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[174.91.135.175]) by smtp.gmail.com with ESMTPSA id n6sm5031793qtx.22.2021.03.22.17.49.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 17:49:38 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: "Kirill A . Shutemov" , Jerome Glisse , Mike Kravetz , Matthew Wilcox , Andrew Morton , Axel Rasmussen , Hugh Dickins , peterx@redhat.com, Nadav Amit , Andrea Arcangeli , Mike Rapoport Subject: [PATCH 14/23] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Date: Mon, 22 Mar 2021 20:49:03 -0400 Message-Id: <20210323004912.35132-15-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210323004912.35132-1-peterx@redhat.com> References: <20210323004912.35132-1-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 8be28bcaa044..766946d3eab0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -715,8 +715,21 @@ 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 entry.val; -- 2.26.2