[PATCH v1 14/39] mm/rmap: introduce folio_add_anon_rmap_[pte|ptes|pmd]()

David Hildenbrand
2023-12-11T15:57:44Z

Let's mimic what we did with folio_add_file_rmap_*() so we can similarly
replace page_add_anon_rmap() next.

Make the compiler always special-case on the granularity by using
__always_inline.

Note that the new functions ignore the RMAP_COMPOUND flag, which we will
remove as soon as page_add_anon_rmap() is gone.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/rmap.h | 6 +++
mm/rmap.c | 118 ++++++++++++++++++++++++++++++-------------
2 files changed, 88 insertions(+), 36 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 7198905dc8be..3b5357cb1c09 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -234,6 +234,12 @@ static inline void __folio_rmap_sanity_checks(struct folio *folio,
* rmap interfaces called when adding or removing pte of page
*/
void folio_move_anon_rmap(struct folio *, struct vm_area_struct *);
+void folio_add_anon_rmap_ptes(struct folio *, struct page *, int nr_pages,
+ struct vm_area_struct *, unsigned long address, rmap_t flags);
+#define folio_add_anon_rmap_pte(folio, page, vma, address, flags) \
+ folio_add_anon_rmap_ptes(folio, page, 1, vma, address, flags)
+void folio_add_anon_rmap_pmd(struct folio *, struct page *,
+ struct vm_area_struct *, unsigned long address, rmap_t flags);
void page_add_anon_rmap(struct page *, struct vm_area_struct *,
unsigned long address, rmap_t flags);
void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
diff --git a/mm/rmap.c b/mm/rmap.c
index c5761986a411..7787499fa2ad 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1300,38 +1300,20 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
unsigned long address, rmap_t flags)
{
struct folio *folio = page_folio(page);
- atomic_t *mapped = &folio->_nr_pages_mapped;
- int nr = 0, nr_pmdmapped = 0;
- bool compound = flags & RMAP_COMPOUND;
- bool first;

- /* Is page being mapped by PTE? Is this its first map to be added? */
- if (likely(!compound)) {
- first = atomic_inc_and_test(&page->_mapcount);
- nr = first;
- if (first && folio_test_large(folio)) {
- nr = atomic_inc_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 */
+ if (likely(!(flags & RMAP_COMPOUND)))
+ folio_add_anon_rmap_pte(folio, page, vma, address, flags);
+ else
+ folio_add_anon_rmap_pmd(folio, page, vma, address, flags);
+}

- first = atomic_inc_and_test(&folio->_entire_mapcount);
- if (first) {
- nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
- if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
- nr_pmdmapped = folio_nr_pages(folio);
- nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
- /* Raced ahead of a remove and another add? */
- if (unlikely(nr < 0))
- nr = 0;
- } else {
- /* Raced ahead of a remove of COMPOUND_MAPPED */
- nr = 0;
- }
- }
- }
+static __always_inline void __folio_add_anon_rmap(struct folio *folio,
+ struct page *page, int nr_pages, struct vm_area_struct *vma,
+ unsigned long address, rmap_t flags, enum rmap_mode mode)
+{
+ unsigned int i, nr, nr_pmdmapped = 0;

+ nr = __folio_add_rmap(folio, page, nr_pages, mode, &nr_pmdmapped);
if (nr_pmdmapped)
__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped);
if (nr)
@@ -1345,18 +1327,34 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
* folio->index right when not given the address of the head
* page.
*/
- VM_WARN_ON_FOLIO(folio_test_large(folio) && !compound, folio);
+ VM_WARN_ON_FOLIO(folio_test_large(folio) &&
+ mode != RMAP_MODE_PMD, folio);
__folio_set_anon(folio, vma, address,
!!(flags & RMAP_EXCLUSIVE));
} else if (likely(!folio_test_ksm(folio))) {
__page_check_anon_rmap(folio, page, vma, address);
}
- if (flags & RMAP_EXCLUSIVE)
- SetPageAnonExclusive(page);
- /* While PTE-mapping a THP we have a PMD and a PTE mapping. */
- VM_WARN_ON_FOLIO((atomic_read(&page->_mapcount) > 0 ||
- (folio_test_large(folio) && folio_entire_mapcount(folio) > 1)) &&
- PageAnonExclusive(page), folio);
+
+ if (flags & RMAP_EXCLUSIVE) {
+ switch (mode) {
+ case RMAP_MODE_PTE:
+ for (i = 0; i < nr_pages; i++)
+ SetPageAnonExclusive(page + i);
+ break;
+ case RMAP_MODE_PMD:
+ SetPageAnonExclusive(page);
+ break;
+ }
+ }
+ for (i = 0; i < nr_pages; i++) {
+ struct page *cur_page = page + i;
+
+ /* While PTE-mapping a THP we have a PMD and a PTE mapping. */
+ VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 ||
+ (folio_test_large(folio) &&
+ folio_entire_mapcount(folio) > 1)) &&
+ PageAnonExclusive(cur_page), folio);
+ }

/*
* For large folio, only mlock it if it's fully mapped to VMA. It's
@@ -1368,6 +1366,54 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
mlock_vma_folio(folio, vma);
}

+/**
+ * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio
+ * @folio: The folio to add the mappings to
+ * @page: The first page to add
+ * @nr_pages: The number of pages which will be mapped
+ * @vma: The vm area in which the mappings are added
+ * @address: The user virtual address of the first page to map
+ * @flags: The rmap flags
+ *
+ * The page range of folio is defined by [first_page, first_page + nr_pages)
+ *
+ * The caller needs to hold the page table lock, and the page must be locked in
+ * the anon_vma case: to serialize mapping,index checking after setting,
+ * and to ensure that an anon folio is not being upgraded racily to a KSM folio
+ * (but KSM folios are never downgraded).
+ */
+void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
+ int nr_pages, struct vm_area_struct *vma, unsigned long address,
+ rmap_t flags)
+{
+ __folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
+ RMAP_MODE_PTE);
+}
+
+/**
+ * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio
+ * @folio: The folio to add the mapping to
+ * @page: The first page to add
+ * @vma: The vm area in which the mapping is added
+ * @address: The user virtual address of the first page to map
+ * @flags: The rmap flags
+ *
+ * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR)
+ *
+ * The caller needs to hold the page table lock, and the page must be locked in
+ * the anon_vma case: to serialize mapping,index checking after setting.
+ */
+void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
+ struct vm_area_struct *vma, unsigned long address, rmap_t flags)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ __folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
+ RMAP_MODE_PMD);
+#else
+ WARN_ON_ONCE(true);
+#endif
+}
+
/**
* folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
* @folio: The folio to add the mapping to.
--
2.43.0