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[184.145.4.219]) by smtp.gmail.com with ESMTPSA id u14sm2089536qkp.80.2021.05.27.13.19.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 13:19:36 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Axel Rasmussen , "Kirill A . Shutemov" , Hugh Dickins , Andrew Morton , Miaohe Lin , Mike Rapoport , Jerome Glisse , Andrea Arcangeli , Nadav Amit , Mike Kravetz , peterx@redhat.com, Jason Gunthorpe , Matthew Wilcox Subject: [PATCH v3 02/27] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Date: Thu, 27 May 2021 16:19:02 -0400 Message-Id: <20210527201927.29586-3-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" X-Rspamd-Queue-Id: 40BE52000ADE Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=KRIpc8Pj; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf11.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: rspam03 X-Stat-Signature: yyt88gqmipz5jp68hre97o8hbyc14juh X-HE-Tag: 1622146772-442731 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: Firstly, pass wp_copy into shmem_mfill_atomic_pte() through the stack. Then apply the UFFD_WP bit properly when the UFFDIO_COPY on shmem is with UFFDIO_COPY_MODE_WP, then wp_copy lands mfill_atomic_install_pte() which = is newly introduced very recently. We need to make sure shmem_mfill_atomic_pte() will always set the dirty b= it in pte even if UFFDIO_COPY_MODE_WP is set. After the rework of minor fault = series on shmem we need to slightly touch up the logic there, since uffd-wp need= s to be applied even if writable=3D=3Dfalse previously (e.g., for shmem privat= e mapping). Note: we must do pte_wrprotect() if !writable in mfill_atomic_install_pte= (), as mk_pte() could return a writable pte (e.g., when VM_SHARED on a shmem fil= e). Signed-off-by: Peter Xu --- include/linux/shmem_fs.h | 4 ++-- mm/shmem.c | 4 ++-- mm/userfaultfd.c | 23 +++++++++++++++-------- 3 files changed, 19 insertions(+), 12 deletions(-) diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index a69ea4d97fdd..0b6a8e871036 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -128,11 +128,11 @@ extern int shmem_mfill_atomic_pte(struct mm_struct = *dst_mm, pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr, unsigned long src_addr, - bool zeropage, + bool zeropage, bool wp_copy, struct page **pagep); #else /* !CONFIG_SHMEM */ #define shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, \ - src_addr, zeropage, pagep) ({ BUG(); 0; }) + src_addr, zeropage, wp_copy, pagep) ({ BUG(); 0; }) #endif /* CONFIG_SHMEM */ #endif /* CONFIG_USERFAULTFD */ =20 diff --git a/mm/shmem.c b/mm/shmem.c index 4085a5cf4a13..5b648cbae37a 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2368,7 +2368,7 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm= , struct vm_area_struct *dst_vma, unsigned long dst_addr, unsigned long src_addr, - bool zeropage, + bool zeropage, bool wp_copy, struct page **pagep) { struct inode *inode =3D file_inode(dst_vma->vm_file); @@ -2439,7 +2439,7 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm= , goto out_release; =20 ret =3D mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, - page, true, false); + page, true, wp_copy); if (ret) goto out_delete_from_cache; =20 diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 462fa6e25e03..3636f5be6390 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -70,14 +70,22 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm= , pmd_t *dst_pmd, =20 _dst_pte =3D mk_pte(page, dst_vma->vm_page_prot); _dst_pte =3D pte_mkdirty(_dst_pte); - if (page_in_cache && !vm_shared) + /* Don't write if uffd-wp wr-protected */ + if (wp_copy) { + _dst_pte =3D pte_mkuffd_wp(_dst_pte); writable =3D false; - if (writable) { - if (wp_copy) - _dst_pte =3D pte_mkuffd_wp(_dst_pte); - else - _dst_pte =3D pte_mkwrite(_dst_pte); } + /* Don't write if page cache privately mapped */ + if (page_in_cache && !vm_shared) + writable =3D false; + if (writable) + _dst_pte =3D pte_mkwrite(_dst_pte); + else + /* + * We need this to make sure write bit removed; as mk_pte() + * could return a pte with write bit set. + */ + _dst_pte =3D pte_wrprotect(_dst_pte); =20 dst_pte =3D pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); =20 @@ -515,11 +523,10 @@ static __always_inline ssize_t mfill_atomic_pte(str= uct mm_struct *dst_mm, err =3D mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, dst_addr); } else { - VM_WARN_ON_ONCE(wp_copy); err =3D shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, mode !=3D MCOPY_ATOMIC_NORMAL, - page); + wp_copy, page); } =20 return err; --=20 2.31.1