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[184.145.4.219]) by smtp.gmail.com with ESMTPSA id g85sm2024356qke.123.2021.05.27.13.23.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 13:23:02 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Mike Rapoport , peterx@redhat.com, Andrew Morton , Mike Kravetz , Jerome Glisse , Miaohe Lin , Nadav Amit , Hugh Dickins , Matthew Wilcox , Jason Gunthorpe , "Kirill A . Shutemov" , Andrea Arcangeli , Axel Rasmussen Subject: [PATCH v3 15/27] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Date: Thu, 27 May 2021 16:22:59 -0400 Message-Id: <20210527202259.31767-1-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527201927.29586-1-peterx@redhat.com> References: <20210527201927.29586-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="US-ASCII" Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LP30Y1p3; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf06.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=peterx@redhat.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 13A66C007765 X-Stat-Signature: axr1f9cgeq8gytkcxtbch8r8tr19iucb X-HE-Tag: 1622146979-550741 Content-Transfer-Encoding: quoted-printable 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 s= hould 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 3453b8ae5f4f..8372b212993a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -777,8 +777,21 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct= mm_struct *src_mm, unsigned long vm_flags =3D dst_vma->vm_flags; pte_t pte =3D *src_pte; struct page *page; - swp_entry_t entry =3D 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; + } =20 + entry =3D pte_to_swp_entry(pte); if (likely(!non_swap_entry(entry))) { if (swap_duplicate(entry) < 0) return -EAGAIN; --=20 2.31.1