Enable readahead by default

fuse.go

@@ -232,9 +232,17 @@ func initMount(c *Conn, conf *mountConfig) error {
 	}
 	c.proto = proto
 
+	maxReadahead := conf.maxReadahead
+	if maxReadahead == 0 {
+		maxReadahead = defaultReadahead
+	}
+	if maxReadahead > r.MaxReadahead {
+		maxReadahead = r.MaxReadahead
+	}
+
 	s := &InitResponse{
 		Library:      proto,
-		MaxReadahead: conf.maxReadahead,
+		MaxReadahead: maxReadahead,
 		MaxWrite:     maxWrite,
 		Flags:        InitBigWrites | conf.initFlags,
 	}

fuse_darwin.go

@@ -7,3 +7,6 @@ package fuse
 // 16MB value. See TestSetxattr16MB and
 // https://github.com/bazil/fuse/issues/42
 const maxWrite = 16 * 1024 * 1024
+
+// Default kernel readahead.
+const defaultReadahead = 128 * 1024

fuse_freebsd.go

@@ -4,3 +4,6 @@ package fuse
 //
 // This number is just a guess.
 const maxWrite = 128 * 1024
+
+// Default kernel readahead.
+const defaultReadahead = 128 * 1024

fuse_linux.go

@@ -5,3 +5,6 @@ package fuse
 // Linux 4.2.0 has been observed to cap this value at 128kB
 // (FUSE_MAX_PAGES_PER_REQ=32, 4kB pages).
 const maxWrite = 128 * 1024
+
+// Default kernel readahead.
+const defaultReadahead = 128 * 1024