linux-kernel - [PATCH v3 10/14] mm/userfaultfd: Support COW PTE

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Message-Id: <20221220072743.3039060-11-shiyn.lin@gmail.com>
Date:   Tue, 20 Dec 2022 15:27:39 +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>,
        Anshuman Khandual <anshuman.khandual@....com>,
        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 10/14] mm/userfaultfd: Support COW PTE

If uffd fills the zeropage or installs to COW-ed PTE, break it first.

Signed-off-by: Chih-En Lin <shiyn.lin@...il.com>
---
 mm/userfaultfd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 650ab6cfd5f49..4ee21c0d42d90 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -69,6 +69,9 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
 	struct inode *inode;
 	pgoff_t offset, max_off;
 
+	if (break_cow_pte(dst_vma, dst_pmd, dst_addr) < 0)
+		return -ENOMEM;
+
 	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
 	_dst_pte = pte_mkdirty(_dst_pte);
 	if (page_in_cache && !vm_shared)
@@ -227,6 +230,9 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm,
 	pgoff_t offset, max_off;
 	struct inode *inode;
 
+	if (break_cow_pte(dst_vma, dst_pmd, dst_addr) < 0)
+		return -ENOMEM;
+
 	_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
 					 dst_vma->vm_page_prot));
 	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
-- 
2.37.3