pvscan, vgchange: add eventactivation option

A new file /run/lvm/event-activation-on is used to transition
from a fixed point in time activation (vgchange -aay) run by
a startup service, to event based activation
(pvscan --cache -aay) run by uevents.

vgchange -aay --vgonline --eventactivation enable
. creates /run/lvm/event-activation-on
. creates /run/lvm/pvs_online/ files for existing PVs
. looks for complete VGs
. creates vg online file
. activates complete VGs

pvscan --cache --eventactivation check ...
. checks if /run/lvm/event-activation-on exists
. if not, does nothing and quits
. if so, does traditional pvscan

If lvm.conf has event_activation=0, then do not create the
event-activation-on file to enable event activation from
vgchange -aay --eventactivation enable.

tools/args.h

@@ -278,6 +278,10 @@ arg(errorwhenfull_ARG, '\0', "errorwhenfull", bool_VAL, 0, 0,
     "(Also see dm-thin-pool kernel module option no_space_timeout.)\n"
     "See \\fBlvmthin\\fP(7) for more information.\n")
 
+arg(eventactivation_ARG, '\0', "eventactivation", string_VAL, 0, 0,
+    "Use a run file to coordinate the transition to event\n"
+    "activation.\n")
+
 arg(force_long_ARG, '\0', "force", 0, ARG_COUNTABLE, 0,
     "Force metadata restore even with thin pool LVs.\n"
     "Use with extreme caution. Most changes to thin metadata\n"

tools/command-lines.in

@@ -1642,14 +1642,15 @@ DESC: Record that a PV is online or offline.
 
 pvscan --cache_long --activate ay
 OO: --ignorelockingfailure, --reportformat ReportFmt,
---major Number, --minor Number, --noudevsync
+--major Number, --minor Number, --noudevsync, --eventactivation String
 OP: PV|String ...
 IO: --background
 ID: pvscan_cache
 DESC: Record that a PV is online and autoactivate the VG if complete.
 
 pvscan --cache_long --listvg PV
-OO: --ignorelockingfailure, --checkcomplete, --vgonline, --udevoutput
+OO: --ignorelockingfailure, --checkcomplete, --vgonline, --udevoutput,
+--eventactivation String
 ID: pvscan_cache
 DESC: Record that a PV is online and list the VG using the PV.
 
@@ -1747,7 +1748,8 @@ DESC: Start or stop processing LV conversions.
 
 vgchange --activate Active
 OO: --activationmode ActivationMode, --ignoreactivationskip, --partial, --sysinit,
---readonly, --ignorelockingfailure, --monitor Bool, --poll Bool, --vgonline, OO_VGCHANGE
+--readonly, --ignorelockingfailure, --monitor Bool, --poll Bool,
+--vgonline, --eventactivation String, OO_VGCHANGE
 OP: VG|Tag|Select ...
 IO: --ignoreskippedcluster
 ID: vgchange_activate

tools/pvscan.c

@@ -20,6 +20,7 @@
 #include "lib/label/hints.h"
 
 #include <dirent.h>
+#include <time.h>
 
 struct pvscan_params {
 	int new_pvs_found;
@@ -46,6 +47,8 @@ static const char *_pvs_online_dir = DEFAULT_RUN_DIR "/pvs_online";
 static const char *_vgs_online_dir = DEFAULT_RUN_DIR "/vgs_online";
 static const char *_pvs_lookup_dir = DEFAULT_RUN_DIR "/pvs_lookup";
 
+static const char *_event_activation_file = DEFAULT_RUN_DIR "/event-activation-on";
+
 static int _pvscan_display_pv(struct cmd_context *cmd,
 				  struct physical_volume *pv,
 				  struct pvscan_params *params)
@@ -179,6 +182,30 @@ out:
 	return ret;
 }
 
+int event_activation_enable(struct cmd_context *cmd)
+{
+	FILE *fp;
+
+	if (!(fp = fopen(_event_activation_file, "w")))
+		return_0;
+	if (fclose(fp))
+                stack;
+	return 1;
+}
+
+int event_activation_is_on(struct cmd_context *cmd)
+{
+	struct stat buf;
+
+	if (!stat(_event_activation_file, &buf))
+		return 1;
+
+	if (errno != ENOENT)
+		log_debug("event_activation_is_on errno %d", errno);
+
+	return 0;
+}
+
 /*
  * Avoid a duplicate pvscan[%d] prefix when logging to the journal.
  * FIXME: this should probably replace if (udevoutput) with
@@ -367,7 +394,7 @@ static void _online_files_remove(const char *dirpath)
 		log_sys_debug("closedir", dirpath);
 }
 
-static int _online_pvid_file_create(struct cmd_context *cmd, struct device *dev, const char *vgname)
+int online_pvid_file_create(struct cmd_context *cmd, struct device *dev, const char *vgname, int ignore_existing, int *exists)
 {
 	char path[PATH_MAX];
 	char buf[MAX_PVID_FILE_SIZE] = { 0 };
@@ -407,8 +434,13 @@ static int _online_pvid_file_create(struct cmd_context *cmd, struct device *dev,
 
 	fd = open(path, O_CREAT | O_EXCL | O_RDWR, S_IRUSR | S_IWUSR);
 	if (fd < 0) {
-		if (errno == EEXIST)
+		if (errno == EEXIST) {
+			if (exists)
+				*exists = 1;
+			if (ignore_existing)
+				return 1;
 			goto check_duplicate;
+		}
 		log_error_pvscan(cmd, "Failed to create online file for %s path %s error %d", dev_name(dev), path, errno);
 		return 0;
 	}
@@ -427,7 +459,6 @@ static int _online_pvid_file_create(struct cmd_context *cmd, struct device *dev,
 	}
 
 	/* We don't care about syncing, these files are not even persistent. */
-
 	if (close(fd))
 		log_sys_debug("close", path);
 
@@ -1412,7 +1443,7 @@ static int _online_devs(struct cmd_context *cmd, int do_all, struct dm_list *pvs
 		 * Create file named for pvid to record this PV is online.
 		 * The command creates/checks online files only when --cache is used.
 		 */
-		if (do_cache && !_online_pvid_file_create(cmd, dev, vg ? vg->name : NULL)) {
+		if (do_cache && !online_pvid_file_create(cmd, dev, vg ? vg->name : NULL, 0, NULL)) {
 			log_error_pvscan(cmd, "PV %s failed to create online file.", dev_name(dev));
 			release_vg(vg);
 			ret = 0;
@@ -1857,6 +1888,7 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
 {
 	struct pvscan_aa_params pp = { 0 };
 	struct dm_list complete_vgnames;
+	const char *ea;
 	int do_activate = arg_is_set(cmd, activate_ARG);
 	int event_activation;
 	int devno_args = 0;
@@ -1930,6 +1962,14 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
 			log_verbose("Ignoring pvscan --cache because event_activation is disabled.");
 			return ECMD_PROCESSED;
 		}
+
+		if ((ea = arg_str_value(cmd, eventactivation_ARG, NULL)) &&
+		    !strcmp(ea, "check") &&
+		    !event_activation_is_on(cmd)) {
+			log_verbose("Ignoring pvscan --cache because event_activation is not started.");
+			return ECMD_PROCESSED;
+		}
+
 		if (!_pvscan_cache_args(cmd, argc, argv, &complete_vgnames))
 			return ECMD_FAILED;
 	}

tools/tools.h

@@ -295,8 +295,11 @@ int lvconvert_cachevol_attach_single(struct cmd_context *cmd,
                                      struct logical_volume *lv,
                                      struct processing_handle *handle);
 
+int online_pvid_file_create(struct cmd_context *cmd, struct device *dev, const char *vgname, int ignore_existing, int *exists);
 void online_vg_file_remove(const char *vgname);
 int online_vg_file_create(struct cmd_context *cmd, const char *vgname);
 void online_dir_setup(struct cmd_context *cmd);
+int event_activation_enable(struct cmd_context *cmd);
+int event_activation_is_on(struct cmd_context *cmd);
 
 #endif

tools/vgchange.c

@@ -194,6 +194,41 @@ int vgchange_background_polling(struct cmd_context *cmd, struct volume_group *vg
 	return 1;
 }
 
+static int _online_pvid_file_create_all(struct cmd_context *cmd)
+{
+	struct lvmcache_info *info;
+	struct dev_iter *iter;
+	struct device *dev;
+	const char *vgname;
+	int exists;
+	int exist_count = 0;
+	int create_count = 0;
+
+	if (!(iter = dev_iter_create(NULL, 0)))
+		return 0;
+	while ((dev = dev_iter_get(cmd, iter))) {
+		if (dev->pvid[0] &&
+		    (info = lvmcache_info_from_pvid(dev->pvid, dev, 0))) {
+			vgname = lvmcache_vgname_from_info(info);
+			if (vgname && !is_orphan_vg(vgname)) {
+				/*
+				 * Ignore exsting pvid file because a pvscan may be creating
+				 * the same file as the same time we are, which is expected.
+				 */
+				exists = 0;
+				online_pvid_file_create(cmd, dev, vgname, 1, &exists);
+				if (exists)
+					exist_count++;
+				else
+					create_count++;
+			}
+		}
+	}
+	dev_iter_destroy(iter);
+	log_debug("PV online files created %d exist %d", create_count, exist_count);
+	return 1;
+}
+
 int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
 		      activation_change_t activate)
 {
@@ -219,6 +254,11 @@ int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
 		return 1;
 	}
 
+	if (arg_is_set(cmd, vgonline_ARG) && !online_vg_file_create(cmd, vg->name)) {
+		log_print("VG %s already online", vg->name);
+		return 1;
+	}
+
 	/*
 	 * Safe, since we never write out new metadata here. Required for
 	 * partial activation to work.
@@ -262,11 +302,6 @@ int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
 		}
 	}
 
-	if (arg_is_set(cmd, vgonline_ARG) && !online_vg_file_create(cmd, vg->name)) {
-		log_print("VG %s finished", vg->name);
-		return 1;
-	}
-
 	if (!_activate_lvs_in_vg(cmd, vg, activate)) {
 		stack;
 		r = 0;
@@ -733,6 +768,7 @@ static int _vgchange_single(struct cmd_context *cmd, const char *vg_name,
 int vgchange(struct cmd_context *cmd, int argc, char **argv)
 {
 	struct processing_handle *handle;
+	const char *ea;
 	uint32_t flags = 0;
 	int ret;
 
@@ -845,6 +881,39 @@ int vgchange(struct cmd_context *cmd, int argc, char **argv)
 			cmd->lockd_vg_enforce_sh = 1;
 	}
 
+	/*
+	 * When enabling event-based activation for pvscan, we first created
+	 * the /run/lvm/event-activation-on file to tell pvscans to begin
+	 * processing new PVs and doing activation for newly completed VGs.  We
+	 * also need to create online files for existing PVs because some VGs
+	 * may be incomplete at this point, and future pvscan commands need to
+	 * find online files for PVs that have already appeared.  The label
+	 * scan gives us the info to know which PVs are present and should have
+	 * pvid online files created.
+	 *
+	 * process_each_vg() usually begins with lock_global() and
+	 * lvmcache_label_scan(), and then processes each VG.  In this case,
+	 * lock_global/lvmcache_label_scan are done before calling
+	 * process_each_vg. This allows a special step to be inserted between
+	 * the label scan and processing vgs. That step creates the pvid online
+	 * files, which requires label scan info.  The lock_global and
+	 * lvmcache_label_scan will be skipped by process_each_vg since they
+	 * are already done here.
+	 */
+	if ((ea = arg_str_value(cmd, eventactivation_ARG, NULL)) && !strcmp(ea, "enable")) {
+		if (!find_config_tree_bool(cmd, global_event_activation_CFG, NULL)) {
+			log_print("Skip event activation enable for lvm.conf event_activation 0.");
+		} else {
+			if (!event_activation_enable(cmd))
+				log_warn("WARNING: failed to enable event activation");
+		}
+		if (!lock_global(cmd, "sh"))
+			return ECMD_FAILED;
+		lvmcache_label_scan(cmd);
+		_online_pvid_file_create_all(cmd);
+		flags |= PROCESS_SKIP_SCAN;
+	}
+
 	if (update)
 		flags |= READ_FOR_UPDATE;
 	else if (arg_is_set(cmd, activate_ARG))