The patch titled
Subject: mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2
Date: Tue, 21 Mar 2023 14:58:42 -0400
v2
Link: https://lkml.kernel.org/r/ZBzOqwF2wrHgBVZb@x1n
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2
+++ a/mm/hugetlb.c
@@ -5478,7 +5478,7 @@ static vm_fault_t hugetlb_wp(struct mm_s
struct folio *pagecache_folio, spinlock_t *ptl)
{
const bool unshare = flags & FAULT_FLAG_UNSHARE;
- pte_t pte, newpte;
+ pte_t pte = huge_ptep_get(ptep);
struct hstate *h = hstate_vma(vma);
struct page *old_page;
struct folio *new_folio;
@@ -5488,6 +5488,17 @@ static vm_fault_t hugetlb_wp(struct mm_s
struct mmu_notifier_range range;
/*
+ * Never handle CoW for uffd-wp protected pages. It should be only
+ * handled when the uffd-wp protection is removed.
+ *
+ * Note that only the CoW optimization path can trigger this and
+ * got skipped, because hugetlb_fault() will always resolve uffd-wp
+ * bit first.
+ */
+ if (huge_pte_uffd_wp(pte))
+ return 0;
+
+ /*
* hugetlb does not support FOLL_FORCE-style write faults that keep the
* PTE mapped R/O such as maybe_mkwrite() would do.
*/
@@ -5500,7 +5511,6 @@ static vm_fault_t hugetlb_wp(struct mm_s
return 0;
}
- pte = huge_ptep_get(ptep);
old_page = pte_page(pte);
delayacct_wpcopy_start();
@@ -5622,10 +5632,8 @@ retry_avoidcopy:
mmu_notifier_invalidate_range(mm, range.start, range.end);
page_remove_rmap(old_page, vma, true);
hugepage_add_new_anon_rmap(new_folio, vma, haddr);
- newpte = make_huge_pte(vma, &new_folio->page, !unshare);
- if (huge_pte_uffd_wp(pte))
- newpte = huge_pte_mkuffd_wp(newpte);
- set_huge_pte_at(mm, haddr, ptep, newpte);
+ set_huge_pte_at(mm, haddr, ptep,
+ make_huge_pte(vma, &new_folio->page, !unshare));
folio_set_hugetlb_migratable(new_folio);
/* Make the old page be freed below */
new_folio = page_folio(old_page);
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path.patch
mm-hugetlb-fix-uffd-wr-protection-for-cow-optimization-path-v2.patch
mm-khugepaged-alloc_charge_hpage-take-care-of-mem-charge-errors.patch
mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch
mm-uffd-uffd_feature_wp_unpopulated.patch
selftests-mm-smoke-test-uffd_feature_wp_unpopulated.patch
mm-thp-rename-transparent_hugepage_never_dax-to-_unsupported.patch
mm-thp-rename-transparent_hugepage_never_dax-to-_unsupported-fix.patch
