diff options
| -rw-r--r-- | runsc/fsgofer/fsgofer.go | 56 |
1 files changed, 33 insertions, 23 deletions
diff --git a/runsc/fsgofer/fsgofer.go b/runsc/fsgofer/fsgofer.go index 60dad642f..c964a2a3b 100644 --- a/runsc/fsgofer/fsgofer.go +++ b/runsc/fsgofer/fsgofer.go @@ -215,6 +215,12 @@ type localFile struct { // readDirMu protects against concurrent Readdir calls. readDirMu sync.Mutex + + // lastDirentOffset is the last offset returned by Readdir(). If another call + // to Readdir is made at the same offset, the file doesn't need to be + // repositioned. This is an important optimization because the caller must + // always make one extra call to detect EOF (empty result, no error). + lastDirentOffset uint64 } func openAnyFileFromParent(parent *localFile, name string) (*fd.FD, string, error) { @@ -470,25 +476,14 @@ func (l *localFile) Mkdir(name string, perm p9.FileMode, uid p9.UID, gid p9.GID) func (l *localFile) Walk(names []string) ([]p9.QID, p9.File, error) { // Duplicate current file if 'names' is empty. if len(names) == 0 { - var newFile *fd.FD - if l.isOpen() { - // File mode may have changed when it was opened, so open a new one. - var err error - newFile, err = openAnyFile(l.hostPath, func(mode int) (*fd.FD, error) { - return fd.Open(l.hostPath, openFlags|mode, 0) - }) - if err != nil { - return nil, nil, extractErrno(err) - } - } else { - newFd, err := syscall.Dup(l.file.FD()) - if err != nil { - return nil, nil, extractErrno(err) - } - newFile = fd.New(newFd) + newFile, err := openAnyFile(l.hostPath, func(mode int) (*fd.FD, error) { + return fd.Open(l.hostPath, openFlags|mode, 0) + }) + if err != nil { + return nil, nil, extractErrno(err) } - stat, err := stat(int(newFile.FD())) + stat, err := stat(newFile.FD()) if err != nil { newFile.Close() return nil, nil, extractErrno(err) @@ -884,14 +879,30 @@ func (l *localFile) Readdir(offset uint64, count uint32) ([]p9.Dirent, error) { l.readDirMu.Lock() defer l.readDirMu.Unlock() - if _, err := syscall.Seek(l.file.FD(), 0, 0); err != nil { - return nil, extractErrno(err) + skip := uint64(0) + + // Check if the file is at the correct position already. If not, seek to the + // beginning and read the entire directory again. + if l.lastDirentOffset != offset { + if _, err := syscall.Seek(l.file.FD(), 0, 0); err != nil { + return nil, extractErrno(err) + } + skip = offset } - return l.readDirent(l.file.FD(), offset, count) + dirents, err := l.readDirent(l.file.FD(), offset, count, skip) + if err == nil { + // On success, remember the offset that was returned at the current + // position. + l.lastDirentOffset = offset + uint64(len(dirents)) + } else { + // On failure, the state is unknown, force call to seek() next time. + l.lastDirentOffset = math.MaxUint64 + } + return dirents, err } -func (l *localFile) readDirent(f int, offset uint64, count uint32) ([]p9.Dirent, error) { +func (l *localFile) readDirent(f int, offset uint64, count uint32, skip uint64) ([]p9.Dirent, error) { // Limit 'count' to cap the slice size that is returned. const maxCount = 100000 if count > maxCount { @@ -904,7 +915,6 @@ func (l *localFile) readDirent(f int, offset uint64, count uint32) ([]p9.Dirent, direntsBuf := make([]byte, 8192) names := make([]string, 0, 100) - skip := offset // Tracks the number of entries to skip. end := offset + uint64(count) for offset < end { dirSize, err := syscall.ReadDirent(f, direntsBuf) @@ -912,7 +922,7 @@ func (l *localFile) readDirent(f int, offset uint64, count uint32) ([]p9.Dirent, return dirents, err } if dirSize <= 0 { - return dirents, nil // EOF + return dirents, nil } names := names[:0] |