From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Piggin Subject: [PATCH 1/3] mm/cow: don't bother write protectig already write-protected huge pages Date: Tue, 28 Aug 2018 21:20:32 +1000 Message-ID: <20180828112034.30875-2-npiggin@gmail.com> References: <20180828112034.30875-1-npiggin@gmail.com> Return-path: In-Reply-To: <20180828112034.30875-1-npiggin@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-mm@kvack.org Cc: Nicholas Piggin , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Andrew Morton , Linus Torvalds List-Id: linux-arch.vger.kernel.org This is the THP equivalent for 1b2de5d039c8 ("mm/cow: don't bother write protecting already write-protected pages"). Explicit hugetlb pages don't get the same treatment because they don't appear to have the right accessor functions. Signed-off-by: Nicholas Piggin --- mm/huge_memory.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9592cbd8530a..d9bae12978ef 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -973,8 +973,11 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, mm_inc_nr_ptes(dst_mm); pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); - pmdp_set_wrprotect(src_mm, addr, src_pmd); - pmd = pmd_mkold(pmd_wrprotect(pmd)); + if (pmd_write(pmd)) { + pmdp_set_wrprotect(src_mm, addr, src_pmd); + pmd = pmd_wrprotect(pmd); + } + pmd = pmd_mkold(pmd); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; @@ -1064,8 +1067,11 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, /* No huge zero pud yet */ } - pudp_set_wrprotect(src_mm, addr, src_pud); - pud = pud_mkold(pud_wrprotect(pud)); + if (pud_write(pud)) { + pudp_set_wrprotect(src_mm, addr, src_pud); + pud = pud_wrprotect(pud); + } + pud = pud_mkold(pud); set_pud_at(dst_mm, addr, dst_pud, pud); ret = 0; -- 2.18.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f196.google.com ([209.85.215.196]:44842 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727579AbeH1PMA (ORCPT ); Tue, 28 Aug 2018 11:12:00 -0400 From: Nicholas Piggin Subject: [PATCH 1/3] mm/cow: don't bother write protectig already write-protected huge pages Date: Tue, 28 Aug 2018 21:20:32 +1000 Message-ID: <20180828112034.30875-2-npiggin@gmail.com> In-Reply-To: <20180828112034.30875-1-npiggin@gmail.com> References: <20180828112034.30875-1-npiggin@gmail.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-mm@kvack.org Cc: Nicholas Piggin , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Andrew Morton , Linus Torvalds Message-ID: <20180828112032.E7PapWIB7sIJMLplpOahwN-5g7XcvJclOIfqQEKdsis@z> This is the THP equivalent for 1b2de5d039c8 ("mm/cow: don't bother write protecting already write-protected pages"). Explicit hugetlb pages don't get the same treatment because they don't appear to have the right accessor functions. Signed-off-by: Nicholas Piggin --- mm/huge_memory.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9592cbd8530a..d9bae12978ef 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -973,8 +973,11 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, mm_inc_nr_ptes(dst_mm); pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); - pmdp_set_wrprotect(src_mm, addr, src_pmd); - pmd = pmd_mkold(pmd_wrprotect(pmd)); + if (pmd_write(pmd)) { + pmdp_set_wrprotect(src_mm, addr, src_pmd); + pmd = pmd_wrprotect(pmd); + } + pmd = pmd_mkold(pmd); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; @@ -1064,8 +1067,11 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, /* No huge zero pud yet */ } - pudp_set_wrprotect(src_mm, addr, src_pud); - pud = pud_mkold(pud_wrprotect(pud)); + if (pud_write(pud)) { + pudp_set_wrprotect(src_mm, addr, src_pud); + pud = pud_wrprotect(pud); + } + pud = pud_mkold(pud); set_pud_at(dst_mm, addr, dst_pud, pud); ret = 0; -- 2.18.0