mirror of
https://github.com/rclone/rclone
synced 2024-12-10 22:33:56 +01:00
928be0f1fd
Stop pre-cache before seeking which stops lots of excess data transfer
215 lines
5.8 KiB
Go
215 lines
5.8 KiB
Go
// +build linux darwin freebsd
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package mount
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import (
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"io"
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"sync"
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"bazil.org/fuse"
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fusefs "bazil.org/fuse/fs"
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"github.com/ncw/rclone/fs"
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"golang.org/x/net/context"
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)
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// ReadFileHandle is an open for read file handle on a File
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type ReadFileHandle struct {
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mu sync.Mutex
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closed bool // set if handle has been closed
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r *fs.Account
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o fs.Object
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readCalled bool // set if read has been called
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offset int64
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}
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func newReadFileHandle(o fs.Object) (*ReadFileHandle, error) {
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r, err := o.Open()
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if err != nil {
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return nil, err
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}
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fh := &ReadFileHandle{
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o: o,
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r: fs.NewAccountWithBuffer(r, o), // account the transfer
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}
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fs.Stats.Transferring(fh.o.Remote())
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return fh, nil
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}
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// Check interface satisfied
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var _ fusefs.Handle = (*ReadFileHandle)(nil)
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// Check interface satisfied
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var _ fusefs.HandleReader = (*ReadFileHandle)(nil)
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// seek to a new offset
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//
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// if reopen is true, then we won't attempt to use an io.Seeker interface
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//
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// Must be called with fh.mu held
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func (fh *ReadFileHandle) seek(offset int64, reopen bool) (err error) {
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fh.r.StopBuffering() // stop the background reading first
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oldReader := fh.r.GetReader()
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r := oldReader
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// Can we seek it directly?
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if do, ok := oldReader.(io.Seeker); !reopen && ok {
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fs.Debugf(fh.o, "ReadFileHandle.seek from %d to %d (io.Seeker)", fh.offset, offset)
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_, err = do.Seek(offset, 0)
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if err != nil {
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fs.Debugf(fh.o, "ReadFileHandle.Read io.Seeker failed: %v", err)
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return err
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}
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} else {
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fs.Debugf(fh.o, "ReadFileHandle.seek from %d to %d", fh.offset, offset)
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// close old one
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err = oldReader.Close()
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if err != nil {
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fs.Debugf(fh.o, "ReadFileHandle.Read seek close old failed: %v", err)
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}
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// re-open with a seek
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r, err = fh.o.Open(&fs.SeekOption{Offset: offset})
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if err != nil {
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fs.Debugf(fh.o, "ReadFileHandle.Read seek failed: %v", err)
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return err
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}
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}
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fh.r.UpdateReader(r)
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fh.offset = offset
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return nil
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}
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// Read from the file handle
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func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) (err error) {
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fh.mu.Lock()
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defer fh.mu.Unlock()
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fs.Debugf(fh.o, "ReadFileHandle.Read size %d offset %d", req.Size, req.Offset)
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if fh.closed {
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fs.Errorf(fh.o, "ReadFileHandle.Read error: %v", errClosedFileHandle)
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return errClosedFileHandle
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}
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doSeek := req.Offset != fh.offset
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var n int
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var newOffset int64
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retries := 0
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buf := make([]byte, req.Size)
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doReopen := false
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for {
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if doSeek {
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// Are we attempting to seek beyond the end of the
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// file - if so just return EOF leaving the underlying
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// file in an unchanged state.
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if req.Offset >= fh.o.Size() {
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fs.Debugf(fh.o, "ReadFileHandle.Read attempt to read beyond end of file: %d > %d", req.Offset, fh.o.Size())
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resp.Data = nil
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return nil
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}
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// Otherwise do the seek
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err = fh.seek(req.Offset, doReopen)
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} else {
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err = nil
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}
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if err == nil {
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if req.Size > 0 {
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fh.readCalled = true
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}
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// One exception to the above is if we fail to fully populate a
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// page cache page; a read into page cache is always page aligned.
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// Make sure we never serve a partial read, to avoid that.
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n, err = io.ReadFull(fh.r, buf)
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newOffset = fh.offset + int64(n)
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// if err == nil && rand.Intn(10) == 0 {
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// err = errors.New("random error")
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// }
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if err == nil {
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break
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} else if (err == io.ErrUnexpectedEOF || err == io.EOF) && newOffset == fh.o.Size() {
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// Have read to end of file - reset error
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err = nil
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break
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}
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}
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if retries >= fs.Config.LowLevelRetries {
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break
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}
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retries++
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fs.Errorf(fh.o, "ReadFileHandle.Read error: low level retry %d/%d: %v", retries, fs.Config.LowLevelRetries, err)
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doSeek = true
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doReopen = true
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}
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if err != nil {
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fs.Errorf(fh.o, "ReadFileHandle.Read error: %v", err)
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} else {
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resp.Data = buf[:n]
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fh.offset = newOffset
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fs.Debugf(fh.o, "ReadFileHandle.Read OK")
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}
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return err
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}
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// close the file handle returning errClosedFileHandle if it has been
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// closed already.
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//
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// Must be called with fh.mu held
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func (fh *ReadFileHandle) close() error {
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if fh.closed {
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return errClosedFileHandle
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}
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fh.closed = true
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fs.Stats.DoneTransferring(fh.o.Remote(), true)
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return fh.r.Close()
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}
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// Check interface satisfied
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var _ fusefs.HandleFlusher = (*ReadFileHandle)(nil)
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// Flush is called each time the file or directory is closed.
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// Because there can be multiple file descriptors referring to a
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// single opened file, Flush can be called multiple times.
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func (fh *ReadFileHandle) Flush(ctx context.Context, req *fuse.FlushRequest) error {
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fh.mu.Lock()
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defer fh.mu.Unlock()
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fs.Debugf(fh.o, "ReadFileHandle.Flush")
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// Ignore the Flush as there is nothing we can sensibly do and
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// it seems quite common for Flush to be called from
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// different threads each of which have read some data.
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if false {
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// If Read hasn't been called then ignore the Flush - Release
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// will pick it up
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if !fh.readCalled {
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fs.Debugf(fh.o, "ReadFileHandle.Flush ignoring flush on unread handle")
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return nil
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}
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err := fh.close()
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if err != nil {
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fs.Errorf(fh.o, "ReadFileHandle.Flush error: %v", err)
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return err
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}
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}
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fs.Debugf(fh.o, "ReadFileHandle.Flush OK")
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return nil
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}
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var _ fusefs.HandleReleaser = (*ReadFileHandle)(nil)
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// Release is called when we are finished with the file handle
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//
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// It isn't called directly from userspace so the error is ignored by
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// the kernel
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func (fh *ReadFileHandle) Release(ctx context.Context, req *fuse.ReleaseRequest) error {
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fh.mu.Lock()
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defer fh.mu.Unlock()
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if fh.closed {
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fs.Debugf(fh.o, "ReadFileHandle.Release nothing to do")
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return nil
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}
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fs.Debugf(fh.o, "ReadFileHandle.Release closing")
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err := fh.close()
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if err != nil {
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fs.Errorf(fh.o, "ReadFileHandle.Release error: %v", err)
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} else {
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fs.Debugf(fh.o, "ReadFileHandle.Release OK")
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}
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return err
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}
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