From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>,
peterx@redhat.com, Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Jerome Glisse <jglisse@redhat.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Nadav Amit <nadav.amit@gmail.com>,
Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Andrea Arcangeli <aarcange@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>
Subject: [PATCH v3 13/27] shmem/userfaultfd: Allows file-back mem to be uffd wr-protected on thps
Date: Thu, 27 May 2021 16:22:50 -0400 [thread overview]
Message-ID: <20210527202250.31663-1-peterx@redhat.com> (raw)
In-Reply-To: <20210527201927.29586-1-peterx@redhat.com>
We don't have "huge" version of PTE_SWP_UFFD_WP_SPECIAL, instead when necessary
we split the thp if the huge page is uffd wr-protected previously.
However split the thp is not enough, because file-backed thp is handled totally
differently comparing to anonymous thps - rather than doing a real split, the
thp pmd will simply got dropped in __split_huge_pmd_locked().
That is definitely not enough if e.g. when there is a thp covers range [0, 2M)
but we want to wr-protect small page resides in [4K, 8K) range, because after
__split_huge_pmd() returns, there will be a none pmd.
Here we leverage the previously introduced change_protection_prepare() macro so
that we'll populate the pmd with a pgtable page. Then change_pte_range() will
do all the rest for us, e.g., install the uffd-wp swap special pte marker at
any pte that we'd like to wr-protect, under the protection of pgtable lock.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/mprotect.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 8ec85b276975..3fcb87b59696 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -306,8 +306,16 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
}
if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
- if (next - addr != HPAGE_PMD_SIZE) {
+ if (next - addr != HPAGE_PMD_SIZE ||
+ /* Uffd wr-protecting a file-backed memory range */
+ unlikely(!vma_is_anonymous(vma) &&
+ (cp_flags & MM_CP_UFFD_WP))) {
__split_huge_pmd(vma, pmd, addr, false, NULL);
+ /*
+ * For file-backed, the pmd could have been
+ * gone; still provide a pte pgtable if needed.
+ */
+ change_protection_prepare(vma, pmd, addr, cp_flags);
} else {
int nr_ptes = change_huge_pmd(vma, pmd, addr,
newprot, cp_flags);
--
2.31.1
next prev parent reply other threads:[~2021-05-27 20:23 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 20:19 [PATCH v3 00/27] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-05-27 20:19 ` [PATCH v3 01/27] mm/shmem: Unconditionally set pte dirty in mfill_atomic_install_pte Peter Xu
2021-05-27 20:19 ` [PATCH v3 02/27] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-05-27 20:19 ` [PATCH v3 03/27] mm: Clear vmf->pte after pte_unmap_same() returns Peter Xu
2021-05-27 20:19 ` [PATCH v3 04/27] mm/userfaultfd: Introduce special pte for unmapped file-backed mem Peter Xu
2021-05-28 8:32 ` Alistair Popple
2021-05-28 12:56 ` Peter Xu
2021-06-03 11:53 ` Alistair Popple
2021-06-03 14:51 ` Peter Xu
2021-06-04 0:55 ` Alistair Popple
2021-06-04 3:14 ` Hugh Dickins
2021-06-04 6:16 ` Alistair Popple
2021-06-04 16:01 ` Peter Xu
2021-06-08 13:18 ` Alistair Popple
2021-06-09 13:06 ` Alistair Popple
2021-06-09 14:43 ` Peter Xu
2021-05-27 20:21 ` [PATCH v3 05/27] mm/swap: Introduce the idea of special swap ptes Peter Xu
2021-05-27 20:21 ` [PATCH v3 06/27] shmem/userfaultfd: Handle uffd-wp special pte in page fault handler Peter Xu
2021-06-17 8:59 ` Alistair Popple
2021-06-17 15:10 ` Peter Xu
2021-05-27 20:21 ` [PATCH v3 07/27] mm: Drop first_index/last_index in zap_details Peter Xu
2021-06-21 12:20 ` Alistair Popple
2021-05-27 20:21 ` [PATCH v3 08/27] mm: Introduce zap_details.zap_flags Peter Xu
2021-06-21 12:09 ` Alistair Popple
2021-06-21 16:16 ` Peter Xu
2021-06-22 2:07 ` Alistair Popple
2021-05-27 20:21 ` [PATCH v3 09/27] mm: Introduce ZAP_FLAG_SKIP_SWAP Peter Xu
2021-06-21 12:36 ` Alistair Popple
2021-06-21 16:26 ` Peter Xu
2021-06-22 2:11 ` Alistair Popple
2021-05-27 20:21 ` [PATCH v3 10/27] mm: Pass zap_flags into unmap_mapping_pages() Peter Xu
2021-05-27 20:22 ` [PATCH v3 11/27] shmem/userfaultfd: Persist uffd-wp bit across zapping for file-backed Peter Xu
2021-06-21 8:41 ` Alistair Popple
2021-06-22 0:40 ` Peter Xu
2021-06-22 12:47 ` Alistair Popple
2021-06-22 15:44 ` Peter Xu
2021-06-23 6:04 ` Alistair Popple
2021-06-23 15:31 ` Peter Xu
2021-07-06 5:40 ` Alistair Popple
2021-07-06 15:35 ` Peter Xu
2021-07-08 2:49 ` Alistair Popple
2021-05-27 20:22 ` [PATCH v3 12/27] shmem/userfaultfd: Allow wr-protect none pte for file-backed mem Peter Xu
2021-05-27 20:22 ` Peter Xu [this message]
2021-05-27 20:22 ` [PATCH v3 14/27] shmem/userfaultfd: Handle the left-overed special swap ptes Peter Xu
2021-05-27 20:22 ` [PATCH v3 15/27] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Peter Xu
2021-05-27 20:23 ` [PATCH v3 16/27] mm/hugetlb: Drop __unmap_hugepage_range definition from hugetlb.h Peter Xu
2021-05-27 20:23 ` [PATCH v3 17/27] mm/hugetlb: Introduce huge pte version of uffd-wp helpers Peter Xu
2021-05-27 20:23 ` [PATCH v3 18/27] hugetlb/userfaultfd: Hook page faults for uffd write protection Peter Xu
2021-05-27 20:23 ` [PATCH v3 19/27] hugetlb/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-05-27 20:23 ` [PATCH v3 20/27] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT Peter Xu
2021-05-27 20:23 ` [PATCH v3 21/27] mm/hugetlb: Introduce huge version of special swap pte helpers Peter Xu
2021-05-27 20:23 ` [PATCH v3 22/27] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Peter Xu
2021-05-27 20:23 ` [PATCH v3 23/27] hugetlb/userfaultfd: Allow wr-protect none ptes Peter Xu
2021-05-27 20:23 ` [PATCH v3 24/27] hugetlb/userfaultfd: Only drop uffd-wp special pte if required Peter Xu
2021-05-27 20:23 ` [PATCH v3 25/27] mm/pagemap: Recognize uffd-wp bit for shmem/hugetlbfs Peter Xu
2021-05-27 20:23 ` [PATCH v3 26/27] mm/userfaultfd: Enable write protection for shmem & hugetlbfs Peter Xu
2021-05-27 20:23 ` [PATCH v3 27/27] userfaultfd/selftests: Enable uffd-wp for shmem/hugetlbfs Peter Xu
2021-06-02 14:40 ` [PATCH v3 00/27] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-06-02 22:36 ` Andrew Morton
2021-06-03 0:09 ` Peter Xu
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