On 8/12/15 4:55 PM, Naoya Horiguchi wrote: > On Mon, Aug 10, 2015 at 07:28:23PM +0800, Wanpeng Li wrote: >> Replace most of put_page in memory error handling by put_hwpoison_page, >> except the ones at the front of soft_offline_page since the page maybe >> THP page and the get refcount in madvise_hwpoison is against the single >> 4KB page instead of the logic in get_hwpoison_page. >> >> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > # Sorry for my late response. > > If I read correctly, get_user_pages_fast() (called by madvise_hwpoison) > for a THP tail page takes a refcount from each of head and tail page. > gup_huge_pmd() does this in the fast path, and get_page_foll() does this > in the slow path (maybe via the following code path) > > get_user_pages_unlocked > __get_user_pages_unlocked > __get_user_pages_locked > __get_user_pages > follow_page_mask > follow_trans_huge_pmd (with FOLL_GET set) > get_page_foll > > So this should be equivalent to what get_hwpoison_page() does for thp pages > with regard to refcounting. > > And I'm expecting that a refcount taken by get_hwpoison_page() is released > by put_hwpoison_page() even if the page's status is changed during error > handling (the typical (or only?) case is successful thp split.) Indeed. :-) > > So I think you can apply put_hwpoison_page() for 3 more callsites in > mm/memory-failure.c. > - MF_MSG_POISONED_HUGE case I have already done this in my patch. > - "soft offline: %#lx page already poisoned" case (you mentioned above) > - "soft offline: %#lx: failed to split THP" case (you mentioned above) You are right, I will send a patch rebased on this one since they are merged. 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>