[PATCH v1 23/39] mm/rmap: introduce folio_remove_rmap_[pte|ptes|pmd]()

David Hildenbrand
2023-12-11T15:58:38Z

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

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

We're adding folio_remove_rmap_ptes() handling right away, as we want to
use that soon for batching rmap operations when unmapping PTE-mapped
large folios.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/rmap.h | 6 ++++
mm/rmap.c | 79 ++++++++++++++++++++++++++++++++++++--------
2 files changed, 71 insertions(+), 14 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 0acebe41ab8e..a266dc0ef99e 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -246,6 +246,12 @@ void folio_add_file_rmap_pmd(struct folio *, struct page *,
struct vm_area_struct *);
void page_remove_rmap(struct page *, struct vm_area_struct *,
bool compound);
+void folio_remove_rmap_ptes(struct folio *, struct page *, int nr_pages,
+ struct vm_area_struct *);
+#define folio_remove_rmap_pte(folio, page, vma) \
+ folio_remove_rmap_ptes(folio, page, 1, vma)
+void folio_remove_rmap_pmd(struct folio *, struct page *,
+ struct vm_area_struct *);

void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *,
unsigned long address, rmap_t flags);
diff --git a/mm/rmap.c b/mm/rmap.c
index 9212726268ba..dc3be5807cee 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1511,25 +1511,38 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
bool compound)
{
struct folio *folio = page_folio(page);
+
+ if (likely(!compound))
+ folio_remove_rmap_pte(folio, page, vma);
+ else
+ folio_remove_rmap_pmd(folio, page, vma);
+}
+
+static __always_inline void __folio_remove_rmap(struct folio *folio,
+ struct page *page, int nr_pages, struct vm_area_struct *vma,
+ enum rmap_mode mode)
+{
atomic_t *mapped = &folio->_nr_pages_mapped;
- int nr = 0, nr_pmdmapped = 0;
- bool last;
+ int last, nr = 0, nr_pmdmapped = 0;
enum node_stat_item idx;

- VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
- VM_BUG_ON_PAGE(compound && !PageHead(page), page);
+ __folio_rmap_sanity_checks(folio, page, nr_pages, mode);

/* 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 */
+ switch (mode) {
+ case RMAP_MODE_PTE:
+ do {
+ last = atomic_add_negative(-1, &page->_mapcount);
+ if (last && folio_test_large(folio)) {
+ last = atomic_dec_return_relaxed(mapped);
+ last = (last < COMPOUND_MAPPED);
+ }

+ if (last)
+ nr++;
+ } while (page++, --nr_pages > 0);
+ break;
+ case RMAP_MODE_PMD:
last = atomic_add_negative(-1, &folio->_entire_mapcount);
if (last) {
nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
@@ -1544,6 +1557,7 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
nr = 0;
}
}
+ break;
}

if (nr_pmdmapped) {
@@ -1565,7 +1579,7 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
* is still mapped.
*/
if (folio_test_large(folio) && folio_test_anon(folio))
- if (!compound || nr < nr_pmdmapped)
+ if (mode == RMAP_MODE_PTE || nr < nr_pmdmapped)
deferred_split_folio(folio);
}

@@ -1580,6 +1594,43 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
munlock_vma_folio(folio, vma);
}

+/**
+ * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
+ * @folio: The folio to remove the mappings from
+ * @page: The first page to remove
+ * @nr_pages: The number of pages that will be removed from the mapping
+ * @vma: The vm area from which the mappings are removed
+ *
+ * The page range of the folio is defined by [page, page + nr_pages)
+ *
+ * The caller needs to hold the page table lock.
+ */
+void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
+ int nr_pages, struct vm_area_struct *vma)
+{
+ __folio_remove_rmap(folio, page, nr_pages, vma, RMAP_MODE_PTE);
+}
+
+/**
+ * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio
+ * @folio: The folio to remove the mapping from
+ * @page: The first page to remove
+ * @vma: The vm area from which the mapping is removed
+ *
+ * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
+ *
+ * The caller needs to hold the page table lock.
+ */
+void folio_remove_rmap_pmd(struct folio *folio, struct page *page,
+ struct vm_area_struct *vma)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ __folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_MODE_PMD);
+#else
+ WARN_ON_ONCE(true);
+#endif
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
--
2.43.0