From a70f354680b47b283dd2782d26d5afa6b1f98684 Mon Sep 17 00:00:00 2001
From: lifubang <lifubang@acmcoder.com>
Date: Fri, 1 May 2020 22:44:59 +0800
Subject: [PATCH] let runc disable swap in cgroup v2

In cgroup v2, when memory and memorySwap set to the same value which is greater than zero,
runc should write zero in `memory.swap.max` to disable swap.

Signed-off-by: lifubang <lifubang@acmcoder.com>
---
 libcontainer/cgroups/fs2/memory.go | 11 +++++++----
 libcontainer/cgroups/systemd/v2.go | 12 ++++++------
 libcontainer/cgroups/utils.go      |  2 +-
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/libcontainer/cgroups/fs2/memory.go b/libcontainer/cgroups/fs2/memory.go
index 681bedd1..1cda30cc 100644
--- a/libcontainer/cgroups/fs2/memory.go
+++ b/libcontainer/cgroups/fs2/memory.go
@@ -45,10 +45,13 @@ func setMemory(dirPath string, cgroup *configs.Cgroup) error {
 	if err != nil {
 		return err
 	}
-	if val := numToStr(swap); val != "" {
-		if err := fscommon.WriteFile(dirPath, "memory.swap.max", val); err != nil {
-			return err
-		}
+	swapStr := numToStr(swap)
+	if swapStr == "" && swap == 0 && cgroup.Resources.MemorySwap > 0 {
+		// memory and memorySwap set to the same value -- disable swap
+		swapStr = "0"
+	}
+	if err := fscommon.WriteFile(dirPath, "memory.swap.max", swapStr); err != nil {
+		return err
 	}
 
 	if val := numToStr(cgroup.Resources.Memory); val != "" {
diff --git a/libcontainer/cgroups/systemd/v2.go b/libcontainer/cgroups/systemd/v2.go
index 77f7696e..282d629f 100644
--- a/libcontainer/cgroups/systemd/v2.go
+++ b/libcontainer/cgroups/systemd/v2.go
@@ -39,12 +39,12 @@ func genV2ResourcesProperties(c *configs.Cgroup) ([]systemdDbus.Property, error)
 		properties = append(properties,
 			newProp("MemoryMax", uint64(c.Resources.Memory)))
 	}
-
-	swap, err := cgroups.ConvertMemorySwapToCgroupV2Value(c.Resources.MemorySwap, c.Resources.Memory)
-	if err != nil {
-		return nil, err
-	}
-	if swap > 0 {
+	// swap is set
+	if c.Resources.MemorySwap != 0 {
+		swap, err := cgroups.ConvertMemorySwapToCgroupV2Value(c.Resources.MemorySwap, c.Resources.Memory)
+		if err != nil {
+			return nil, err
+		}
 		properties = append(properties,
 			newProp("MemorySwapMax", uint64(swap)))
 	}
diff --git a/libcontainer/cgroups/utils.go b/libcontainer/cgroups/utils.go
index f1e11160..8cdd6b7e 100644
--- a/libcontainer/cgroups/utils.go
+++ b/libcontainer/cgroups/utils.go
@@ -639,7 +639,7 @@ func ConvertMemorySwapToCgroupV2Value(memorySwap, memory int64) (int64, error) {
 		return 0, fmt.Errorf("invalid memory value: %d", memory)
 	}
 	if memorySwap < memory {
-		return 0, errors.New("memory+swap limit should be > memory limit")
+		return 0, errors.New("memory+swap limit should be >= memory limit")
 	}
 
 	return memorySwap - memory, nil