mm/rmap: abstract large mapcount operations for large folios (!hugetlb)

Let's abstract the operations so we can extend these operations easily.

Link: https://lkml.kernel.org/r/20250303163014.1128035-10-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 34 insertions, 12 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index e795610bade8..d1e888cc97a5 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -173,6 +173,30 @@ static inline void anon_vma_merge(struct vm_area_struct *vma,
 
 struct anon_vma *folio_get_anon_vma(const struct folio *folio);
 
+static inline void folio_set_large_mapcount(struct folio *folio, int mapcount,
+		struct vm_area_struct *vma)
+{
+	/* Note: mapcounts start at -1. */
+	atomic_set(&folio->_large_mapcount, mapcount - 1);
+}
+
+static inline void folio_add_large_mapcount(struct folio *folio,
+		int diff, struct vm_area_struct *vma)
+{
+	atomic_add(diff, &folio->_large_mapcount);
+}
+
+static inline void folio_sub_large_mapcount(struct folio *folio,
+		int diff, struct vm_area_struct *vma)
+{
+	atomic_sub(diff, &folio->_large_mapcount);
+}
+
+#define folio_inc_large_mapcount(folio, vma) \
+	folio_add_large_mapcount(folio, 1, vma)
+#define folio_dec_large_mapcount(folio, vma) \
+	folio_sub_large_mapcount(folio, 1, vma)
+
 /* RMAP flags, currently only relevant for some anon rmap operations. */
 typedef int __bitwise rmap_t;
 
@@ -352,12 +376,12 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio,
 		do {
 			atomic_inc(&page->_mapcount);
 		} while (page++, --nr_pages > 0);
-		atomic_add(orig_nr_pages, &folio->_large_mapcount);
+		folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
 		break;
 	case RMAP_LEVEL_PMD:
 	case RMAP_LEVEL_PUD:
 		atomic_inc(&folio->_entire_mapcount);
-		atomic_inc(&folio->_large_mapcount);
+		folio_inc_large_mapcount(folio, dst_vma);
 		break;
 	}
 }
@@ -451,7 +475,7 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 				ClearPageAnonExclusive(page);
 			atomic_inc(&page->_mapcount);
 		} while (page++, --nr_pages > 0);
-		atomic_add(orig_nr_pages, &folio->_large_mapcount);
+		folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
 		break;
 	case RMAP_LEVEL_PMD:
 	case RMAP_LEVEL_PUD:
@@ -461,7 +485,7 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 			ClearPageAnonExclusive(page);
 		}
 		atomic_inc(&folio->_entire_mapcount);
-		atomic_inc(&folio->_large_mapcount);
+		folio_inc_large_mapcount(folio, dst_vma);
 		break;
 	}
 	return 0;
diff --git a/mm/rmap.c b/mm/rmap.c
index 8a7d023b02e0..08846b7eced6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1266,7 +1266,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
 		    atomic_add_return_relaxed(first, mapped) < ENTIRELY_MAPPED)
 			nr = first;
 
-		atomic_add(orig_nr_pages, &folio->_large_mapcount);
+		folio_add_large_mapcount(folio, orig_nr_pages, vma);
 		break;
 	case RMAP_LEVEL_PMD:
 	case RMAP_LEVEL_PUD:
@@ -1290,7 +1290,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
 				nr = 0;
 			}
 		}
-		atomic_inc(&folio->_large_mapcount);
+		folio_inc_large_mapcount(folio, vma);
 		break;
 	}
 	return nr;
@@ -1556,14 +1556,12 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 				SetPageAnonExclusive(page);
 		}
 
-		/* increment count (starts at -1) */
-		atomic_set(&folio->_large_mapcount, nr - 1);
+		folio_set_large_mapcount(folio, nr, vma);
 		atomic_set(&folio->_nr_pages_mapped, nr);
 	} else {
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_entire_mapcount, 0);
-		/* increment count (starts at -1) */
-		atomic_set(&folio->_large_mapcount, 0);
+		folio_set_large_mapcount(folio, 1, vma);
 		atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
 		if (exclusive)
 			SetPageAnonExclusive(&folio->page);
@@ -1665,7 +1663,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 			break;
 		}
 
-		atomic_sub(nr_pages, &folio->_large_mapcount);
+		folio_sub_large_mapcount(folio, nr_pages, vma);
 		do {
 			last += atomic_add_negative(-1, &page->_mapcount);
 		} while (page++, --nr_pages > 0);
@@ -1678,7 +1676,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 		break;
 	case RMAP_LEVEL_PMD:
 	case RMAP_LEVEL_PUD:
-		atomic_dec(&folio->_large_mapcount);
+		folio_dec_large_mapcount(folio, vma);
 		last = atomic_add_negative(-1, &folio->_entire_mapcount);
 		if (last) {
 			nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);