lock btree writes

fix https://github.com/chrislusf/seaweedfs/issues/930

weed/filer2/memdb/memdb_store.go

@@ -7,6 +7,7 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/util"
 	"github.com/google/btree"
 	"strings"
+	"sync"
 )
 
 func init() {
@@ -14,7 +15,8 @@ func init() {
 }
 
 type MemDbStore struct {
-	tree *btree.BTree
+	tree     *btree.BTree
+	treeLock sync.Mutex
 }
 
 type entryItem struct {
@@ -46,7 +48,9 @@ func (store *MemDbStore) RollbackTransaction(ctx context.Context) error {
 
 func (store *MemDbStore) InsertEntry(ctx context.Context, entry *filer2.Entry) (err error) {
 	// println("inserting", entry.FullPath)
+	store.treeLock.Lock()
 	store.tree.ReplaceOrInsert(entryItem{entry})
+	store.treeLock.Unlock()
 	return nil
 }
 
@@ -54,7 +58,9 @@ func (store *MemDbStore) UpdateEntry(ctx context.Context, entry *filer2.Entry) (
 	if _, err = store.FindEntry(ctx, entry.FullPath); err != nil {
 		return fmt.Errorf("no such file %s : %v", entry.FullPath, err)
 	}
+	store.treeLock.Lock()
 	store.tree.ReplaceOrInsert(entryItem{entry})
+	store.treeLock.Unlock()
 	return nil
 }
 
@@ -68,7 +74,9 @@ func (store *MemDbStore) FindEntry(ctx context.Context, fullpath filer2.FullPath
 }
 
 func (store *MemDbStore) DeleteEntry(ctx context.Context, fullpath filer2.FullPath) (err error) {
+	store.treeLock.Lock()
 	store.tree.Delete(entryItem{&filer2.Entry{FullPath: fullpath}})
+	store.treeLock.Unlock()
 	return nil
 }