Commit e135826b authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/rmap: introduce and use hugetlb_remove_rmap() 

hugetlb rmap handling differs quite a lot from "ordinary" rmap code.  For
example, hugetlb currently only supports entire mappings, and treats any
mapping as mapped using a single "logical PTE".  Let's move it out of the
way so we can overhaul our "ordinary" rmap.  implementation/interface.

Let's introduce and use hugetlb_remove_rmap() and remove the hugetlb code
from page_remove_rmap().  This effectively removes one check on the
small-folio path as well.

Add sanity checks that we end up with the right folios in the right
functions.

Note: all possible candidates that need care are page_remove_rmap() that
      pass compound=true.

Link: https://lkml.kernel.org/r/20231220224504.646757-3-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarYin Fengwei <fengwei.yin@intel.com>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Reviewed-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 9d5fafd5

include/linux/rmap.h

+7 −0
Original line number Diff line number Diff line
@@ -211,6 +211,13 @@ void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *, 
void hugetlb_add_new_anon_rmap(struct folio *, struct vm_area_struct *,

		unsigned long address);



static inline void hugetlb_remove_rmap(struct folio *folio)

{

	VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);



	atomic_dec(&folio->_entire_mapcount);

}



static inline void __page_dup_rmap(struct page *page, bool compound)

{

	if (compound) {

mm/hugetlb.c

+2 −2
Original line number Diff line number Diff line
@@ -5676,7 +5676,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, 
					make_pte_marker(PTE_MARKER_UFFD_WP),

					sz);

		hugetlb_count_sub(pages_per_huge_page(h), mm);

		page_remove_rmap(page, vma, true);

		hugetlb_remove_rmap(page_folio(page));



		spin_unlock(ptl);

		tlb_remove_page_size(tlb, page, huge_page_size(h));
@@ -5987,7 +5987,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, 


		/* Break COW or unshare */

		huge_ptep_clear_flush(vma, haddr, ptep);

		page_remove_rmap(&old_folio->page, vma, true);

		hugetlb_remove_rmap(old_folio);

		hugetlb_add_new_anon_rmap(new_folio, vma, haddr);

		if (huge_pte_uffd_wp(pte))

			newpte = huge_pte_mkuffd_wp(newpte);

mm/rmap.c

+9 −9
Original line number Diff line number Diff line
@@ -1480,15 +1480,9 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma, 
	bool last;

	enum node_stat_item idx;



	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);

	VM_BUG_ON_PAGE(compound && !PageHead(page), page);



	/* Hugetlb pages are not counted in NR_*MAPPED */

	if (unlikely(folio_test_hugetlb(folio))) {

		/* hugetlb pages are always mapped with pmds */

		atomic_dec(&folio->_entire_mapcount);

		return;

	}



	/* Is page being unmapped by PTE? Is this its last map to be removed? */

	if (likely(!compound)) {

		last = atomic_add_negative(-1, &page->_mapcount);
@@ -1846,7 +1840,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, 
			dec_mm_counter(mm, mm_counter_file(&folio->page));

		}

discard:

		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));

		if (unlikely(folio_test_hugetlb(folio)))

			hugetlb_remove_rmap(folio);

		else

			page_remove_rmap(subpage, vma, false);

		if (vma->vm_flags & VM_LOCKED)

			mlock_drain_local();

		folio_put(folio);
@@ -2199,7 +2196,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, 
			 */

		}



		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));

		if (unlikely(folio_test_hugetlb(folio)))

			hugetlb_remove_rmap(folio);

		else

			page_remove_rmap(subpage, vma, false);

		if (vma->vm_flags & VM_LOCKED)

			mlock_drain_local();

		folio_put(folio);