[PATCH v2 11/20] mm/rmap: use folio_large_nr_pages() in add/remove functions

David Hildenbrand
2025-02-24T16:56:31Z

Let's just use the "large" variant in code where we are sure that we
have a large folio in our hands: this way we are sure that we don't
perform any unnecessary "large" checks.

While at it, convert the VM_BUG_ON_VMA to a VM_WARN_ON_ONCE.

Maybe in the future there will not be a difference in that regard
between large and small folios; in that case, unifying the handling again
will be easy. E.g., folio_large_nr_pages() will simply translate to
folio_nr_pages() until we replace all instances.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/rmap.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 08846b7eced60..c9922928616ee 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1274,7 +1274,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
if (first) {
nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
- nr_pages = folio_nr_pages(folio);
+ nr_pages = folio_large_nr_pages(folio);
/*
* We only track PMD mappings of PMD-sized
* folios separately.
@@ -1522,14 +1522,11 @@ void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, rmap_t flags)
{
- const int nr = folio_nr_pages(folio);
const bool exclusive = flags & RMAP_EXCLUSIVE;
- int nr_pmdmapped = 0;
+ int nr = 1, nr_pmdmapped = 0;

VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
- VM_BUG_ON_VMA(address < vma->vm_start ||
- address + (nr << PAGE_SHIFT) > vma->vm_end, vma);

/*
* VM_DROPPABLE mappings don't swap; instead they're just dropped when
@@ -1547,6 +1544,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
} else if (!folio_test_pmd_mappable(folio)) {
int i;

+ nr = folio_large_nr_pages(folio);
for (i = 0; i < nr; i++) {
struct page *page = folio_page(folio, i);

@@ -1559,6 +1557,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
folio_set_large_mapcount(folio, nr, vma);
atomic_set(&folio->_nr_pages_mapped, nr);
} else {
+ nr = folio_large_nr_pages(folio);
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
folio_set_large_mapcount(folio, 1, vma);
@@ -1568,6 +1567,9 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
nr_pmdmapped = nr;
}

+ VM_WARN_ON_ONCE(address < vma->vm_start ||
+ address + (nr << PAGE_SHIFT) > vma->vm_end);
+
__folio_mod_stat(folio, nr, nr_pmdmapped);
mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
}
@@ -1681,7 +1683,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
if (last) {
nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
if (likely(nr < ENTIRELY_MAPPED)) {
- nr_pages = folio_nr_pages(folio);
+ nr_pages = folio_large_nr_pages(folio);
if (level == RMAP_LEVEL_PMD)
nr_pmdmapped = nr_pages;
nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
--
2.48.1