmsg_fd != -1)
+		close(kmsg_fd);
+	return r;
+}