Repository: opencontainers/runc
Pull request #4077 (2023-10-19 23:25:18)

[1.1] libct/cg: support hugetlb rsvd
This is a backport of #4073 and #4086 to release-1.1 branch.

----

This adds support for `hugetlb.<pagesize>.rsvd` limiting and accounting.

The previous non-rsvd max/limit_in_bytes does not account for reserved huge page memory, making it possible for a processes to reserve all the huge page memory, without being able to allocate it (due to cgroup restrictions).

In practice this makes it possible to successfully mmap more huge page memory than allowed via the cgroup settings, but when using the memory the process will get a SIGBUS and crash. This is bad for applications trying to mmap at startup (and it succeeds), but the program crashes when starting to use the memory. eg. postgres is doing this by default.

This also keeps writing to the old max/limit_in_bytes, for backward compatibility.

More info can be found here: https://lkml.org/lkml/2020/2/3/1153

(commit message mostly written by Odin Ugedal)

kolyshkin: CI is broken, see #4078 and #4079 
kolyshkin: Need to merge #4081 first
lifubang: 😢 There is no `CGROUP_V1` and `CGROUP_V2` in `release-1.1`, it uses `CGROUP_UNIFIED=no` to check cgroup v1/v2.

Patch:
diff --git a/libcontainer/cgroups/fs/hugetlb.go b/libcontainer/cgroups/fs/hugetlb.go
index 8ddd6fdd..50f8f30c 100644
--- a/libcontainer/cgroups/fs/hugetlb.go
+++ b/libcontainer/cgroups/fs/hugetlb.go
@@ -1,6 +1,8 @@
 package fs
 
 import (
+	"errors"
+	"os"
 	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer/cgroups"
@@ -19,8 +21,23 @@ func (s *HugetlbGroup) Apply(path string, _ *configs.Resources, pid int) error {
 }
 
 func (s *HugetlbGroup) Set(path string, r *configs.Resources) error {
+	const suffix = ".limit_in_bytes"
+	skipRsvd := false
+
 	for _, hugetlb := range r.HugetlbLimit {
-		if err := cgroups.WriteFile(path, "hugetlb."+hugetlb.Pagesize+".limit_in_bytes", strconv.FormatUint(hugetlb.Limit, 10)); err != nil {
+		prefix := "hugetlb." + hugetlb.Pagesize
+		val := strconv.FormatUint(hugetlb.Limit, 10)
+		if err := cgroups.WriteFile(path, prefix+suffix, val); err != nil {
+			return err
+		}
+		if skipRsvd {
+			continue
+		}
+		if err := cgroups.WriteFile(path, prefix+".rsvd"+suffix, val); err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				skipRsvd = true
+				continue
+			}
 			return err
 		}
 	}
@@ -32,24 +49,29 @@ func (s *HugetlbGroup) GetStats(path string, stats *cgroups.Stats) error {
 	if !cgroups.PathExists(path) {
 		return nil
 	}
+	rsvd := ".rsvd"
 	hugetlbStats := cgroups.HugetlbStats{}
 	for _, pageSize := range cgroups.HugePageSizes() {
-		usage := "hugetlb." + pageSize + ".usage_in_bytes"
-		value, err := fscommon.GetCgroupParamUint(path, usage)
+	again:
+		prefix := "hugetlb." + pageSize + rsvd
+
+		value, err := fscommon.GetCgroupParamUint(path, prefix+".usage_in_bytes")
 		if err != nil {
+			if rsvd != "" && errors.Is(err, os.ErrNotExist) {
+				rsvd = ""
+				goto again
+			}
 			return err
 		}
 		hugetlbStats.Usage = value
 
-		maxUsage := "hugetlb." + pageSize + ".max_usage_in_bytes"
-		value, err = fscommon.GetCgroupParamUint(path, maxUsage)
+		value, err = fscommon.GetCgroupParamUint(path, prefix+".max_usage_in_bytes")
 		if err != nil {
 			return err
 		}
 		hugetlbStats.MaxUsage = value
 
-		failcnt := "hugetlb." + pageSize + ".failcnt"
-		value, err = fscommon.GetCgroupParamUint(path, failcnt)
+		value, err = fscommon.GetCgroupParamUint(path, prefix+".failcnt")
 		if err != nil {
 			return err
 		}
diff --git a/libcontainer/cgroups/fs2/hugetlb.go b/libcontainer/cgroups/fs2/hugetlb.go
index c92a7e64..2ce2631e 100644
--- a/libcontainer/cgroups/fs2/hugetlb.go
+++ b/libcontainer/cgroups/fs2/hugetlb.go
@@ -1,6 +1,8 @@
 package fs2
 
 import (
+	"errors"
+	"os"
 	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer/cgroups"
@@ -16,8 +18,22 @@ func setHugeTlb(dirPath string, r *configs.Resources) error {
 	if !isHugeTlbSet(r) {
 		return nil
 	}
+	const suffix = ".max"
+	skipRsvd := false
 	for _, hugetlb := range r.HugetlbLimit {
-		if err := cgroups.WriteFile(dirPath, "hugetlb."+hugetlb.Pagesize+".max", strconv.FormatUint(hugetlb.Limit, 10)); err != nil {
+		prefix := "hugetlb." + hugetlb.Pagesize
+		val := strconv.FormatUint(hugetlb.Limit, 10)
+		if err := cgroups.WriteFile(dirPath, prefix+suffix, val); err != nil {
+			return err
+		}
+		if skipRsvd {
+			continue
+		}
+		if err := cgroups.WriteFile(dirPath, prefix+".rsvd"+suffix, val); err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				skipRsvd = true
+				continue
+			}
 			return err
 		}
 	}
@@ -27,15 +43,21 @@ func setHugeTlb(dirPath string, r *configs.Resources) error {
 
 func statHugeTlb(dirPath string, stats *cgroups.Stats) error {
 	hugetlbStats := cgroups.HugetlbStats{}
+	rsvd := ".rsvd"
 	for _, pagesize := range cgroups.HugePageSizes() {
-		value, err := fscommon.GetCgroupParamUint(dirPath, "hugetlb."+pagesize+".current")
+	again:
+		prefix := "hugetlb." + pagesize + rsvd
+		value, err := fscommon.GetCgroupParamUint(dirPath, prefix+".current")
 		if err != nil {
+			if rsvd != "" && errors.Is(err, os.ErrNotExist) {
+				rsvd = ""
+				goto again
+			}
 			return err
 		}
 		hugetlbStats.Usage = value
 
-		fileName := "hugetlb." + pagesize + ".events"
-		value, err = fscommon.GetValueByKey(dirPath, fileName, "max")
+		value, err = fscommon.GetValueByKey(dirPath, prefix+".events", "max")
 		if err != nil {
 			return err
 		}


Test patch:
diff --git a/libcontainer/cgroups/fs/hugetlb_test.go b/libcontainer/cgroups/fs/hugetlb_test.go
index f4aea7eb..17b4945a 100644
--- a/libcontainer/cgroups/fs/hugetlb_test.go
+++ b/libcontainer/cgroups/fs/hugetlb_test.go
@@ -21,6 +21,11 @@ const (
 	limit    = "hugetlb.%s.limit_in_bytes"
 	maxUsage = "hugetlb.%s.max_usage_in_bytes"
 	failcnt  = "hugetlb.%s.failcnt"
+
+	rsvdUsage    = "hugetlb.%s.rsvd.usage_in_bytes"
+	rsvdLimit    = "hugetlb.%s.rsvd.limit_in_bytes"
+	rsvdMaxUsage = "hugetlb.%s.rsvd.max_usage_in_bytes"
+	rsvdFailcnt  = "hugetlb.%s.rsvd.failcnt"
 )
 
 func TestHugetlbSetHugetlb(t *testing.T) {
@@ -52,13 +57,15 @@ func TestHugetlbSetHugetlb(t *testing.T) {
 	}
 
 	for _, pageSize := range cgroups.HugePageSizes() {
-		limit := fmt.Sprintf(limit, pageSize)
-		value, err := fscommon.GetCgroupParamUint(path, limit)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if value != hugetlbAfter {
-			t.Fatalf("Set hugetlb.limit_in_bytes failed. Expected: %v, Got: %v", hugetlbAfter, value)
+		for _, f := range []string{limit, rsvdLimit} {
+			limit := fmt.Sprintf(f, pageSize)
+			value, err := fscommon.GetCgroupParamUint(path, limit)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if value != hugetlbAfter {
+				t.Fatalf("Set %s failed. Expected: %v, Got: %v", limit, hugetlbAfter, value)
+			}
 		}
 	}
 }
@@ -85,6 +92,28 @@ func TestHugetlbStats(t *testing.T) {
 	}
 }
 
+func TestHugetlbRStatsRsvd(t *testing.T) {
+	path := tempDir(t, "hugetlb")
+	for _, pageSize := range cgroups.HugePageSizes() {
+		writeFileContents(t, path, map[string]string{
+			fmt.Sprintf(rsvdUsage, pageSize):    hugetlbUsageContents,
+			fmt.Sprintf(rsvdMaxUsage, pageSize): hugetlbMaxUsageContents,
+			fmt.Sprintf(rsvdFailcnt, pageSize):  hugetlbFailcnt,
+		})
+	}
+
+	hugetlb := &HugetlbGroup{}
+	actualStats := *cgroups.NewStats()
+	err := hugetlb.GetStats(path, &actualStats)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expectedStats := cgroups.HugetlbStats{Usage: 128, MaxUsage: 256, Failcnt: 100}
+	for _, pageSize := range cgroups.HugePageSizes() {
+		expectHugetlbStatEquals(t, expectedStats, actualStats.HugetlbStats[pageSize])
+	}
+}
+
 func TestHugetlbStatsNoUsageFile(t *testing.T) {
 	path := tempDir(t, "hugetlb")
 	writeFileContents(t, path, map[string]string{
diff --git a/tests/integration/cgroups.bats b/tests/integration/cgroups.bats
index e6e136e7..810eaf8a 100644
--- a/tests/integration/cgroups.bats
+++ b/tests/integration/cgroups.bats
@@ -187,6 +187,70 @@ function setup() {
 	[[ "$weights" == *"$major:$minor 444"* ]]
 }
 
+# Convert size in KB to hugetlb size suffix.
+convert_hugetlb_size() {
+	local size=$1
+	local units=("KB" "MB" "GB")
+	local idx=0
+
+	while ((size >= 1024)); do
+		((size /= 1024))
+		((idx++))
+	done
+
+	echo "$size${units[$idx]}"
+}
+
+@test "runc run (hugetlb limits)" {
+	requires cgroups_hugetlb
+	[ $EUID -ne 0 ] && requires rootless_cgroup
+	# shellcheck disable=SC2012 # ls is fine here.
+	mapfile -t sizes_kb < <(ls /sys/kernel/mm/hugepages/ | sed -e 's/.*hugepages-//' -e 's/kB$//') #
+	if [ "${#sizes_kb[@]}" -lt 1 ]; then
+		skip "requires hugetlb"
+	fi
+
+	# Create two arrays:
+	#  - sizes: hugetlb cgroup file suffixes;
+	#  - limits: limits for each size.
+	for size in "${sizes_kb[@]}"; do
+		sizes+=("$(convert_hugetlb_size "$size")")
+		# Limit to 1 page.
+		limits+=("$((size * 1024))")
+	done
+
+	# Set per-size limits.
+	for ((i = 0; i < ${#sizes[@]}; i++)); do
+		size="${sizes[$i]}"
+		limit="${limits[$i]}"
+		update_config '.linux.resources.hugepageLimits += [{ pagesize: "'"$size"'", limit: '"$limit"' }]'
+	done
+
+	set_cgroups_path
+	runc run -d --console-socket "$CONSOLE_SOCKET" test_hugetlb
+	[ "$status" -eq 0 ]
+
+	lim="max"
+	[ "$CGROUP_UNIFIED" = "no" ] && lim="limit_in_bytes"
+
+	optional=("")
+	# Add rsvd, if available.
+	if test -f "$(get_cgroup_path hugetlb)/hugetlb.${sizes[0]}.rsvd.$lim"; then
+		optional+=(".rsvd")
+	fi
+
+	# Check if the limits are as expected.
+	for ((i = 0; i < ${#sizes[@]}; i++)); do
+		size="${sizes[$i]}"
+		limit="${limits[$i]}"
+		for rsvd in "${optional[@]}"; do
+			param="hugetlb.${size}${rsvd}.$lim"
+			echo "checking $param"
+			check_cgroup_value "$param" "$limit"
+		done
+	done
+}
+
 @test "runc run (cgroup v2 resources.unified only)" {
 	requires root cgroups_v2
 
diff --git a/tests/integration/helpers.bash b/tests/integration/helpers.bash
index 23e32e97..12650593 100644
--- a/tests/integration/helpers.bash
+++ b/tests/integration/helpers.bash
@@ -226,19 +226,27 @@ function set_cgroups_path() {
 	update_config '.linux.cgroupsPath |= "'"${OCI_CGROUPS_PATH}"'"'
 }
 
-# Get a value from a cgroup file.
-function get_cgroup_value() {
-	local source=$1
-	local cgroup var current
-
+# Get a path to cgroup directory, based on controller name.
+# Parameters:
+#  $1: controller name (like "pids") or a file name (like "pids.max").
+function get_cgroup_path() {
 	if [ "$CGROUP_UNIFIED" = "yes" ]; then
-		cgroup=$CGROUP_PATH
-	else
-		var=${source%%.*}             # controller name (e.g. memory)
-		var=CGROUP_${var^^}_BASE_PATH # variable name (e.g. CGROUP_MEMORY_BASE_PATH)
-		eval cgroup=\$"${var}${REL_CGROUPS_PATH}"
+		echo "$CGROUP_PATH"
+		return
 	fi
-	cat "$cgroup/$source"
+
+	local var cgroup
+	var=${1%%.*}                  # controller name (e.g. memory)
+	var=CGROUP_${var^^}_BASE_PATH # variable name (e.g. CGROUP_MEMORY_BASE_PATH)
+	eval cgroup=\$"${var}${REL_CGROUPS_PATH}"
+	echo "$cgroup"
+}
+
+# Get a value from a cgroup file.
+function get_cgroup_value() {
+	local cgroup
+	cgroup="$(get_cgroup_path "$1")"
+	cat "$cgroup/$1"
 }
 
 # Helper to check a if value in a cgroup file matches the expected one.