linux-kernel - [PATCH v5 12/17] mm/userfaultfd: Support COW PTE

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Date:   Fri, 14 Apr 2023 22:23:36 +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 (Oracle)" <willy@...radead.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        John Hubbard <jhubbard@...dia.com>,
        Nadav Amit <namit@...are.com>, Barry Song <baohua@...nel.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
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        Namhyung Kim <namhyung@...nel.org>,
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        Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Joey Gouly <joey.gouly@....com>,
        Chih-En Lin <shiyn.lin@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        "Zach O'Keefe" <zokeefe@...gle.com>,
        Gautam Menghani <gautammenghani201@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Brown <broonie@...nel.org>,
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        Andrei Vagin <avagin@...il.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexey Gladkov <legion@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Dinglan Peng <peng301@...due.edu>,
        Pedro Fonseca <pfonseca@...due.edu>,
        Jim Huang <jserv@...s.ncku.edu.tw>,
        Huichun Feng <foxhoundsk.tw@...il.com>
Subject: [PATCH v5 12/17] 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 53c3d916ff66..f5e0a97d6a3d 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -70,6 +70,9 @@ 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))
+		return -ENOMEM;
+
 	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
 	_dst_pte = pte_mkdirty(_dst_pte);
 	if (page_in_cache && !vm_shared)
@@ -215,6 +218,9 @@ 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))
+		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);
-- 
2.34.1