> Apologies for the tardy response, this patch slipped past me. Never mind. > I've tested this patch out, unfortunately it treats huge pmds as regular > pmds and attempts to traverse them rather than fall back to a slow path. > The fix for this is very minor, please see my suggestion below. OK. I'll fix it. > > As an aside, I would like to extend this fast_gup to include full huge > page support and include a __get_user_pages_fast implementation. This will > hopefully fix a problem that was brought to my attention by Grazvydas > Ignotas whereby a FUTEX_WAIT on a THP tail page will cause an infinite > loop due to the stock implementation of __get_user_pages_fast always > returning 0. I'll add the __get_user_pages_fast implementation. BTW, HugeTLB on ARM wasn't supported yet. There is no problem to add gup_huge_pmd. But I think it need a test for hugepages. > I would suggest: > if (pmd_none(*pmdp) || pmd_bad(*pmdp)) > return 0; > as this will pick up pmds that can't be traversed, and fall back to the > slow path. Thanks for your suggestion. I'll prepare the v2 patch. Best regards, Chanho Park -- 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>