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package file
import (
"io/ioutil"
"os"
"path/filepath"
"strconv"
"syscall"
"github.com/containers/storage"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
// FileLocks is a struct enabling POSIX lock locking in a shared memory
// segment.
type FileLocks struct { // nolint
lockPath string
valid bool
}
// CreateFileLock sets up a directory containing the various lock files.
func CreateFileLock(path string) (*FileLocks, error) {
_, err := os.Stat(path)
if err == nil {
return nil, errors.Wrapf(syscall.EEXIST, "directory %s exists", path)
}
if err := os.MkdirAll(path, 0711); err != nil {
return nil, errors.Wrapf(err, "cannot create %s", path)
}
locks := new(FileLocks)
locks.lockPath = path
locks.valid = true
return locks, nil
}
// OpenFileLock opens an existing directory with the lock files.
func OpenFileLock(path string) (*FileLocks, error) {
_, err := os.Stat(path)
if err != nil {
return nil, errors.Wrapf(err, "accessing directory %s", path)
}
locks := new(FileLocks)
locks.lockPath = path
locks.valid = true
return locks, nil
}
// Close closes an existing shared-memory segment.
// The segment will be rendered unusable after closing.
// WARNING: If you Close() while there are still locks locked, these locks may
// fail to release, causing a program freeze.
// Close() is only intended to be used while testing the locks.
func (locks *FileLocks) Close() error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
err := os.RemoveAll(locks.lockPath)
if err != nil {
return errors.Wrapf(err, "deleting directory %s", locks.lockPath)
}
return nil
}
func (locks *FileLocks) getLockPath(lck uint32) string {
return filepath.Join(locks.lockPath, strconv.FormatInt(int64(lck), 10))
}
// AllocateLock allocates a lock and returns the index of the lock that was allocated.
func (locks *FileLocks) AllocateLock() (uint32, error) {
if !locks.valid {
return 0, errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
id := uint32(0)
for ; ; id++ {
path := locks.getLockPath(id)
f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
if err != nil {
if os.IsExist(err) {
continue
}
return 0, errors.Wrapf(err, "creating lock file")
}
f.Close()
break
}
return id, nil
}
// AllocateGivenLock allocates the given lock from the shared-memory
// segment for use by a container or pod.
// If the lock is already in use or the index is invalid an error will be
// returned.
func (locks *FileLocks) AllocateGivenLock(lck uint32) error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
f, err := os.OpenFile(locks.getLockPath(lck), os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
if err != nil {
return errors.Wrapf(err, "error creating lock %d", lck)
}
f.Close()
return nil
}
// DeallocateLock frees a lock in a shared-memory segment so it can be
// reallocated to another container or pod.
// The given lock must be already allocated, or an error will be returned.
func (locks *FileLocks) DeallocateLock(lck uint32) error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
if err := os.Remove(locks.getLockPath(lck)); err != nil {
return errors.Wrapf(err, "deallocating lock %d", lck)
}
return nil
}
// DeallocateAllLocks frees all locks so they can be reallocated to
// other containers and pods.
func (locks *FileLocks) DeallocateAllLocks() error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
files, err := ioutil.ReadDir(locks.lockPath)
if err != nil {
return errors.Wrapf(err, "error reading directory %s", locks.lockPath)
}
var lastErr error
for _, f := range files {
p := filepath.Join(locks.lockPath, f.Name())
err := os.Remove(p)
if err != nil {
lastErr = err
logrus.Errorf("deallocating lock %s", p)
}
}
return lastErr
}
// LockFileLock locks the given lock.
func (locks *FileLocks) LockFileLock(lck uint32) error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
l, err := storage.GetLockfile(locks.getLockPath(lck))
if err != nil {
return errors.Wrapf(err, "error acquiring lock")
}
l.Lock()
return nil
}
// UnlockFileLock unlocks the given lock.
func (locks *FileLocks) UnlockFileLock(lck uint32) error {
if !locks.valid {
return errors.Wrapf(syscall.EINVAL, "locks have already been closed")
}
l, err := storage.GetLockfile(locks.getLockPath(lck))
if err != nil {
return errors.Wrapf(err, "error acquiring lock")
}
l.Unlock()
return nil
}
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