From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755197AbcFQDEn (ORCPT ); Thu, 16 Jun 2016 23:04:43 -0400 Received: from mga11.intel.com ([192.55.52.93]:37717 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754804AbcFQDEm (ORCPT ); Thu, 16 Jun 2016 23:04:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,481,1459839600"; d="scan'208";a="123462600" From: "Huang, Ying" 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 Subject: [PATCH] MADVISE_FREE, THP: Fix madvise_free_huge_pmd return value after splitting Date: Thu, 16 Jun 2016 20:03:54 -0700 Message-Id: <1466132640-18932-1-git-send-email-ying.huang@intel.com> X-Mailer: git-send-email 2.8.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. 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 @@ -1655,14 +1655,9 @@ int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, if (next - addr != HPAGE_PMD_SIZE) { get_page(page); spin_unlock(ptl); - if (split_huge_page(page)) { - put_page(page); - unlock_page(page); - goto out_unlocked; - } + split_huge_page(page); put_page(page); unlock_page(page); - ret = 1; goto out_unlocked; } -- 2.8.1