backport of https://github.com/majestrate/XD/commit/4ce9d0ac14a84fcc8a419b46b996de984b1fce79

diff --git a/src/xd/lib/fs/std.go b/src/xd/lib/fs/std.go
index 2e2c9f8..76615b2 100644
--- a/src/xd/lib/fs/std.go
+++ b/src/xd/lib/fs/std.go
@@ -39,7 +39,7 @@ func (f stdFs) OpenFileReadOnly(fname string) (ReadFile, error) {
 }
 
 func (f stdFs) OpenFileWriteOnly(fname string) (WriteFile, error) {
-	return os.OpenFile(fname, os.O_CREATE|os.O_WRONLY, 0600)
+	return os.OpenFile(fname, os.O_WRONLY|os.O_CREATE, 0755)
 }
 
 func (f stdFs) RemoveAll(fname string) error {
diff --git a/src/xd/lib/mktorrent/mktorrent.go b/src/xd/lib/mktorrent/mktorrent.go
index b6a58f7..a7dcaca 100644
--- a/src/xd/lib/mktorrent/mktorrent.go
+++ b/src/xd/lib/mktorrent/mktorrent.go
@@ -26,10 +26,12 @@ func mkTorrentSingle(f fs.Driver, fpath string, pieceLength uint32) (*metainfo.T
 			err = nil
 			d := sha1.Sum(buff[0:n])
 			info.Pieces = append(info.Pieces, d[:]...)
+			info.Length += uint64(n)
 			break
 		} else if err == nil {
 			d := sha1.Sum(buff)
 			info.Pieces = append(info.Pieces, d[:]...)
+			info.Length += uint64(n)
 		} else {
 			return nil, err
 		}
diff --git a/src/xd/lib/storage/fs.go b/src/xd/lib/storage/fs.go
index fbe8e91..cd6c630 100644
--- a/src/xd/lib/storage/fs.go
+++ b/src/xd/lib/storage/fs.go
@@ -100,7 +100,7 @@ func (t *fsTorrent) Allocate() (err error) {
 	return
 }
 
-func (t fsTorrent) openfileRead(i metainfo.FileInfo) (f fs.ReadFile, err error) {
+func (t *fsTorrent) openfileRead(i metainfo.FileInfo) (f fs.ReadFile, err error) {
 	var fname string
 	if t.meta.IsSingleFile() {
 		fname = t.FilePath()
@@ -111,7 +111,7 @@ func (t fsTorrent) openfileRead(i metainfo.FileInfo) (f fs.ReadFile, err error)
 	return
 }
 
-func (t fsTorrent) openfileWrite(i metainfo.FileInfo) (f fs.WriteFile, err error) {
+func (t *fsTorrent) openfileWrite(i metainfo.FileInfo) (f fs.WriteFile, err error) {
 	var fname string
 	if t.meta.IsSingleFile() {
 		fname = t.FilePath()
@@ -122,7 +122,7 @@ func (t fsTorrent) openfileWrite(i metainfo.FileInfo) (f fs.WriteFile, err error
 	return
 }
 
-func (t fsTorrent) readFileAt(fi metainfo.FileInfo, b []byte, off int64) (n int, err error) {
+func (t *fsTorrent) readFileAt(fi metainfo.FileInfo, b []byte, off int64) (n int, err error) {
 
 	// from github.com/anacrolix/torrent
 	var f fs.ReadFile
@@ -149,6 +149,7 @@ func (t fsTorrent) readFileAt(fi metainfo.FileInfo, b []byte, off int64) (n int,
 }
 
 func (t *fsTorrent) ReadAt(b []byte, off int64) (n int, err error) {
+	l := len(b)
 	files := t.meta.Info.GetFiles()
 	// from github.com/anacrolix/torrent
 	for _, fi := range files {
@@ -158,6 +159,7 @@ func (t *fsTorrent) ReadAt(b []byte, off int64) (n int, err error) {
 			n += n1
 			off += int64(n1)
 			b = b[n1:]
+
 			if len(b) == 0 {
 				// Got what we need.
 				return
@@ -299,9 +301,8 @@ func (t *fsTorrent) GetPiece(r common.PieceRequest, pc *common.PieceData) (err e
 	t.access.Lock()
 	sz := t.meta.Info.PieceLength
 	offset := int64(r.Begin) + (int64(sz) * int64(r.Index))
-	if pc.Data == nil || uint32(len(pc.Data)) != r.Length {
-		pc.Data = make([]byte, r.Length)
-	}
+	pc.Data = make([]byte, r.Length)
+	log.Debugf("get piece %d offset=%d len=%d", r.Index, r.Begin, r.Length)
 	if t.st.pooledIO() {
 		iop := readIOP{
 			offset:    offset,
@@ -324,20 +325,17 @@ func (t *fsTorrent) GetPiece(r common.PieceRequest, pc *common.PieceData) (err e
 }
 
 func (t *fsTorrent) VerifyPiece(idx uint32) (err error) {
-	var pc common.PieceData
-	err = t.verifyPiece(idx, &pc)
-	return
-}
-
-func (t *fsTorrent) verifyPiece(idx uint32, pc *common.PieceData) (err error) {
 	l := t.meta.LengthOfPiece(idx)
 	r := common.PieceRequest{
 		Index:  idx,
 		Length: l,
 	}
-	err = t.GetPiece(r, pc)
+	var pc common.PieceData
+	pc.Data = make([]byte, l)
+	pc.Index = idx
+	err = t.GetPiece(r, &pc)
 	if err == nil {
-		if t.meta.Info.CheckPiece(pc) {
+		if t.meta.Info.CheckPiece(&pc) {
 			t.bf.Set(pc.Index)
 		} else {
 			t.bf.Unset(pc.Index)
@@ -352,18 +350,15 @@ func (t *fsTorrent) VerifyAll() (err error) {
 		err = ErrNoMetaInfo
 		return
 	}
-	var pc common.PieceData
 	t.bfmtx.Lock()
 	t.checking = true
 	log.Infof("checking local data for %s", t.Name())
 	t.ensureBitfield()
 	info := t.MetaInfo().Info
 	sz := info.NumPieces()
-	pc.Data = make([]byte, info.PieceLength)
 	idx := uint32(0)
 	for idx < sz {
-		t := t
-		err = t.verifyPiece(uint32(idx), &pc)
+		err = t.VerifyPiece(uint32(idx))
 		if err == common.ErrInvalidPiece {
 			err = nil
 		} else if err != nil {
diff --git a/src/xd/lib/storage/storage_test.go b/src/xd/lib/storage/storage_test.go
index 1f57421..12339c3 100644
--- a/src/xd/lib/storage/storage_test.go
+++ b/src/xd/lib/storage/storage_test.go
@@ -6,6 +6,7 @@ import (
 	"testing"
 	"xd/lib/common"
 	"xd/lib/fs"
+	"xd/lib/log"
 	"xd/lib/metainfo"
 	"xd/lib/mktorrent"
 )
@@ -26,6 +27,8 @@ func createRandomTorrent(testFname string) (*metainfo.TorrentFile, error) {
 
 func TestStorage(t *testing.T) {
 
+	log.SetLevel("debug")
+
 	st := &FsStorage{
 		MetaDir:    "storage",
 		DataDir:    "data",
@@ -61,24 +64,30 @@ func TestStorage(t *testing.T) {
 	}
 	var pc common.PieceData
 	err = torrent.GetPiece(common.PieceRequest{
-		Index:  0,
+		Index:  1,
 		Begin:  0,
 		Length: 16384,
 	}, &pc)
 
 	if err != nil {
+		t.Log(err.Error())
 		t.Fail()
 		return
 	}
 
+	log.Infof("put chunk: idx=%d offset=%d", pc.Index, pc.Begin)
+
 	err = torrent.PutChunk(&pc)
 	if err != nil {
+		t.Log(err.Error())
 		t.Fail()
 		return
 	}
 
-	err = torrent.VerifyPiece(0)
+	log.Infof("verify piece 1")
+	err = torrent.VerifyPiece(1)
 	if err != nil {
+		t.Log(err.Error())
 		t.Fail()
 		return
 	}