rclone/cmd/mount/read.go

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