fuse: check mount point available before do runmount

1. Use more readable mount point information
2. Fix some typos

eg:

$ df -Th
Filesystem              Type            Size  Used Avail Use% Mounted on
localhost:8888:/        fuse.seaweedfs  206G   512  206G   1% /mnt/weedfs

$ mount | grep weedfs
localhost:8888:/ on /mnt/weedfs type fuse.seaweedfs (rw,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other)

Signed-off-by: Lei Liu <lei01.liu@horizon.ai>

weed/command/mount_darwin.go

@@ -7,3 +7,7 @@ import (
 func osSpecificMountOptions() []fuse.MountOption {
 	return []fuse.MountOption{}
 }
+
+func checkMountPointAvailable(dir string) bool {
+	return true
+}

weed/command/mount_freebsd.go

@@ -7,3 +7,7 @@ import (
 func osSpecificMountOptions() []fuse.MountOption {
 	return []fuse.MountOption{}
 }
+
+func checkMountPointAvailable(dir string) bool {
+	return true
+}

weed/command/mount_linux.go

@@ -1,6 +1,7 @@
 package command
 
 import (
+	"github.com/chrislusf/seaweedfs/weed/util"
 	"github.com/seaweedfs/fuse"
 )
 
@@ -9,3 +10,16 @@ func osSpecificMountOptions() []fuse.MountOption {
 		fuse.AllowNonEmptyMount(),
 	}
 }
+
+func checkMountPointAvailable(dir string) bool {
+	mountPoint := dir
+	if mountPoint != "/" && strings.HasSuffix(mountPoint, "/") {
+		mountPoint = mountPoint[0 : len(mountPoint)-1]
+	}
+
+	if mounted, err := util.Mounted(mountPoint); err != nil || mounted {
+		return false
+	}
+
+	return true
+}

weed/command/mount_std.go

@@ -12,15 +12,14 @@ import (
 	"strings"
 	"time"
 
-	"github.com/chrislusf/seaweedfs/weed/security"
-	"github.com/jacobsa/daemonize"
-	"github.com/spf13/viper"
-
 	"github.com/chrislusf/seaweedfs/weed/filesys"
 	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/security"
 	"github.com/chrislusf/seaweedfs/weed/util"
+	"github.com/jacobsa/daemonize"
 	"github.com/seaweedfs/fuse"
 	"github.com/seaweedfs/fuse/fs"
+	"github.com/spf13/viper"
 )
 
 func runMount(cmd *Command, args []string) bool {
@@ -88,12 +87,17 @@ func RunMount(filer, filerMountRootPath, dir, collection, replication, dataCente
 		}
 	}
 
+	if isValid := checkMountPointAvailable(dir); !isValid {
+		glog.Fatalf("Expected mount to still be active, target mount point: %s, please check!", dir)
+		return false
+	}
+
 	mountName := path.Base(dir)
 
 	options := []fuse.MountOption{
 		fuse.VolumeName(mountName),
-		fuse.FSName("SeaweedFS"),
-		fuse.Subtype("SeaweedFS"),
+		fuse.FSName(filer + ":" + filerMountRootPath),
+		fuse.Subtype("seaweedfs"),
 		fuse.NoAppleDouble(),
 		fuse.NoAppleXattr(),
 		fuse.NoBrowse(),

weed/util/mount.go

@@ -0,0 +1,136 @@
+package util
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+const (
+	/* 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+	   (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+
+	   (1) mount ID:  unique identifier of the mount (may be reused after umount)
+	   (2) parent ID:  ID of parent (or of self for the top of the mount tree)
+	   (3) major:minor:  value of st_dev for files on filesystem
+	   (4) root:  root of the mount within the filesystem
+	   (5) mount point:  mount point relative to the process's root
+	   (6) mount options:  per mount options
+	   (7) optional fields:  zero or more fields of the form "tag[:value]"
+	   (8) separator:  marks the end of the optional fields
+	   (9) filesystem type:  name of filesystem of the form "type[.subtype]"
+	   (10) mount source:  filesystem specific information or "none"
+	   (11) super options:  per super block options*/
+	mountinfoFormat = "%d %d %d:%d %s %s %s %s"
+)
+
+// Info reveals information about a particular mounted filesystem. This
+// struct is populated from the content in the /proc/<pid>/mountinfo file.
+type Info struct {
+	// ID is a unique identifier of the mount (may be reused after umount).
+	ID int
+
+	// Parent indicates the ID of the mount parent (or of self for the top of the
+	// mount tree).
+	Parent int
+
+	// Major indicates one half of the device ID which identifies the device class.
+	Major int
+
+	// Minor indicates one half of the device ID which identifies a specific
+	// instance of device.
+	Minor int
+
+	// Root of the mount within the filesystem.
+	Root string
+
+	// Mountpoint indicates the mount point relative to the process's root.
+	Mountpoint string
+
+	// Opts represents mount-specific options.
+	Opts string
+
+	// Optional represents optional fields.
+	Optional string
+
+	// Fstype indicates the type of filesystem, such as EXT3.
+	Fstype string
+
+	// Source indicates filesystem specific information or "none".
+	Source string
+
+	// VfsOpts represents per super block options.
+	VfsOpts string
+}
+
+// Mounted determines if a specified mountpoint has been mounted.
+// On Linux it looks at /proc/self/mountinfo and on Solaris at mnttab.
+func Mounted(mountpoint string) (bool, error) {
+	entries, err := parseMountTable()
+	if err != nil {
+		return false, err
+	}
+
+	// Search the table for the mountpoint
+	for _, e := range entries {
+		if e.Mountpoint == mountpoint {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// Parse /proc/self/mountinfo because comparing Dev and ino does not work from
+// bind mounts
+func parseMountTable() ([]*Info, error) {
+	f, err := os.Open("/proc/self/mountinfo")
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	return parseInfoFile(f)
+}
+
+func parseInfoFile(r io.Reader) ([]*Info, error) {
+	var (
+		s   = bufio.NewScanner(r)
+		out = []*Info{}
+	)
+
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+
+		var (
+			p              = &Info{}
+			text           = s.Text()
+			optionalFields string
+		)
+
+		if _, err := fmt.Sscanf(text, mountinfoFormat,
+			&p.ID, &p.Parent, &p.Major, &p.Minor,
+			&p.Root, &p.Mountpoint, &p.Opts, &optionalFields); err != nil {
+			return nil, fmt.Errorf("Scanning '%s' failed: %s", text, err)
+		}
+		// Safe as mountinfo encodes mountpoints with spaces as \040.
+		index := strings.Index(text, " - ")
+		postSeparatorFields := strings.Fields(text[index+3:])
+		if len(postSeparatorFields) < 3 {
+			return nil, fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
+		}
+
+		if optionalFields != "-" {
+			p.Optional = optionalFields
+		}
+
+		p.Fstype = postSeparatorFields[0]
+		p.Source = postSeparatorFields[1]
+		p.VfsOpts = strings.Join(postSeparatorFields[2:], " ")
+		out = append(out, p)
+	}
+	return out, nil
+}