vfs: allows ftruncate to open a file even if it has been deleted (#5664)

cmd/mount_test.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -27,6 +28,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"syscall"
 	"testing"
 	"time"
 
@@ -167,6 +169,44 @@ func TestMount(t *testing.T) {
 	}
 }
 
+func TestFtruncate(t *testing.T) {
+	mountTemp(t, nil, nil, nil)
+	defer umountTemp(t)
+
+	fpath := fmt.Sprintf("%s/f1.txt", testMountPoint)
+	if err := os.WriteFile(fpath, []byte("test"), 0644); err != nil {
+		t.Fatalf("write file failed: %s", err)
+	}
+	file, err := os.OpenFile(fpath, os.O_RDWR, 0644)
+	if err != nil {
+		t.Fatalf("open file failed: %s", err)
+	}
+	if err = syscall.Ftruncate(int(file.Fd()), 1024); err != nil {
+		t.Fatalf("ftruncate failed: %s", err)
+	}
+	fileInfo, err := os.Stat(fpath)
+	if err != nil {
+		t.Fatalf("stat file failed: %s", err)
+	}
+	if fileInfo.Size() != 1024 {
+		t.Fatalf("ftruncate failed: file size is %d, expect 1024", fileInfo.Size())
+	}
+	if err = os.Remove(fpath); err != nil {
+		t.Fatalf("remove file failed: %s", err)
+	}
+	if _, err = os.Stat(fpath); !errors.Is(err, syscall.ENOENT) {
+		t.Fatalf("file still exists after delete: %s", err)
+	}
+	err = syscall.Ftruncate(int(file.Fd()), 2048)
+	if err != nil {
+		t.Fatalf("ftruncate failed: %s", err)
+	}
+	file.Close()
+	_, err = os.Stat(fpath)
+	if !errors.Is(err, syscall.ENOENT) {
+		t.Fatalf("file still exists after close: %s", err)
+	}
+}
 func TestUpdateFstab(t *testing.T) {
 	if runtime.GOOS != "linux" {
 		t.SkipNow()

pkg/meta/interface.go

@@ -89,6 +89,7 @@ const (
 	SetAttrCtime
 	SetAttrAtimeNow
 	SetAttrMtimeNow
+	SetAttrCtimeNow
 	SetAttrFlag = 1 << 15
 )
 

pkg/meta/redis.go

@@ -1041,7 +1041,7 @@ func (m *redisMeta) doTruncate(ctx Context, inode Ino, flags uint8, length uint6
 			return err
 		}
 		m.parseAttr(a, &t)
-		if t.Typ != TypeFile || t.Flags&(FlagImmutable|FlagAppend) != 0 || t.Parent > TrashInode {
+		if t.Typ != TypeFile || t.Flags&(FlagImmutable|FlagAppend) != 0 || (flags == 0 && t.Parent > TrashInode) {
 			return syscall.EPERM
 		}
 		if !skipPermCheck {

pkg/meta/sql.go

@@ -1280,7 +1280,7 @@ func (m *dbMeta) doTruncate(ctx Context, inode Ino, flags uint8, length uint64,
 		if !ok {
 			return syscall.ENOENT
 		}
-		if nodeAttr.Type != TypeFile || nodeAttr.Flags&(FlagImmutable|FlagAppend) != 0 || nodeAttr.Parent > TrashInode {
+		if nodeAttr.Type != TypeFile || nodeAttr.Flags&(FlagImmutable|FlagAppend) != 0 || (flags == 0 && nodeAttr.Parent > TrashInode) {
 			return syscall.EPERM
 		}
 		m.parseAttr(&nodeAttr, attr)

pkg/meta/tkv.go

@@ -963,7 +963,7 @@ func (m *kvMeta) doTruncate(ctx Context, inode Ino, flags uint8, length uint64,
 		}
 		t := Attr{}
 		m.parseAttr(a, &t)
-		if t.Typ != TypeFile || t.Flags&(FlagImmutable|t.Flags&FlagAppend) != 0 || t.Parent > TrashInode {
+		if t.Typ != TypeFile || t.Flags&(FlagImmutable|t.Flags&FlagAppend) != 0 || (flags == 0 && t.Parent > TrashInode) {
 			return syscall.EPERM
 		}
 		if !skipPermCheck {

pkg/vfs/vfs.go

@@ -615,7 +615,8 @@ func (v *VFS) Truncate(ctx Context, ino Ino, size int64, fh uint64, attr *Attr)
 			err = syscall.EACCES
 			return
 		}
-		err = v.Meta.Truncate(ctx, ino, 0, uint64(size), attr, true)
+		// flags = 1 means the file is opened, so we don't need to check if it's in the trash
+		err = v.Meta.Truncate(ctx, ino, 1, uint64(size), attr, true)
 	}
 	if err == 0 {
 		v.writer.Truncate(ino, uint64(size))

pkg/vfs/vfs_unix.go

@@ -155,13 +155,17 @@ func (v *VFS) SetAttr(ctx Context, ino Ino, set int, fh uint64, mode, uid, gid u
 		}
 		return
 	}
-	err = syscall.EINVAL
 	var attr = &Attr{}
 	if set&meta.SetAttrSize != 0 {
 		err = v.Truncate(ctx, ino, int64(size), fh, attr)
 		if err != 0 {
 			return
 		}
+		if (set &^ (meta.SetAttrSize | meta.SetAttrCtime | meta.SetAttrCtimeNow)) == 0 {
+			v.UpdateLength(ino, attr)
+			entry = &meta.Entry{Inode: ino, Attr: attr}
+			return
+		}
 	}
 	if set&meta.SetAttrMode != 0 {
 		attr.Mode = uint16(mode & 07777)