lv/vgchange: do not try to connect to lvmetad if socket absent and --sysinit -aay used

If using lv/vgchange --sysinit -aay and lvmetad is enabled, we'd like to
avoid the direct activation and rely on autoactivation instead so
it fits system initialization scripts.

But if we're calling lv/vgchange --sysinit -aay too early when even
lvmetad service is not started yet, we just need to do the direct
activation instead without printing any error messages (while
trying to connect to lvmetad and not finding its socket).

This patch adds two helper functions - "lvmetad_socket_present" and
"lvmetad_used" which can be used to check for this condition properly
and avoid these lvmetad connections when the socket is not present
(and hence lvmetad is not yet running).

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.105 -
 =====================================
+  Do not connect to lvmetad on vg/lvchange --sysinit -aay and socket absent.
   Use lv_check_not_in_use() when testing device in use before merging.
   Move test for target present from init_snapshot_merge() to lvconvert.
   Check for failure of lvmcache_add_mda() when writing pv.

daemons/lvmetad/lvmetad-client.h

@@ -17,6 +17,8 @@
 
 #include "daemon-client.h"
 
+#define LVMETAD_SOCKET DEFAULT_RUN_DIR "/lvmetad.socket"
+
 struct volume_group;
 
 /* Different types of replies we may get from lvmetad. */
@@ -64,7 +66,7 @@ static inline daemon_handle lvmetad_open(const char *socket)
 {
 	daemon_info lvmetad_info = {
 		.path = "lvmetad",
-		.socket = socket ?: DEFAULT_RUN_DIR "/lvmetad.socket",
+		.socket = socket ?: LVMETAD_SOCKET,
 		.protocol = "lvmetad",
 		.protocol_version = 1,
 		.autostart = 0

daemons/lvmetad/lvmetad-core.c

@@ -29,6 +29,8 @@
 #include <math.h>  /* fabs() */
 #include <float.h> /* DBL_EPSILON */
 
+#define LVMETAD_SOCKET DEFAULT_RUN_DIR "/lvmetad.socket"
+
 typedef struct {
 	log_state *log; /* convenience */
 	const char *log_config;
@@ -1209,7 +1211,7 @@ int main(int argc, char *argv[])
 
 	if (!s.socket_path) {
 		_socket_override = 0;
-		s.socket_path = DEFAULT_RUN_DIR "/lvmetad.socket";
+		s.socket_path = LVMETAD_SOCKET;
 	}
 	ls.log_config = "";
 

lib/cache/lvmetad.c

@@ -72,6 +72,22 @@ void lvmetad_connect_or_warn(void)
 			 strerror(_lvmetad.error));
 }
 
+int lvmetad_used(void)
+{
+	return _lvmetad_use;
+}
+
+int lvmetad_socket_present(void)
+{
+	const char *socket = _lvmetad_socket ?: LVMETAD_SOCKET;
+	int r;
+
+	if ((r = access(socket, F_OK)) && errno != ENOENT)
+		log_sys_error("lvmetad_socket_present", "");
+
+	return !r;
+}
+
 int lvmetad_active(void)
 {
 	if (!_lvmetad_use)

lib/cache/lvmetad.h

@@ -43,6 +43,19 @@ void lvmetad_set_active(int);
  */
 void lvmetad_set_socket(const char *);
 
+/*
+ * Check whether lvmetad is used.
+ */
+int lvmetad_used(void);
+
+/*
+ * Check if lvmetad socket is present (either the one set by lvmetad_set_socket
+ * or the default one if not set). For example, this may be used before calling
+ * lvmetad_active() check that does connect to the socket - this would produce
+ * various connection errors if the socket is not present.
+ */
+int lvmetad_socket_present(void);
+
 /*
  * Check whether lvmetad is active (where active means both that it is running
  * and that we have a working connection with it).
@@ -149,6 +162,8 @@ int lvmetad_pvscan_all_devs(struct cmd_context *cmd, activation_handler handler)
 #    define lvmetad_disconnect()	do { } while (0)
 #    define lvmetad_set_active(a)	do { } while (0)
 #    define lvmetad_set_socket(a)	do { } while (0)
+#    define lvmetad_used()	(0)
+#    define lvmetad_socket_present()	(0)
 #    define lvmetad_active()	(0)
 #    define lvmetad_connect_or_warn()	do { } while (0)
 #    define lvmetad_set_token(a)	do { } while (0)

tools/lvchange.c

@@ -1235,11 +1235,33 @@ int lvchange(struct cmd_context *cmd, int argc, char **argv)
 		return EINVALID_CMD_LINE;
 	}
 
-	if (arg_count(cmd, sysinit_ARG) && lvmetad_active() &&
+	/*
+	 * If --sysinit -aay is used and at the same time lvmetad is used,
+	 * we want to rely on autoactivation to take place. Also, we
+	 * need to take special care here as lvmetad service does
+	 * not neet to be running at this moment yet - it could be
+	 * just too early during system initialization time.
+	*/
+	if (arg_count(cmd, sysinit_ARG) && lvmetad_used() &&
 	    arg_uint_value(cmd, activate_ARG, 0) == CHANGE_AAY) {
-		log_warn("lvmetad is active while using --sysinit -a ay, "
-			 "skipping manual activation");
-		return ECMD_PROCESSED;
+		if (!lvmetad_socket_present()) {
+			/*
+			 * If lvmetad socket is not present yet,
+			 * the service is just not started. It'll
+			 * be started a bit later so we need to do
+			 * the activation without lvmetad which means
+			 * direct activation instead of autoactivation.
+			*/
+			log_warn("lvmetad is not active yet, using direct activation during sysinit");
+			lvmetad_set_active(0);
+		} else if (lvmetad_active()) {
+			/*
+			 * If lvmetad is active already, we want
+			 * to make use of the autoactivation.
+			*/
+			log_warn("lvmetad is active, skipping direct activation during sysinit");
+			return ECMD_PROCESSED;
+		}
 	}
 
 	return process_each_lv(cmd, argc, argv,

tools/vgchange.c

@@ -616,11 +616,33 @@ int vgchange(struct cmd_context *cmd, int argc, char **argv)
 		return EINVALID_CMD_LINE;
 	}
 
-	if (arg_count(cmd, sysinit_ARG) && lvmetad_active() &&
+	/*
+	 * If --sysinit -aay is used and at the same time lvmetad is used,
+	 * we want to rely on autoactivation to take place. Also, we
+	 * need to take special care here as lvmetad service does
+	 * not neet to be running at this moment yet - it could be
+	 * just too early during system initialization time.
+	 */
+	if (arg_count(cmd, sysinit_ARG) && lvmetad_used() &&
 	    arg_uint_value(cmd, activate_ARG, 0) == CHANGE_AAY) {
-		log_warn("lvmetad is active while using --sysinit -a ay, "
-			 "skipping manual activation");
-		return ECMD_PROCESSED;
+		if (!lvmetad_socket_present()) {
+			/*
+			 * If lvmetad socket is not present yet,
+			 * the service is just not started. It'll
+			 * be started a bit later so we need to do
+			 * the activation without lvmetad which means
+			 * direct activation instead of autoactivation.
+			 */
+			log_warn("lvmetad is not active yet, using direct activation during sysinit");
+			lvmetad_set_active(0);
+		} else if (lvmetad_active()) {
+			/*
+			 * If lvmetad is active already, we want
+			 * to make use of the autoactivation.
+			 */
+			log_warn("lvmetad is active, skipping direct activation during sysinit");
+			return ECMD_PROCESSED;
+		}
 	}
 
 	if (arg_count(cmd, clustered_ARG) && !argc && !arg_count(cmd, yes_ARG) &&