Try to resolve cgroup issue

Udev wants us to not start mdmon under its cgroup (it kills mdmon if we
leave it in udev's cgroup), so as part of the mdmon startup process, set
the child process to be part of the systemd cgroup instead.  However, if
we don't have cgroups, or there is no systemd cgroup, then just silently
move on.

Signed-off-by: Doug Ledford <dledford@redhat.com>

mdadm-3.2.6-cgroup.patch

@@ -0,0 +1,33 @@
+diff -up mdadm-3.2.6/util.c.cgroup mdadm-3.2.6/util.c
+--- mdadm-3.2.6/util.c.cgroup	2012-11-15 16:48:03.327035349 -0500
++++ mdadm-3.2.6/util.c	2012-11-15 17:07:16.628751041 -0500
+@@ -1611,6 +1611,21 @@ int mdmon_running(int devnum)
+ 	return 0;
+ }
+ 
++void set_cgroup(char *group)
++{
++	char pid[8];
++	char pathbuf[PATH_MAX];
++	int tasks_fd;
++
++	snprintf(pathbuf, PATH_MAX, "/sys/fs/cgroup/%s/tasks", group);
++	tasks_fd = open(pathbuf, O_WRONLY);
++	if (tasks_fd >= 0) {
++		snprintf(pid, sizeof(pid), "%d", getpid());
++		write(tasks_fd, pid, strlen(pid));
++		close(tasks_fd);
++	}
++}
++
+ int start_mdmon(int devnum)
+ {
+ 	int i, skipped;
+@@ -1653,6 +1668,7 @@ int start_mdmon(int devnum)
+ 
+ 		for (i=0; paths[i]; i++)
+ 			if (paths[i][0]) {
++				set_cgroup("systemd");
+ 				if (__offroot) {
+ 					execl(paths[i], "mdmon", "--offroot",
+ 					      devnum2devname(devnum),

mdadm.spec

@@ -1,7 +1,7 @@
 Summary:     The mdadm program controls Linux md devices (software RAID arrays)
 Name:        mdadm
 Version:     3.2.6
-Release:     1%{?dist}
+Release:     2%{?dist}
 Source:      http://www.kernel.org/pub/linux/utils/raid/mdadm/mdadm-%{version}.tar.xz
 Source1:     mdmonitor.init
 Source2:     raid-check
@@ -12,6 +12,7 @@ Source6:     mdmonitor.service
 Source7:     mdmonitor-takeover.service
 Source8:     mdadm.conf
 Source9:     mdadm_event.conf
+Patch0:      mdadm-3.2.6-cgroup.patch
 # Fedora customization patches
 Patch97:     mdadm-3.2.6-udev.patch
 Patch98:     mdadm-2.5.2-static.patch
@@ -54,6 +55,7 @@ is not used as the system init process.
 
 %prep
 %setup -q
+%patch0 -p1 -b .cgroup
 
 # Fedora customization patches
 %patch97 -p1 -b .udev
@@ -135,6 +137,9 @@ rm -rf %{buildroot}
 %{_initrddir}/*
 
 %changelog
+* Thu Nov 15 2012 Doug Ledford <dledford@redhat.com> - 3.2.6-2
+- Modify mdadm to set the cgroup of mdmon to systemd if it's available
+- Related bz873576 (and others)
 
 * Thu Oct 25 2012 Jes Sorensen <Jes.Sorensen@redhat.com> - 3.2.6-1
 - Upgrade to mdadm-3.2.6