Hi all: Today, i wrote to a partition which already mounted using dd.So the fs was destroyed completedly. So i asked why dd can write? I remembed the flag O_EXCL which prevent other operation. I review the code and found it used FMODE_EXCL.But why dd can write? In open(2): > In general, the behavior of O_EXCL is undefined if it is used without O_CREAT. There is one > exception: on Linux 2.6 and later, O_EXCL can be used without O_CREAT if pathname refers to a > block device. If the block device is in use by the system (e.g., mounted), open() fails with the > error EBUSY. But understand from the literal meaning, EXCL means opened exclusively.I think it like mutex-operation. Can someone please tell me why? Thanks! Jianpeng?韬{.n?????%??檩??w?{.n???{饼?z鳐??骅w*jg????????G??⒏⒎?:+v????????????"??????