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authorDavid Hildenbrand <david@redhat.com>2022-12-22 23:55:11 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-01-12 03:14:19 +0300
commit44f86392bdd165da7e43d3c772aeb1e128ffd6c8 (patch)
treee5a8bbbc2a0edc6b645a9a007179818134f44f3a /mm/hugetlb.c
parent0e678153f5be7e6c8d28835f5a678618da4b7a9c (diff)
downloadlinux-44f86392bdd165da7e43d3c772aeb1e128ffd6c8.tar.xz
mm/hugetlb: fix uffd-wp handling for migration entries in hugetlb_change_protection()
We have to update the uffd-wp SWP PTE bit independent of the type of migration entry. Currently, if we're unlucky and we want to install/clear the uffd-wp bit just while we're migrating a read-only mapped hugetlb page, we would miss to set/clear the uffd-wp bit. Further, if we're processing a readable-exclusive migration entry and neither want to set or clear the uffd-wp bit, we could currently end up losing the uffd-wp bit. Note that the same would hold for writable migrating entries, however, having a writable migration entry with the uffd-wp bit set would already mean that something went wrong. Note that the change from !is_readable_migration_entry -> writable_migration_entry is harmless and actually cleaner, as raised by Miaohe Lin and discussed in [1]. [1] https://lkml.kernel.org/r/90dd6a93-4500-e0de-2bf0-bf522c311b0c@huawei.com Link: https://lkml.kernel.org/r/20221222205511.675832-3-david@redhat.com Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes") Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Peter Xu <peterx@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c17
1 files changed, 9 insertions, 8 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3f0686b54701..bd7d39227344 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6662,10 +6662,9 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
} else if (unlikely(is_hugetlb_entry_migration(pte))) {
swp_entry_t entry = pte_to_swp_entry(pte);
struct page *page = pfn_swap_entry_to_page(entry);
+ pte_t newpte = pte;
- if (!is_readable_migration_entry(entry)) {
- pte_t newpte;
-
+ if (is_writable_migration_entry(entry)) {
if (PageAnon(page))
entry = make_readable_exclusive_migration_entry(
swp_offset(entry));
@@ -6673,13 +6672,15 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
entry = make_readable_migration_entry(
swp_offset(entry));
newpte = swp_entry_to_pte(entry);
- if (uffd_wp)
- newpte = pte_swp_mkuffd_wp(newpte);
- else if (uffd_wp_resolve)
- newpte = pte_swp_clear_uffd_wp(newpte);
- set_huge_pte_at(mm, address, ptep, newpte);
pages++;
}
+
+ if (uffd_wp)
+ newpte = pte_swp_mkuffd_wp(newpte);
+ else if (uffd_wp_resolve)
+ newpte = pte_swp_clear_uffd_wp(newpte);
+ if (!pte_same(pte, newpte))
+ set_huge_pte_at(mm, address, ptep, newpte);
} else if (unlikely(is_pte_marker(pte))) {
/* No other markers apply for now. */
WARN_ON_ONCE(!pte_marker_uffd_wp(pte));