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[184.145.104.227]) by smtp.gmail.com with ESMTPSA id v66sm3103621qkd.113.2021.04.27.09.13.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Apr 2021 09:13:44 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Nadav Amit , Miaohe Lin , Mike Rapoport , Andrea Arcangeli , Hugh Dickins , peterx@redhat.com, Jerome Glisse , Mike Kravetz , Jason Gunthorpe , Matthew Wilcox , Andrew Morton , Axel Rasmussen , "Kirill A . Shutemov" Subject: [PATCH v2 14/24] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Date: Tue, 27 Apr 2021 12:13:07 -0400 Message-Id: <20210427161317.50682-15-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210427161317.50682-1-peterx@redhat.com> References: <20210427161317.50682-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 47638A000192 X-Stat-Signature: zuucf4djx3gct5di6jae7mftu4duqrw1 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf15; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619540024-674352 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 872fb59192277..f1cdc613b5887 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;