Commit c5c54003 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/rmap: move folio_test_anon() check out of __folio_set_anon() 

Let's handle it in the caller; no need for the "first" check based on the
mapcount.

We really only end up with !anon pages in page_add_anon_rmap() via
do_swap_page(), where we hold the folio lock.  So races are not possible. 
Add a VM_WARN_ON_FOLIO() to make sure that we really hold the folio lock.

In the future, we might want to let do_swap_page() use
folio_add_new_anon_rmap() on new pages instead: however, we might have to
pass then whether the folio is exclusive or not.  So keep it in there for
now.

For hugetlb we never expect to have a non-anon page in
hugepage_add_anon_rmap().  Remove that code, along with some other checks
that are either not required or were checked in
hugepage_add_new_anon_rmap() already.

Link: https://lkml.kernel.org/r/20230913125113.313322-4-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c66db8c0

mm/rmap.c

+8 −15
Original line number Diff line number Diff line
@@ -1135,9 +1135,6 @@ static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma, 


	BUG_ON(!anon_vma);



	if (folio_test_anon(folio))

		return;



	/*

	 * If the folio isn't exclusive to this vma, we must use the _oldest_

	 * possible anon_vma for the folio mapping!
@@ -1239,11 +1236,11 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, 
	if (nr)

		__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);



	if (likely(!folio_test_ksm(folio))) {

		if (first)

	if (unlikely(!folio_test_anon(folio))) {

		VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);

		__folio_set_anon(folio, vma, address,

				 !!(flags & RMAP_EXCLUSIVE));

		else

	} else if (likely(!folio_test_ksm(folio))) {

		__page_check_anon_rmap(folio, page, vma, address);

	}

	if (flags & RMAP_EXCLUSIVE)
@@ -2541,17 +2538,13 @@ void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma, 
			    unsigned long address, rmap_t flags)

{

	struct folio *folio = page_folio(page);

	struct anon_vma *anon_vma = vma->anon_vma;

	int first;



	BUG_ON(!folio_test_locked(folio));

	BUG_ON(!anon_vma);

	VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);



	first = atomic_inc_and_test(&folio->_entire_mapcount);

	VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);

	VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);

	if (first)

		__folio_set_anon(folio, vma, address,

				 !!(flags & RMAP_EXCLUSIVE));

	if (flags & RMAP_EXCLUSIVE)

		SetPageAnonExclusive(page);

}