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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 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 bit 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 needs to be applied even if writable==false previously (e.g., for shmem private 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 file). 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 */ 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 = file_inode(dst_vma->vm_file); @@ -2439,7 +2439,7 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, goto out_release; ret = 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; 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, _dst_pte = mk_pte(page, dst_vma->vm_page_prot); _dst_pte = pte_mkdirty(_dst_pte); - if (page_in_cache && !vm_shared) + /* Don't write if uffd-wp wr-protected */ + if (wp_copy) { + _dst_pte = pte_mkuffd_wp(_dst_pte); writable = false; - if (writable) { - if (wp_copy) - _dst_pte = pte_mkuffd_wp(_dst_pte); - else - _dst_pte = pte_mkwrite(_dst_pte); } + /* Don't write if page cache privately mapped */ + if (page_in_cache && !vm_shared) + writable = false; + if (writable) + _dst_pte = 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 = pte_wrprotect(_dst_pte); dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); @@ -515,11 +523,10 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, err = mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, dst_addr); } else { - VM_WARN_ON_ONCE(wp_copy); err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, mode != MCOPY_ATOMIC_NORMAL, - page); + wp_copy, page); } return err; -- 2.31.1