On 8/10/15 4:50 PM, Naoya Horiguchi wrote: > On Mon, Aug 10, 2015 at 04:29:18PM +0800, Wanpeng Li wrote: >> Hi Naoya, >> >> On 8/10/15 4:10 PM, Naoya Horiguchi wrote: >>> On Mon, Aug 10, 2015 at 02:32:30PM +0800, Wanpeng Li wrote: >>>> THP pages will get a refcount in madvise_hwpoison() w/ MF_COUNT_INCREASED >>>> flag, however, the refcount is still held when fail to split THP pages. >>>> >>>> Fix it by reducing the refcount of THP pages when fail to split THP. >>>> >>>> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> >>> It seems that the same conditional put_page() would be added to >>> "soft offline: %#lx page already poisoned" branch too, right? >> PageHWPoison() is just called before the soft_offline_page() in >> madvise_hwpoion(). I think the PageHWPosion() >> check in soft_offline_page() makes more sense for the other >> soft_offline_page() callsites which don't have the >> refcount held. > What I am worried is a race like below: > > CPU0 CPU1 > > madvise_hwpoison > get_user_pages_fast > PageHWPoison check (false) > memory_failure > TestSetPageHWPoison > soft_offline_page > PageHWPoison check (true) > return -EBUSY (without put_page) Indeed, there is a race even through it is rared happen. > > It's rare and madvise_hwpoison() is testing feature, so this never causes > real problems in production systems, so it's not a big deal. > My suggestion is maybe just for code correctness thing ... Thanks for your proposal, I will add your suggestion in v2 and post out after we have a uniform solution for patch 2/2. :) Regards, Wanpeng Li > > Thanks, > Naoya Horiguchi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>