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Tue, 16 Oct 2018 06:14:05 -0700 (PDT) From: Nicholas Piggin To: Andrew Morton Subject: [PATCH v2 2/5] mm/cow: don't bother write protecting already write-protected huge pages Date: Tue, 16 Oct 2018 23:13:40 +1000 Message-Id: <20181016131343.20556-3-npiggin@gmail.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20181016131343.20556-1-npiggin@gmail.com> References: <20181016131343.20556-1-npiggin@gmail.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Linus Torvalds , Linux Kernel Mailing List , Nicholas Piggin , linux-mm , Ley Foon Tan , ppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This is the HugePage / THP equivalent for 1b2de5d039c8 ("mm/cow: don't bother write protecting already write-protected pages"). Signed-off-by: Nicholas Piggin --- mm/huge_memory.c | 14 ++++++++++---- mm/hugetlb.c | 2 +- 2 files changed, 11 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 58269f8ba7c4..0fb0e3025f98 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; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 5c390f5a5207..54a4dcb6ee21 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3287,7 +3287,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, } set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz); } else { - if (cow) { + if (cow && huge_pte_write(entry)) { /* * No need to notify as we are downgrading page * table protection not changing it to point -- 2.18.0