On Tue, Aug 23, 2011 at 1:30 AM, Aditya Kali <adityakali@xxxxxxxxxx> wrote: > 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 ? Sorry for noise and thank you for your explanation, you are right. IMHO, we can clear BH_Delayed and set BH_Mapped instead. Yongqiang. > >> 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 >> > -- 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
