On Mon, Aug 22, 2011 at 6:54 AM, Yongqiang Yang <xiaoqiangnk@xxxxxxxxx> wrote: > Hi, > > I can not find the patch - attempt to fix race in bigalloc code path - > in the mailing list. > > I don't think this patch can work. set_buffers_da_mapped() is called > under i_data_sem, so it can not lock page. If the page is not locked, > calling page_has_buffers() is not secure as Jan pointed out > previously. If a page is partially mapped(block size < page size), > setting BH_Da_Mapped without locking page is not safe too. > The BH_Da_Mapped is set only during page writeback when the page is locked (in write_cache_pages_da). So, the setting of BH_Da_Mapped should be safe, no ? > BTW: find_delalloc_range() does not lock page as ext4_fiemap_cb(). > As Jan said, it can crash system. BUT we can not lock page in both > scenarios, because i_data_sem is hold. So delayed extent list is > necessary. I have finished the code implementing delayed extent list, > which needs some further testing. > > > What are your opinions? > I agree that having a delayed extent list will greatly simply this solution in this case. > > -- > Best Wishes > Yongqiang Yang > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
