Re: [PATCH 2/7] mm: thp: introduce transhuge_vma_size_ok() helper

[Hillf Danton <hdanton@sina.com>]

On Fri, 20 May 2022 14:16:00 -0700 Yang Shi wrote:
> There are couple of places that check whether the vma size is ok for
> THP or not, they are open coded and duplicate, introduce
> transhuge_vma_size_ok() helper to do the job.
> 
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
>  include/linux/huge_mm.h | 17 +++++++++++++++++
>  mm/huge_memory.c        |  5 +----
>  mm/khugepaged.c         | 12 ++++++------
>  3 files changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 648cb3ce7099..a8f61db47f2a 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -116,6 +116,18 @@ extern struct kobj_attribute shmem_enabled_attr;
>  
>  extern unsigned long transparent_hugepage_flags;
>  
> +/*
> + * The vma size has to be large enough to hold an aligned HPAGE_PMD_SIZE area.
> + */
> +static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma)
> +{
> +	if (round_up(vma->vm_start, HPAGE_PMD_SIZE) <
> +	    (vma->vm_end & HPAGE_PMD_MASK))
> +		return true;
> +
> +	return false;
> +}
> +
>  static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
>  		unsigned long addr)
>  {
> @@ -345,6 +357,11 @@ static inline bool transparent_hugepage_active(struct vm_area_struct *vma)
>  	return false;
>  }
>  
> +static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma)
> +{
> +	return false;
> +}
> +
>  static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
>  		unsigned long addr)
>  {
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 80e8b58b4f39..d633f97452c1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -71,10 +71,7 @@ unsigned long huge_zero_pfn __read_mostly = ~0UL;
>  
>  bool transparent_hugepage_active(struct vm_area_struct *vma)
>  {
> -	/* The addr is used to check if the vma size fits */
> -	unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
> -
> -	if (!transhuge_vma_suitable(vma, addr))
> +	if (!transhuge_vma_size_ok(vma))
>  		return false;

Given the comment added in 4/7, this patch adds change in semantic.
If that is intened, add some words in log message for it.

>  	if (vma_is_anonymous(vma))
>  		return __transparent_hugepage_enabled(vma);