On 18.12.23 17:22, Ryan Roberts wrote:
On 11/12/2023 15:56, David Hildenbrand wrote:
Let's use folio_add_anon_rmap_ptes(), batching the rmap operations.
While at it, use more folio operations (but only in the code branch we're
touching), use VM_WARN_ON_FOLIO(), and pass RMAP_EXCLUSIVE instead of
manually setting PageAnonExclusive.
We should never see non-anon pages on that branch: otherwise, the
existing page_add_anon_rmap() call would have been flawed already.
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/huge_memory.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1f5634b2f374..82ad68fe0d12 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2398,6 +2398,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long haddr, bool freeze)
{
struct mm_struct *mm = vma->vm_mm;
+ struct folio *folio;
struct page *page;
pgtable_t pgtable;
pmd_t old_pmd, _pmd;
@@ -2493,16 +2494,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
uffd_wp = pmd_swp_uffd_wp(old_pmd);
} else {
page = pmd_page(old_pmd);
+ folio = page_folio(page);
if (pmd_dirty(old_pmd)) {
dirty = true;
- SetPageDirty(page);
+ folio_set_dirty(folio);
}
write = pmd_write(old_pmd);
young = pmd_young(old_pmd);
soft_dirty = pmd_soft_dirty(old_pmd);
uffd_wp = pmd_uffd_wp(old_pmd);
- VM_BUG_ON_PAGE(!page_count(page), page);
+ VM_WARN_ON_FOLIO(!folio_ref_count(folio), folio);
+ VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
Is this warning really correct? file-backed memory can be PMD-mapped with
CONFIG_READ_ONLY_THP_FOR_FS, so presumably it can also have the need to be
remapped as pte? Although I guess if we did have a file-backed folio, it
definitely wouldn't be correct to call page_add_anon_rmap() /
folio_add_anon_rmap_ptes()...
Yes, see the patch description where I spell that out.
PTE-remapping a file-back folio will simply zap the PMD and refault from
the page cache after creating a page table.
So this is anon-only code.
--
Cheers,
David / dhildenb
