From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
Mike Kravetz <mike.kravetz@oracle.com>,
David Hildenbrand <david@redhat.com>,
Alistair Popple <apopple@nvidia.com>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Hugh Dickins <hughd@google.com>,
Tiberiu Georgescu <tiberiu.georgescu@nutanix.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Nadav Amit <nadav.amit@gmail.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Jerome Glisse <jglisse@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Miaohe Lin <linmiaohe@huawei.com>,
peterx@redhat.com
Subject: [PATCH v5 03/26] mm: Clear vmf->pte after pte_unmap_same() returns
Date: Thu, 15 Jul 2021 16:13:59 -0400 [thread overview]
Message-ID: <20210715201422.211004-4-peterx@redhat.com> (raw)
In-Reply-To: <20210715201422.211004-1-peterx@redhat.com>
pte_unmap_same() will always unmap the pte pointer. After the unmap, vmf->pte
will not be valid any more. We should clear it.
It was safe only because no one is accessing vmf->pte after pte_unmap_same()
returns, since the only caller of pte_unmap_same() (so far) is do_swap_page(),
where vmf->pte will in most cases be overwritten very soon.
pte_unmap_same() will be used in other places in follow up patches, so that
vmf->pte will not always be re-written. This patch enables us to call
functions like finish_fault() because that'll conditionally unmap the pte by
checking vmf->pte first. Or, alloc_set_pte() will make sure to allocate a new
pte even after calling pte_unmap_same().
Since we'll need to modify vmf->pte, directly pass in vmf into pte_unmap_same()
and then we can also avoid the long parameter list.
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/memory.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 747a01d495f2..0e0de08a2cd5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2724,19 +2724,20 @@ EXPORT_SYMBOL_GPL(apply_to_existing_page_range);
* proceeding (but do_wp_page is only called after already making such a check;
* and do_anonymous_page can safely check later on).
*/
-static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
- pte_t *page_table, pte_t orig_pte)
+static inline int pte_unmap_same(struct vm_fault *vmf)
{
int same = 1;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION)
if (sizeof(pte_t) > sizeof(unsigned long)) {
- spinlock_t *ptl = pte_lockptr(mm, pmd);
+ spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
spin_lock(ptl);
- same = pte_same(*page_table, orig_pte);
+ same = pte_same(*vmf->pte, vmf->orig_pte);
spin_unlock(ptl);
}
#endif
- pte_unmap(page_table);
+ pte_unmap(vmf->pte);
+ /* After unmap of pte, the pointer is invalid now - clear it. */
+ vmf->pte = NULL;
return same;
}
@@ -3487,7 +3488,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
vm_fault_t ret = 0;
void *shadow = NULL;
- if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
+ if (!pte_unmap_same(vmf))
goto out;
entry = pte_to_swp_entry(vmf->orig_pte);
--
2.31.1
next prev parent reply other threads:[~2021-07-15 20:14 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 20:13 [PATCH v5 00/26] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-07-15 20:13 ` [PATCH v5 01/26] mm/shmem: Unconditionally set pte dirty in mfill_atomic_install_pte Peter Xu
2021-07-15 20:13 ` [PATCH v5 02/26] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-07-15 20:13 ` Peter Xu [this message]
2021-07-15 20:14 ` [PATCH v5 04/26] mm/userfaultfd: Introduce special pte for unmapped file-backed mem Peter Xu
2021-07-15 20:14 ` [PATCH v5 05/26] mm/swap: Introduce the idea of special swap ptes Peter Xu
2021-07-16 5:50 ` Alistair Popple
2021-07-16 19:11 ` Peter Xu
2021-07-21 11:28 ` Alistair Popple
2021-07-21 21:35 ` Peter Xu
2021-07-22 1:08 ` Alistair Popple
2021-07-22 15:21 ` Peter Xu
2021-07-15 20:14 ` [PATCH v5 06/26] shmem/userfaultfd: Handle uffd-wp special pte in page fault handler Peter Xu
2021-07-15 20:14 ` [PATCH v5 07/26] mm: Drop first_index/last_index in zap_details Peter Xu
2021-07-15 20:14 ` [PATCH v5 08/26] mm: Introduce zap_details.zap_flags Peter Xu
2021-07-15 20:14 ` [PATCH v5 09/26] mm: Introduce ZAP_FLAG_SKIP_SWAP Peter Xu
2021-07-15 20:14 ` [PATCH v5 10/26] shmem/userfaultfd: Persist uffd-wp bit across zapping for file-backed Peter Xu
2021-07-15 20:15 ` [PATCH v5 11/26] shmem/userfaultfd: Allow wr-protect none pte for file-backed mem Peter Xu
2021-07-15 20:16 ` [PATCH v5 12/26] shmem/userfaultfd: Allows file-back mem to be uffd wr-protected on thps Peter Xu
2021-07-15 20:16 ` [PATCH v5 13/26] shmem/userfaultfd: Handle the left-overed special swap ptes Peter Xu
2021-07-15 20:16 ` [PATCH v5 14/26] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Peter Xu
2021-07-15 20:16 ` [PATCH v5 15/26] mm/hugetlb: Drop __unmap_hugepage_range definition from hugetlb.h Peter Xu
2021-07-15 20:16 ` [PATCH v5 16/26] mm/hugetlb: Introduce huge pte version of uffd-wp helpers Peter Xu
2021-07-15 20:16 ` [PATCH v5 17/26] hugetlb/userfaultfd: Hook page faults for uffd write protection Peter Xu
2021-07-20 15:37 ` kernel test robot
2021-07-21 21:50 ` Peter Xu
2021-07-15 20:16 ` [PATCH v5 18/26] hugetlb/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-07-20 23:59 ` kernel test robot
2021-07-15 20:16 ` [PATCH v5 19/26] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT Peter Xu
2021-07-21 8:24 ` kernel test robot
2021-07-15 20:16 ` [PATCH v5 20/26] mm/hugetlb: Introduce huge version of special swap pte helpers Peter Xu
2021-07-15 20:16 ` [PATCH v5 21/26] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Peter Xu
2021-07-15 20:16 ` [PATCH v5 22/26] hugetlb/userfaultfd: Allow wr-protect none ptes Peter Xu
2021-07-15 20:16 ` [PATCH v5 23/26] hugetlb/userfaultfd: Only drop uffd-wp special pte if required Peter Xu
2021-07-15 20:16 ` [PATCH v5 24/26] mm/pagemap: Recognize uffd-wp bit for shmem/hugetlbfs Peter Xu
2021-07-19 9:53 ` Tiberiu Georgescu
2021-07-19 16:03 ` Peter Xu
2021-07-19 17:23 ` Tiberiu Georgescu
2021-07-19 17:56 ` Peter Xu
2021-07-21 14:38 ` Ivan Teterevkov
2021-07-21 16:19 ` David Hildenbrand
2021-07-21 19:54 ` Ivan Teterevkov
2021-07-21 22:28 ` Peter Xu
2021-07-21 22:57 ` Peter Xu
2021-07-22 6:27 ` David Hildenbrand
2021-07-22 16:08 ` Peter Xu
2021-07-15 20:16 ` [PATCH v5 25/26] mm/userfaultfd: Enable write protection for shmem & hugetlbfs Peter Xu
2021-07-15 20:16 ` [PATCH v5 26/26] userfaultfd/selftests: Enable uffd-wp for shmem/hugetlbfs Peter Xu
2021-07-19 19:21 ` [PATCH v5 00/26] userfaultfd-wp: Support shmem and hugetlbfs David Hildenbrand
2021-07-19 20:12 ` Peter Xu
2021-07-22 18:30 ` Peter Xu
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