option to multipath to not modify the bindinfs file

initramfs is mounted read-write causing multipath to update the
initramfs bindings file and name all multipath devices it finds using
friendly names. The actual changes to the file are thrown away as they
are only written to the memory image rather than to the disk image. This
may cause the in memory updated initramfs bindings file inconsistent
with the actual bindings file in the active root file system image when
devices are added or removed.

In other words, the boot time updated initramfs bindings file may have
'uuid1 map to mpatha' and 'uuid2 map to mpathb', but the active root fs
bindings file may have 'uuid1 map to mpathb' and 'uuid2 map to mpatha'

The option, -B, will not modify the bindings file. It will only use the
bindings file if needed.  This option to multipath should be used when
invoked in the initramfs context to avoid the inconsistency.

Signed-off-by: Malahal Naineni (malahal@us.ibm.com)

7 files changed, 16 insertions, 6 deletions

diff --git a/libmultipath/alias.c b/libmultipath/alias.c
index d4b94ee..4159ec6 100644
--- a/libmultipath/alias.c
+++ b/libmultipath/alias.c
@@ -353,7 +353,8 @@ allocate_binding(int fd, char *wwid, int id, char *prefix)
 }
 
 char *
-get_user_friendly_alias(char *wwid, char *file, char *prefix)
+get_user_friendly_alias(char *wwid, char *file, char *prefix,
+			int bindings_read_only)
 {
 	char *alias;
 	int fd, scan_fd, id;
@@ -394,7 +395,7 @@ get_user_friendly_alias(char *wwid, char *file, char *prefix)
 		return NULL;
 	}
 
-	if (!alias && can_write)
+	if (!alias && can_write && !bindings_read_only)
 		alias = allocate_binding(fd, wwid, id, prefix);
 
 	fclose(f);
diff --git a/libmultipath/alias.h b/libmultipath/alias.h
index 832959b..c489a86 100644
--- a/libmultipath/alias.h
+++ b/libmultipath/alias.h
@@ -8,5 +8,6 @@
 "# alias wwid\n" \
 "#\n"
 
-char *get_user_friendly_alias(char *wwid, char *file, char *prefix);
+char *get_user_friendly_alias(char *wwid, char *file, char *prefix,
+			      int bindings_readonly);
 char *get_user_friendly_wwid(char *alias, char *file);
diff --git a/libmultipath/config.c b/libmultipath/config.c
index 0083cfb..00acf96 100644
--- a/libmultipath/config.c
+++ b/libmultipath/config.c
@@ -458,6 +458,7 @@ load_config (char * file)
 	conf->minio = 1000;
 	conf->max_fds = 0;
 	conf->bindings_file = DEFAULT_BINDINGS_FILE;
+	conf->bindings_read_only = 0;
 	conf->multipath_dir = set_default(DEFAULT_MULTIPATHDIR);
 	conf->flush_on_last_del = 0;
 	conf->attribute_flags = 0;
diff --git a/libmultipath/config.h b/libmultipath/config.h
index 18bfff9..5a5f81b 100644
--- a/libmultipath/config.h
+++ b/libmultipath/config.h
@@ -74,6 +74,7 @@ struct config {
 	int rr_weight;
 	int no_path_retry;
 	int user_friendly_names;
+	int bindings_read_only;
 	int pg_timeout;
 	int max_fds;
 	int force_reload;
diff --git a/libmultipath/propsel.c b/libmultipath/propsel.c
index 9944675..80e0c40 100644
--- a/libmultipath/propsel.c
+++ b/libmultipath/propsel.c
@@ -245,7 +245,7 @@ select_alias (struct multipath * mp)
 		if (conf->user_friendly_names) {
 			select_alias_prefix(mp);
 			mp->alias = get_user_friendly_alias(mp->wwid,
-					conf->bindings_file, mp->alias_prefix);
+					conf->bindings_file, mp->alias_prefix, conf->bindings_read_only);
 		}
 		if (mp->alias == NULL)
 			mp->alias = dm_get_name(mp->wwid);
diff --git a/multipath/main.c b/multipath/main.c
index 1689efd..0f28185 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -350,7 +350,7 @@ main (int argc, char *argv[])
 		condlog(0, "multipath tools need sysfs mounted");
 		exit(1);
 	}
-	while ((arg = getopt(argc, argv, ":dhl::FfM:v:p:b:r")) != EOF ) {
+	while ((arg = getopt(argc, argv, ":dhl::FfM:v:p:b:Br")) != EOF ) {
 		switch(arg) {
 		case 1: printf("optarg : %s\n",optarg);
 			break;
@@ -364,6 +364,9 @@ main (int argc, char *argv[])
 		case 'b':
 			conf->bindings_file = optarg;
 			break;
+		case 'B':
+			conf->bindings_read_only = 1;
+			break;
 		case 'd':
 			conf->dry_run = 1;
 			break;
diff --git a/multipath/multipath.8 b/multipath/multipath.8
index 7ba7126..2a6e0aa 100644
--- a/multipath/multipath.8
+++ b/multipath/multipath.8
@@ -6,7 +6,7 @@ multipath \- Device mapper target autoconfig
 .RB [\| \-v\ \c
 .IR verbosity \|]
 .RB [\| \-d \|]
-.RB [\| \-h | \-l | \-ll | \-f | \-F \|]
+.RB [\| \-h | \-l | \-ll | \-f | \-F | \-B \|]
 .RB [\| \-p\ \c
 .BR failover | multibus | group_by_serial | group_by_prio | group_by_node_name \|]
 .RB [\| device \|]
@@ -47,6 +47,9 @@ flush a multipath device map specified as parameter, if unused
 .B \-F
 flush all unused multipath device maps
 .TP
+.B \-B
+treat the bindings file as read only
+.TP
 .BI \-p " policy"
 force maps to specified policy:
 .RS 1.2i