8000 stage0/gc: try to avoid double overlay mounts by lucab · Pull Request #3806 · rkt/rkt · GitHub
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stage0/gc: try to avoid double overlay mounts #3806

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Sep 21, 2017
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stage0/gc: try to avoid double overlay mounts #3806

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50 changes: 36 additions & 14 deletions rkt/gc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (

"github.com/hashicorp/errwrap"
"github.com/rkt/rkt/common"
"github.com/rkt/rkt/pkg/mountinfo"
pkgPod "github.com/rkt/rkt/pkg/pod"
"github.com/rkt/rkt/stage0"
"github.com/rkt/rkt/store/imagestore"
Expand Down Expand Up @@ -197,29 +198,51 @@ func emptyGarbage() error {
return nil
}

func mountPodStage1(ts *treestore.Store, p *pkgPod.Pod) error {
// mountPodStage1 tries to remount stage1 image overlay in case
// it is not anymore available in place (e.g. a reboot happened
// in-between). If an overlay mount is already there, we assume
// stage1 image is properly in place and we don't perform any
// further actions. A boolean is returned to signal whether a
// a new mount was performed.
func mountPodStage1(ts *treestore.Store, p *pkgPod.Pod) (bool, error) {
if !p.UsesOverlay() {
return nil
return false, nil
}

s1Id, err := p.GetStage1TreeStoreID()
if err != nil {
return errwrap.Wrap(errors.New("error getting stage1 treeStoreID"), err)
< 8000 /td> return false, errwrap.Wrap(errors.New("error getting stage1 treeStoreID"), err)
}
s1rootfs := ts.GetRootFS(s1Id)

stage1Dir := common.Stage1RootfsPath(p.Path())

if mounts, err := mountinfo.ParseMounts(0); err == nil {
for _, m := range mounts {
if m.MountPoint == stage1Dir {
// stage1 image overlay already in place
return false, nil
}
}
}

overlayDir := filepath.Join(p.Path(), "overlay")
imgDir := filepath.Join(overlayDir, s1Id)
upperDir := filepath.Join(imgDir, "upper")
workDir := filepath.Join(imgDir, "work")

opts := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", s1rootfs, upperDir, workDir)
if err := syscall.Mount("overlay", stage1Dir, "overlay", 0, opts); err != nil {
return errwrap.Wrap(errors.New("error mounting stage1"), err)
err = syscall.Mount("overlay", stage1Dir, "overlay", 0, opts)
if err != nil {
// -EBUSY means the overlay mount is already present.
// This behavior was introduced in Linux 4.13, double-mounts were allowed
// in older kernels.
if err == syscall.EBUSY {
stderr.Println("mount detected on stage1 target, skipping overlay mount")
return false, nil
}
return false, errwrap.Wrap(errors.New("error mounting stage1"), err)
}

return nil
return true, nil
}

// deletePod cleans up files and resource associated with the pod
Expand Down Expand Up @@ -250,16 +273,15 @@ func deletePod(p *pkgPod.Pod) bool {
stage0.InitDebug()
}

if err := mountPodStage1(ts, p); err == nil {
if newMount, err := mountPodStage1(ts, p); err == nil {
if err = stage0.GC(p.Path(), p.UUID, globalFlags.LocalConfigDir); err != nil {
stderr.PrintE(fmt.Sprintf("problem performing stage1 GC on %q", p.UUID), err)
}
// an overlay fs can be mounted over itself, let's unmount it here
// if we mounted it before to avoid problems when running
// stage0.MountGC
if p.UsesOverlay() {
// Linux <4.13 allows an overlay fs to be mounted over itself, so let's
// unmount it here to avoid problems when running stage0.MountGC
if p.UsesOverlay() && newMount {
stage1Mnt := common.Stage1RootfsPath(p.Path())
if err := syscall.Unmount(stage1Mnt, 0); err != nil {
if err := syscall.Unmount(stage1Mnt, 0); err != nil && err != syscall.EBUSY {
stderr.PrintE("error unmounting stage1", err)
}
}
Expand Down
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