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overlay & native snapshotters: Usage() result differs across ext4 and XFS #7909

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overlay & native snapshotters: Usage() result differs across ext4 and XFS#7909
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kind/enhancement
@AkihiroSuda

Description

@AkihiroSuda
AkihiroSuda
opened on Jan 3, 2023

Description

A fresh active snapshot is reported to take 4.0 KiB on ext4, 0.0 B on XFS.

Probably this is not a bug, though, but some downstreams may want the size information to be consistent regardless to the backing filesystem.

Steps to reproduce the issue

ext4:

$ sudo ctr snapshot prepare foo
$ sudo ctr snapshot usage
KEY SIZE    INODES 
foo 4.0 KiB 1

XFS:

$ sudo ctr snapshot prepare foo
$ sudo ctr snapshot usage
KEY SIZE  INODES 
foo 0.0 B 1

Describe the results you received and expected

Received: 4 KiB vs 0.0 B
Expected: consistent result

What version of containerd are you using?

containerd github.com/containerd/containerd v1.6.14 9ba4b25

Any other relevant information

On XFS distros TestContainerStats (cri-integration) fails during checking s.GetWritableLayer().GetUsedBytes().GetValue() != 0 because of this difference:

containerd/integration/container_stats_test.go

Lines 32 to 72 in 88c8480

// Test to verify for a container ID
func TestContainerStats(t *testing.T) {
t.Logf("Create a pod config and run sandbox container")
sb, sbConfig := PodSandboxConfigWithCleanup(t, "sandbox1", "stats")
pauseImage := images.Get(images.Pause)
EnsureImageExists(t, pauseImage)
t.Logf("Create a container config and run container in a pod")
containerConfig := ContainerConfig(
"container1",
pauseImage,
WithTestLabels(),
WithTestAnnotations(),
)
cn, err := runtimeService.CreateContainer(sb, containerConfig, sbConfig)
require.NoError(t, err)
defer func() {
assert.NoError(t, runtimeService.RemoveContainer(cn))
}()
require.NoError(t, runtimeService.StartContainer(cn))
defer func() {
assert.NoError(t, runtimeService.StopContainer(cn, 10))
}()
t.Logf("Fetch stats for container")
var s *runtime.ContainerStats
require.NoError(t, Eventually(func() (bool, error) {
s, err = runtimeService.ContainerStats(cn)
if err != nil {
return false, err
}
if s.GetWritableLayer().GetUsedBytes().GetValue() != 0 {
return true, nil
}
return false, nil
}, time.Second, 30*time.Second))
t.Logf("Verify stats received for container %q", cn)
testStats(t, s, containerConfig)
}

Show configuration if it is related to CRI plugin.

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