Fix: set Swappiness when no mem limits

This hard codes -1 on inspect for Docker's API to return `null` and be compatible

Fixes: #23824

Signed-off-by: Nicola Sella <nsella@redhat.com>

Author: inknos

docs/source/markdown/podman-container-inspect.1.md.in

@@ -296,7 +296,7 @@ $ podman container inspect foobar
             "KernelMemory": 0,
             "MemoryReservation": 0,
             "MemorySwap": 0,
-            "MemorySwappiness": 0,
+            "MemorySwappiness": -1,
             "OomKillDisable": false,
             "PidsLimit": 2048,
             "Ulimits": [],

libpod/container_inspect_freebsd.go

@@ -11,6 +11,7 @@ func (c *Container) platformInspectContainerHostConfig(ctrSpec *spec.Spec, hostC
 	// Not sure what to put here. FreeBSD jails use pids from the
 	// global pool but can only see their own pids.
 	hostConfig.PidMode = "host"
+	hostConfig.MemorySwappiness = -1
 
 	// UTS namespace mode
 	hostConfig.UTSMode = c.NamespaceMode(spec.UTSNamespace, ctrSpec)

libpod/container_inspect_linux.go

@@ -50,6 +50,7 @@ func (c *Container) platformInspectContainerHostConfig(ctrSpec *spec.Spec, hostC
 				hostConfig.CpusetCpus = ctrSpec.Linux.Resources.CPU.Cpus
 				hostConfig.CpusetMems = ctrSpec.Linux.Resources.CPU.Mems
 			}
+			hostConfig.MemorySwappiness = -1
 			if ctrSpec.Linux.Resources.Memory != nil {
 				if ctrSpec.Linux.Resources.Memory.Limit != nil {
 					hostConfig.Memory = *ctrSpec.Linux.Resources.Memory.Limit
@@ -62,9 +63,6 @@ func (c *Container) platformInspectContainerHostConfig(ctrSpec *spec.Spec, hostC
 				}
 				if ctrSpec.Linux.Resources.Memory.Swappiness != nil {
 					hostConfig.MemorySwappiness = int64(*ctrSpec.Linux.Resources.Memory.Swappiness)
-				} else {
-					// Swappiness has a default of -1
-					hostConfig.MemorySwappiness = -1
 				}
 				if ctrSpec.Linux.Resources.Memory.DisableOOMKiller != nil {
 					hostConfig.OomKillDisable = *ctrSpec.Linux.Resources.Memory.DisableOOMKiller

pkg/api/handlers/compat/containers.go

@@ -543,6 +543,11 @@ func LibpodToContainerJSON(l *libpod.Container, sz bool) (*handlers.LegacyImageI
 		hc.CgroupnsMode = container.CgroupnsModeHost
 	}
 
+	// Docker reports null instead of -1 for unset Swappiness
+	if hc.MemorySwappiness != nil && *hc.MemorySwappiness == -1 {
+		hc.MemorySwappiness = nil
+	}
+
 	// k8s-file == json-file
 	if hc.LogConfig.Type == define.KubernetesLogging {
 		hc.LogConfig.Type = define.JSONLogging

test/apiv2/20-containers.at

@@ -870,6 +870,16 @@ t GET containers/$cid/json 200 \
 t DELETE containers/$cid 204
 podman rmi test1
 
+# test MemorySwappiness
+podman run -d --rm --name swappiness_with_mem_limit --memory 200M $IMAGE top
+podman run -d --rm --name swappiness_without_mem_limit $IMAGE top
+
+t GET containers/swappiness_with_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+t GET containers/swappiness_without_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+
+podman stop -t0 swappiness_with_mem_limit swappiness_without_mem_limit
 
 # test if API support -1 for ulimits https://github.com/containers/podman/issues/24886
 

test/e2e/container_clone_test.go

@@ -140,7 +140,7 @@ var _ = Describe("Podman container clone", func() {
 		cloneInspect.WaitWithDefaultTimeout()
 		Expect(cloneInspect).To(ExitCleanly())
 		cloneData = cloneInspect.InspectContainerToJSON()
-		Expect(cloneData[0].HostConfig).To(HaveField("MemorySwappiness", int64(0)))
+		Expect(cloneData[0].HostConfig).To(HaveField("MemorySwappiness", int64(-1)))
 	})
 
 	It("podman container clone in a pod", func() {