From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Benjamin Marzinski <bmarzins@redhat.com>

Date: Thu, 18 Apr 2019 12:49:46 -0500

Subject: [PATCH] BZ 1700451: check on multipathd without starting it

When "multipath -u" is run, it checks if multipathd is running.

Currently it does this by trying to connect to the mutipathd socket.

This can cause problems during boot.  The multipathd.socket systemd unit

file will cause "multipath -u" to wait until multipathd has been started

before continuing.  If there is a lot of activity on the system,

multipathd may not start up immediately, causing block device

initialization to be delayed, potentially until after systemd times

waiting for the device.  To avoid this, multipath now checks if

multipathd is running by reading /run/multipathd.pid and checking the

/proc/<pid>/comm to verify that multipathd is really running with this

pid. This avoids forcing "multipath -u" to wait on multipathd starting

up.

As an alternative to this patch, multipath could simply switch the order

of the calls to systemd_service_enabled() and mpath_connect(). This would

make multipath only try to connect with multipathd if it wasn't enabled in

systemd, so that it wouldn't autostart.

Another alternative is to do away with multipathd.socket. Since multipathd

needs to always be running in order to get uevents, there isn't much value

in having it autoactivate when it gets an interactive command.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>

---

 multipath/main.c | 60 +++++++++++++++++++++++++++++++++++++++++++-----

 1 file changed, 54 insertions(+), 6 deletions(-)

diff --git a/multipath/main.c b/multipath/main.c

index e7771c0..632ce4d 100644

--- a/multipath/main.c

+++ b/multipath/main.c

@@ -852,6 +852,58 @@ out:

 	return r;

 }

+int is_multipathd_running(void)

+{

+	FILE *f = NULL;

+	char buf[16];

+	char path[PATH_MAX];

+	int pid;

+	char *end;

+

+	f = fopen(DEFAULT_PIDFILE, "r");

+	if (!f) {

+		if (errno != ENOENT)

+			condlog(4, "can't open " DEFAULT_PIDFILE ": %s",

+				strerror(errno));

+		return 0;

+	}

+	if (!fgets(buf, sizeof(buf), f)) {

+		if (ferror(f))

+			condlog(4, "read of " DEFAULT_PIDFILE " failed: %s",

+				strerror(errno));

+		fclose(f);

+		return 0;

+	}

+	fclose(f);

+	errno = 0;

+	strchop(buf);

+	pid = strtol(buf, &end, 10);

+	if (errno != 0 || pid <= 0 || *end != '\0') {

+		condlog(4, "invalid contents in " DEFAULT_PIDFILE ": '%s'",

+			buf);

+		return 0;

+	}

+	snprintf(path, sizeof(path), "/proc/%d/comm", pid);

+	f = fopen(path, "r");

+	if (!f) {

+		if (errno != ENOENT)

+			condlog(4, "can't open %s: %s", path, strerror(errno));

+		return 0;

+	}

+	if (!fgets(buf, sizeof(buf), f)) {

+		if (ferror(f))

+			condlog(4, "read of %s failed: %s", path,

+				strerror(errno));

+		fclose(f);

+		return 0;

+	}

+	fclose(f);

+	strchop(buf);

+	if (strcmp(buf, "multipathd") != 0)

+		return 0;

+	return 1;

+}

+

 int

 main (int argc, char *argv[])

 {

@@ -1034,17 +1086,13 @@ main (int argc, char *argv[])

 	}

 	if (cmd == CMD_VALID_PATH &&

 	    dev_type == DEV_UEVENT) {

-		int fd;

-

-		fd = mpath_connect();

-		if (fd == -1) {

+		if (!is_multipathd_running()) {

 			condlog(3, "%s: daemon is not running", dev);

 			if (!systemd_service_enabled(dev)) {

 				r = print_cmd_valid(RTVL_NO, NULL, conf);

 				goto out;

 			}

-		} else

-			mpath_disconnect(fd);

+		}

 	}

 	if (cmd == CMD_REMOVE_WWID && !dev) {

-- 

2.17.2