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mm/hugetlb: handle pte markers in page faults 

Allow hugetlb code to handle pte markers just like none ptes.  It's mostly
there, we just need to make sure we don't assume hugetlb_no_page() only
handles none pte, so when detecting pte change we should use pte_same()
rather than pte_none().  We need to pass in the old_pte to do the
comparison.

Check the original pte to see whether it's a pte marker, if it is, we
should recover uffd-wp bit on the new pte to be installed, so that the
next write will be trapped by uffd.

Link: https://lkml.kernel.org/r/20220405014909.14761-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2022-05-12 20:22:54 -07:00 committed by Andrew Morton
parent 5a90d5a103
commit c64e912c86
1 changed files with 14 additions and 4 deletions
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18
mm/hugetlb.c
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@ -5438,7 +5438,8 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
struct vm_area_struct *vma,
struct address_space *mapping, pgoff_t idx,
unsigned long address, pte_t *ptep, unsigned int flags)
unsigned long address, pte_t *ptep,
pte_t old_pte, unsigned int flags)
{
struct hstate *h = hstate_vma(vma);
vm_fault_t ret = VM_FAULT_SIGBUS;
@ -5565,7 +5566,8 @@ retry:
ptl = huge_pte_lock(h, mm, ptep);
ret = 0;
if (!huge_pte_none(huge_ptep_get(ptep)))
/* If pte changed from under us, retry */
if (!pte_same(huge_ptep_get(ptep), old_pte))
goto backout;
if (anon_rmap) {
@ -5575,6 +5577,12 @@ retry:
page_dup_file_rmap(page, true);
new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
&& (vma->vm_flags & VM_SHARED)));
/*
* If this pte was previously wr-protected, keep it wr-protected even
* if populated.
*/
if (unlikely(pte_marker_uffd_wp(old_pte)))
new_pte = huge_pte_wrprotect(huge_pte_mkuffd_wp(new_pte));
set_huge_pte_at(mm, haddr, ptep, new_pte);
hugetlb_count_add(pages_per_huge_page(h), mm);
@ -5692,8 +5700,10 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
entry = huge_ptep_get(ptep);
if (huge_pte_none(entry)) {
ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags);
/* PTE markers should be handled the same way as none pte */
if (huge_pte_none_mostly(entry)) {
ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep,
entry, flags);
goto out_mutex;
}