mm/rmap: introduce folio_remove_rmap_[pte|ptes|pmd]()

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.

Link: https://lkml.kernel.org/r/20231220224504.646757-24-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index bf6cb79aa7a0a9c88be69c2d7c68078e02fb1315..57e045093f0476d09fe20f30a82e18855d344477 100644 (file)
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -243,6 +243,12 @@ 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 2b386b9f6791c9393f3094b24ee1578543045509..127318075395367588ebc568778d32100ac7d223 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1510,25 +1510,37 @@ 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_level level)
+{
        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);
-
-       /* 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 */
+       __folio_rmap_sanity_checks(folio, page, nr_pages, level);
+
+       switch (level) {
+       case RMAP_LEVEL_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_LEVEL_PMD:
                last = atomic_add_negative(-1, &folio->_entire_mapcount);
                if (last) {
                        nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
@@ -1543,6 +1555,7 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
                                nr = 0;
                        }
                }
+               break;
        }
 
        if (nr_pmdmapped) {
@@ -1564,7 +1577,7 @@ 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 (level == RMAP_LEVEL_PTE || nr < nr_pmdmapped)
                                deferred_split_folio(folio);
        }
 
@@ -1579,6 +1592,43 @@ 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_LEVEL_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_LEVEL_PMD);
+#else
+       WARN_ON_ONCE(true);
+#endif
+}
+
 /*
  * @arg: enum ttu_flags will be passed to this argument
  */