Commit c64e912c authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

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: default avatarPeter 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 5a90d5a1

mm/hugetlb.c

+14 −4
Original line number Diff line number Diff line
@@ -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 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, 


	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 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, 
		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;

	}