Re: [PATCH 3/8] mm: Return the address from page_mapped_in_vma()

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/3/1 5:20, Matthew Wilcox (Oracle) wrote:
> The only user of this function calls page_address_in_vma() immediately
> after page_mapped_in_vma() calculates it and uses it to return true/false.
> Return the address instead, allowing memory-failure to skip the call
> to page_address_in_vma().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/rmap.h |  2 +-
>  mm/memory-failure.c  | 22 ++++++++++++++--------
>  mm/page_vma_mapped.c | 14 +++++++-------
>  3 files changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index b7944a833668..ba027a4d9abf 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -698,7 +698,7 @@ int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
>  
>  void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked);
>  
> -int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
> +unsigned long page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
>  
>  /*
>   * rmap_walk_control: To control rmap traversing for specific needs
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 7f8473c08ae3..40a8964954e5 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -462,10 +462,11 @@ static void __add_to_kill(struct task_struct *tsk, struct page *p,
>  }
>  
>  static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
> -				  struct vm_area_struct *vma,
> -				  struct list_head *to_kill)
> +		struct vm_area_struct *vma, struct list_head *to_kill,
> +		unsigned long addr)
>  {
> -	unsigned long addr = page_address_in_vma(p, vma);
> +	if (addr == -EFAULT)
> +		return;
>  	__add_to_kill(tsk, p, vma, to_kill, addr);
>  }
>  
> @@ -609,12 +610,13 @@ static void collect_procs_anon(struct folio *folio, struct page *page,
>  			continue;
>  		anon_vma_interval_tree_foreach(vmac, &av->rb_root,
>  					       pgoff, pgoff) {
> +			unsigned long addr;
> +
>  			vma = vmac->vma;
>  			if (vma->vm_mm != t->mm)
>  				continue;
> -			if (!page_mapped_in_vma(page, vma))
> -				continue;
> -			add_to_kill_anon_file(t, page, vma, to_kill);
> +			addr = page_mapped_in_vma(page, vma);
> +			add_to_kill_anon_file(t, page, vma, to_kill, addr);
>  		}
>  	}
>  	rcu_read_unlock();
> @@ -642,6 +644,8 @@ static void collect_procs_file(struct folio *folio, struct page *page,
>  			continue;
>  		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
>  				      pgoff) {
> +			unsigned long addr;
> +
>  			/*
>  			 * Send early kill signal to tasks where a vma covers
>  			 * the page but the corrupted page is not necessarily
> @@ -649,8 +653,10 @@ static void collect_procs_file(struct folio *folio, struct page *page,
>  			 * Assume applications who requested early kill want
>  			 * to be informed of all such data corruptions.
>  			 */
> -			if (vma->vm_mm == t->mm)
> -				add_to_kill_anon_file(t, page, vma, to_kill);
> +			if (vma->vm_mm != t->mm)
> +				continue;
> +			addr = page_address_in_vma(page, vma);
> +			add_to_kill_anon_file(t, page, vma, to_kill, addr);
>  		}
>  	}
>  	rcu_read_unlock();
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index 74d2de15fb5e..e9e208b4ac4b 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -319,11 +319,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>   * @page: the page to test
>   * @vma: the VMA to test
>   *
> - * Returns 1 if the page is mapped into the page tables of the VMA, 0
> - * if the page is not mapped into the page tables of this VMA.  Only
> - * valid for normal file or anonymous VMAs.
> + * Return: If the page is mapped into the page tables of the VMA, the
> + * address that the page is mapped at.  -EFAULT if the page is not mapped.
> + * Only valid for normal file or anonymous VMAs.
>   */
> -int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
> +unsigned long page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
>  {
>  	struct page_vma_mapped_walk pvmw = {
>  		.pfn = page_to_pfn(page),
> @@ -334,9 +334,9 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
>  
>  	pvmw.address = vma_address(page, vma);
>  	if (pvmw.address == -EFAULT)
> -		return 0;
> +		return -EFAULT;
>  	if (!page_vma_mapped_walk(&pvmw))
> -		return 0;
> +		return -EFAULT;
>  	page_vma_mapped_walk_done(&pvmw);
> -	return 1;
> +	return pvmw.address;

page_mapped_in_vma is only called by collect_procs_anon. Will it be better to make it under CONFIG_MEMORY_FAILURE?

Anyway, this patch looks good to me. Thanks.

Acked-by: Miaohe Lin <linmiaohe@huawei.com>