On Fri, Jun 17, 2016 at 08:59:31AM -0700, Huang, Ying wrote: > Minchan Kim <minchan@xxxxxxxxxx> writes: > > > Hi, > > > > On Thu, Jun 16, 2016 at 08:03:54PM -0700, Huang, Ying wrote: > >> From: Huang Ying <ying.huang@xxxxxxxxx> > >> > >> madvise_free_huge_pmd should return 0 if the fallback PTE operations are > >> required. In madvise_free_huge_pmd, if part pages of THP are discarded, > >> the THP will be split and fallback PTE operations should be used if > >> splitting succeeds. But the original code will make fallback PTE > >> operations skipped, after splitting succeeds. Fix that via make > >> madvise_free_huge_pmd return 0 after splitting successfully, so that the > >> fallback PTE operations will be done. > > > > You're right. Thanks! > > > >> > >> Know issues: if my understanding were correct, return 1 from > >> madvise_free_huge_pmd means the following processing for the PMD should > >> be skipped, while return 0 means the following processing is still > >> needed. So the function should return 0 only if the THP is split > >> successfully or the PMD is not trans huge. But the pmd_trans_unstable > >> after madvise_free_huge_pmd guarantee the following processing will be > >> skipped for huge PMD. So current code can run properly. But if my > >> understanding were correct, we can clean up return code of > >> madvise_free_huge_pmd accordingly. > > > > I like your clean up. Just a minor comment below. > > > >> > >> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > >> --- > >> mm/huge_memory.c | 7 +------ > >> 1 file changed, 1 insertion(+), 6 deletions(-) > >> > >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c > >> index 2ad52d5..64dc95d 100644 > >> --- a/mm/huge_memory.c > >> +++ b/mm/huge_memory.c > > > > First of all, let's change ret from int to bool. > > And then, add description in the function entry. > > > > /* > > * Return true if we do MADV_FREE successfully on entire pmd page. > > * Otherwise, return false. > > */ > > > > And do not set to 1 if it is huge_zero_pmd but just goto out to > > return false. > > Do you want to fold the cleanup with this patch or do that in another > patch? I prefer separating cleanup and bug fix so that we can send only bug fix patch to stable tree. Thanks. -- 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>