Added support for setting max-pages via config

fuse/api.go

@@ -167,6 +167,10 @@ type MountOptions struct {
 	// Options passed to syscall.Mount, the default value used by fusermount
 	// is syscall.MS_NOSUID|syscall.MS_NODEV
 	DirectMountFlags uintptr
+
+	// Number of pages to request.  If less than 32, use default (i.e. 32). This number is
+	// capped at the kernel maximum i.e. 256.
+	MaxPages uint16
 }
 
 // RawFileSystem is an interface close to the FUSE wire protocol.

fuse/opcode.go

@@ -130,6 +130,17 @@ func doInit(server *Server, req *request) {
 		out.Minor = input.Minor
 	}
 
+	if (input.Flags & CAP_MAX_PAGES) == CAP_MAX_PAGES {
+		out.Flags |= CAP_MAX_PAGES
+		if server.opts.MaxPages < 32 {
+			out.MaxPages = 32 // The minimum allowed by the kernel
+		} else if server.opts.MaxPages > 256 {
+			out.MaxPages = 256 // The maximum allowed by the kernel
+		} else {
+			out.MaxPages = server.opts.MaxPages
+		}
+	}
+
 	if out.Minor <= 22 {
 		tweaked := *req.handler
 

fuse/server.go

@@ -19,8 +19,8 @@ import (
 )
 
 const (
-	// The kernel caps writes at 128k.
-	MAX_KERNEL_WRITE = 128 * 1024
+	// The kernel caps writes at 1 MiB (from 4.20+).
+	MAX_KERNEL_WRITE = 1 * 1024 * 1024
 )
 
 // Server contains the logic for reading from the FUSE device and