Minchan Kim <[email protected]> writes: > On Fri, Jun 17, 2016 at 08:59:31AM -0700, Huang, Ying wrote: >> Minchan Kim <[email protected]> writes: >> >> > Hi, >> > >> > On Thu, Jun 16, 2016 at 08:03:54PM -0700, Huang, Ying wrote: >> >> From: Huang Ying <[email protected]> >> >> >> >> 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" <[email protected]> >> >> --- >> >> 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.
Sure. Best Regards, Huang, Ying
