[LTP] [PATCH 13/16] controllers: update memcg/functional to use newer cgroup lib

[Luke Nowakowski-Krijger]

Update memcg_lib.sh to uses the newer cgroup lib to cleanup the mounting
and checking of the memory controller.

There are still some tests that make sense for v2 and should be modified
in a future patch, but since most of the tests are testing specific v1
memory controller features lets just skip it for now if v2 is mounted.

Signed-off-by: Luke Nowakowski-Krijger <luke.nowakowskikrijger@canonical.com>
---
 .../memcg/functional/memcg_force_empty.sh     |  2 +-
 .../controllers/memcg/functional/memcg_lib.sh | 54 ++++++++++---------
 2 files changed, 30 insertions(+), 26 deletions(-)

diff --git a/testcases/kernel/controllers/memcg/functional/memcg_force_empty.sh b/testcases/kernel/controllers/memcg/functional/memcg_force_empty.sh
index 92ac25938..6252e46bf 100755
--- a/testcases/kernel/controllers/memcg/functional/memcg_force_empty.sh
+++ b/testcases/kernel/controllers/memcg/functional/memcg_force_empty.sh
@@ -51,7 +51,7 @@ test6()
 {
 	# writing to non-empty top mem cgroup's force_empty
 	# should return failure
-	EXPECT_FAIL echo 1 \> /dev/memcg/memory.force_empty
+	EXPECT_FAIL echo 1 \> "$mount_point/memory.force_empty"
 }
 
 tst_run
diff --git a/testcases/kernel/controllers/memcg/functional/memcg_lib.sh b/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
index 1b76b6597..3c20c2f97 100755
--- a/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
+++ b/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
@@ -45,20 +45,20 @@ orig_shmmax=
 
 memcg_require_memsw()
 {
-	if ! [ -e /dev/memcg/memory.limit_in_bytes ]; then
-		tst_brk TBROK "/dev/memcg must be mounted before calling memcg_require_memsw"
+	if ! [ -e "$mount_point/memory.limit_in_bytes" ]; then
+		tst_brk TBROK "$mount_point must be mounted before calling memcg_require_memsw"
 	fi
-	if ! [ -e /dev/memcg/memory.memsw.limit_in_bytes ]; then
+	if ! [ -e "$mount_point/memory.memsw.limit_in_bytes" ]; then
 		tst_brk TCONF "mem+swap is not enabled"
 	fi
 }
 
 memcg_require_hierarchy_disabled()
 {
-	if [ ! -e "/dev/memcg/memory.use_hierarchy" ]; then
-		tst_brk TBROK "/dev/memcg must be mounted before calling memcg_require_hierarchy_disabled"
+	if [ ! -e "$mount_point/memory.use_hierarchy" ]; then
+		tst_brk TBROK "$mount_point must be mounted before calling memcg_require_hierarchy_disabled"
 	fi
-	if [ $(cat /dev/memcg/memory.use_hierarchy) -eq 1 ]; then
+	if [ "$(cat "$mount_point/memory.use_hierarchy")" -eq 1 ]; then
 		tst_brk TCONF "Test requires root cgroup memory.use_hierarchy=0"
 	fi
 }
@@ -100,12 +100,19 @@ memcg_adjust_limit_for_kmem()
 
 memcg_setup()
 {
-	if ! is_cgroup_subsystem_available_and_enabled "memory"; then
-		tst_brk TCONF "Either kernel does not support Memory Resource Controller or feature not enabled"
+	cgroup_require "memory"
+	cgroup_v=$(cgroup_get_version "memory")
+
+	# Most of the tests here are testing specific parts of the cgroup v1 memory interface that is
+	# not present for cgroup2, so if it is already mounted on a cgroup2 hierarchy we should skip
+	# the test.
+	# Some tests still make sense in v2 and should be modified in a future patch
+	if [ "$cgroup_v" = "V2" ]; then
+		tst_brk TCONF "memory controller mounted on cgroup v2 hierarchy, skipping test."
 	fi
 
-	ROD mkdir /dev/memcg
-	ROD mount -t cgroup -omemory memcg /dev/memcg
+	mount_point=$(cgroup_get_mountpoint "memory")
+	test_dir=$(cgroup_get_test_path "memory")
 
 	# For kernels older than v5.11 the default value for
 	# memory.use_hierarchy is 0 and some of tests (memcg_stat_test.sh and
@@ -118,15 +125,15 @@ memcg_setup()
 	# Starting with kernel v5.11, the non-hierarchical mode is not
 	# available. See Linux kernel commit bef8620cd8e0 ("mm: memcg:
 	# deprecate the non-hierarchical mode").
-	orig_memory_use_hierarchy=$(cat /dev/memcg/memory.use_hierarchy)
+	orig_memory_use_hierarchy=$(cat "$mount_point/memory.use_hierarchy")
 	if [ -z "$orig_memory_use_hierarchy" ];then
-		tst_res TINFO "cat /dev/memcg/ failed"
+		tst_res TINFO "cat $mount_point failed"
 	elif [ "$orig_memory_use_hierarchy" = "0" ];then
 		orig_memory_use_hierarchy=""
 	else
-		echo 0 > /dev/memcg/memory.use_hierarchy 2>/dev/null
+		echo 0 > "$mount_point/memory.use_hierarchy" 2>/dev/null
 		if [ $? -ne 0 ];then
-			tst_res TINFO "set /dev/memcg/memory.use_hierarchy to 0 failed"
+			tst_res TINFO "set $mount_point/memory.use_hierarchy to 0 failed"
 		fi
 	fi
 
@@ -139,22 +146,19 @@ memcg_cleanup()
 
 	cd $TST_TMPDIR
 	# In order to remove all subgroups, we have to remove them recursively
-	if [ -e /dev/memcg/ltp_$$ ]; then
-		ROD find /dev/memcg/ltp_$$ -depth -type d -delete
+	if [ -e $test_dir ]; then
+		ROD find $test_dir -depth -type d -delete
 	fi
 
 	if [ -n "$orig_memory_use_hierarchy" ];then
-		echo $orig_memory_use_hierarchy > /dev/memcg/memory.use_hierarchy
+		echo $orig_memory_use_hierarchy > $mount_point/memory.use_hierarchy
 		if [ $? -ne 0 ];then
-			tst_res TINFO "restore /dev/memcg/memory.use_hierarchy failed"
+			tst_res TINFO "restore $mount_point/memory.use_hierarchy failed"
 		fi
 		orig_memory_use_hierarchy=""
 	fi
 
-	if [ -e "/dev/memcg" ]; then
-		umount /dev/memcg
-		rmdir /dev/memcg
-	fi
+	cgroup_cleanup
 
 	[ "$MEMCG_SHMMAX" = "1" ] && shmmax_cleanup
 }
@@ -398,8 +402,8 @@ test_limit_in_bytes()
 
 memcg_testfunc()
 {
-	ROD mkdir /dev/memcg/ltp_$$
-	cd /dev/memcg/ltp_$$
+	ROD mkdir $test_dir/ltp_$$
+	cd $test_dir/ltp_$$
 
 	if type ${MEMCG_TESTFUNC}1 > /dev/null 2>&1; then
 		${MEMCG_TESTFUNC}$1 $1 "$2"
@@ -408,7 +412,7 @@ memcg_testfunc()
 	fi
 
 	cd $TST_TMPDIR
-	ROD rmdir /dev/memcg/ltp_$$
+	ROD rmdir $test_dir/ltp_$$
 }
 
 memcg_no_testfunc()
-- 
2.32.0