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Merge pull request #4388 from AkihiroSuda/fix-mount-wait-no-child-processes

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mount: retry executing the helper binary on ECHILD
This commit is contained in:
Derek McGowan 2020-07-23 23:20:16 -07:00 committed by GitHub
commit 67f19bfdd8
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1 changed files with 28 additions and 4 deletions
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32
mount/mount_linux.go
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@ -363,10 +363,34 @@ func (m *Mount) mountWithHelper(helperBinary, typePrefix, target string) error {
args = append(args, "-o", o) args = append(args, "-o", o)
} }
args = append(args, "-t", strings.TrimPrefix(m.Type, typePrefix)) args = append(args, "-t", strings.TrimPrefix(m.Type, typePrefix))
cmd := exec.Command(helperBinary, args...)
out, err := cmd.CombinedOutput() infoBeforeMount, err := Lookup(target)
if err != nil { if err != nil {
return errors.Wrapf(err, "mount helper [%s %v] failed: %q", helperBinary, args, string(out)) return err
} }
return nil
// cmd.CombinedOutput() may intermittently return ECHILD because of our signal handling in shim.
// See #4387 and wait(2).
const retriesOnECHILD = 10
for i := 0; i < retriesOnECHILD; i++ {
cmd := exec.Command(helperBinary, args...)
out, err := cmd.CombinedOutput()
if err == nil {
return nil
}
if !errors.Is(err, unix.ECHILD) {
return errors.Wrapf(err, "mount helper [%s %v] failed: %q", helperBinary, args, string(out))
}
// We got ECHILD, we are not sure whether the mount was successful.
// If the mount ID has changed, we are sure we got some new mount, but still not sure it is fully completed.
// So we attempt to unmount the new mount before retrying.
infoAfterMount, err := Lookup(target)
if err != nil {
return err
}
if infoAfterMount.ID != infoBeforeMount.ID {
_ = unmount(target, 0)
}
}
return errors.Errorf("mount helper [%s %v] failed with ECHILD (retired %d times)", helperBinary, args, retriesOnECHILD)
} }