Re: [PATCH v2 1/2] mm: improve readability of transparent_hugepage_enabled()

[Michal Hocko <mhocko@kernel.org>]

On Tue 13-06-17 16:08:26, Dan Williams wrote:
> Turn the macro into a static inline and rewrite the condition checks for
> better readability in preparation for adding another condition.
> 
> Cc: Jan Kara <jack@suse.cz>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> [ross: fix logic to make conversion equivalent]
> Acked-by: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

This is really a nice deobfuscation! Please note this will conflict with
http://lkml.kernel.org/r/1496415802-30944-1-git-send-email-rppt@linux.vnet.ibm.com

Trivial to resolve but I thought I should give you a heads up.

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  include/linux/huge_mm.h |   32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index a3762d49ba39..c8119e856eb1 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -85,14 +85,23 @@ extern struct kobj_attribute shmem_enabled_attr;
>  
>  extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
>  
> -#define transparent_hugepage_enabled(__vma)				\
> -	((transparent_hugepage_flags &					\
> -	  (1<<TRANSPARENT_HUGEPAGE_FLAG) ||				\
> -	  (transparent_hugepage_flags &					\
> -	   (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG) &&			\
> -	   ((__vma)->vm_flags & VM_HUGEPAGE))) &&			\
> -	 !((__vma)->vm_flags & VM_NOHUGEPAGE) &&			\
> -	 !is_vma_temporary_stack(__vma))
> +extern unsigned long transparent_hugepage_flags;
> +
> +static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma)
> +{
> +	if ((vma->vm_flags & VM_NOHUGEPAGE) || is_vma_temporary_stack(vma))
> +		return false;
> +
> +	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
> +		return true;
> +
> +	if (transparent_hugepage_flags &
> +				(1 << TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG))
> +		return !!(vma->vm_flags & VM_HUGEPAGE);
> +
> +	return false;
> +}
> +
>  #define transparent_hugepage_use_zero_page()				\
>  	(transparent_hugepage_flags &					\
>  	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
> @@ -104,8 +113,6 @@ extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
>  #define transparent_hugepage_debug_cow() 0
>  #endif /* CONFIG_DEBUG_VM */
>  
> -extern unsigned long transparent_hugepage_flags;
> -
>  extern unsigned long thp_get_unmapped_area(struct file *filp,
>  		unsigned long addr, unsigned long len, unsigned long pgoff,
>  		unsigned long flags);
> @@ -223,7 +230,10 @@ void mm_put_huge_zero_page(struct mm_struct *mm);
>  
>  #define hpage_nr_pages(x) 1
>  
> -#define transparent_hugepage_enabled(__vma) 0
> +static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma)
> +{
> +	return false;
> +}
>  
>  static inline void prep_transhuge_page(struct page *page) {}
>  
> 
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-- 
Michal Hocko
SUSE Labs

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