cgroups: Support configurable cgroup mount dir in release agent

The example cgroup release agent packaged and installed with
SLURM assumes a base directory of /cgroup for all mounted
subsystems. Since the mount point is now configurable in SLURM,
this script needs to be augmented to determine the location
of the subsystem mount point at runtime.

etc/cgroup.release_common.example

@@ -13,10 +13,21 @@
 # to ensure coherency of the cgroups contents.
 #
 
-base_path=/cgroup
 progname=$(basename $0)
 subsystem=${progname##*_}
-orphancg=${base_path}/${subsystem}/orphan
+
+get_mount_dir()
+{
+    local lssubsys=$(type -p lssubsys)
+    if [ -x $lssubsys ]; then
+        $lssubsys -m $subsystem | awk '{print $2}'
+    else
+        awk "/release_agent=$0/ { print \$2 }"
+    fi
+}
+
+mountdir=$(get_mount_dir)
+orphancg=${mountdir}/orphan
 
 if [[ $# -eq 0 ]]
 then
@@ -30,8 +41,8 @@ then
     mkdir ${orphancg}
     case ${subsystem} in 
 	cpuset)
-	    cat ${base_path}/${subsystem}/cpuset.cpus > ${orphancg}/cpuset.cpus
-	    cat ${base_path}/${subsystem}/cpuset.mems > ${orphancg}/cpuset.mems
+	    cat ${mountdir}/cpuset.cpus > ${orphancg}/cpuset.cpus
+	    cat ${mountdir}/cpuset.mems > ${orphancg}/cpuset.mems
 	    ;;
 	*)
 	    ;;
@@ -42,7 +53,7 @@ fi
 if [[ $# -eq 1 ]]
 then
 
-    rmcg=${base_path}/${subsystem}$@
+    rmcg=${mountdir}$@
 
     # try to extract the uid cgroup from the input one
     # ( extract /uid_% from /uid%/job_*...)
@@ -51,13 +62,13 @@ then
     then
 	# not a slurm job pattern, perhaps the uidcg, just remove 
 	# the dir with a lock and exit
-	flock -x ${base_path}/${subsystem} -c "rmdir ${rmcg}"
+	flock -x ${mountdir} -c "rmdir ${rmcg}"
 	exit $?
     fi
 
-    if [[ -d ${base_path}/${subsystem} ]]
+    if [[ -d ${mountdir} ]]
     then
-	flock -x ${base_path}/${subsystem} -c "$0 sync $@"
+	flock -x ${mountdir} -c "$0 sync $@"
     fi
 
     exit $?
@@ -68,7 +79,7 @@ elif [[ $# -eq 2 ]] && [[ $1 == "sync" ]]
 then
 
     shift
-    rmcg=${base_path}/${subsystem}$@
+    rmcg=${mountdir}$@
     uidcg=${rmcg%/job_*}
 
     # remove this cgroup