support read-only mode (#520)

* support read-only mode

* fix build and update docs

* fix json tag

cmd/gateway.go

@@ -143,8 +143,9 @@ func (g *GateWay) NewGatewayLayer(creds auth.Credentials) (minio.ObjectLayer, er
 	c := g.ctx
 	addr := c.Args().Get(0)
 	m := meta.NewClient(addr, &meta.Config{
-		Retries: 10,
-		Strict:  true,
+		Retries:  10,
+		Strict:   true,
+		ReadOnly: c.Bool("read-only"),
 	})
 	format, err := m.Load()
 	if err != nil {

cmd/mount.go

@@ -84,10 +84,17 @@ func mount(c *cli.Context) error {
 			logger.Fatalf("create %s: %s", mp, err)
 		}
 	}
+	var readOnly = c.Bool("read-only")
+	for _, o := range strings.Split(c.String("o"), ",") {
+		if o == "ro" {
+			readOnly = true
+		}
+	}
 	m := meta.NewClient(addr, &meta.Config{
 		Retries:     10,
 		Strict:      true,
 		CaseInsensi: strings.HasSuffix(mp, ":") && runtime.GOOS == "windows",
+		ReadOnly:    readOnly,
 		MountPoint:  mp,
 	})
 	format, err := m.Load()

cmd/mount_unix.go

@@ -109,6 +109,10 @@ func mount_flags() []cli.Flag {
 			Name:  "enable-xattr",
 			Usage: "enable extended attributes (xattr)",
 		},
+		&cli.BoolFlag{
+			Name:  "read-only",
+			Usage: "allow lookup/read operations only",
+		},
 	}
 }
 

docs/en/command_reference.md

@@ -143,6 +143,9 @@ dir entry cache timeout in seconds (default: 1)
 `--enable-xattr`\
 enable extended attributes (xattr) (default: false)
 
+`--read-only`\
+allow lookup/read operations only (default: false)
+
 `--get-timeout value`\
 the max number of seconds to download an object (default: 60)
 

docs/zh_cn/command_reference.md

@@ -145,6 +145,9 @@ dir entry cache timeout in seconds (default: 1)
 `--enable-xattr`\
 enable extended attributes (xattr) (default: false)
 
+`--read-only`\
+allow lookup/read operations only (default: false)
+
 `--get-timeout value`\
 the max number of seconds to download an object (default: 60)
 

pkg/fs/fs.go

@@ -263,7 +263,13 @@ func (fs *FileSystem) Open(ctx meta.Context, path string, flags uint32) (f *File
 			if err != 0 {
 				return nil, err
 			}
-			err = fs.m.Open(ctx, fi.inode, uint8(flags), nil)
+			var oflags uint32 = syscall.O_RDONLY
+			if flags == vfs.MODE_MASK_W {
+				oflags = syscall.O_WRONLY
+			} else if flags&vfs.MODE_MASK_W != 0 {
+				oflags = syscall.O_RDWR
+			}
+			err = fs.m.Open(ctx, fi.inode, oflags, nil)
 			if err != 0 {
 				return
 			}

pkg/meta/config.go

@@ -20,6 +20,7 @@ type Config struct {
 	Strict      bool // update ctime
 	Retries     int
 	CaseInsensi bool
+	ReadOnly    bool
 	MountPoint  string
 }
 

pkg/meta/interface.go

@@ -265,7 +265,7 @@ type Meta interface {
 	// Create creates a file in a directory with given name.
 	Create(ctx Context, parent Ino, name string, mode uint16, cumask uint16, inode *Ino, attr *Attr) syscall.Errno
 	// Open checks permission on a node and track it as open.
-	Open(ctx Context, inode Ino, flags uint8, attr *Attr) syscall.Errno
+	Open(ctx Context, inode Ino, flags uint32, attr *Attr) syscall.Errno
 	// Close a file.
 	Close(ctx Context, inode Ino) syscall.Errno
 	// Read returns the list of slices on the given chunk.

pkg/meta/redis.go

@@ -243,6 +243,9 @@ func (r *redisMeta) Load() (*Format, error) {
 }
 
 func (r *redisMeta) NewSession() error {
+	if r.conf.ReadOnly {
+		return nil
+	}
 	var err error
 	r.sid, err = r.rdb.Incr(Background, "nextsession").Result()
 	if err != nil {
@@ -852,6 +855,9 @@ func shouldRetry(err error, retryOnFailure bool) bool {
 }
 
 func (r *redisMeta) txn(ctx Context, txf func(tx *redis.Tx) error, keys ...string) syscall.Errno {
+	if r.conf.ReadOnly {
+		return syscall.EROFS
+	}
 	var err error
 	var khash = fnv.New32()
 	_, _ = khash.Write([]byte(keys[0]))
@@ -1902,11 +1908,14 @@ func (r *redisMeta) deleteInode(inode Ino) error {
 	return err
 }
 
-func (r *redisMeta) Open(ctx Context, inode Ino, flags uint8, attr *Attr) syscall.Errno {
+func (r *redisMeta) Open(ctx Context, inode Ino, flags uint32, attr *Attr) syscall.Errno {
 	var err syscall.Errno
 	if attr != nil {
 		err = r.GetAttr(ctx, inode, attr)
 	}
+	if r.conf.ReadOnly && flags&(syscall.O_WRONLY|syscall.O_RDWR|syscall.O_TRUNC|syscall.O_APPEND) != 0 {
+		return syscall.EROFS
+	}
 	if err == 0 {
 		r.Lock()
 		r.openFiles[inode] = r.openFiles[inode] + 1
@@ -1965,7 +1974,7 @@ func (r *redisMeta) Read(ctx Context, inode Ino, indx uint32, chunks *[]Slice) s
 	}
 	ss := readSlices(vals)
 	*chunks = buildSlice(ss)
-	if len(vals) >= 5 || len(*chunks) >= 5 {
+	if !r.conf.ReadOnly && (len(vals) >= 5 || len(*chunks) >= 5) {
 		go r.compactChunk(inode, indx, false)
 	}
 	return 0

pkg/meta/sql.go

@@ -285,6 +285,9 @@ func (m *dbMeta) NewSession() error {
 	if err := m.engine.Sync2(new(session)); err != nil { // old client has no info field
 		return err
 	}
+	if m.conf.ReadOnly {
+		return nil
+	}
 	v, err := m.incrCounter("nextSession", 1)
 	if err != nil {
 		return fmt.Errorf("create session: %s", err)
@@ -484,6 +487,9 @@ func (m *dbMeta) shouldRetry(err error) bool {
 }
 
 func (m *dbMeta) txn(f func(s *xorm.Session) error) error {
+	if m.conf.ReadOnly {
+		return syscall.EROFS
+	}
 	start := time.Now()
 	defer func() { txDist.Observe(time.Since(start).Seconds()) }()
 	var err error
@@ -1665,11 +1671,14 @@ func (m *dbMeta) deleteInode(inode Ino) error {
 	return err
 }
 
-func (m *dbMeta) Open(ctx Context, inode Ino, flags uint8, attr *Attr) syscall.Errno {
+func (m *dbMeta) Open(ctx Context, inode Ino, flags uint32, attr *Attr) syscall.Errno {
 	var err syscall.Errno
 	if attr != nil {
 		err = m.GetAttr(ctx, inode, attr)
 	}
+	if m.conf.ReadOnly && flags&(syscall.O_WRONLY|syscall.O_RDWR|syscall.O_TRUNC|syscall.O_APPEND) != 0 {
+		return syscall.EROFS
+	}
 	if err == 0 {
 		m.Lock()
 		m.openFiles[inode] = m.openFiles[inode] + 1
@@ -1709,7 +1718,7 @@ func (m *dbMeta) Read(ctx Context, inode Ino, indx uint32, chunks *[]Slice) sysc
 	}
 	ss := readSliceBuf(c.Slices)
 	*chunks = buildSlice(ss)
-	if len(c.Slices)/sliceBytes >= 5 || len(*chunks) >= 5 {
+	if !m.conf.ReadOnly && (len(c.Slices)/sliceBytes >= 5 || len(*chunks) >= 5) {
 		go m.compactChunk(inode, indx, false)
 	}
 	return 0

pkg/vfs/fill.go

@@ -94,7 +94,7 @@ func resolve(p string, inode *Ino, attr *Attr) syscall.Errno {
 			break
 		}
 		if i > 0 {
-			if err = m.Access(ctx, parent, 1, attr); err != 0 {
+			if err = m.Access(ctx, parent, MODE_MASK_R|MODE_MASK_X, attr); err != 0 {
 				return err
 			}
 		}

pkg/vfs/helpers.go

@@ -23,6 +23,12 @@ import (
 	"github.com/juicedata/juicefs/pkg/meta"
 )
 
+const (
+	MODE_MASK_R = 4
+	MODE_MASK_W = 2
+	MODE_MASK_X = 1
+)
+
 func strerr(errno syscall.Errno) string {
 	if errno == 0 {
 		return "OK"

pkg/vfs/vfs.go

@@ -412,7 +412,7 @@ func Open(ctx Context, ino Ino, flags uint32) (entry *meta.Entry, fh uint64, err
 		return
 	}
 
-	err = m.Open(ctx, ino, uint8(flags), attr)
+	err = m.Open(ctx, ino, flags, attr)
 	if err != 0 {
 		return
 	}

pkg/vfs/vfs_unix.go

@@ -31,12 +31,6 @@ import (
 const O_ACCMODE = syscall.O_ACCMODE
 const F_UNLCK = syscall.F_UNLCK
 
-const (
-	MODE_MASK_R = 4
-	MODE_MASK_W = 2
-	MODE_MASK_X = 1
-)
-
 type Statfs struct {
 	Bsize  uint32
 	Blocks uint64

sdk/java/libjfs/main.go

@@ -214,6 +214,7 @@ func freeHandle(fd int) {
 
 type javaConf struct {
 	MetaURL        string `json:"meta"`
+	ReadOnly       bool   `json:"readOnly"`
 	CacheDir       string `json:"cacheDir"`
 	CacheSize      int64  `json:"cacheSize"`
 	FreeSpace      string `json:"freeSpace"`
@@ -313,7 +314,7 @@ func jfs_init(cname, jsonConf, user, group, superuser, supergroup *C.char) uintp
 		utils.InitLoggers(false)
 
 		addr := jConf.MetaURL
-		m := meta.NewClient(addr, &meta.Config{Retries: 10, Strict: true})
+		m := meta.NewClient(addr, &meta.Config{Retries: 10, Strict: true, ReadOnly: jConf.ReadOnly})
 		format, err := m.Load()
 		if err != nil {
 			logger.Fatalf("load setting: %s", err)

sdk/java/src/main/java/io/juicefs/JuiceFileSystemImpl.java

@@ -310,6 +310,7 @@ public class JuiceFileSystemImpl extends FileSystem {
     for (String key : bkeys) {
       obj.put(key, Boolean.valueOf(getConf(conf, key, "false")));
     }
+    obj.put("readOnly", Boolean.valueOf(getConf(conf, "read-only", "false")));
     obj.put("cacheDir", getConf(conf, "cache-dir", "memory"));
     obj.put("cacheSize", Integer.valueOf(getConf(conf, "cache-size", "100")));
     obj.put("cacheFullBlock", Boolean.valueOf(getConf(conf, "cache-full-block", "true")));