The patch titled
Subject: mm/hugetlb: allow uffd wr-protect none ptes
has been added to the -mm tree. Its filename is
mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-allow-uffd-wr-protect-none-ptes
+++ a/mm/hugetlb.c
@@ -6225,7 +6225,7 @@ unsigned long hugetlb_change_protection(
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;
@@ -6245,13 +6245,19 @@ unsigned long hugetlb_change_protection(
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;
@@ -6281,12 +6287,20 @@ unsigned long hugetlb_change_protection(
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));
@@ -6300,6 +6314,12 @@ unsigned long hugetlb_change_protection(
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);
}
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-introduce-pte_marker-swap-entry.patch
mm-teach-core-mm-about-pte-markers.patch
mm-check-against-orig_pte-for-finish_fault.patch
mm-uffd-pte_marker_uffd_wp.patch
mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
mm-shmem-handle-uffd-wp-special-pte-in-page-fault-handler.patch
mm-shmem-persist-uffd-wp-bit-across-zapping-for-file-backed.patch
mm-shmem-allow-uffd-wr-protect-none-pte-for-file-backed-mem.patch
mm-shmem-allows-file-back-mem-to-be-uffd-wr-protected-on-thps.patch
mm-shmem-handle-uffd-wp-during-fork.patch
mm-hugetlb-introduce-huge-pte-version-of-uffd-wp-helpers.patch
mm-hugetlb-hook-page-faults-for-uffd-write-protection.patch
mm-hugetlb-take-care-of-uffdio_copy_mode_wp.patch
mm-hugetlb-handle-uffdio_writeprotect.patch
mm-hugetlb-handle-pte-markers-in-page-faults.patch
mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
mm-hugetlb-only-drop-uffd-wp-special-pte-if-required.patch
mm-hugetlb-handle-uffd-wp-during-fork.patch
mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch
mm-pagemap-recognize-uffd-wp-bit-for-shmem-hugetlbfs.patch
mm-uffd-enable-write-protection-for-shmem-hugetlbfs.patch
mm-enable-pte-markers-by-default.patch
selftests-uffd-enable-uffd-wp-for-shmem-hugetlbfs.patch
