linux-kernel - Re: [RFC PATCH 06/26] mm: make free_p?d

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Date:   Tue, 28 Jun 2022 13:35:11 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     James Houghton <jthoughton@...gle.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Jue Wang <juew@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 06/26] mm: make free_p?d_range functions public

On 06/24/22 17:36, James Houghton wrote:
> This makes them usable for HugeTLB page table freeing operations.
> After HugeTLB high-granularity mapping, the page table for a HugeTLB VMA
> can get more complex, and these functions handle freeing page tables
> generally.
> 

Hmmmm?

free_pgd_range is not generally called directly for hugetlb mappings.
There is a wrapper hugetlb_free_pgd_range which can have architecture
specific implementations.  It makes me wonder if these lower level
routines can be directly used on hugetlb mappings.  My 'guess' is that any
such details will be hidden in the callers.  Suspect this will become clear
in later patches.
-- 
Mike Kravetz

> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>  include/linux/mm.h | 7 +++++++
>  mm/memory.c        | 8 ++++----
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index bc8f326be0ce..07f5da512147 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1847,6 +1847,13 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
>  
>  struct mmu_notifier_range;
>  
> +void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd, unsigned long addr);
> +void free_pmd_range(struct mmu_gather *tlb, pud_t *pud, unsigned long addr,
> +		unsigned long end, unsigned long floor, unsigned long ceiling);
> +void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d, unsigned long addr,
> +		unsigned long end, unsigned long floor, unsigned long ceiling);
> +void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd, unsigned long addr,
> +		unsigned long end, unsigned long floor, unsigned long ceiling);
>  void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
>  		unsigned long end, unsigned long floor, unsigned long ceiling);
>  int
> diff --git a/mm/memory.c b/mm/memory.c
> index 7a089145cad4..bb3b9b5b94fb 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -227,7 +227,7 @@ static void check_sync_rss_stat(struct task_struct *task)
>   * Note: this doesn't free the actual pages themselves. That
>   * has been handled earlier when unmapping all the memory regions.
>   */
> -static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
> +void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
>  			   unsigned long addr)
>  {
>  	pgtable_t token = pmd_pgtable(*pmd);
> @@ -236,7 +236,7 @@ static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
>  	mm_dec_nr_ptes(tlb->mm);
>  }
>  
> -static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
> +inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
>  				unsigned long addr, unsigned long end,
>  				unsigned long floor, unsigned long ceiling)
>  {
> @@ -270,7 +270,7 @@ static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
>  	mm_dec_nr_pmds(tlb->mm);
>  }
>  
> -static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
> +inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
>  				unsigned long addr, unsigned long end,
>  				unsigned long floor, unsigned long ceiling)
>  {
> @@ -304,7 +304,7 @@ static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
>  	mm_dec_nr_puds(tlb->mm);
>  }
>  
> -static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd,
> +inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd,
>  				unsigned long addr, unsigned long end,
>  				unsigned long floor, unsigned long ceiling)
>  {
> -- 
> 2.37.0.rc0.161.g10f37bed90-goog
>