fuse: add pollhack that compiles on Darwin too

fuse/poll.go

+package fuse
+
+// Go 1.9 introduces polling for file I/O. The implementation causes
+// the runtime's epoll to take up the last GOMAXPROCS slot, and if
+// that happens, we won't have any threads left to service FUSE's
+// _OP_POLL request. Prevent this by forcing _OP_POLL to happen, so we
+// can say ENOSYS and prevent further _OP_POLL requests.
+const pollHackName = ".go-fuse-epoll-hack"
+const pollHackInode = ^uint64(0)

fuse/poll_darwin.go

+package fuse
+
+import (
+	"path/filepath"
+	"syscall"
+	"unsafe"
+)
+
+type pollFd struct {
+	Fd      int32
+	Events  int16
+	Revents int16
+}
+
+func sysPoll(fds []pollFd, timeout int) (n int, err error) {
+	r0, _, e1 := syscall.Syscall(syscall.SYS_POLL, uintptr(unsafe.Pointer(&fds[0])),
+		uintptr(len(fds)), uintptr(timeout))
+	n = int(r0)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return n, err
+}
+
+func pollHack(mountPoint string) error {
+	const (
+		POLLIN    = 0x1
+		POLLPRI   = 0x2
+		POLLOUT   = 0x4
+		POLLRDHUP = 0x2000
+		POLLERR   = 0x8
+		POLLHUP   = 0x10
+	)
+
+	fd, err := syscall.Open(filepath.Join(mountPoint, pollHackName), syscall.O_CREAT|syscall.O_TRUNC|syscall.O_RDWR, 0644)
+	if err != nil {
+		return err
+	}
+	pollData := []pollFd{{
+		Fd:     int32(fd),
+		Events: POLLIN | POLLPRI | POLLOUT,
+	}}
+
+	// Trigger _OP_POLL, so we can say ENOSYS. We don't care about
+	// the return value.
+	sysPoll(pollData, 0)
+	syscall.Close(fd)
+	return nil
+}

fuse/poll_linux.go

+package fuse
+
+import (
+	"path/filepath"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+func pollHack(mountPoint string) error {
+	fd, err := syscall.Creat(filepath.Join(mountPoint, pollHackName), syscall.O_CREAT)
+	if err != nil {
+		return err
+	}
+	pollData := []unix.PollFd{{
+		Fd:     int32(fd),
+		Events: unix.POLLIN | unix.POLLPRI | unix.POLLOUT,
+	}}
+
+	// Trigger _OP_POLL, so we can say ENOSYS. We don't care about
+	// the return value.
+	unix.Poll(pollData, 0)
+	syscall.Close(fd)
+	return nil
+}

fuse/server.go

@@ -15,8 +15,6 @@ import (
 	"syscall"
 	"time"
 	"unsafe"
-
-	"golang.org/x/sys/unix"
 )
 
 const (
@@ -57,9 +55,6 @@ type Server struct {
 	ready chan error
 }
 
-const pollHackName = ".go-fuse-epoll-hack"
-const pollHackInode = ^uint64(0)
-
 // SetDebug is deprecated. Use MountOptions.Debug instead.
 func (ms *Server) SetDebug(dbg bool) {
 	// This will typically trigger the race detector.
@@ -598,25 +593,3 @@ func (ms *Server) WaitMount() error {
 	}
 	return pollHack(ms.mountPoint)
 }
-
-// Go 1.9 introduces polling for file I/O. The implementation causes
-// the runtime's epoll to take up the last GOMAXPROCS slot, and if
-// that happens, we won't have any threads left to service FUSE's
-// _OP_POLL request. Prevent this by forcing _OP_POLL to happen, so we
-// can say ENOSYS and prevent further _OP_POLL requests.
-func pollHack(mountPoint string) error {
-	fd, err := syscall.Creat(filepath.Join(mountPoint, pollHackName), syscall.O_CREAT)
-	if err != nil {
-		return err
-	}
-	pollData := []unix.PollFd{{
-		Fd:     int32(fd),
-		Events: unix.POLLIN | unix.POLLPRI | unix.POLLOUT,
-	}}
-
-	// Trigger _OP_POLL, so we can say ENOSYS. We don't care about
-	// the return value.
-	unix.Poll(pollData, 0)
-	syscall.Close(fd)
-	return nil
-}