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[dm-devel] [PATCH 10/17] multipathd: delay reloads during creation



lvm needs PV devices to not be suspended while the udev rules are
running, for them to be correctly identified as PVs. However, multipathd
will often be in a situation where it will create a multipath device
upon seeing a path, and then immediately reload the device upon seeing
another path.  If multipath is reloading a device while processing the
udev event from its creation, lvm can fail to identify it as a PV. This
can cause systems to fail to boot. Unfortunately, using udev
synchronization cookies to solve this issue would cause a host of other
issues that could only be avoided by a pretty substantial change in how
multipathd does locking and event processing. The good news is that
multipathd is already listening to udev events itself, and can make sure
that it isn't reloading when it shouldn't be.

This patch makes multipathd delay or refuse any reloads that would
happen between the time when it creates a device, and when it receives
the change uevent from the device creation. The only reloads that it
refuses are from the multipathd interactive commands that make no sense
on a not fully started device.  Otherwise, it processes the event or
command, and sets a flag to either mark that device for an update, or
to signal that multipathd needs a reconfigure. When the udev event for
the creation arrives, multipath will reload the device if necessary. If
a reconfigure has been requested, and no devices are currently being
created, multipathd will also do the reconfigure then.

Also this patch adds a configurable timer "missing_uev_msg_delay"
defaulting to 30 seconds. If the udev creation event has not arrived
after this timeout has triggered, multipathd will start printing
messages alerting the user of this every "missing_uev_msg_delay"
seconds.

Signed-off-by: Benjamin Marzinski <bmarzins redhat com>
---
 libmultipath/config.c      |   1 +
 libmultipath/config.h      |   2 +
 libmultipath/configure.c   |   4 ++
 libmultipath/defaults.h    |   1 +
 libmultipath/dict.c        |   4 ++
 libmultipath/structs.h     |   2 +
 multipath.conf.defaults    |   1 +
 multipath/multipath.conf.5 |   8 +++
 multipathd/cli_handlers.c  |  65 +++++++++++++++++++++----
 multipathd/main.c          | 119 +++++++++++++++++++++++++++++++++++++++++++--
 multipathd/main.h          |   1 +
 11 files changed, 195 insertions(+), 13 deletions(-)

diff --git a/libmultipath/config.c b/libmultipath/config.c
index b038b47..b06d1eb 100644
--- a/libmultipath/config.c
+++ b/libmultipath/config.c
@@ -621,6 +621,7 @@ load_config (char * file, struct udev *udev)
 	conf->uid_attribute = set_default(DEFAULT_UID_ATTRIBUTE);
 	conf->retrigger_tries = DEFAULT_RETRIGGER_TRIES;
 	conf->retrigger_delay = DEFAULT_RETRIGGER_DELAY;
+	conf->uev_msg_delay = DEFAULT_UEV_MSG_DELAY;
 
 	/*
 	 * preload default hwtable
diff --git a/libmultipath/config.h b/libmultipath/config.h
index d6a1d4f..93acfa4 100644
--- a/libmultipath/config.h
+++ b/libmultipath/config.h
@@ -138,6 +138,8 @@ struct config {
 	int retrigger_tries;
 	int retrigger_delay;
 	int ignore_new_devs;
+	int delayed_reconfig;
+	int uev_msg_delay;
 	unsigned int version[3];
 
 	char * dev;
diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index 1ab3324..8d5ed2f 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -676,6 +676,10 @@ domap (struct multipath * mpp, char * params)
 			 */
 			if (mpp->action != ACT_CREATE)
 				mpp->action = ACT_NOTHING;
+			else {
+				mpp->wait_for_udev = 1;
+				mpp->uev_msg_tick = conf->uev_msg_delay;
+			}
 		}
 		dm_setgeometry(mpp);
 		return DOMAP_OK;
diff --git a/libmultipath/defaults.h b/libmultipath/defaults.h
index 7e847ae..24a0495 100644
--- a/libmultipath/defaults.h
+++ b/libmultipath/defaults.h
@@ -22,6 +22,7 @@
 #define DEFAULT_UEVENT_STACKSIZE 256
 #define DEFAULT_RETRIGGER_DELAY 10
 #define DEFAULT_RETRIGGER_TRIES 3
+#define DEFAULT_UEV_MSG_DELAY 30
 
 #define DEFAULT_CHECKINT	5
 #define MAX_CHECKINT(a)		(a << 2)
diff --git a/libmultipath/dict.c b/libmultipath/dict.c
index 661456f..192495c 100644
--- a/libmultipath/dict.c
+++ b/libmultipath/dict.c
@@ -396,6 +396,9 @@ declare_def_snprint(retrigger_tries, print_int)
 declare_def_handler(retrigger_delay, set_int)
 declare_def_snprint(retrigger_delay, print_int)
 
+declare_def_handler(uev_msg_delay, set_int)
+declare_def_snprint(uev_msg_delay, print_int)
+
 static int
 def_config_dir_handler(vector strvec)
 {
@@ -1371,6 +1374,7 @@ init_keywords(void)
 	install_keyword("uxsock_timeout", &def_uxsock_timeout_handler, &snprint_def_uxsock_timeout);
 	install_keyword("retrigger_tries", &def_retrigger_tries_handler, &snprint_def_retrigger_tries);
 	install_keyword("retrigger_delay", &def_retrigger_delay_handler, &snprint_def_retrigger_delay);
+	install_keyword("missing_uev_msg_delay", &def_uev_msg_delay_handler, &snprint_def_uev_msg_delay);
 	__deprecated install_keyword("default_selector", &def_selector_handler, NULL);
 	__deprecated install_keyword("default_path_grouping_policy", &def_pgpolicy_handler, NULL);
 	__deprecated install_keyword("default_uid_attribute", &def_uid_attribute_handler, NULL);
diff --git a/libmultipath/structs.h b/libmultipath/structs.h
index c56221b..b313fca 100644
--- a/libmultipath/structs.h
+++ b/libmultipath/structs.h
@@ -226,6 +226,8 @@ struct multipath {
 	int bestpg;
 	int queuedio;
 	int action;
+	int wait_for_udev;
+	int uev_msg_tick;
 	int pgfailback;
 	int failback_tick;
 	int rr_weight;
diff --git a/multipath.conf.defaults b/multipath.conf.defaults
index 6adff28..1ab58e4 100644
--- a/multipath.conf.defaults
+++ b/multipath.conf.defaults
@@ -29,6 +29,7 @@
 #	config_dir "/etc/multipath/conf.d"
 #	delay_watch_checks no
 #	delay_wait_checks no
+#	missing_uev_msg_delay 30
 #}
 #blacklist {
 #	devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
index 6980010..aac95fd 100644
--- a/multipath/multipath.conf.5
+++ b/multipath/multipath.conf.5
@@ -488,6 +488,14 @@ can be processed. This will result in errors like
 In these cases it is recommended to increase the CLI timeout to avoid
 those issues. The default is
 .I 1000
+.TP
+.B missing_uev_msg_delay
+Controls how long multipathd will wait, after a new multipath device is created,
+to receive a change event from udev for the device, before printing a warning
+message. This warning message will print every
+.I missing_uev_msg_delay
+seconds until the uevent is received. the default is
+.I 30
 .
 .SH "blacklist section"
 The
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index a44281f..21fe00e 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -623,6 +623,11 @@ cli_reload(void *v, char **reply, int *len, void *data)
 		condlog(0, "%s: invalid map name. cannot reload", mapname);
 		return 1;
 	}
+	if (mpp->wait_for_udev) {
+		condlog(2, "%s: device not fully created, failing reload",
+			mpp->alias);
+		return 1;
+	}
 
 	return reload_map(vecs, mpp, 0);
 }
@@ -669,6 +674,12 @@ cli_resize(void *v, char **reply, int *len, void *data)
 		return 1;
 	}
 
+	if (mpp->wait_for_udev) {
+		condlog(2, "%s: device not fully created, failing resize",
+			mpp->alias);
+		return 1;
+	}
+
 	pgp = VECTOR_SLOT(mpp->pg, 0);
 
 	if (!pgp){
@@ -833,6 +844,12 @@ cli_reconfigure(void * v, char ** reply, int * len, void * data)
 {
 	struct vectors * vecs = (struct vectors *)data;
 
+	if (need_to_delay_reconfig(vecs)) {
+		conf->delayed_reconfig = 1;
+		condlog(2, "delaying reconfigure (operator)");
+		return 0;
+	}
+
 	condlog(2, "reconfigure (operator)");
 
 	return reconfigure(vecs);
@@ -843,17 +860,25 @@ cli_suspend(void * v, char ** reply, int * len, void * data)
 {
 	struct vectors * vecs = (struct vectors *)data;
 	char * param = get_keyparam(v, MAP);
-	int r = dm_simplecmd_noflush(DM_DEVICE_SUSPEND, param, 0, 0);
+	int r;
+	struct multipath * mpp;
 
 	param = convert_dev(param, 0);
-	condlog(2, "%s: suspend (operator)", param);
+	mpp = find_mp_by_alias(vecs->mpvec, param);
+	if (!mpp)
+		return 1;
 
-	if (!r) /* error */
+	if (mpp->wait_for_udev) {
+		condlog(2, "%s: device not fully created, failing suspend",
+			mpp->alias);
 		return 1;
+	}
 
-	struct multipath * mpp = find_mp_by_alias(vecs->mpvec, param);
+	r = dm_simplecmd_noflush(DM_DEVICE_SUSPEND, param, 0, 0);
 
-	if (!mpp)
+	condlog(2, "%s: suspend (operator)", param);
+
+	if (!r) /* error */
 		return 1;
 
 	dm_get_info(param, &mpp->dmi);
@@ -865,17 +890,25 @@ cli_resume(void * v, char ** reply, int * len, void * data)
 {
 	struct vectors * vecs = (struct vectors *)data;
 	char * param = get_keyparam(v, MAP);
-	int r = dm_simplecmd_noflush(DM_DEVICE_RESUME, param, 0, 0);
+	int r;
+	struct multipath * mpp;
 
 	param = convert_dev(param, 0);
-	condlog(2, "%s: resume (operator)", param);
+	mpp = find_mp_by_alias(vecs->mpvec, param);
+	if (!mpp)
+		return 1;
 
-	if (!r) /* error */
+	if (mpp->wait_for_udev) {
+		condlog(2, "%s: device not fully created, failing resume",
+			mpp->alias);
 		return 1;
+	}
 
-	struct multipath * mpp = find_mp_by_alias(vecs->mpvec, param);
+	r = dm_simplecmd_noflush(DM_DEVICE_RESUME, param, 0, 0);
 
-	if (!mpp)
+	condlog(2, "%s: resume (operator)", param);
+
+	if (!r) /* error */
 		return 1;
 
 	dm_get_info(param, &mpp->dmi);
@@ -908,9 +941,21 @@ cli_reinstate(void * v, char ** reply, int * len, void * data)
 int
 cli_reassign (void * v, char ** reply, int * len, void * data)
 {
+	struct vectors * vecs = (struct vectors *)data;
 	char * param = get_keyparam(v, MAP);
+	struct multipath *mpp;
 
 	param = convert_dev(param, 0);
+	mpp = find_mp_by_alias(vecs->mpvec, param);
+	if (!mpp)
+		return 1;
+
+	if (mpp->wait_for_udev) {
+		condlog(2, "%s: device not fully created, failing reassign",
+			mpp->alias);
+		return 1;
+	}
+
 	condlog(3, "%s: reset devices (operator)", param);
 
 	dm_reassign(param);
diff --git a/multipathd/main.c b/multipathd/main.c
index 06876b9..ea14e03 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -262,6 +262,47 @@ flush_map(struct multipath * mpp, struct vectors * vecs, int nopaths)
 	return 0;
 }
 
+int
+update_map (struct multipath *mpp, struct vectors *vecs)
+{
+	int retries = 3;
+	char params[PARAMS_SIZE] = {0};
+
+retry:
+	condlog(4, "%s: updating new map", mpp->alias);
+	if (adopt_paths(vecs->pathvec, mpp, 1)) {
+		condlog(0, "%s: failed to adopt paths for new map update",
+			mpp->alias);
+		retries = -1;
+		goto fail;
+	}
+	verify_paths(mpp, vecs);
+	mpp->flush_on_last_del = FLUSH_UNDEF;
+	mpp->action = ACT_RELOAD;
+
+	if (setup_map(mpp, params, PARAMS_SIZE)) {
+		condlog(0, "%s: failed to setup new map in update", mpp->alias);
+		retries = -1;
+		goto fail;
+	}
+	if (domap(mpp, params) <= 0 && retries-- > 0) {
+		condlog(0, "%s: map_udate sleep", mpp->alias);
+		sleep(1);
+		goto retry;
+	}
+	dm_lib_release();
+
+fail:
+	if (setup_multipath(vecs, mpp))
+		return 1;
+
+	sync_map_state(mpp);
+
+	if (retries < 0)
+		condlog(0, "%s: failed reload in new map update", mpp->alias);
+	return 0;
+}
+
 static int
 uev_add_map (struct uevent * uev, struct vectors * vecs)
 {
@@ -304,6 +345,20 @@ ev_add_map (char * dev, char * alias, struct vectors * vecs)
 	mpp = find_mp_by_alias(vecs->mpvec, alias);
 
 	if (mpp) {
+		if (mpp->wait_for_udev > 1) {
+			if (update_map(mpp, vecs))
+			/* setup multipathd removed the map */
+				return 1;
+		}
+		if (mpp->wait_for_udev) {
+			mpp->wait_for_udev = 0;
+			if (conf->delayed_reconfig &&
+			    !need_to_delay_reconfig(vecs)) {
+				condlog(2, "reconfigure (delayed)");
+				reconfigure(vecs);
+				return 0;
+			}
+		}
 		/*
 		 * Not really an error -- we generate our own uevent
 		 * if we create a multipath mapped device as a result
@@ -495,7 +550,14 @@ ev_add_path (struct path * pp, struct vectors * vecs)
 		condlog(0, "%s: failed to get path uid", pp->dev);
 		goto fail; /* leave path added to pathvec */
 	}
-	mpp = pp->mpp = find_mp_by_wwid(vecs->mpvec, pp->wwid);
+	mpp = find_mp_by_wwid(vecs->mpvec, pp->wwid);
+	if (mpp && mpp->wait_for_udev) {
+		mpp->wait_for_udev = 2;
+		orphan_path(pp, "waiting for create to complete");
+		return 0;
+	}
+
+	pp->mpp = mpp;
 rescan:
 	if (mpp) {
 		if (mpp->size != pp->size) {
@@ -678,6 +740,12 @@ ev_remove_path (struct path *pp, struct vectors * vecs)
 				" removal of path %s", mpp->alias, pp->dev);
 			goto fail;
 		}
+
+		if (mpp->wait_for_udev) {
+			mpp->wait_for_udev = 2;
+			goto out;
+		}
+
 		/*
 		 * reload the map
 		 */
@@ -735,6 +803,11 @@ uev_update_path (struct uevent *uev, struct vectors * vecs)
 		condlog(2, "%s: update path write_protect to '%d' (uevent)",
 			uev->kernel, ro);
 		if (pp->mpp) {
+			if (pp->mpp->wait_for_udev) {
+				pp->mpp->wait_for_udev = 2;
+				return 0;
+			}
+
 			retval = reload_map(vecs, pp->mpp, 0);
 
 			condlog(2, "%s: map %s reloaded (retval %d)",
@@ -1075,6 +1148,20 @@ followover_should_failback(struct path * pp)
 }
 
 static void
+missing_uev_message_tick(vector mpvec)
+{
+	struct multipath * mpp;
+	unsigned int i;
+
+	vector_foreach_slot (mpvec, mpp, i) {
+		if (mpp->wait_for_udev && --mpp->uev_msg_tick <= 0) {
+			condlog(0, "%s: startup incomplete. Still waiting on udev", mpp->alias);
+			mpp->uev_msg_tick = conf->uev_msg_delay;
+		}
+	}
+}
+
+static void
 defered_failback_tick (vector mpvec)
 {
 	struct multipath * mpp;
@@ -1378,6 +1465,9 @@ check_path (struct vectors * vecs, struct path * pp)
 
 	pp->state = newstate;
 
+
+	if (pp->mpp->wait_for_udev)
+		return 1;
 	/*
 	 * path prio refreshing
 	 */
@@ -1440,6 +1530,7 @@ checkerloop (void *ap)
 		if (vecs->mpvec) {
 			defered_failback_tick(vecs->mpvec);
 			retry_count_tick(vecs->mpvec);
+			missing_uev_message_tick(vecs->mpvec);
 		}
 		if (count)
 			count--;
@@ -1545,6 +1636,22 @@ configure (struct vectors * vecs, int start_waiters)
 }
 
 int
+need_to_delay_reconfig(struct vectors * vecs)
+{
+	struct multipath *mpp;
+	int i;
+
+	if (!VECTOR_SIZE(vecs->mpvec))
+		return 0;
+
+	vector_foreach_slot(vecs->mpvec, mpp, i) {
+		if (mpp->wait_for_udev)
+			return 1;
+	}
+	return 0;
+}
+
+int
 reconfigure (struct vectors * vecs)
 {
 	struct config * old = conf;
@@ -1633,12 +1740,18 @@ void
 handle_signals(void)
 {
 	if (reconfig_sig && running_state == DAEMON_RUNNING) {
-		condlog(2, "reconfigure (signal)");
 		pthread_cleanup_push(cleanup_lock,
 				&gvecs->lock);
 		lock(gvecs->lock);
 		pthread_testcancel();
-		reconfigure(gvecs);
+		if (need_to_delay_reconfig(gvecs)) {
+			conf->delayed_reconfig = 1;
+			condlog(2, "delaying reconfigure (signal)");
+		}
+		else {
+			condlog(2, "reconfigure (signal)");
+			reconfigure(gvecs);
+		}
 		lock_cleanup_pop(gvecs->lock);
 	}
 	if (log_reset_sig) {
diff --git a/multipathd/main.h b/multipathd/main.h
index 10378ef..2f706d2 100644
--- a/multipathd/main.h
+++ b/multipathd/main.h
@@ -18,6 +18,7 @@ extern pid_t daemon_pid;
 
 void exit_daemon(void);
 const char * daemon_status(void);
+int need_to_delay_reconfig (struct vectors *);
 int reconfigure (struct vectors *);
 int ev_add_path (struct path *, struct vectors *);
 int ev_remove_path (struct path *, struct vectors *);
-- 
1.8.3.1


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