Commit 91b2978a authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/huge_memory: batch rmap operations in __split_huge_pmd_locked() 

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.

Link: https://lkml.kernel.org/r/20231220224504.646757-16-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarYin Fengwei <fengwei.yin@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8bd51300

mm/huge_memory.c

+15 −8
Original line number Diff line number Diff line
@@ -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);



		/*

		 * Without "freeze", we'll simply split the PMD, propagating the
@@ -2519,11 +2522,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
		 *

		 * See page_try_share_anon_rmap(): invalidate PMD first.

		 */

		anon_exclusive = PageAnon(page) && PageAnonExclusive(page);

		anon_exclusive = PageAnonExclusive(page);

		if (freeze && anon_exclusive && page_try_share_anon_rmap(page))

			freeze = false;

		if (!freeze)

			page_ref_add(page, HPAGE_PMD_NR - 1);

		if (!freeze) {

			rmap_t rmap_flags = RMAP_NONE;



			folio_ref_add(folio, HPAGE_PMD_NR - 1);

			if (anon_exclusive)

				rmap_flags |= RMAP_EXCLUSIVE;

			folio_add_anon_rmap_ptes(folio, page, HPAGE_PMD_NR,

						 vma, haddr, rmap_flags);

		}

	}



	/*
@@ -2566,8 +2576,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
			entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));

			if (write)

				entry = pte_mkwrite(entry, vma);

			if (anon_exclusive)

				SetPageAnonExclusive(page + i);

			if (!young)

				entry = pte_mkold(entry);

			/* NOTE: this may set soft-dirty too on some archs */
@@ -2577,7 +2585,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
				entry = pte_mksoft_dirty(entry);

			if (uffd_wp)

				entry = pte_mkuffd_wp(entry);

			page_add_anon_rmap(page + i, vma, addr, RMAP_NONE);

		}

		VM_BUG_ON(!pte_none(ptep_get(pte)));

		set_pte_at(mm, addr, pte, entry);