api: show the memory limit specified for the container

use the memory limit specified for the container instead of reading it
from the cgroup.  It is not reliable to read it from the cgroup since
the container could have been moved to a different cgroup and in
general the OCI runtime might create a sub-cgroup (like crun does).

Closes: containers#14676

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/api/handlers/compat/containers_stats.go

@@ -132,6 +132,12 @@ streamLabel: // A label to flatten the scope
 			InstanceID: "",
 		}
 
+		cfg := ctnr.Config()
+		memoryLimit := cgroupStat.Memory.Usage.Limit
+		if cfg.Spec.Linux != nil && cfg.Spec.Linux.Resources != nil && cfg.Spec.Linux.Resources.Memory != nil && *cfg.Spec.Linux.Resources.Memory.Limit > 0 {
+			memoryLimit = uint64(*cfg.Spec.Linux.Resources.Memory.Limit)
+		}
+
 		systemUsage, _ := cgroups.GetSystemCPUUsage()
 		s := StatsJSON{
 			Stats: Stats{
@@ -173,7 +179,7 @@ streamLabel: // A label to flatten the scope
 					MaxUsage:          cgroupStat.Memory.Usage.Limit,
 					Stats:             nil,
 					Failcnt:           0,
-					Limit:             cgroupStat.Memory.Usage.Limit,
+					Limit:             memoryLimit,
 					Commit:            0,
 					CommitPeak:        0,
 					PrivateWorkingSet: 0,

test/apiv2/20-containers.at

@@ -95,6 +95,17 @@ fi
 
 t DELETE libpod/containers/$cid 200 .[0].Id=$cid
 
+# Issue #14676: make sure the stats show the memory limit specified for the container
+if root; then
+    CTRNAME=ctr-with-limit
+    podman run --name $CTRNAME -d -m 512m -v /tmp:/tmp $IMAGE top
+
+    t GET libpod/containers/$CTRNAME/stats?stream=false 200 \
+    .memory_stats.limit=536870912
+
+    podman rm -f $CTRNAME
+fi
+
 # Issue #6799: it should be possible to start a container, even w/o args.
 t POST libpod/containers/create?name=test_noargs Image=${IMAGE} 201 \
   .Id~[0-9a-f]\\{64\\}