[PATCH v3 07/11] mm/rmap: convert "enum rmap_level" to "enum pgtable_level"

[David Hildenbrand <david@redhat.com>]

Let's factor it out, and convert all checks for unsupported levels to
BUILD_BUG(). The code is written in a way such that force-inlining will
optimize out the levels.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/pgtable.h |  8 ++++++
 include/linux/rmap.h    | 60 +++++++++++++++++++----------------------
 mm/rmap.c               | 56 +++++++++++++++++++++-----------------
 3 files changed, 66 insertions(+), 58 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 4c035637eeb77..bff5c4241bf2e 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1958,6 +1958,14 @@ static inline bool arch_has_pfn_modify_check(void)
 /* Page-Table Modification Mask */
 typedef unsigned int pgtbl_mod_mask;
 
+enum pgtable_level {
+	PGTABLE_LEVEL_PTE = 0,
+	PGTABLE_LEVEL_PMD,
+	PGTABLE_LEVEL_PUD,
+	PGTABLE_LEVEL_P4D,
+	PGTABLE_LEVEL_PGD,
+};
+
 #endif /* !__ASSEMBLY__ */
 
 #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 6cd020eea37a2..9d40d127bdb78 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -394,18 +394,8 @@ typedef int __bitwise rmap_t;
 /* The anonymous (sub)page is exclusive to a single process. */
 #define RMAP_EXCLUSIVE		((__force rmap_t)BIT(0))
 
-/*
- * Internally, we're using an enum to specify the granularity. We make the
- * compiler emit specialized code for each granularity.
- */
-enum rmap_level {
-	RMAP_LEVEL_PTE = 0,
-	RMAP_LEVEL_PMD,
-	RMAP_LEVEL_PUD,
-};
-
 static inline void __folio_rmap_sanity_checks(const struct folio *folio,
-		const struct page *page, int nr_pages, enum rmap_level level)
+		const struct page *page, int nr_pages, enum pgtable_level level)
 {
 	/* hugetlb folios are handled separately. */
 	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
@@ -427,18 +417,18 @@ static inline void __folio_rmap_sanity_checks(const struct folio *folio,
 	VM_WARN_ON_FOLIO(page_folio(page + nr_pages - 1) != folio, folio);
 
 	switch (level) {
-	case RMAP_LEVEL_PTE:
+	case PGTABLE_LEVEL_PTE:
 		break;
-	case RMAP_LEVEL_PMD:
+	case PGTABLE_LEVEL_PMD:
 		/*
 		 * We don't support folios larger than a single PMD yet. So
-		 * when RMAP_LEVEL_PMD is set, we assume that we are creating
+		 * when PGTABLE_LEVEL_PMD is set, we assume that we are creating
 		 * a single "entire" mapping of the folio.
 		 */
 		VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PMD_NR, folio);
 		VM_WARN_ON_FOLIO(nr_pages != HPAGE_PMD_NR, folio);
 		break;
-	case RMAP_LEVEL_PUD:
+	case PGTABLE_LEVEL_PUD:
 		/*
 		 * Assume that we are creating a single "entire" mapping of the
 		 * folio.
@@ -447,7 +437,7 @@ static inline void __folio_rmap_sanity_checks(const struct folio *folio,
 		VM_WARN_ON_FOLIO(nr_pages != HPAGE_PUD_NR, folio);
 		break;
 	default:
-		VM_WARN_ON_ONCE(true);
+		BUILD_BUG();
 	}
 
 	/*
@@ -567,14 +557,14 @@ static inline void hugetlb_remove_rmap(struct folio *folio)
 
 static __always_inline void __folio_dup_file_rmap(struct folio *folio,
 		struct page *page, int nr_pages, struct vm_area_struct *dst_vma,
-		enum rmap_level level)
+		enum pgtable_level level)
 {
 	const int orig_nr_pages = nr_pages;
 
 	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
 
 	switch (level) {
-	case RMAP_LEVEL_PTE:
+	case PGTABLE_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
 			atomic_inc(&folio->_mapcount);
 			break;
@@ -587,11 +577,13 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio,
 		}
 		folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
 		break;
-	case RMAP_LEVEL_PMD:
-	case RMAP_LEVEL_PUD:
+	case PGTABLE_LEVEL_PMD:
+	case PGTABLE_LEVEL_PUD:
 		atomic_inc(&folio->_entire_mapcount);
 		folio_inc_large_mapcount(folio, dst_vma);
 		break;
+	default:
+		BUILD_BUG();
 	}
 }
 
@@ -609,13 +601,13 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio,
 static inline void folio_dup_file_rmap_ptes(struct folio *folio,
 		struct page *page, int nr_pages, struct vm_area_struct *dst_vma)
 {
-	__folio_dup_file_rmap(folio, page, nr_pages, dst_vma, RMAP_LEVEL_PTE);
+	__folio_dup_file_rmap(folio, page, nr_pages, dst_vma, PGTABLE_LEVEL_PTE);
 }
 
 static __always_inline void folio_dup_file_rmap_pte(struct folio *folio,
 		struct page *page, struct vm_area_struct *dst_vma)
 {
-	__folio_dup_file_rmap(folio, page, 1, dst_vma, RMAP_LEVEL_PTE);
+	__folio_dup_file_rmap(folio, page, 1, dst_vma, PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -632,7 +624,7 @@ static inline void folio_dup_file_rmap_pmd(struct folio *folio,
 		struct page *page, struct vm_area_struct *dst_vma)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	__folio_dup_file_rmap(folio, page, HPAGE_PMD_NR, dst_vma, RMAP_LEVEL_PTE);
+	__folio_dup_file_rmap(folio, page, HPAGE_PMD_NR, dst_vma, PGTABLE_LEVEL_PTE);
 #else
 	WARN_ON_ONCE(true);
 #endif
@@ -640,7 +632,7 @@ static inline void folio_dup_file_rmap_pmd(struct folio *folio,
 
 static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 		struct page *page, int nr_pages, struct vm_area_struct *dst_vma,
-		struct vm_area_struct *src_vma, enum rmap_level level)
+		struct vm_area_struct *src_vma, enum pgtable_level level)
 {
 	const int orig_nr_pages = nr_pages;
 	bool maybe_pinned;
@@ -665,7 +657,7 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 	 * copying if the folio maybe pinned.
 	 */
 	switch (level) {
-	case RMAP_LEVEL_PTE:
+	case PGTABLE_LEVEL_PTE:
 		if (unlikely(maybe_pinned)) {
 			for (i = 0; i < nr_pages; i++)
 				if (PageAnonExclusive(page + i))
@@ -687,8 +679,8 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 		} while (page++, --nr_pages > 0);
 		folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
 		break;
-	case RMAP_LEVEL_PMD:
-	case RMAP_LEVEL_PUD:
+	case PGTABLE_LEVEL_PMD:
+	case PGTABLE_LEVEL_PUD:
 		if (PageAnonExclusive(page)) {
 			if (unlikely(maybe_pinned))
 				return -EBUSY;
@@ -697,6 +689,8 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 		atomic_inc(&folio->_entire_mapcount);
 		folio_inc_large_mapcount(folio, dst_vma);
 		break;
+	default:
+		BUILD_BUG();
 	}
 	return 0;
 }
@@ -730,7 +724,7 @@ static inline int folio_try_dup_anon_rmap_ptes(struct folio *folio,
 		struct vm_area_struct *src_vma)
 {
 	return __folio_try_dup_anon_rmap(folio, page, nr_pages, dst_vma,
-					 src_vma, RMAP_LEVEL_PTE);
+					 src_vma, PGTABLE_LEVEL_PTE);
 }
 
 static __always_inline int folio_try_dup_anon_rmap_pte(struct folio *folio,
@@ -738,7 +732,7 @@ static __always_inline int folio_try_dup_anon_rmap_pte(struct folio *folio,
 		struct vm_area_struct *src_vma)
 {
 	return __folio_try_dup_anon_rmap(folio, page, 1, dst_vma, src_vma,
-					 RMAP_LEVEL_PTE);
+					 PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -770,7 +764,7 @@ static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio,
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	return __folio_try_dup_anon_rmap(folio, page, HPAGE_PMD_NR, dst_vma,
-					 src_vma, RMAP_LEVEL_PMD);
+					 src_vma, PGTABLE_LEVEL_PMD);
 #else
 	WARN_ON_ONCE(true);
 	return -EBUSY;
@@ -778,7 +772,7 @@ static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio,
 }
 
 static __always_inline int __folio_try_share_anon_rmap(struct folio *folio,
-		struct page *page, int nr_pages, enum rmap_level level)
+		struct page *page, int nr_pages, enum pgtable_level level)
 {
 	VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
 	VM_WARN_ON_FOLIO(!PageAnonExclusive(page), folio);
@@ -873,7 +867,7 @@ static __always_inline int __folio_try_share_anon_rmap(struct folio *folio,
 static inline int folio_try_share_anon_rmap_pte(struct folio *folio,
 		struct page *page)
 {
-	return __folio_try_share_anon_rmap(folio, page, 1, RMAP_LEVEL_PTE);
+	return __folio_try_share_anon_rmap(folio, page, 1, PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -904,7 +898,7 @@ static inline int folio_try_share_anon_rmap_pmd(struct folio *folio,
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	return __folio_try_share_anon_rmap(folio, page, HPAGE_PMD_NR,
-					   RMAP_LEVEL_PMD);
+					   PGTABLE_LEVEL_PMD);
 #else
 	WARN_ON_ONCE(true);
 	return -EBUSY;
diff --git a/mm/rmap.c b/mm/rmap.c
index 84a8d8b02ef77..0e9c4041f8687 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1265,7 +1265,7 @@ static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
 
 static __always_inline void __folio_add_rmap(struct folio *folio,
 		struct page *page, int nr_pages, struct vm_area_struct *vma,
-		enum rmap_level level)
+		enum pgtable_level level)
 {
 	atomic_t *mapped = &folio->_nr_pages_mapped;
 	const int orig_nr_pages = nr_pages;
@@ -1274,7 +1274,7 @@ static __always_inline void __folio_add_rmap(struct folio *folio,
 	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
 
 	switch (level) {
-	case RMAP_LEVEL_PTE:
+	case PGTABLE_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
 			nr = atomic_inc_and_test(&folio->_mapcount);
 			break;
@@ -1300,11 +1300,11 @@ static __always_inline void __folio_add_rmap(struct folio *folio,
 
 		folio_add_large_mapcount(folio, orig_nr_pages, vma);
 		break;
-	case RMAP_LEVEL_PMD:
-	case RMAP_LEVEL_PUD:
+	case PGTABLE_LEVEL_PMD:
+	case PGTABLE_LEVEL_PUD:
 		first = atomic_inc_and_test(&folio->_entire_mapcount);
 		if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) {
-			if (level == RMAP_LEVEL_PMD && first)
+			if (level == PGTABLE_LEVEL_PMD && first)
 				nr_pmdmapped = folio_large_nr_pages(folio);
 			nr = folio_inc_return_large_mapcount(folio, vma);
 			if (nr == 1)
@@ -1323,7 +1323,7 @@ static __always_inline void __folio_add_rmap(struct folio *folio,
 				 * We only track PMD mappings of PMD-sized
 				 * folios separately.
 				 */
-				if (level == RMAP_LEVEL_PMD)
+				if (level == PGTABLE_LEVEL_PMD)
 					nr_pmdmapped = nr_pages;
 				nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
 				/* Raced ahead of a remove and another add? */
@@ -1336,6 +1336,8 @@ static __always_inline void __folio_add_rmap(struct folio *folio,
 		}
 		folio_inc_large_mapcount(folio, vma);
 		break;
+	default:
+		BUILD_BUG();
 	}
 	__folio_mod_stat(folio, nr, nr_pmdmapped);
 }
@@ -1427,7 +1429,7 @@ static void __page_check_anon_rmap(const struct folio *folio,
 
 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_level level)
+		unsigned long address, rmap_t flags, enum pgtable_level level)
 {
 	int i;
 
@@ -1440,20 +1442,22 @@ static __always_inline void __folio_add_anon_rmap(struct folio *folio,
 
 	if (flags & RMAP_EXCLUSIVE) {
 		switch (level) {
-		case RMAP_LEVEL_PTE:
+		case PGTABLE_LEVEL_PTE:
 			for (i = 0; i < nr_pages; i++)
 				SetPageAnonExclusive(page + i);
 			break;
-		case RMAP_LEVEL_PMD:
+		case PGTABLE_LEVEL_PMD:
 			SetPageAnonExclusive(page);
 			break;
-		case RMAP_LEVEL_PUD:
+		case PGTABLE_LEVEL_PUD:
 			/*
 			 * Keep the compiler happy, we don't support anonymous
 			 * PUD mappings.
 			 */
 			WARN_ON_ONCE(1);
 			break;
+		default:
+			BUILD_BUG();
 		}
 	}
 
@@ -1507,7 +1511,7 @@ void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
 		rmap_t flags)
 {
 	__folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
-			      RMAP_LEVEL_PTE);
+			      PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -1528,7 +1532,7 @@ void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	__folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
-			      RMAP_LEVEL_PMD);
+			      PGTABLE_LEVEL_PMD);
 #else
 	WARN_ON_ONCE(true);
 #endif
@@ -1609,7 +1613,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 
 static __always_inline void __folio_add_file_rmap(struct folio *folio,
 		struct page *page, int nr_pages, struct vm_area_struct *vma,
-		enum rmap_level level)
+		enum pgtable_level level)
 {
 	VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
 
@@ -1634,7 +1638,7 @@ static __always_inline void __folio_add_file_rmap(struct folio *folio,
 void folio_add_file_rmap_ptes(struct folio *folio, struct page *page,
 		int nr_pages, struct vm_area_struct *vma)
 {
-	__folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
+	__folio_add_file_rmap(folio, page, nr_pages, vma, PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -1651,7 +1655,7 @@ void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
 		struct vm_area_struct *vma)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	__folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
+	__folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, PGTABLE_LEVEL_PMD);
 #else
 	WARN_ON_ONCE(true);
 #endif
@@ -1672,7 +1676,7 @@ void folio_add_file_rmap_pud(struct folio *folio, struct page *page,
 {
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
 	defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
-	__folio_add_file_rmap(folio, page, HPAGE_PUD_NR, vma, RMAP_LEVEL_PUD);
+	__folio_add_file_rmap(folio, page, HPAGE_PUD_NR, vma, PGTABLE_LEVEL_PUD);
 #else
 	WARN_ON_ONCE(true);
 #endif
@@ -1680,7 +1684,7 @@ void folio_add_file_rmap_pud(struct folio *folio, struct page *page,
 
 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)
+		enum pgtable_level level)
 {
 	atomic_t *mapped = &folio->_nr_pages_mapped;
 	int last = 0, nr = 0, nr_pmdmapped = 0;
@@ -1689,7 +1693,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
 
 	switch (level) {
-	case RMAP_LEVEL_PTE:
+	case PGTABLE_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
 			nr = atomic_add_negative(-1, &folio->_mapcount);
 			break;
@@ -1719,11 +1723,11 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 
 		partially_mapped = nr && atomic_read(mapped);
 		break;
-	case RMAP_LEVEL_PMD:
-	case RMAP_LEVEL_PUD:
+	case PGTABLE_LEVEL_PMD:
+	case PGTABLE_LEVEL_PUD:
 		if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) {
 			last = atomic_add_negative(-1, &folio->_entire_mapcount);
-			if (level == RMAP_LEVEL_PMD && last)
+			if (level == PGTABLE_LEVEL_PMD && last)
 				nr_pmdmapped = folio_large_nr_pages(folio);
 			nr = folio_dec_return_large_mapcount(folio, vma);
 			if (!nr) {
@@ -1743,7 +1747,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 			nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
 			if (likely(nr < ENTIRELY_MAPPED)) {
 				nr_pages = folio_large_nr_pages(folio);
-				if (level == RMAP_LEVEL_PMD)
+				if (level == PGTABLE_LEVEL_PMD)
 					nr_pmdmapped = nr_pages;
 				nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
 				/* Raced ahead of another remove and an add? */
@@ -1757,6 +1761,8 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 
 		partially_mapped = nr && nr < nr_pmdmapped;
 		break;
+	default:
+		BUILD_BUG();
 	}
 
 	/*
@@ -1796,7 +1802,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 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(folio, page, nr_pages, vma, PGTABLE_LEVEL_PTE);
 }
 
 /**
@@ -1813,7 +1819,7 @@ 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);
+	__folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, PGTABLE_LEVEL_PMD);
 #else
 	WARN_ON_ONCE(true);
 #endif
@@ -1834,7 +1840,7 @@ void folio_remove_rmap_pud(struct folio *folio, struct page *page,
 {
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
 	defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
-	__folio_remove_rmap(folio, page, HPAGE_PUD_NR, vma, RMAP_LEVEL_PUD);
+	__folio_remove_rmap(folio, page, HPAGE_PUD_NR, vma, PGTABLE_LEVEL_PUD);
 #else
 	WARN_ON_ONCE(true);
 #endif
-- 
2.50.1