Re: [PATCH v6 10/12] mm: constify various inline functions for improved const-correctness

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Mon, Sep 01, 2025 at 10:50:19PM +0200, Max Kellermann wrote:
> We select certain test functions plus folio_migrate_refs() from
> mm_inline.h which either invoke each other, functions that are already
> const-ified, or no further functions.
>
> It is therefore relatively trivial to const-ify them, which
> provides a basis for further const-ification further up the call
> stack.
>
> One exception is the function folio_migrate_refs() which does write to
> the "new" folio pointer; there, only the "old" folio pointer is being
> constified; only its "flags" field is read, but nothing written.
>
> Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
> Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>

LGTM, so:

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

> ---
>  include/linux/mm_inline.h | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index 150302b4a905..d6c1011b38f2 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -25,7 +25,7 @@
>   * 0 if @folio is a normal anonymous folio, a tmpfs folio or otherwise
>   * ram or swap backed folio.
>   */
> -static inline int folio_is_file_lru(struct folio *folio)
> +static inline int folio_is_file_lru(const struct folio *folio)
>  {
>  	return !folio_test_swapbacked(folio);
>  }
> @@ -84,7 +84,7 @@ static __always_inline void __folio_clear_lru_flags(struct folio *folio)
>   * Return: The LRU list a folio should be on, as an index
>   * into the array of LRU lists.
>   */
> -static __always_inline enum lru_list folio_lru_list(struct folio *folio)
> +static __always_inline enum lru_list folio_lru_list(const struct folio *folio)
>  {
>  	enum lru_list lru;
>
> @@ -141,7 +141,7 @@ static inline int lru_tier_from_refs(int refs, bool workingset)
>  	return workingset ? MAX_NR_TIERS - 1 : order_base_2(refs);
>  }
>
> -static inline int folio_lru_refs(struct folio *folio)
> +static inline int folio_lru_refs(const struct folio *folio)
>  {
>  	unsigned long flags = READ_ONCE(folio->flags.f);
>
> @@ -154,14 +154,14 @@ static inline int folio_lru_refs(struct folio *folio)
>  	return ((flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF) + 1;
>  }
>
> -static inline int folio_lru_gen(struct folio *folio)
> +static inline int folio_lru_gen(const struct folio *folio)
>  {
>  	unsigned long flags = READ_ONCE(folio->flags.f);
>
>  	return ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
>  }
>
> -static inline bool lru_gen_is_active(struct lruvec *lruvec, int gen)
> +static inline bool lru_gen_is_active(const struct lruvec *lruvec, int gen)
>  {
>  	unsigned long max_seq = lruvec->lrugen.max_seq;
>
> @@ -217,12 +217,13 @@ static inline void lru_gen_update_size(struct lruvec *lruvec, struct folio *foli
>  	VM_WARN_ON_ONCE(lru_gen_is_active(lruvec, old_gen) && !lru_gen_is_active(lruvec, new_gen));
>  }
>
> -static inline unsigned long lru_gen_folio_seq(struct lruvec *lruvec, struct folio *folio,
> +static inline unsigned long lru_gen_folio_seq(const struct lruvec *lruvec,
> +					      const struct folio *folio,
>  					      bool reclaiming)
>  {
>  	int gen;
>  	int type = folio_is_file_lru(folio);
> -	struct lru_gen_folio *lrugen = &lruvec->lrugen;
> +	const struct lru_gen_folio *lrugen = &lruvec->lrugen;
>
>  	/*
>  	 * +-----------------------------------+-----------------------------------+
> @@ -302,7 +303,7 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
>  	return true;
>  }
>
> -static inline void folio_migrate_refs(struct folio *new, struct folio *old)
> +static inline void folio_migrate_refs(struct folio *new, const struct folio *old)
>  {
>  	unsigned long refs = READ_ONCE(old->flags.f) & LRU_REFS_MASK;
>
> @@ -330,7 +331,7 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
>  	return false;
>  }
>
> -static inline void folio_migrate_refs(struct folio *new, struct folio *old)
> +static inline void folio_migrate_refs(struct folio *new, const struct folio *old)
>  {
>
>  }
> @@ -508,7 +509,7 @@ static inline void dec_tlb_flush_pending(struct mm_struct *mm)
>  	atomic_dec(&mm->tlb_flush_pending);
>  }
>
> -static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
> +static inline bool mm_tlb_flush_pending(const struct mm_struct *mm)
>  {
>  	/*
>  	 * Must be called after having acquired the PTL; orders against that
> @@ -521,7 +522,7 @@ static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
>  	return atomic_read(&mm->tlb_flush_pending);
>  }
>
> -static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
> +static inline bool mm_tlb_flush_nested(const struct mm_struct *mm)
>  {
>  	/*
>  	 * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
> @@ -605,7 +606,7 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
>  	return false;
>  }
>
> -static inline bool vma_has_recency(struct vm_area_struct *vma)
> +static inline bool vma_has_recency(const struct vm_area_struct *vma)
>  {
>  	if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))
>  		return false;
> --
> 2.47.2
>