Re: [PATCH v2 1/3] mm: make dev_pagemap_mapping_shift() externally visible

[Paolo Bonzini]

On 14/11/18 22:51, Barret Rhoden wrote:
> KVM has a use case for determining the size of a dax mapping.  The KVM
> code has easy access to the address and the mm; hence the change in
> parameters.
> 
> Signed-off-by: Barret Rhoden <brho@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>  include/linux/mm.h  |  3 +++
>  mm/memory-failure.c | 38 +++-----------------------------------
>  mm/util.c           | 34 ++++++++++++++++++++++++++++++++++
>  3 files changed, 40 insertions(+), 35 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5411de93a363..51215d695753 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -935,6 +935,9 @@ static inline bool is_pci_p2pdma_page(const struct page *page)
>  }
>  #endif /* CONFIG_DEV_PAGEMAP_OPS */
>  
> +unsigned long dev_pagemap_mapping_shift(unsigned long address,
> +					struct mm_struct *mm);
> +
>  static inline void get_page(struct page *page)
>  {
>  	page = compound_head(page);
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 0cd3de3550f0..c3f2c6a8607e 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -265,40 +265,6 @@ void shake_page(struct page *p, int access)
>  }
>  EXPORT_SYMBOL_GPL(shake_page);
>  
> -static unsigned long dev_pagemap_mapping_shift(struct page *page,
> -		struct vm_area_struct *vma)
> -{
> -	unsigned long address = vma_address(page, vma);
> -	pgd_t *pgd;
> -	p4d_t *p4d;
> -	pud_t *pud;
> -	pmd_t *pmd;
> -	pte_t *pte;
> -
> -	pgd = pgd_offset(vma->vm_mm, address);
> -	if (!pgd_present(*pgd))
> -		return 0;
> -	p4d = p4d_offset(pgd, address);
> -	if (!p4d_present(*p4d))
> -		return 0;
> -	pud = pud_offset(p4d, address);
> -	if (!pud_present(*pud))
> -		return 0;
> -	if (pud_devmap(*pud))
> -		return PUD_SHIFT;
> -	pmd = pmd_offset(pud, address);
> -	if (!pmd_present(*pmd))
> -		return 0;
> -	if (pmd_devmap(*pmd))
> -		return PMD_SHIFT;
> -	pte = pte_offset_map(pmd, address);
> -	if (!pte_present(*pte))
> -		return 0;
> -	if (pte_devmap(*pte))
> -		return PAGE_SHIFT;
> -	return 0;
> -}
> -
>  /*
>   * Failure handling: if we can't find or can't kill a process there's
>   * not much we can do.	We just print a message and ignore otherwise.
> @@ -329,7 +295,9 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
>  	tk->addr = page_address_in_vma(p, vma);
>  	tk->addr_valid = 1;
>  	if (is_zone_device_page(p))
> -		tk->size_shift = dev_pagemap_mapping_shift(p, vma);
> +		tk->size_shift =
> +			dev_pagemap_mapping_shift(vma_address(page, vma),
> +						  vma->vm_mm);
>  	else
>  		tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
>  
> diff --git a/mm/util.c b/mm/util.c
> index 8bf08b5b5760..61bc9bab931d 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -780,3 +780,37 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
>  out:
>  	return res;
>  }
> +
> +unsigned long dev_pagemap_mapping_shift(unsigned long address,
> +					struct mm_struct *mm)
> +{
> +	pgd_t *pgd;
> +	p4d_t *p4d;
> +	pud_t *pud;
> +	pmd_t *pmd;
> +	pte_t *pte;
> +
> +	pgd = pgd_offset(mm, address);
> +	if (!pgd_present(*pgd))
> +		return 0;
> +	p4d = p4d_offset(pgd, address);
> +	if (!p4d_present(*p4d))
> +		return 0;
> +	pud = pud_offset(p4d, address);
> +	if (!pud_present(*pud))
> +		return 0;
> +	if (pud_devmap(*pud))
> +		return PUD_SHIFT;
> +	pmd = pmd_offset(pud, address);
> +	if (!pmd_present(*pmd))
> +		return 0;
> +	if (pmd_devmap(*pmd))
> +		return PMD_SHIFT;
> +	pte = pte_offset_map(pmd, address);
> +	if (!pte_present(*pte))
> +		return 0;
> +	if (pte_devmap(*pte))
> +		return PAGE_SHIFT;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(dev_pagemap_mapping_shift);
> 

Andrew,

can you ack this patch?

Thanks,

Paolo