| Message ID | 20211217113049.23850-3-david@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | mm: COW fixes part 1: fix the COW security issue for THP and hugetlb | expand |
On Fri, Dec 17, 2021 at 3:33 AM David Hildenbrand <david@redhat.com> wrote: > > Let's consolidate the mapcount logic to make it easier to understand and > to prepare for further changes. > > Reviewed-by: Peter Xu <peterx@redhat.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Yang Shi <shy828301@gmail.com> > --- > mm/huge_memory.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index e5483347291c..4751d03947da 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2101,21 +2101,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > pte = pte_offset_map(&_pmd, addr); > BUG_ON(!pte_none(*pte)); > set_pte_at(mm, addr, pte, entry); > - if (!pmd_migration) > - atomic_inc(&page[i]._mapcount); > pte_unmap(pte); > } > > if (!pmd_migration) { > + /* Sub-page mapcount accounting for above small mappings. */ > + int val = 1; > + > /* > * Set PG_double_map before dropping compound_mapcount to avoid > * false-negative page_mapped(). > + * > + * The first to set PageDoubleMap() has to increment all > + * sub-page mapcounts by one. > */ > - if (compound_mapcount(page) > 1 && > - !TestSetPageDoubleMap(page)) { > - for (i = 0; i < HPAGE_PMD_NR; i++) > - atomic_inc(&page[i]._mapcount); > - } > + if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) > + val++; > + > + for (i = 0; i < HPAGE_PMD_NR; i++) > + atomic_add(val, &page[i]._mapcount); > > lock_page_memcg(page); > if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { > -- > 2.31.1 >
On Fri, Dec 17, 2021 at 12:30:40PM +0100, David Hildenbrand wrote: > Let's consolidate the mapcount logic to make it easier to understand and > to prepare for further changes. > > Reviewed-by: Peter Xu <peterx@redhat.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e5483347291c..4751d03947da 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2101,21 +2101,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, pte = pte_offset_map(&_pmd, addr); BUG_ON(!pte_none(*pte)); set_pte_at(mm, addr, pte, entry); - if (!pmd_migration) - atomic_inc(&page[i]._mapcount); pte_unmap(pte); } if (!pmd_migration) { + /* Sub-page mapcount accounting for above small mappings. */ + int val = 1; + /* * Set PG_double_map before dropping compound_mapcount to avoid * false-negative page_mapped(). + * + * The first to set PageDoubleMap() has to increment all + * sub-page mapcounts by one. */ - if (compound_mapcount(page) > 1 && - !TestSetPageDoubleMap(page)) { - for (i = 0; i < HPAGE_PMD_NR; i++) - atomic_inc(&page[i]._mapcount); - } + if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) + val++; + + for (i = 0; i < HPAGE_PMD_NR; i++) + atomic_add(val, &page[i]._mapcount); lock_page_memcg(page); if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {