From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id E8E3E6B025E for ; Mon, 20 Jun 2016 11:48:33 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id 143so321644931pfx.0 for ; Mon, 20 Jun 2016 08:48:33 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id m123si24809644pfm.8.2016.06.20.08.48.33 for ; Mon, 20 Jun 2016 08:48:33 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH] MADVISE_FREE, THP: Fix madvise_free_huge_pmd return value after splitting References: <1466132640-18932-1-git-send-email-ying.huang@intel.com> <20160617053102.GA2374@bbox> <87inx7lsbg.fsf@yhuang-mobile.sh.intel.com> <20160619235450.GA3194@blaptop> Date: Mon, 20 Jun 2016 08:48:32 -0700 In-Reply-To: <20160619235450.GA3194@blaptop> (Minchan Kim's message of "Mon, 20 Jun 2016 08:54:50 +0900") Message-ID: <877fdjamjz.fsf@yhuang-mobile.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: "Huang, Ying" , Andrew Morton , "Kirill A. Shutemov" , Vlastimil Babka , Jerome Marchand , Andrea Arcangeli , Ebru Akagunduz , linux-mm@kvack.org, linux-kernel@vger.kernel.org Minchan Kim writes: > On Fri, Jun 17, 2016 at 08:59:31AM -0700, Huang, Ying wrote: >> Minchan Kim writes: >> >> > Hi, >> > >> > On Thu, Jun 16, 2016 at 08:03:54PM -0700, Huang, Ying wrote: >> >> From: Huang Ying >> >> >> >> 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" >> >> --- >> >> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org