Mount concurrent read (#4400)

* fix:mount deadlock

* feat: concurrent read

* fix

* Remove useless code

* fix

---------

Co-authored-by: zemul <zhouzemiao@ihuman.com>

weed/mount/weedfs_file_lseek.go

@@ -35,10 +35,10 @@ func (wfs *WFS) Lseek(cancel <-chan struct{}, in *fuse.LseekIn, out *fuse.LseekO
 	}
 
 	// lock the file until the proper offset was calculated
-	fh.Lock()
-	defer fh.Unlock()
-	fh.entryLock.Lock()
-	defer fh.entryLock.Unlock()
+	fh.RLock()
+	defer fh.RUnlock()
+	fh.entryLock.RLock()
+	defer fh.entryLock.RUnlock()
 
 	fileSize := int64(filer.FileSize(fh.GetEntry()))
 	offset := max(int64(in.Offset), 0)