linux-kernel - [PATCH v3 06/14] mm/ksm: Break COW PTE before modify shared PTE

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Message-Id: <20221220072743.3039060-7-shiyn.lin@gmail.com>
Date:   Tue, 20 Dec 2022 15:27:35 +0800
From:   Chih-En Lin <shiyn.lin@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        John Hubbard <jhubbard@...dia.com>,
        Nadav Amit <namit@...are.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Yang Shi <shy828301@...il.com>, Peter Xu <peterx@...hat.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Alex Sierra <alex.sierra@....com>,
        Xianting Tian <xianting.tian@...ux.alibaba.com>,
        Colin Cross <ccross@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Barry Song <baohua@...nel.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>, Yu Zhao <yuzhao@...gle.com>,
        Tong Tiangen <tongtiangen@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Li kunyu <kunyu@...china.com>,
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        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Gautam Menghani <gautammenghani201@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Brown <broonie@...nel.org>, Will Deacon <will@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Barret Rhoden <brho@...gle.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Dinglan Peng <peng301@...due.edu>,
        Pedro Fonseca <pfonseca@...due.edu>,
        Jim Huang <jserv@...s.ncku.edu.tw>,
        Huichun Feng <foxhoundsk.tw@...il.com>,
        Chih-En Lin <shiyn.lin@...il.com>
Subject: [PATCH v3 06/14] mm/ksm: Break COW PTE before modify shared PTE

Break COW PTE before merge the page that reside in COW-ed PTE.

Signed-off-by: Chih-En Lin <shiyn.lin@...il.com>
---
 mm/ksm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index c19fcca9bc03d..896a14c44a858 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1017,7 +1017,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
 			      pte_t *orig_pte)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	DEFINE_PAGE_VMA_WALK(pvmw, page, vma, 0, 0);
+	DEFINE_PAGE_VMA_WALK(pvmw, page, vma, 0, PVMW_BREAK_COW_PTE);
 	int swapped;
 	int err = -EFAULT;
 	struct mmu_notifier_range range;
@@ -1136,6 +1136,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
 	barrier();
 	if (!pmd_present(pmde) || pmd_trans_huge(pmde))
 		goto out;
+	if (break_cow_pte(vma, pmd, addr) < 0)
+		goto out;
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr,
 				addr + PAGE_SIZE);
-- 
2.37.3