diff --git a/fuseops/ops.go b/fuseops/ops.go
index d73c42c..5a857bf 100644
--- a/fuseops/ops.go
+++ b/fuseops/ops.go
@@ -384,25 +384,25 @@ type ReadDirOp struct {
 	// offset, and return array offsets into that cached listing.
 	Offset DirOffset
 
-	// The maximum number of bytes to return in ReadDirResponse.Data. A smaller
-	// number is acceptable.
-	Size int
-
-	// Set by the file system: a buffer consisting of a sequence of FUSE
-	// directory entries in the format generated by fuse_add_direntry
-	// (http://goo.gl/qCcHCV), which is consumed by parse_dirfile
-	// (http://goo.gl/2WUmD2). Use fuseutil.AppendDirent to generate this data.
+	// The destination buffer, whose length gives the size of the read.
 	//
-	// The buffer must not exceed the length specified in ReadDirRequest.Size. It
-	// is okay for the final entry to be truncated; parse_dirfile copes with this
-	// by ignoring the partial record.
+	// The output data should consist of a sequence of FUSE directory entries in
+	// the format generated by fuse_add_direntry (http://goo.gl/qCcHCV), which is
+	// consumed by parse_dirfile (http://goo.gl/2WUmD2). Use
+	// fuseutil.AppendDirent to generate this data.
+	//
+	// It is okay for the final entry to be truncated if it doesn't fit;
+	// parse_dirfile copes with this by ignoring the partial record.
 	//
 	// Each entry returned exposes a directory offset to the user that may later
 	// show up in ReadDirRequest.Offset. See notes on that field for more
 	// information.
-	//
-	// An empty buffer indicates the end of the directory has been reached.
-	Data []byte
+	Dst []byte
+
+	// Set by the file system: the number of bytes read into Dst. It is okay for
+	// this to be less than len(Dst) if there is less data available. A value of
+	// zero means that the end of the directory has been reached.
+	BytesRead int
 }
 
 // Release a previously-minted directory handle. The kernel sends this when
@@ -455,20 +455,21 @@ type ReadFileOp struct {
 	Inode  InodeID
 	Handle HandleID
 
-	// The range of the file to read.
+	// The offset within the file at which to read.
+	Offset int64
+
+	// The destination buffer, whose length gives the size of the read.
+	Dst []byte
+
+	// Set by the file system: the number of bytes read.
 	//
-	// The FUSE documentation requires that exactly the number of bytes be
-	// returned, except in the case of EOF or error (http://goo.gl/ZgfBkF). This
-	// appears to be because it uses file mmapping machinery
+	// The FUSE documentation requires that exactly the requested number of bytes
+	// be returned, except in the case of EOF or error (http://goo.gl/ZgfBkF).
+	// This appears to be because it uses file mmapping machinery
 	// (http://goo.gl/SGxnaN) to read a page at a time. It appears to understand
 	// where EOF is by checking the inode size (http://goo.gl/0BkqKD), returned
 	// by a previous call to LookUpInode, GetInodeAttributes, etc.
-	Offset int64
-	Size   int
-
-	// Set by the file system: the data read. If this is less than the requested
-	// size, it indicates EOF. An error should not be returned in this case.
-	Data []byte
+	BytesRead int
 }
 
 // Write data to a file previously opened with CreateFile or OpenFile.