mount: fix retry on network failure when reading off crypt - fixes #1042

cmd/mount/read.go

@@ -20,7 +20,6 @@ type ReadFileHandle struct {
 	o          fs.Object
 	readCalled bool // set if read has been called
 	offset     int64
-	retries    int // number of times we have retried
 }
 
 func newReadFileHandle(o fs.Object) (*ReadFileHandle, error) {
@@ -44,11 +43,13 @@ var _ fusefs.HandleReader = (*ReadFileHandle)(nil)
 
 // seek to a new offset
 //
+// if reopen is true, then we won't attempt to use an io.Seeker interface
+//
 // Must be called with fh.mu held
-func (fh *ReadFileHandle) seek(offset int64) error {
+func (fh *ReadFileHandle) seek(offset int64, reopen bool) error {
 	// Can we seek it directly?
 	oldReader := fh.r.GetReader()
-	if do, ok := oldReader.(io.Seeker); ok {
+	if do, ok := oldReader.(io.Seeker); !reopen && ok {
 		fs.Debug(fh.o, "ReadFileHandle.seek from %d to %d (io.Seeker)", fh.offset, offset)
 		_, err := do.Seek(offset, 0)
 		if err != nil {
@@ -75,7 +76,7 @@ func (fh *ReadFileHandle) seek(offset int64) error {
 }
 
 // Read from the file handle
-func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) error {
+func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) (err error) {
 	fh.mu.Lock()
 	defer fh.mu.Unlock()
 	fs.Debug(fh.o, "ReadFileHandle.Read size %d offset %d", req.Size, req.Offset)
@@ -84,10 +85,11 @@ func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp
 		return errClosedFileHandle
 	}
 	doSeek := req.Offset != fh.offset
-	var err error
 	var n int
 	var newOffset int64
+	retries := 0
 	buf := make([]byte, req.Size)
+	doReopen := false
 	for {
 		if doSeek {
 			// Are we attempting to seek beyond the end of the
@@ -98,11 +100,12 @@ func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp
 				resp.Data = nil
 				return nil
 			}
-			err := fh.seek(req.Offset)
+			// Otherwise do the seek
-			if err != nil {
+			err = fh.seek(req.Offset, doReopen)
-				return err
+		} else {
-			}
+			err = nil
 		}
+		if err == nil {
 			if req.Size > 0 {
 				fh.readCalled = true
 			}
@@ -117,22 +120,27 @@ func (fh *ReadFileHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp
 			if err == nil {
 				break
 			} else if (err == io.ErrUnexpectedEOF || err == io.EOF) && newOffset == fh.o.Size() {
-			// Read to end of file
+				// Have read to end of file - reset error
+				err = nil
 				break
 			}
-		if fh.retries >= fs.Config.LowLevelRetries {
-			fs.ErrorLog(fh.o, "ReadFileHandle.Read error: %v", err)
-			return err
 		}
-		fh.retries++
+		if retries >= fs.Config.LowLevelRetries {
-		fs.ErrorLog(fh.o, "ReadFileHandle.Read error: low level retry %d/%d: %v", fh.retries, fs.Config.LowLevelRetries, err)
+			break
+		}
+		retries++
+		fs.ErrorLog(fh.o, "ReadFileHandle.Read error: low level retry %d/%d: %v", retries, fs.Config.LowLevelRetries, err)
 		doSeek = true
+		doReopen = true
 	}
-	fh.retries = 0 // reset retries
+	if err != nil {
+		fs.ErrorLog(fh.o, "ReadFileHandle.Read error: %v", err)
+	} else {
 		resp.Data = buf[:n]
 		fh.offset = newOffset
 		fs.Debug(fh.o, "ReadFileHandle.Read OK")
-	return nil
+	}
+	return err
 }
 
 // close the file handle returning errClosedFileHandle if it has been