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libct/cg: retry opening a cgroup file #4442

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libct/cg: retry opening a cgroup file #4442

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24 changes: 20 additions & 4 deletions libcontainer/cgroups/file.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ import (
"errors"
"fmt"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"sync"
Expand All @@ -25,7 +25,24 @@ func OpenFile(dir, file string, flags int) (*os.File, error) {
if dir == "" {
return nil, fmt.Errorf("no directory specified for %s", file)
}
return openFile(dir, file, flags)
path := filepath.Join(dir, utils.CleanPath(file))
dir = filepath.Dir(path)
try := 0
const maxRetries = 3
for {
fd, err := openFile(path, flags)
switch {
case err == nil:
return fd, nil
case errors.Is(err, unix.ENOENT) || errors.Is(err, unix.ENODEV):
if try > maxRetries || unix.Access(dir, unix.F_OK) != nil {
return nil, err
}
try++
default:
return nil, err
}
}
}

// ReadFile reads data from a cgroup file in dir.
Expand Down Expand Up @@ -140,14 +157,13 @@ func prepareOpenat2() error {
return prepErr
}

func openFile(dir, file string, flags int) (*os.File, error) {
func openFile(path string, flags int) (*os.File, error) {
mode := os.FileMode(0)
if TestMode && flags&os.O_WRONLY != 0 {
// "emulate" cgroup fs for unit tests
flags |= os.O_TRUNC | os.O_CREATE
mode = 0o600
}
path := path.Join(dir, utils.CleanPath(file))
if prepareOpenat2() != nil {
return openFallback(path, flags, mode)
}
Expand Down