mdmon: periodically retry to create the socket

If initial socket creation fails, EROFS, set a periodic alarm to wake up
the manager and retry.  Include a kernel patch that will wake us up if
the mount flags are changed.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

kernel-patch-2.6.27

@@ -0,0 +1,36 @@
+touch_mnt_namespace when the mount flags change
+
+From: Dan Williams <dan.j.williams@intel.com>
+
+Daemons that need to be launched while the rootfs is read-only can now
+poll /proc/mounts to be notified when their O_RDWR requests may no
+longer end in EROFS.
+
+Cc: Kay Sievers <kay.sievers@vrfy.org>
+Cc: Neil Brown <neilb@suse.de>
+Signed-off-by: Dan Williams <dan.j.williams@intel.com>
+---
+
+ fs/namespace.c |    7 ++++++-
+ 1 files changed, 6 insertions(+), 1 deletions(-)
+
+
+diff --git a/fs/namespace.c b/fs/namespace.c
+index 6e283c9..1bd5ba2 100644
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1553,8 +1553,13 @@ static noinline int do_remount(struct nameidata *nd, int flags, int mnt_flags,
+ 	if (!err)
+ 		nd->path.mnt->mnt_flags = mnt_flags;
+ 	up_write(&sb->s_umount);
+-	if (!err)
++	if (!err) {
+ 		security_sb_post_remount(nd->path.mnt, flags, data);
++
++		spin_lock(&vfsmount_lock);
++		touch_mnt_namespace(nd->path.mnt->mnt_ns);
++		spin_unlock(&vfsmount_lock);
++	}
+ 	return err;
+ }
+ 

managemon.c

@@ -606,10 +606,13 @@ void do_manager(struct supertype *container)
 {
 	struct mdstat_ent *mdstat;
 	sigset_t set;
+	int proc_fd;
 
 	sigprocmask(SIG_UNBLOCK, NULL, &set);
 	sigdelset(&set, SIGUSR1);
 	sigdelset(&set, SIGHUP);
+	sigdelset(&set, SIGALRM);
+	proc_fd = open("/proc/mounts", O_RDONLY);
 
 	do {
 
@@ -627,12 +630,14 @@ void do_manager(struct supertype *container)
 
 			read_sock(container);
 
-			if (socket_hup_requested) {
+			if (container->sock < 0 || socket_hup_requested) {
 				close(container->sock);
 				container->sock = make_control_sock(container->devname);
 				make_pidfile(container->devname, 0);
 				socket_hup_requested = 0;
 			}
+			if (container->sock < 0)
+				alarm(30);
 
 			free_mdstat(mdstat);
 		}
@@ -642,9 +647,12 @@ void do_manager(struct supertype *container)
 
 		manager_ready = 1;
 
-		if (update_queue == NULL)
-			mdstat_wait_fd(container->sock, &set);
-		else
+		if (update_queue == NULL) {
+			if (container->sock < 0)
+				mdstat_wait_fd(proc_fd, &set);
+			else
+				mdstat_wait_fd(container->sock, &set);
+		} else
 			/* If an update is happening, just wait for signal */
 			pselect(0, NULL, NULL, NULL, NULL, &set);
 	} while(1);

mdmon.c

@@ -282,8 +282,6 @@ int main(int argc, char *argv[])
 	}
 
 	container->sock = make_control_sock(container->devname);
-	if (container->sock < 0)
-		fprintf(stderr, "mdmon: Cannot create socket in /var/run/mdadm\n");
 	container->arrays = NULL;
 
 	mdi = sysfs_read(mdfd, container->devnum,
@@ -356,10 +354,12 @@ int main(int argc, char *argv[])
 	sigemptyset(&set);
 	sigaddset(&set, SIGUSR1);
 	sigaddset(&set, SIGHUP);
+	sigaddset(&set, SIGALRM);
 	sigprocmask(SIG_BLOCK, &set, NULL);
 	act.sa_handler = wake_me;
 	act.sa_flags = 0;
 	sigaction(SIGUSR1, &act, NULL);
+	sigaction(SIGALRM, &act, NULL);
 	act.sa_handler = hup;
 	sigaction(SIGHUP, &act, NULL);
 	act.sa_handler = SIG_IGN;