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* [PATCH v2] libmpathpersist: fix code for skipping multipathd path registration
@ 2025-12-08 21:12 Benjamin Marzinski
  2025-12-09 12:01 ` Martin Wilck
  0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Marzinski @ 2025-12-08 21:12 UTC (permalink / raw)
  To: Christophe Varoqui; +Cc: device-mapper development, Martin Wilck

When libmpathpersist notifies multipathd that a key has been registered,
cli_setprstatus() calls pr_register_active_paths() with a flag to let it
know that the paths are likely already registered, and it can skip
re-registering them, as long as the number of active paths matches the
number of registered keys. This shortcut can fail, causing multipathd to
not register needed paths, if either a path becomes usable and another
becomes unusable while libmpathpersist is running or if there already
were registered keys for I_T Nexus's that don't correspond to path
devices.

To make this shortcut work in cases like that, this commit adds a new
multipathd command "setprstatus map <map> pathlist <pathlist>", where
<pathlist> is a quoted, comma separated list of scsi path devices.
libmpathpersist will send out the list of paths it registered the key
on. pr_register_active_paths() will skip calling mpath_pr_event_handle()
for paths on that list.

In order to deal with the possiblity of a preempt occuring while
libmpathpersist was running, the code still needs to check that it has
the expected number of keys.

Fixes: f7d6cd17 ("multipathd: Fix race while registering PR key")
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---

Was patch 4/4 of "multipath-tools: Yet Another PR fix"
Changes in v2 (assuming we agree to use this patch at all):
added a semi-colon after the "skip" label to make clang happy.

 libmpathpersist/mpath_persist_int.c |  6 +--
 libmpathpersist/mpath_updatepr.c    | 48 +++++++++++++++++-----
 libmpathpersist/mpathpr.h           |  4 +-
 multipathd/callbacks.c              |  1 +
 multipathd/cli.c                    |  1 +
 multipathd/cli.h                    |  2 +
 multipathd/cli_handlers.c           | 39 ++++++++++++++++--
 multipathd/main.c                   | 62 +++++++++++++++++++----------
 multipathd/main.h                   |  3 +-
 multipathd/multipathd.8.in          |  6 +++
 10 files changed, 133 insertions(+), 39 deletions(-)

diff --git a/libmpathpersist/mpath_persist_int.c b/libmpathpersist/mpath_persist_int.c
index 91c53419..14f7ba83 100644
--- a/libmpathpersist/mpath_persist_int.c
+++ b/libmpathpersist/mpath_persist_int.c
@@ -1001,12 +1001,12 @@ int do_mpath_persistent_reserve_out(vector curmp, vector pathvec, int fd,
 	case MPATH_PROUT_REG_SA:
 	case MPATH_PROUT_REG_IGN_SA:
 		if (unregistering)
-			update_prflag(mpp->alias, 0);
+			update_prflag(mpp, 0);
 		else
-			update_prflag(mpp->alias, 1);
+			update_prflag(mpp, 1);
 		break;
 	case MPATH_PROUT_CLEAR_SA:
-		update_prflag(mpp->alias, 0);
+		update_prflag(mpp, 0);
 		if (mpp->prkey_source == PRKEY_SOURCE_FILE)
 			update_prkey(mpp->alias, 0);
 		break;
diff --git a/libmpathpersist/mpath_updatepr.c b/libmpathpersist/mpath_updatepr.c
index bd8ed2be..bc9c79e2 100644
--- a/libmpathpersist/mpath_updatepr.c
+++ b/libmpathpersist/mpath_updatepr.c
@@ -20,8 +20,9 @@
 #include "uxsock.h"
 #include "mpathpr.h"
 #include "structs.h"
+#include "strbuf.h"
 
-static char *do_pr(char *alias, char *str)
+static char *do_pr(char *alias, const char *str)
 {
 	int fd;
 	char *reply;
@@ -51,24 +52,27 @@ static char *do_pr(char *alias, char *str)
 	return reply;
 }
 
-static int do_update_pr(char *alias, char *cmd, char *key)
+static int do_update_pr(char *alias, char *cmd, const char *data)
 {
-	char str[256];
+	STRBUF_ON_STACK(buf);
 	char *reply = NULL;
 	int ret = -1;
 
-	if (key)
-		snprintf(str, sizeof(str), "%s map %s key %s", cmd, alias, key);
+	if (data)
+		print_strbuf(&buf, "%s map %s %s %s", cmd, alias,
+			     strcmp(cmd, "setprkey") ? "pathlist" : "key",
+			     data);
 	else
-		snprintf(str, sizeof(str), "%s map %s", cmd, alias);
+		print_strbuf(&buf, "%s map %s", cmd, alias);
 
-	reply = do_pr(alias, str);
+	reply = do_pr(alias, get_strbuf_str(&buf));
 	if (reply) {
 		if (strncmp(reply, "ok", 2) == 0)
 			ret = 0;
 		else
 			ret = -1;
-		condlog(ret ? 0 : 4, "%s: message=%s reply=%s", alias, str, reply);
+		condlog(ret ? 0 : 4, "%s: message=%s reply=%s", alias,
+			get_strbuf_str(&buf), reply);
 	}
 
 	free(reply);
@@ -106,9 +110,31 @@ int get_prhold(char *mapname)
 	return do_get_pr(mapname, "getprhold");
 }
 
-int update_prflag(char *mapname, int set) {
-	return do_update_pr(mapname, (set)? "setprstatus" : "unsetprstatus",
-			    NULL);
+int update_prflag(struct multipath *mpp, int set)
+{
+	STRBUF_ON_STACK(buf);
+	int i, j;
+	bool first = true;
+	struct pathgroup *pgp = NULL;
+	struct path *pp = NULL;
+
+	if (!set)
+		return do_update_pr(mpp->alias, "unsetprstatus", NULL);
+
+	append_strbuf_str(&buf, "\"");
+	vector_foreach_slot (mpp->pg, pgp, j) {
+		vector_foreach_slot (pgp->paths, pp, i) {
+			if (pp->state == PATH_UP || pp->state == PATH_GHOST) {
+				if (first) {
+					append_strbuf_str(&buf, pp->dev);
+					first = false;
+				} else
+					print_strbuf(&buf, " %s", pp->dev);
+			}
+		}
+	}
+	append_strbuf_str(&buf, "\"");
+	return do_update_pr(mpp->alias, "setprstatus", get_strbuf_str(&buf));
 }
 
 int update_prhold(char *mapname, bool set)
diff --git a/libmpathpersist/mpathpr.h b/libmpathpersist/mpathpr.h
index 99d6b82f..adbfc865 100644
--- a/libmpathpersist/mpathpr.h
+++ b/libmpathpersist/mpathpr.h
@@ -1,12 +1,14 @@
 #ifndef MPATHPR_H_INCLUDED
 #define MPATHPR_H_INCLUDED
 
+#include "structs.h"
+
 /*
  * This header file contains symbols that are only used by
  * libmpathpersist internally.
  */
 
-int update_prflag(char *mapname, int set);
+int update_prflag(struct multipath *mpp, int set);
 int update_prkey_flags(char *mapname, uint64_t prkey, uint8_t sa_flags);
 int get_prflag(char *mapname);
 int get_prhold(char *mapname);
diff --git a/multipathd/callbacks.c b/multipathd/callbacks.c
index b6b57f45..1129855b 100644
--- a/multipathd/callbacks.c
+++ b/multipathd/callbacks.c
@@ -59,6 +59,7 @@ void init_handler_callbacks(void)
 	set_unlocked_handler_callback(VRB_SHUTDOWN, HANDLER(cli_shutdown));
 	set_handler_callback(VRB_GETPRSTATUS | Q1_MAP, HANDLER(cli_getprstatus));
 	set_handler_callback(VRB_SETPRSTATUS | Q1_MAP, HANDLER(cli_setprstatus));
+	set_handler_callback(VRB_SETPRSTATUS | Q1_MAP | Q2_PATHLIST, HANDLER(cli_setprstatus_list));
 	set_handler_callback(VRB_UNSETPRSTATUS | Q1_MAP, HANDLER(cli_unsetprstatus));
 	set_handler_callback(VRB_FORCEQ | Q1_DAEMON, HANDLER(cli_force_no_daemon_q));
 	set_handler_callback(VRB_RESTOREQ | Q1_DAEMON, HANDLER(cli_restore_no_daemon_q));
diff --git a/multipathd/cli.c b/multipathd/cli.c
index d0e6cebc..0d679c86 100644
--- a/multipathd/cli.c
+++ b/multipathd/cli.c
@@ -227,6 +227,7 @@ load_keys (void)
 	r += add_key(keys, "getprhold", VRB_GETPRHOLD, 0);
 	r += add_key(keys, "setprhold", VRB_SETPRHOLD, 0);
 	r += add_key(keys, "unsetprhold", VRB_UNSETPRHOLD, 0);
+	r += add_key(keys, "pathlist", KEY_PATHLIST, 1);
 
 	if (r) {
 		free_keys(keys);
diff --git a/multipathd/cli.h b/multipathd/cli.h
index 5a943a45..3e607389 100644
--- a/multipathd/cli.h
+++ b/multipathd/cli.h
@@ -62,6 +62,7 @@ enum {
 	KEY_LOCAL		= 81,
 	KEY_GROUP		= 82,
 	KEY_KEY			= 83,
+	KEY_PATHLIST		= 84,
 };
 
 /*
@@ -94,6 +95,7 @@ enum {
 	Q2_LOCAL		= KEY_LOCAL << 16,
 	Q2_GROUP		= KEY_GROUP << 16,
 	Q2_KEY			= KEY_KEY << 16,
+	Q2_PATHLIST		= KEY_PATHLIST << 16,
 
 	/* byte 3: qualifier 3 */
 	Q3_FMT			= KEY_FMT << 24,
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index 2812d01e..5770dcec 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -31,6 +31,7 @@
 #include "foreign.h"
 #include "strbuf.h"
 #include "cli_handlers.h"
+#include <ctype.h>
 
 static struct path *
 find_path_by_str(const struct vector_s *pathvec, const char *str,
@@ -1276,8 +1277,8 @@ cli_getprstatus (void * v, struct strbuf *reply, void * data)
 	return 0;
 }
 
-static int
-cli_setprstatus(void * v, struct strbuf *reply, void * data)
+static int do_setprstatus(void * v, struct strbuf *reply, void * data,
+			  const struct vector_s *registered_paths)
 {
 	struct multipath * mpp;
 	struct vectors * vecs = (struct vectors *)data;
@@ -1291,7 +1292,7 @@ cli_setprstatus(void * v, struct strbuf *reply, void * data)
 
 	if (mpp->prflag != PR_SET) {
 		set_pr(mpp);
-		pr_register_active_paths(mpp, true);
+		pr_register_active_paths(mpp, registered_paths);
 		if (mpp->prflag == PR_SET)
 			condlog(2, "%s: prflag set", param);
 		else
@@ -1302,6 +1303,38 @@ cli_setprstatus(void * v, struct strbuf *reply, void * data)
 	return 0;
 }
 
+static int
+cli_setprstatus(void * v, struct strbuf *reply, void * data)
+{
+	return do_setprstatus(v, reply, data, NULL);
+}
+
+static int
+cli_setprstatus_list(void * v, struct strbuf *reply, void * data)
+{
+	int r;
+	struct vector_s registered_paths = { .allocated = 0 };
+	char *ptr = get_keyparam(v, KEY_PATHLIST);
+
+	while (isspace(*ptr))
+		ptr++;
+	while (*ptr) {
+		if (!vector_alloc_slot(&registered_paths)) {
+			r = -ENOMEM;
+			goto out;
+		}
+		vector_set_slot(&registered_paths, ptr);
+		while (*ptr && !isspace(*ptr))
+			ptr++;
+		while (isspace(*ptr))
+			*ptr++ = '\0';
+	}
+	r = do_setprstatus(v, reply, data, &registered_paths);
+out:
+	vector_reset(&registered_paths);
+	return r;
+}
+
 static int
 cli_unsetprstatus(void * v, struct strbuf *reply, void * data)
 {
diff --git a/multipathd/main.c b/multipathd/main.c
index a7650639..f00444b4 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -630,28 +630,50 @@ flush_map_nopaths(struct multipath *mpp, struct vectors *vecs) {
 	return true;
 }
 
-void pr_register_active_paths(struct multipath *mpp, bool check_nr_active)
+/*
+ * If reg_paths in non-NULL, it is a vector of paths that libmpathpersist
+ * registered. If the number of registered keys is smaller than the number
+ * of registered paths, then likely a preempt that occurred while
+ * libmpathpersist was registering the key. As long as there are still some
+ * registered keys, treat the preempt as happening first, and make sure to
+ * register keys on all the paths. If the number of registered keys is at
+ * least as large as the number of registered paths, then no preempt happened,
+ * and multipathd does not need to re-register the paths that libmpathpersist
+ * handled
+ */
+void pr_register_active_paths(struct multipath *mpp,
+			      const struct vector_s *reg_paths)
 {
-	unsigned int i, j, nr_keys = 0;
-	unsigned int nr_active = 0;
+	unsigned int i, j, k, nr_keys = 0;
+	unsigned int wanted_nr = VECTOR_SIZE(reg_paths);
 	struct path *pp;
 	struct pathgroup *pgp;
-
-	if (check_nr_active) {
-		nr_active = count_active_paths(mpp);
-		if (!nr_active)
-			return;
-	}
+	char *pathname;
 
 	vector_foreach_slot (mpp->pg, pgp, i) {
 		vector_foreach_slot (pgp->paths, pp, j) {
 			if (mpp->prflag == PR_UNSET)
 				return;
-			if (pp->state == PATH_UP || pp->state == PATH_GHOST) {
-				nr_keys = mpath_pr_event_handle(pp, nr_keys, nr_active);
-				if (check_nr_active && nr_keys == nr_active)
-					return;
+			if (pp->state != PATH_UP && pp->state != PATH_GHOST)
+				continue;
+			if (wanted_nr && nr_keys) {
+				vector_foreach_slot(reg_paths, pathname, k) {
+					if (strcmp(pp->dev, pathname) == 0 ||
+					    strcmp(pp->dev_t, pathname) == 0) {
+						goto skip;
+					}
+				}
+			}
+			nr_keys = mpath_pr_event_handle(pp, nr_keys, wanted_nr);
+			if (nr_keys && nr_keys < wanted_nr) {
+				/*
+				 * Incorrect number of registered keys. Need
+				 * to register all devices
+				 */
+				wanted_nr = 0;
 			}
+skip:
+			; /* a statement must follow a label on pre C23 clang */
 		}
 	}
 }
@@ -739,7 +761,7 @@ fail:
 
 	sync_map_state(mpp, false);
 
-	pr_register_active_paths(mpp, false);
+	pr_register_active_paths(mpp, NULL);
 
 	if (VECTOR_SIZE(offline_paths) != 0)
 		handle_orphaned_offline_paths(offline_paths);
@@ -1413,7 +1435,7 @@ rescan:
 
 	if (retries >= 0) {
 		if ((mpp->prflag == PR_SET && prflag != PR_SET) || start_waiter)
-			pr_register_active_paths(mpp, false);
+			pr_register_active_paths(mpp, NULL);
 		condlog(2, "%s [%s]: path added to devmap %s",
 			pp->dev, pp->dev_t, mpp->alias);
 		return 0;
@@ -2658,7 +2680,7 @@ update_path_state (struct vectors * vecs, struct path * pp)
 				"reservation registration", pp->dev);
 			mpath_pr_event_handle(pp, 0, 0);
 			if (pp->mpp->prflag == PR_SET && prflag != PR_SET)
-				pr_register_active_paths(pp->mpp, false);
+				pr_register_active_paths(pp->mpp, NULL);
 		}
 
 		/*
@@ -3319,7 +3341,7 @@ configure (struct vectors * vecs, enum force_reload_types reload_type)
 	vector_foreach_slot(mpvec, mpp, i){
 		if (remember_wwid(mpp->wwid) == 1)
 			trigger_paths_udev_change(mpp, true);
-		pr_register_active_paths(mpp, false);
+		pr_register_active_paths(mpp, NULL);
 	}
 
 	/*
@@ -4370,8 +4392,8 @@ static int update_map_pr(struct multipath *mpp, struct path *pp, unsigned int *n
  *
  * nr_keys_wanted: Only used if nr_keys_needed is 0, so we don't know how
  * many keys we currently have. If nr_keys_wanted in non-zero and the
- * number of keys found by the initial call to update_map_pr() matches it,
- * exit early, since we have all the keys we are expecting.
+ * number of keys found by the initial call to update_map_pr() is at least
+ * as large as it, exit early, since we have all the keys we are expecting.
  *
  * The function returns the number of keys that are registered or 0 if
  * it's unknown.
@@ -4394,7 +4416,7 @@ mpath_pr_event_handle(struct path *pp, unsigned int nr_keys_needed,
 		nr_keys_needed = 1;
 		if (update_map_pr(mpp, pp, &nr_keys_needed) != MPATH_PR_SUCCESS)
 			return 0;
-		if (nr_keys_wanted && nr_keys_wanted == nr_keys_needed)
+		if (nr_keys_wanted && nr_keys_wanted <= nr_keys_needed)
 			return nr_keys_needed;
 	}
 
diff --git a/multipathd/main.h b/multipathd/main.h
index 6d60ee81..85b533cd 100644
--- a/multipathd/main.h
+++ b/multipathd/main.h
@@ -54,5 +54,6 @@ int resize_map(struct multipath *mpp, unsigned long long size,
 	       struct vectors *vecs);
 void set_pr(struct multipath *mpp);
 void unset_pr(struct multipath *mpp);
-void pr_register_active_paths(struct multipath *mpp, bool check_active_nr);
+void pr_register_active_paths(struct multipath *mpp,
+			      const struct vector_s *registered_paths);
 #endif /* MAIN_H_INCLUDED */
diff --git a/multipathd/multipathd.8.in b/multipathd/multipathd.8.in
index 7ffb8d4c..38a243e3 100644
--- a/multipathd/multipathd.8.in
+++ b/multipathd/multipathd.8.in
@@ -348,6 +348,12 @@ Restores configured queue_without_daemon mode.
 Enable persistent reservation management on $map.
 .
 .TP
+.B setprstatus map|multipath $map pathlist $pathlist
+Enable persistent reservation management on $map, and notify multipathd of
+the paths that have been registered, so it doesn't attempt to re-register
+them.
+.
+.TP
 .B unsetprstatus map|multipath $map
 Disable persistent reservation management on $map.
 .
-- 
2.50.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread
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2025-12-08 21:12 [PATCH v2] libmpathpersist: fix code for skipping multipathd path registration Benjamin Marzinski
2025-12-09 12:01 ` Martin Wilck
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