fuse: document Blksize and Blocks in Attr

Change-Id: I1c098b6c06ab62aa7877e47aa3d99f37e9a83e5c

fuse/types_linux.go

@@ -16,8 +16,10 @@ const (
 )
 
 type Attr struct {
-	Ino       uint64
-	Size      uint64
+	Ino  uint64
+	Size uint64
+
+	// Blocks is the number of 512-byte blocks that the file occupies on disk.
 	Blocks    uint64
 	Atime     uint64
 	Mtime     uint64
@@ -28,7 +30,9 @@ type Attr struct {
 	Mode      uint32
 	Nlink     uint32
 	Owner
-	Rdev    uint32
+	Rdev uint32
+
+	// Blksize is the preferred size for file system operations.
 	Blksize uint32
 	Padding uint32
 }