Let's factor it out, optimize for small folios, and compact it a bit.
Well, we're adding the range part, but that will surely come in handy
soon -- and it's now wasier to compare it with __folio_add_rmap_range().
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/rmap.c | 90 +++++++++++++++++++++++++++++++++----------------------
1 file changed, 55 insertions(+), 35 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index da7fa46a18fc..80ac53633332 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1155,6 +1155,57 @@ static unsigned int __folio_add_rmap_range(struct folio *folio,
return nr;
}
+static unsigned int __folio_remove_rmap_range(struct folio *folio,
+ struct page *page, unsigned int nr_pages,
+ struct vm_area_struct *vma, bool compound, int *nr_pmdmapped)
+{
+ atomic_t *mapped = &folio->_nr_pages_mapped;
+ int last, count, nr = 0;
+
+ VM_WARN_ON_FOLIO(compound && page != &folio->page, folio);
+ VM_WARN_ON_FOLIO(compound && !folio_test_pmd_mappable(folio), folio);
+ VM_WARN_ON_FOLIO(compound && nr_pages != folio_nr_pages(folio), folio);
+ VM_WARN_ON_FOLIO(!folio_test_large(folio) && nr_pages != 1, folio);
+
+ if (likely(!folio_test_large(folio)))
+ return atomic_add_negative(-1, &page->_mapcount);
+
+ /* Is page being unmapped by PTE? Is this its last map to be removed? */
+ if (!compound) {
+ folio_add_large_mapcount(folio, -nr_pages, vma);
+ count = nr_pages;
+ do {
+ last = atomic_add_negative(-1, &page->_mapcount);
+ if (last) {
+ last = atomic_dec_return_relaxed(mapped);
+ if (last < COMPOUND_MAPPED)
+ nr++;
+ }
+ } while (page++, --count > 0);
+ } else if (folio_test_pmd_mappable(folio)) {
+ /* That test is redundant: it's for safety or to optimize out */
+
+ folio_dec_large_mapcount(folio, vma);
+ last = atomic_add_negative(-1, &folio->_entire_mapcount);
+ if (last) {
+ nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
+ if (likely(nr < COMPOUND_MAPPED)) {
+ *nr_pmdmapped = folio_nr_pages(folio);
+ nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
+ /* Raced ahead of another remove and an add? */
+ if (unlikely(nr < 0))
+ nr = 0;
+ } else {
+ /* An add of COMPOUND_MAPPED raced ahead */
+ nr = 0;
+ }
+ }
+ } else {
+ VM_WARN_ON_ONCE_FOLIO(true, folio);
+ }
+ return nr;
+}
+
/**
* folio_move_anon_rmap - move a folio to our anon_vma
* @folio: The folio to move to our anon_vma
@@ -1439,13 +1490,10 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
bool compound)
{
struct folio *folio = page_folio(page);
- atomic_t *mapped = &folio->_nr_pages_mapped;
- int nr = 0, nr_pmdmapped = 0;
- bool last;
+ unsigned long nr_pages = compound ? folio_nr_pages(folio) : 1;
+ unsigned int nr, nr_pmdmapped = 0;
enum node_stat_item idx;
- 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 */
@@ -1454,36 +1502,8 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
return;
}
- if (folio_test_large(folio))
- folio_dec_large_mapcount(folio, vma);
-
- /* Is page being unmapped by PTE? Is this its last map to be removed? */
- if (likely(!compound)) {
- last = atomic_add_negative(-1, &page->_mapcount);
- nr = last;
- if (last && folio_test_large(folio)) {
- nr = atomic_dec_return_relaxed(mapped);
- nr = (nr < COMPOUND_MAPPED);
- }
- } else if (folio_test_pmd_mappable(folio)) {
- /* That test is redundant: it's for safety or to optimize out */
-
- last = atomic_add_negative(-1, &folio->_entire_mapcount);
- if (last) {
- nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
- if (likely(nr < COMPOUND_MAPPED)) {
- nr_pmdmapped = folio_nr_pages(folio);
- nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
- /* Raced ahead of another remove and an add? */
- if (unlikely(nr < 0))
- nr = 0;
- } else {
- /* An add of COMPOUND_MAPPED raced ahead */
- nr = 0;
- }
- }
- }
-
+ nr = __folio_remove_rmap_range(folio, page, nr_pages, vma, compound,
+ &nr_pmdmapped);
if (nr_pmdmapped) {
if (folio_test_anon(folio))
idx = NR_ANON_THPS;
--
2.41.0
