Re: [PATCH v1 26/29] mm: rename PAGE_MAPPING_* to FOLIO_MAPPING_*

From: Lorenzo Stoakes
Date: Tue Jul 01 2025 - 09:25:26 EST

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On Mon, Jun 30, 2025 at 03:00:07PM +0200, David Hildenbrand wrote:
> Now that the mapping flags are only used for folios, let's rename the
> defines.
>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

As the official King of Churn (TM) I approve of this :)

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>

> ---
> fs/proc/page.c | 4 ++--
> include/linux/fs.h | 2 +-
> include/linux/mm_types.h | 1 -
> include/linux/page-flags.h | 20 ++++++++++----------
> include/linux/pagemap.h | 2 +-
> mm/gup.c | 4 ++--
> mm/internal.h | 2 +-
> mm/ksm.c | 4 ++--
> mm/rmap.c | 16 ++++++++--------
> mm/util.c | 6 +++---
> 10 files changed, 30 insertions(+), 31 deletions(-)
>
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 999af26c72985..0cdc78c0d23fa 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -149,7 +149,7 @@ u64 stable_page_flags(const struct page *page)
>
> k = folio->flags;
> mapping = (unsigned long)folio->mapping;
> - is_anon = mapping & PAGE_MAPPING_ANON;
> + is_anon = mapping & FOLIO_MAPPING_ANON;
>
> /*
> * pseudo flags for the well known (anonymous) memory mapped pages
> @@ -158,7 +158,7 @@ u64 stable_page_flags(const struct page *page)
> u |= 1 << KPF_MMAP;
> if (is_anon) {
> u |= 1 << KPF_ANON;
> - if (mapping & PAGE_MAPPING_KSM)
> + if (mapping & FOLIO_MAPPING_KSM)
> u |= 1 << KPF_KSM;
> }
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c68c9a07cda33..9b0de18746815 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -526,7 +526,7 @@ struct address_space {
> /*
> * On most architectures that alignment is already the case; but
> * must be enforced here for CRIS, to let the least significant bit
> - * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
> + * of struct folio's "mapping" pointer be used for FOLIO_MAPPING_ANON.
> */
>
> /* XArray tags, for tagging dirty and writeback pages in the pagecache. */
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 804d269a4f5e8..1ec273b066915 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -105,7 +105,6 @@ struct page {
> unsigned int order;
> };
> };
> - /* See page-flags.h for PAGE_MAPPING_FLAGS */
> struct address_space *mapping;
> union {
> pgoff_t __folio_index; /* Our offset within mapping. */
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index b42986a578b71..23b1e458dfeda 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -695,10 +695,10 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
> /*
> * On an anonymous folio mapped into a user virtual memory area,
> * folio->mapping points to its anon_vma, not to a struct address_space;
> - * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
> + * with the FOLIO_MAPPING_ANON bit set to distinguish it. See rmap.h.
> *
> * On an anonymous folio in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
> - * the PAGE_MAPPING_ANON_KSM bit may be set along with the PAGE_MAPPING_ANON
> + * the FOLIO_MAPPING_ANON_KSM bit may be set along with the FOLIO_MAPPING_ANON
> * bit; and then folio->mapping points, not to an anon_vma, but to a private
> * structure which KSM associates with that merged folio. See ksm.h.
> *
> @@ -713,21 +713,21 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
> * false before calling the following functions (e.g., folio_test_anon).
> * See mm/slab.h.
> */
> -#define PAGE_MAPPING_ANON 0x1
> -#define PAGE_MAPPING_ANON_KSM 0x2
> -#define PAGE_MAPPING_KSM (PAGE_MAPPING_ANON | PAGE_MAPPING_ANON_KSM)
> -#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_ANON_KSM)
> +#define FOLIO_MAPPING_ANON 0x1
> +#define FOLIO_MAPPING_ANON_KSM 0x2
> +#define FOLIO_MAPPING_KSM (FOLIO_MAPPING_ANON | FOLIO_MAPPING_ANON_KSM)
> +#define FOLIO_MAPPING_FLAGS (FOLIO_MAPPING_ANON | FOLIO_MAPPING_ANON_KSM)
>
> static __always_inline bool folio_test_anon(const struct folio *folio)
> {
> - return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
> + return ((unsigned long)folio->mapping & FOLIO_MAPPING_ANON) != 0;
> }
>
> static __always_inline bool PageAnonNotKsm(const struct page *page)
> {
> unsigned long flags = (unsigned long)page_folio(page)->mapping;
>
> - return (flags & PAGE_MAPPING_FLAGS) == PAGE_MAPPING_ANON;
> + return (flags & FOLIO_MAPPING_FLAGS) == FOLIO_MAPPING_ANON;
> }
>
> static __always_inline bool PageAnon(const struct page *page)
> @@ -743,8 +743,8 @@ static __always_inline bool PageAnon(const struct page *page)
> */
> static __always_inline bool folio_test_ksm(const struct folio *folio)
> {
> - return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) ==
> - PAGE_MAPPING_KSM;
> + return ((unsigned long)folio->mapping & FOLIO_MAPPING_FLAGS) ==
> + FOLIO_MAPPING_KSM;
> }
> #else
> FOLIO_TEST_FLAG_FALSE(ksm)
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index e63fbfbd5b0f3..10a222e68b851 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -502,7 +502,7 @@ static inline pgoff_t mapping_align_index(struct address_space *mapping,
> static inline bool mapping_large_folio_support(struct address_space *mapping)
> {
> /* AS_FOLIO_ORDER is only reasonable for pagecache folios */
> - VM_WARN_ONCE((unsigned long)mapping & PAGE_MAPPING_ANON,
> + VM_WARN_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON,
> "Anonymous mapping always supports large folio");
>
> return mapping_max_folio_order(mapping) > 0;
> diff --git a/mm/gup.c b/mm/gup.c
> index 30d320719fa23..adffe663594dc 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2804,9 +2804,9 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
> return false;
>
> /* Anonymous folios pose no problem. */
> - mapping_flags = (unsigned long)mapping & PAGE_MAPPING_FLAGS;
> + mapping_flags = (unsigned long)mapping & FOLIO_MAPPING_FLAGS;
> if (mapping_flags)
> - return mapping_flags & PAGE_MAPPING_ANON;
> + return mapping_flags & FOLIO_MAPPING_ANON;
>
> /*
> * At this point, we know the mapping is non-null and points to an
> diff --git a/mm/internal.h b/mm/internal.h
> index e84217e27778d..c29ddec7ade3d 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -149,7 +149,7 @@ static inline void *folio_raw_mapping(const struct folio *folio)
> {
> unsigned long mapping = (unsigned long)folio->mapping;
>
> - return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
> + return (void *)(mapping & ~FOLIO_MAPPING_FLAGS);
> }
>
> /*
> diff --git a/mm/ksm.c b/mm/ksm.c
> index ef73b25fd65a6..2b0210d41c553 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -893,7 +893,7 @@ static struct folio *ksm_get_folio(struct ksm_stable_node *stable_node,
> unsigned long kpfn;
>
> expected_mapping = (void *)((unsigned long)stable_node |
> - PAGE_MAPPING_KSM);
> + FOLIO_MAPPING_KSM);
> again:
> kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */
> folio = pfn_folio(kpfn);
> @@ -1070,7 +1070,7 @@ static inline void folio_set_stable_node(struct folio *folio,
> struct ksm_stable_node *stable_node)
> {
> VM_WARN_ON_FOLIO(folio_test_anon(folio) && PageAnonExclusive(&folio->page), folio);
> - folio->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM);
> + folio->mapping = (void *)((unsigned long)stable_node | FOLIO_MAPPING_KSM);
> }
>
> #ifdef CONFIG_SYSFS
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 34311f654d0c2..de14fb6963c24 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -503,12 +503,12 @@ struct anon_vma *folio_get_anon_vma(const struct folio *folio)
>
> rcu_read_lock();
> anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
> - if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
> + if ((anon_mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON)
> goto out;
> if (!folio_mapped(folio))
> goto out;
>
> - anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
> + anon_vma = (struct anon_vma *) (anon_mapping - FOLIO_MAPPING_ANON);
> if (!atomic_inc_not_zero(&anon_vma->refcount)) {
> anon_vma = NULL;
> goto out;
> @@ -550,12 +550,12 @@ struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
> retry:
> rcu_read_lock();
> anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
> - if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
> + if ((anon_mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON)
> goto out;
> if (!folio_mapped(folio))
> goto out;
>
> - anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
> + anon_vma = (struct anon_vma *) (anon_mapping - FOLIO_MAPPING_ANON);
> root_anon_vma = READ_ONCE(anon_vma->root);
> if (down_read_trylock(&root_anon_vma->rwsem)) {
> /*
> @@ -1334,9 +1334,9 @@ void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
> VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
> VM_BUG_ON_VMA(!anon_vma, vma);
>
> - anon_vma += PAGE_MAPPING_ANON;
> + anon_vma += FOLIO_MAPPING_ANON;
> /*
> - * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
> + * Ensure that anon_vma and the FOLIO_MAPPING_ANON bit are written
> * simultaneously, so a concurrent reader (eg folio_referenced()'s
> * folio_test_anon()) will not see one without the other.
> */
> @@ -1367,10 +1367,10 @@ static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
> /*
> * page_idle does a lockless/optimistic rmap scan on folio->mapping.
> * Make sure the compiler doesn't split the stores of anon_vma and
> - * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
> + * the FOLIO_MAPPING_ANON type identifier, otherwise the rmap code
> * could mistake the mapping for a struct address_space and crash.
> */
> - anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
> + anon_vma = (void *) anon_vma + FOLIO_MAPPING_ANON;
> WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
> folio->index = linear_page_index(vma, address);
> }
> diff --git a/mm/util.c b/mm/util.c
> index 0b270c43d7d12..20bbfe4ce1b8b 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -670,9 +670,9 @@ struct anon_vma *folio_anon_vma(const struct folio *folio)
> {
> unsigned long mapping = (unsigned long)folio->mapping;
>
> - if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
> + if ((mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON)
> return NULL;
> - return (void *)(mapping - PAGE_MAPPING_ANON);
> + return (void *)(mapping - FOLIO_MAPPING_ANON);
> }
>
> /**
> @@ -699,7 +699,7 @@ struct address_space *folio_mapping(struct folio *folio)
> return swap_address_space(folio->swap);
>
> mapping = folio->mapping;
> - if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
> + if ((unsigned long)mapping & FOLIO_MAPPING_FLAGS)
> return NULL;
>
> return mapping;
> --
> 2.49.0
>

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