-// A UnixVolume is a Volume backed by a locally mounted disk.
-//
package main
import (
// A UnixVolume stores and retrieves blocks in a local directory.
type UnixVolume struct {
- root string // path to the volume's root directory
- serialize bool
- readonly bool
- mutex sync.Mutex
+ // path to the volume's root directory
+ root string
+ // something to lock during IO, typically a sync.Mutex (or nil
+ // to skip locking)
+ locker sync.Locker
+ readonly bool
}
+// Touch sets the timestamp for the given locator to the current time
func (v *UnixVolume) Touch(loc string) error {
if v.readonly {
return MethodDisabledError
return err
}
defer f.Close()
- if v.serialize {
- v.mutex.Lock()
- defer v.mutex.Unlock()
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
}
if e := lockfile(f); e != nil {
return e
return syscall.Utime(p, &utime)
}
+// Mtime returns the stored timestamp for the given locator.
func (v *UnixVolume) Mtime(loc string) (time.Time, error) {
p := v.blockPath(loc)
- if fi, err := os.Stat(p); err != nil {
+ fi, err := os.Stat(p)
+ if err != nil {
return time.Time{}, err
- } else {
- return fi.ModTime(), nil
}
+ return fi.ModTime(), nil
}
-// Open the given file, apply the serialize lock if enabled, and call
-// the given function if and when the file is ready to read.
+// Lock the locker (if one is in use), open the file for reading, and
+// call the given function if and when the file is ready to read.
func (v *UnixVolume) getFunc(path string, fn func(io.Reader) error) error {
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
+ }
f, err := os.Open(path)
if err != nil {
return err
}
defer f.Close()
- if v.serialize {
- v.mutex.Lock()
- defer v.mutex.Unlock()
- }
return fn(f)
}
if err == nil {
if stat.Size() < 0 {
err = os.ErrInvalid
- } else if stat.Size() > BLOCKSIZE {
+ } else if stat.Size() > BlockSize {
err = TooLongError
}
}
}
// Compare returns nil if Get(loc) would return the same content as
-// cmp. It is functionally equivalent to Get() followed by
+// expect. It is functionally equivalent to Get() followed by
// bytes.Compare(), but uses less memory.
-//
-// TODO(TC): Before returning CollisionError, compute the MD5 digest
-// of the data on disk (i.e., known-to-be-equal data in cmp +
-// remaining data on disk) and return DiskHashError instead of
-// CollisionError if it doesn't equal loc[:32].
-func (v *UnixVolume) Compare(loc string, cmp []byte) error {
+func (v *UnixVolume) Compare(loc string, expect []byte) error {
path := v.blockPath(loc)
stat, err := v.stat(path)
if err != nil {
if int64(bufLen) > stat.Size() {
bufLen = int(stat.Size())
}
+ cmp := expect
buf := make([]byte, bufLen)
return v.getFunc(path, func(rdr io.Reader) error {
// Loop invariants: all data read so far matched what
// reader.
for {
n, err := rdr.Read(buf)
- if n > len(cmp) {
- // file on disk is too long
- return CollisionError
- } else if n > 0 && bytes.Compare(cmp[:n], buf[:n]) != 0 {
- return CollisionError
+ if n > len(cmp) || bytes.Compare(cmp[:n], buf[:n]) != 0 {
+ return collisionOrCorrupt(loc[:32], expect[:len(expect)-len(cmp)], buf[:n], rdr)
}
cmp = cmp[n:]
if err == io.EOF {
if len(cmp) != 0 {
- // file on disk is too short
- return CollisionError
+ return collisionOrCorrupt(loc[:32], expect[:len(expect)-len(cmp)], nil, nil)
}
return nil
} else if err != nil {
}
bpath := v.blockPath(loc)
- if v.serialize {
- v.mutex.Lock()
- defer v.mutex.Unlock()
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
}
if _, err := tmpfile.Write(block); err != nil {
log.Printf("%s: writing to %s: %s\n", v, bpath, err)
}
}
+// Delete deletes the block data from the unix storage
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()
if v.readonly {
return MethodDisabledError
}
- if v.serialize {
- v.mutex.Lock()
- defer v.mutex.Unlock()
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
}
p := v.blockPath(loc)
f, err := os.OpenFile(p, os.O_RDWR|os.O_APPEND, 0644)
}
// IsFull returns true if the free space on the volume is less than
-// MIN_FREE_KILOBYTES.
+// MinFreeKilobytes.
//
func (v *UnixVolume) IsFull() (isFull bool) {
fullSymlink := v.root + "/full"
}
if avail, err := v.FreeDiskSpace(); err == nil {
- isFull = avail < MIN_FREE_KILOBYTES
+ isFull = avail < MinFreeKilobytes
} else {
log.Printf("%s: FreeDiskSpace: %s\n", v, err)
isFull = false
return fmt.Sprintf("[UnixVolume %s]", v.root)
}
+// Writable returns false if all future Put, Mtime, and Delete calls are expected to fail.
func (v *UnixVolume) Writable() bool {
return !v.readonly
}
projects / arvados.git / blobdiff