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[184.144.111.238]) by smtp.gmail.com with ESMTPSA id l5sm2958062qkb.62.2021.07.15.13.16.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jul 2021 13:16:13 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Axel Rasmussen , Nadav Amit , Jerome Glisse , "Kirill A . Shutemov" , Jason Gunthorpe , Alistair Popple , Andrew Morton , David Hildenbrand , peterx@redhat.com, Andrea Arcangeli , Matthew Wilcox , Mike Kravetz , Tiberiu Georgescu , Hugh Dickins , Miaohe Lin , Mike Rapoport Subject: [PATCH v5 14/26] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Date: Thu, 15 Jul 2021 16:16:10 -0400 Message-Id: <20210715201610.211610-1-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210715201422.211004-1-peterx@redhat.com> References: <20210715201422.211004-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It should be handled similarly like other uffd-wp wr-protected ptes: we should pass it over when the dst_vma has VM_UFFD_WP armed, otherwise drop it. Signed-off-by: Peter Xu --- mm/memory.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 223781f115e9..af91bee934c7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -776,8 +776,21 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, unsigned long vm_flags = dst_vma->vm_flags; pte_t pte = *src_pte; struct page *page; - swp_entry_t entry = pte_to_swp_entry(pte); + swp_entry_t entry; + + if (unlikely(is_swap_special_pte(pte))) { + /* + * uffd-wp special swap pte is the only possibility for now. + * If dst vma is registered with uffd-wp, copy it over. + * Otherwise, ignore this pte as if it's a none pte would work. + */ + WARN_ON_ONCE(!pte_swp_uffd_wp_special(pte)); + if (userfaultfd_wp(dst_vma)) + set_pte_at(dst_mm, addr, dst_pte, pte); + return 0; + } + entry = pte_to_swp_entry(pte); if (likely(!non_swap_entry(entry))) { if (swap_duplicate(entry) < 0) return -EIO; -- 2.31.1