diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 7ae1e69..e68d8c3 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -223,6 +223,8 @@
 		i_size_write(inode, 0);
 		spin_unlock(&fc->lock);
 		fuse_invalidate_attr(inode);
+		if (fc->writeback_cache)
+			file_update_time(file);
 	}
 	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
 		fuse_link_write_file(file);
@@ -232,18 +234,26 @@
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	int err;
+	bool lock_inode = (file->f_flags & O_TRUNC) &&
+			  fc->atomic_o_trunc &&
+			  fc->writeback_cache;
 
 	err = generic_file_open(inode, file);
 	if (err)
 		return err;
 
+	if (lock_inode)
+		mutex_lock(&inode->i_mutex);
+
 	err = fuse_do_open(fc, get_node_id(inode), file, isdir);
-	if (err)
-		return err;
 
-	fuse_finish_open(inode, file);
+	if (!err)
+		fuse_finish_open(inode, file);
 
-	return 0;
+	if (lock_inode)
+		mutex_unlock(&inode->i_mutex);
+
+	return err;
 }
 
 static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode)