stats: get mem limit from the cgroup

b25b330 introduced this behaviour.

It was fine at the time because we didn't support "container update",
so the limit could not be changed at runtime.  Since it is not
possible to change the memory limit at runtime, read the limit as
reported from the cgroup.

containers/crun#1217 is required for crun.

[NO NEW TESTS NEEDED] needs a new crun release

Closes: containers#18621

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

libpod/stats_linux.go

@@ -5,7 +5,6 @@ package libpod
 
 import (
 	"fmt"
-	"math"
 	"strings"
 	"syscall"
 	"time"
@@ -59,7 +58,7 @@ func (c *Container) getPlatformContainerStats(stats *define.ContainerStats, prev
 	// calc the average cpu usage for the time the container is running
 	stats.AvgCPU = calculateCPUPercent(cgroupStats, 0, now, uint64(c.state.StartedTime.UnixNano()))
 	stats.MemUsage = cgroupStats.MemoryStats.Usage.Usage
-	stats.MemLimit = c.getMemLimit()
+	stats.MemLimit = c.getMemLimit(cgroupStats.MemoryStats.Usage.Total)
 	stats.MemPerc = (float64(stats.MemUsage) / float64(stats.MemLimit)) * 100
 	stats.PIDs = 0
 	if conState == define.ContainerStateRunning || conState == define.ContainerStatePaused {
@@ -83,14 +82,7 @@ func (c *Container) getPlatformContainerStats(stats *define.ContainerStats, prev
 }
 
 // getMemory limit returns the memory limit for a container
-func (c *Container) getMemLimit() uint64 {
-	memLimit := uint64(math.MaxUint64)
-
-	resources := c.LinuxResources()
-	if resources != nil && resources.Memory != nil && resources.Memory.Limit != nil {
-		memLimit = uint64(*resources.Memory.Limit)
-	}
-
+func (c *Container) getMemLimit(memLimit uint64) uint64 {
 	si := &syscall.Sysinfo_t{}
 	err := syscall.Sysinfo(si)
 	if err != nil {