mdmon: don't lie to systemd.

Now that mdmon responds fairly well to SIGTERM, stop lying to
systemd about being started on the initrd.

Note that if mdmon is rerun (--takeover) for some reason, and systemd
chooses to kill processes before remounting / readonly, then the
unmount will hang.

If systemd ever lets us tell it that we don't want to be killed until
root is readonly, then we should do that.

Signed-off-by: NeilBrown <neilb@suse.de>

mdadm.h

@@ -1390,6 +1390,8 @@ extern void fmt_devname(char *name, int num);
 extern char *stat2devnm(struct stat *st);
 extern char *fd2devnm(int fd);
 
+extern int in_initrd(void);
+
 #define _ROUND_UP(val, base)	(((val) + (base) - 1) & ~(base - 1))
 #define ROUND_UP(val, base)	_ROUND_UP(val, (typeof(val))(base))
 #define ROUND_UP_PTR(ptr, base)	((typeof(ptr)) \

mdmon.c

@@ -298,10 +298,14 @@ int main(int argc, char *argv[])
 		{NULL, 0, NULL, 0}
 	};
 
-	/*
-	 * Always change process name to @dmon to avoid systemd killing it
-	 */
-	argv[0][0] = '@';
+	if (in_initrd()) {
+		/*
+		 * set first char of argv[0] to @. This is used by
+		 * systemd to signal that the task was launched from
+		 * initrd/initramfs and should be preserved during shutdown
+		 */
+		argv[0][0] = '@';
+	}
 
 	while ((opt = getopt_long(argc, argv, "thaF", options, NULL)) != -1) {
 		switch (opt) {

util.c

@@ -29,6 +29,8 @@
 #include	<sys/wait.h>
 #include	<sys/un.h>
 #include	<sys/resource.h>
+#include	<sys/vfs.h>
+#include	<linux/magic.h>
 #include	<ctype.h>
 #include	<dirent.h>
 #include	<signal.h>
@@ -1937,3 +1939,12 @@ void enable_fds(int devices)
 	lim.rlim_cur = fds;
 	setrlimit(RLIMIT_NOFILE, &lim);
 }
+
+int in_initrd(void)
+{
+	/* This is based on similar function in systemd. */
+	struct statfs s;
+	return  statfs("/", &s) >= 0 &&
+		(s.f_type == TMPFS_MAGIC ||
+		 s.f_type == RAMFS_MAGIC);
+}