On Mon, Aug 11, 2025 at 01:26:27PM +0200, David Hildenbrand wrote:
> 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 <da...@redhat.com>
Nice cleanup! This LGTM, so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.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
>
