On Tue, May 7, 2013 at 10:41 PM, KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx> wrote: > On Tue, May 7, 2013 at 8:51 PM, Jerome Glisse <j.glisse@xxxxxxxxx> wrote: >> On Tue, May 7, 2013 at 8:47 PM, KOSAKI Motohiro >> <kosaki.motohiro@xxxxxxxxx> wrote: >>> On Tue, May 7, 2013 at 6:58 PM, <j.glisse@xxxxxxxxx> wrote: >>>> From: Jerome Glisse <jglisse@xxxxxxxxxx> >>>> >>>> Do not increase page count if FOLL_GET is not set. None of the >>>> current user can trigger the issue because none of the current >>>> user call __get_user_pages with both the pages array ptr non >>>> NULL and the FOLL_GET flags non set in other word all caller >>>> of __get_user_pages that don't set the FOLL_GET flags also call >>>> with pages == NULL. >>> >>> Because, __get_user_pages() doesn't allow pages==NULL and FOLL_GET is on. >> >> Yes but this allow pages != NULL and FOLL_GET not set and as i said >> there is no such user of that yet and this is exactly what i was >> trying to use. > > Why? The following bug_on inhibit both case. Yes i get lost on the double negation, but still my patch is correct and i am not using gup but follow_hugetlb_page directly and i run into the issue. My patch does not change the behavior for current user, just fix assumption new user might have when not setting the FOLL_GET flags. >>> VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); -- 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>