selftests/vm: make charge_reserved_hugetlb.sh work with existing cgroup setting

The hugetlb cgroup reservation test charge_reserved_hugetlb.sh assume
that no cgroup filesystems are mounted before running the test.  That is
not true in many cases.  As a result, the test fails to run.  Fix that
by querying the current cgroup mount setting and using the existing
cgroup setup instead before attempting to freshly mount a cgroup
filesystem.

Similar change is also made for hugetlb_reparenting_test.sh as well,
though it still has problem if cgroup v2 isn't used.

The patched test scripts were run on a centos 8 based system to verify
that they ran properly.

Link: https://lkml.kernel.org/r/20220106201359.1646575-1-longman@redhat.com
Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Mina Almasry <almasrymina@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 14 deletions

diff --git a/tools/testing/selftests/vm/charge_reserved_hugetlb.sh b/tools/testing/selftests/vm/charge_reserved_hugetlb.sh
index fe8fcfb334e0..a5cb4b09a46c 100644
--- a/tools/testing/selftests/vm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/vm/charge_reserved_hugetlb.sh
@@ -24,19 +24,23 @@ if [[ "$1" == "-cgroup-v2" ]]; then
   reservation_usage_file=rsvd.current
 fi
 
-cgroup_path=/dev/cgroup/memory
-if [[ ! -e $cgroup_path ]]; then
-  mkdir -p $cgroup_path
-  if [[ $cgroup2 ]]; then
+if [[ $cgroup2 ]]; then
+  cgroup_path=$(mount -t cgroup2 | head -1 | awk -e '{print $3}')
+  if [[ -z "$cgroup_path" ]]; then
+    cgroup_path=/dev/cgroup/memory
     mount -t cgroup2 none $cgroup_path
-  else
+    do_umount=1
+  fi
+  echo "+hugetlb" >$cgroup_path/cgroup.subtree_control
+else
+  cgroup_path=$(mount -t cgroup | grep ",hugetlb" | awk -e '{print $3}')
+  if [[ -z "$cgroup_path" ]]; then
+    cgroup_path=/dev/cgroup/memory
     mount -t cgroup memory,hugetlb $cgroup_path
+    do_umount=1
   fi
 fi
-
-if [[ $cgroup2 ]]; then
-  echo "+hugetlb" >/dev/cgroup/memory/cgroup.subtree_control
-fi
+export cgroup_path
 
 function cleanup() {
   if [[ $cgroup2 ]]; then
@@ -108,7 +112,7 @@ function setup_cgroup() {
 
 function wait_for_hugetlb_memory_to_get_depleted() {
   local cgroup="$1"
-  local path="/dev/cgroup/memory/$cgroup/hugetlb.${MB}MB.$reservation_usage_file"
+  local path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$reservation_usage_file"
   # Wait for hugetlbfs memory to get depleted.
   while [ $(cat $path) != 0 ]; do
     echo Waiting for hugetlb memory to get depleted.
@@ -121,7 +125,7 @@ function wait_for_hugetlb_memory_to_get_reserved() {
   local cgroup="$1"
   local size="$2"
 
-  local path="/dev/cgroup/memory/$cgroup/hugetlb.${MB}MB.$reservation_usage_file"
+  local path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$reservation_usage_file"
   # Wait for hugetlbfs memory to get written.
   while [ $(cat $path) != $size ]; do
     echo Waiting for hugetlb memory reservation to reach size $size.
@@ -134,7 +138,7 @@ function wait_for_hugetlb_memory_to_get_written() {
   local cgroup="$1"
   local size="$2"
 
-  local path="/dev/cgroup/memory/$cgroup/hugetlb.${MB}MB.$fault_usage_file"
+  local path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$fault_usage_file"
   # Wait for hugetlbfs memory to get written.
   while [ $(cat $path) != $size ]; do
     echo Waiting for hugetlb memory to reach size $size.
@@ -574,5 +578,7 @@ for populate in "" "-o"; do
   done     # populate
 done       # method
 
-umount $cgroup_path
-rmdir $cgroup_path
+if [[ $do_umount ]]; then
+  umount $cgroup_path
+  rmdir $cgroup_path
+fi