Commit 60dfaad6 authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

mm/hugetlb: allow uffd wr-protect none ptes 

Teach hugetlbfs code to wr-protect none ptes just in case the page cache
existed for that pte.  Meanwhile we also need to be able to recognize a
uffd-wp marker pte and remove it for uffd_wp_resolve.

Since at it, introduce a variable "psize" to replace all references to the
huge page size fetcher.

Link: https://lkml.kernel.org/r/20220405014912.14815-1-peterx@redhat.com


Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.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 Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c64e912c

mm/hugetlb.c

+24 −4
Original line number Diff line number Diff line
@@ -6251,7 +6251,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
	pte_t *ptep;

	pte_t pte;

	struct hstate *h = hstate_vma(vma);

	unsigned long pages = 0;

	unsigned long pages = 0, psize = huge_page_size(h);

	bool shared_pmd = false;

	struct mmu_notifier_range range;

	bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
@@ -6271,13 +6271,19 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 


	mmu_notifier_invalidate_range_start(&range);

	i_mmap_lock_write(vma->vm_file->f_mapping);

	for (; address < end; address += huge_page_size(h)) {

	for (; address < end; address += psize) {

		spinlock_t *ptl;

		ptep = huge_pte_offset(mm, address, huge_page_size(h));

		ptep = huge_pte_offset(mm, address, psize);

		if (!ptep)

			continue;

		ptl = huge_pte_lock(h, mm, ptep);

		if (huge_pmd_unshare(mm, vma, &address, ptep)) {

			/*

			 * When uffd-wp is enabled on the vma, unshare

			 * shouldn't happen at all.  Warn about it if it

			 * happened due to some reason.

			 */

			WARN_ON_ONCE(uffd_wp || uffd_wp_resolve);

			pages++;

			spin_unlock(ptl);

			shared_pmd = true;
@@ -6307,12 +6313,20 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
				else if (uffd_wp_resolve)

					newpte = pte_swp_clear_uffd_wp(newpte);

				set_huge_swap_pte_at(mm, address, ptep,

						     newpte, huge_page_size(h));

						     newpte, psize);

				pages++;

			}

			spin_unlock(ptl);

			continue;

		}

		if (unlikely(pte_marker_uffd_wp(pte))) {

			/*

			 * This is changing a non-present pte into a none pte,

			 * no need for huge_ptep_modify_prot_start/commit().

			 */

			if (uffd_wp_resolve)

				huge_pte_clear(mm, address, ptep, psize);

		}

		if (!huge_pte_none(pte)) {

			pte_t old_pte;

			unsigned int shift = huge_page_shift(hstate_vma(vma));
@@ -6326,6 +6340,12 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
				pte = huge_pte_clear_uffd_wp(pte);

			huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);

			pages++;

		} else {

			/* None pte */

			if (unlikely(uffd_wp))

				/* Safe to modify directly (none->non-present). */

				set_huge_pte_at(mm, address, ptep,

						make_pte_marker(PTE_MARKER_UFFD_WP));

		}

		spin_unlock(ptl);

	}