Ensure `weed fuse` master process exits after mounted (#6809)

* Ensure fuse master process wait for mounted

* Validate parent PID input in fuse command

weed/command/fuse.go

@@ -2,9 +2,12 @@ package command
 
 import (
 	"fmt"
+	"math"
 	"os"
+	"os/signal"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 )
 
@@ -105,6 +108,14 @@ func runFuse(cmd *Command, args []string) bool {
 		switch parameter.name {
 		case "child":
 			masterProcess = false
+			if parsed, err := strconv.ParseInt(parameter.value, 10, 64); err == nil {
+				if parsed > math.MaxInt || parsed <= 0 {
+					panic(fmt.Errorf("parent PID %s is invalid", err))
+				}
+				mountOptions.fuseCommandPid = int(parsed)
+			} else {
+				panic(fmt.Errorf("parent PID %s is invalid", err))
+			}
 		case "arg0":
 			mountOptions.dir = &parameter.value
 		case "filer":
@@ -211,7 +222,12 @@ func runFuse(cmd *Command, args []string) bool {
 			panic(err)
 		}
 
-		argv := append(os.Args, "-o", "child")
+		// pass our PID to the child process
+		pid := os.Getpid()
+		argv := append(os.Args, "-o", "child="+strconv.Itoa(pid))
+
+		c := make(chan os.Signal, 1)
+		signal.Notify(c, syscall.SIGUSR1)
 
 		attr := os.ProcAttr{}
 		attr.Env = os.Environ()
@@ -228,8 +244,11 @@ func runFuse(cmd *Command, args []string) bool {
 			panic(fmt.Errorf("master process can not release child process: %s", err))
 		}
 
+		select {
+		case <-c:
 			return true
 		}
+	}
 
 	if fusermountPath != "" {
 		if err := os.Setenv("PATH", fusermountPath); err != nil {

weed/command/mount.go

@@ -34,6 +34,7 @@ type MountOptions struct {
 	localSocket        *string
 	disableXAttr       *bool
 	extraOptions       []string
+	fuseCommandPid     int
 }
 
 var (
@@ -72,6 +73,7 @@ func init() {
 	mountOptions.debugPort = cmdMount.Flag.Int("debug.port", 6061, "http port for debugging")
 	mountOptions.localSocket = cmdMount.Flag.String("localSocket", "", "default to /tmp/seaweedfs-mount-<mount_dir_hash>.sock")
 	mountOptions.disableXAttr = cmdMount.Flag.Bool("disableXAttr", false, "disable xattr")
+	mountOptions.fuseCommandPid = 0
 
 	mountCpuProfile = cmdMount.Flag.String("cpuprofile", "", "cpu profile output file")
 	mountMemProfile = cmdMount.Flag.String("memprofile", "", "memory profile output file")

weed/command/mount_std.go

@@ -13,6 +13,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
 	"github.com/hanwen/go-fuse/v2/fuse"
@@ -268,6 +269,15 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		unmount.Unmount(dir)
 	})
 
+	if mountOptions.fuseCommandPid != 0 {
+		// send a signal to the parent process to notify that the mount is ready
+		err = syscall.Kill(mountOptions.fuseCommandPid, syscall.SIGUSR1)
+		if err != nil {
+			fmt.Printf("failed to notify parent process: %v\n", err)
+			return false
+		}
+	}
+
 	grpcS := pb.NewGrpcServer()
 	mount_pb.RegisterSeaweedMountServer(grpcS, seaweedFileSystem)
 	reflection.Register(grpcS)