// request.
//
type UnixVolume struct {
- root string // path to this volume
- queue chan *IORequest
+ root string // path to this volume
+ queue chan *IORequest
+ readonly bool
}
func (v *UnixVolume) IOHandler() {
}
}
-func MakeUnixVolume(root string, serialize bool) (v UnixVolume) {
+func MakeUnixVolume(root string, serialize bool, readonly bool) *UnixVolume {
+ v := &UnixVolume{
+ root: root,
+ queue: nil,
+ readonly: readonly,
+ }
if serialize {
- v = UnixVolume{root, make(chan *IORequest)}
+ v.queue =make(chan *IORequest)
go v.IOHandler()
- } else {
- v = UnixVolume{root, nil}
}
- return
+ return v
}
func (v *UnixVolume) Get(loc string) ([]byte, error) {
}
func (v *UnixVolume) Put(loc string, block []byte) error {
+ if v.readonly {
+ return MethodDisabledError
+ }
if v.queue == nil {
return v.Write(loc, block)
}
}
func (v *UnixVolume) Touch(loc string) error {
+ if v.readonly {
+ return MethodDisabledError
+ }
p := v.blockPath(loc)
f, err := os.OpenFile(p, os.O_RDWR|os.O_APPEND, 0644)
if err != nil {
return err
}
- lockfile(f)
+ defer f.Close()
+ if e := lockfile(f); e != nil {
+ return e
+ }
defer unlockfile(f)
now := time.Now().Unix()
utime := syscall.Utimbuf{now, now}
return syscall.Utime(p, &utime)
}
+func (v *UnixVolume) Mtime(loc string) (time.Time, error) {
+ p := v.blockPath(loc)
+ if fi, err := os.Stat(p); err != nil {
+ return time.Time{}, err
+ } else {
+ return fi.ModTime(), nil
+ }
+}
+
// Read retrieves a block identified by the locator string "loc", and
// returns its contents as a byte slice.
//
}
func (v *UnixVolume) Delete(loc string) error {
+ // Touch() must be called before calling Write() on a block. Touch()
+ // also uses lockfile(). This avoids a race condition between Write()
+ // and Delete() because either (a) the file will be deleted and Touch()
+ // will signal to the caller that the file is not present (and needs to
+ // be re-written), or (b) Touch() will update the file's timestamp and
+ // Delete() will read the correct up-to-date timestamp and choose not to
+ // delete the file.
+
+ if v.readonly {
+ return MethodDisabledError
+ }
p := v.blockPath(loc)
f, err := os.OpenFile(p, os.O_RDWR|os.O_APPEND, 0644)
if err != nil {
return err
}
- lockfile(f)
+ defer f.Close()
+ if e := lockfile(f); e != nil {
+ return e
+ }
defer unlockfile(f)
- // Return PermissionError if the block has been PUT more recently
- // than -permission_ttl. This guards against a race condition
- // where a block is old enough that Data Manager has added it to
- // the trash list, but the user submitted a PUT for the block
- // since then.
+ // If the block has been PUT more recently than -permission_ttl,
+ // return success without removing the block. This guards against
+ // a race condition where a block is old enough that Data Manager
+ // has added it to the trash list, but the user submitted a PUT
+ // for the block since then.
if fi, err := os.Stat(p); err != nil {
return err
} else {
if time.Since(fi.ModTime()) < permission_ttl {
- return PermissionError
+ return nil
}
}
return os.Remove(p)
return fmt.Sprintf("[UnixVolume %s]", v.root)
}
+func (v *UnixVolume) Writable() bool {
+ return !v.readonly
+}
+
// lockfile and unlockfile use flock(2) to manage kernel file locks.
-func lockfile(f os.File) error {
+func lockfile(f *os.File) error {
return syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
}
-func unlockfile(f os.File) error {
+func unlockfile(f *os.File) error {
return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
}