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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Feb 2019 08:28:54 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1Q8SrXF26935372 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Feb 2019 08:28:53 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B96F2A405C; Tue, 26 Feb 2019 08:28:53 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5A53BA405B; Tue, 26 Feb 2019 08:28:52 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.84]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 26 Feb 2019 08:28:52 +0000 (GMT) Date: Tue, 26 Feb 2019 10:28:50 +0200 From: Mike Rapoport To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Hugh Dickins , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: Re: [PATCH v2 10/26] userfaultfd: wp: add UFFDIO_COPY_MODE_WP References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-11-peterx@redhat.com> <20190225155836.GD24917@rapoport-lnx> <20190226050942.GF13653@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190226050942.GF13653@xz-x1> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19022608-0016-0000-0000-0000025AFA6C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022608-0017-0000-0000-000032B55B4A Message-Id: <20190226082850.GC11981@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-26_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902260065 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 26, 2019 at 01:09:42PM +0800, Peter Xu wrote: > On Mon, Feb 25, 2019 at 05:58:37PM +0200, Mike Rapoport wrote: > > On Tue, Feb 12, 2019 at 10:56:16AM +0800, Peter Xu wrote: > > > From: Andrea Arcangeli > > > > > > This allows UFFDIO_COPY to map pages wrprotected. > > write protected please :) > > Sure! > > > > > > > Signed-off-by: Andrea Arcangeli > > > Signed-off-by: Peter Xu > > > > Except for two additional nits below > > > > Reviewed-by: Mike Rapoport > > > > > --- > > > fs/userfaultfd.c | 5 +++-- > > > include/linux/userfaultfd_k.h | 2 +- > > > include/uapi/linux/userfaultfd.h | 11 +++++----- > > > mm/userfaultfd.c | 36 ++++++++++++++++++++++---------- > > > 4 files changed, 35 insertions(+), 19 deletions(-) > > > > > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > > > index b397bc3b954d..3092885c9d2c 100644 > > > --- a/fs/userfaultfd.c > > > +++ b/fs/userfaultfd.c > > > @@ -1683,11 +1683,12 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx, > > > ret = -EINVAL; > > > if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) > > > goto out; > > > - if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) > > > + if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) > > > goto out; > > > if (mmget_not_zero(ctx->mm)) { > > > ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, > > > - uffdio_copy.len, &ctx->mmap_changing); > > > + uffdio_copy.len, &ctx->mmap_changing, > > > + uffdio_copy.mode); > > > mmput(ctx->mm); > > > } else { > > > return -ESRCH; > > > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > > > index c6590c58ce28..765ce884cec0 100644 > > > --- a/include/linux/userfaultfd_k.h > > > +++ b/include/linux/userfaultfd_k.h > > > @@ -34,7 +34,7 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); > > > > > > extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, > > > unsigned long src_start, unsigned long len, > > > - bool *mmap_changing); > > > + bool *mmap_changing, __u64 mode); > > > extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, > > > unsigned long dst_start, > > > unsigned long len, > > > diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h > > > index 48f1a7c2f1f0..297cb044c03f 100644 > > > --- a/include/uapi/linux/userfaultfd.h > > > +++ b/include/uapi/linux/userfaultfd.h > > > @@ -203,13 +203,14 @@ struct uffdio_copy { > > > __u64 dst; > > > __u64 src; > > > __u64 len; > > > +#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) > > > /* > > > - * There will be a wrprotection flag later that allows to map > > > - * pages wrprotected on the fly. And such a flag will be > > > - * available if the wrprotection ioctl are implemented for the > > > - * range according to the uffdio_register.ioctls. > > > + * UFFDIO_COPY_MODE_WP will map the page wrprotected on the > > > + * fly. UFFDIO_COPY_MODE_WP is available only if the > > > + * wrprotection ioctl are implemented for the range according > > > > ^ is > > Will fix. > > > > > > + * to the uffdio_register.ioctls. > > > */ > > > -#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) > > > +#define UFFDIO_COPY_MODE_WP ((__u64)1<<1) > > > __u64 mode; > > > > > > /* > > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > > > index d59b5a73dfb3..73a208c5c1e7 100644 > > > --- a/mm/userfaultfd.c > > > +++ b/mm/userfaultfd.c > > > @@ -25,7 +25,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, > > > struct vm_area_struct *dst_vma, > > > unsigned long dst_addr, > > > unsigned long src_addr, > > > - struct page **pagep) > > > + struct page **pagep, > > > + bool wp_copy) > > > { > > > struct mem_cgroup *memcg; > > > pte_t _dst_pte, *dst_pte; > > > @@ -71,9 +72,9 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, > > > if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false)) > > > goto out_release; > > > > > > - _dst_pte = mk_pte(page, dst_vma->vm_page_prot); > > > - if (dst_vma->vm_flags & VM_WRITE) > > > - _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); > > > + _dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot)); > > > + if (dst_vma->vm_flags & VM_WRITE && !wp_copy) > > > + _dst_pte = pte_mkwrite(_dst_pte); > > > > > > dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); > > > if (dst_vma->vm_file) { > > > @@ -399,7 +400,8 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, > > > unsigned long dst_addr, > > > unsigned long src_addr, > > > struct page **page, > > > - bool zeropage) > > > + bool zeropage, > > > + bool wp_copy) > > > { > > > ssize_t err; > > > > > > @@ -416,11 +418,13 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, > > > if (!(dst_vma->vm_flags & VM_SHARED)) { > > > if (!zeropage) > > > err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, > > > - dst_addr, src_addr, page); > > > + dst_addr, src_addr, page, > > > + wp_copy); > > > else > > > err = mfill_zeropage_pte(dst_mm, dst_pmd, > > > dst_vma, dst_addr); > > > } else { > > > + VM_WARN_ON(wp_copy); /* WP only available for anon */ > > > if (!zeropage) > > > err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd, > > > dst_vma, dst_addr, > > > @@ -438,7 +442,8 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, > > > unsigned long src_start, > > > unsigned long len, > > > bool zeropage, > > > - bool *mmap_changing) > > > + bool *mmap_changing, > > > + __u64 mode) > > > { > > > struct vm_area_struct *dst_vma; > > > ssize_t err; > > > @@ -446,6 +451,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, > > > unsigned long src_addr, dst_addr; > > > long copied; > > > struct page *page; > > > + bool wp_copy; > > > > > > /*> * Sanitize the command parameters: > > > @@ -502,6 +508,14 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, > > > dst_vma->vm_flags & VM_SHARED)) > > > goto out_unlock; > > > > > > + /* > > > + * validate 'mode' now that we know the dst_vma: don't allow > > > + * a wrprotect copy if the userfaultfd didn't register as WP. > > > + */ > > > + wp_copy = mode & UFFDIO_COPY_MODE_WP; > > > + if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) > > > + goto out_unlock; > > [1] > > > > + > > > /* > > > * If this is a HUGETLB vma, pass off to appropriate routine > > > */ > > > > I think for hugetlb we should return an error if wp_copy==true. > > It might be worth adding wp_copy parameter to __mcopy_atomic_hugetlb() in > > advance and return the error from there, in a hope it will also support > > UFFD_WP some day :) > > Now we should have failed even earlier if someone wants to register a > hugetlbfs VMA with UFFD_WP because now vma_can_userfault() only allows > anonymous memory for it: > > static inline bool vma_can_userfault(struct vm_area_struct *vma, > unsigned long vm_flags) > { > /* FIXME: add WP support to hugetlbfs and shmem */ > return vma_is_anonymous(vma) || > ((is_vm_hugetlb_page(vma) || vma_is_shmem(vma)) && > !(vm_flags & VM_UFFD_WP)); > } > > And, as long as a VMA is not tagged with UFFD_WP, the page copy will > fail with -EINVAL directly above at [1] when setting the wp_copy flag. > So IMHO we should have already covered the case. > > Considering these, I would think we could simply postpone the changes > to __mcopy_atomic_hugetlb() until adding hugetlbfs support on uffd-wp. > Mike, what do you think? Ok, fair enough. > Thanks! > > -- > Peter Xu > -- Sincerely yours, Mike.