Re: [PATCH v3] mm,thp: reduce ifdef'ery for THP in generic code

[Vineet Gupta]

On Friday 09 October 2015 05:13 PM, Vineet Gupta wrote:
> - pgtable-generic.c: Fold individual #ifdef for each helper into a top
>   level #ifdef. Makes code more readable
> 
> - Converted the stub helpers for !THP to BUILD_BUG() vs. runtime BUG()
> 
> Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>

Sorry for sounding pushy - an Ack here will unblock me from dumping boat load of
patches into linux-next via my tree !

Thx,
-Vineet

> ---
> Somehow the msg didn't make it to mailing list !
> ---
>  include/asm-generic/pgtable.h | 37 ++++++++++++++++++++++++++++++-------
>  mm/pgtable-generic.c          | 24 +++---------------------
>  2 files changed, 33 insertions(+), 28 deletions(-)
> 
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 29c57b2cb344..3eabbbbfd578 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -30,9 +30,19 @@ extern int ptep_set_access_flags(struct vm_area_struct *vma,
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  extern int pmdp_set_access_flags(struct vm_area_struct *vma,
>  				 unsigned long address, pmd_t *pmdp,
>  				 pmd_t entry, int dirty);
> +#else
> +static inline int pmdp_set_access_flags(struct vm_area_struct *vma,
> +					unsigned long address, pmd_t *pmdp,
> +					pmd_t entry, int dirty)
> +{
> +	BUILD_BUG();
> +	return 0;
> +}
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
> @@ -64,12 +74,12 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
>  		set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
>  	return r;
>  }
> -#else /* CONFIG_TRANSPARENT_HUGEPAGE */
> +#else
>  static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
>  					    unsigned long address,
>  					    pmd_t *pmdp)
>  {
> -	BUG();
> +	BUILD_BUG();
>  	return 0;
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> @@ -81,8 +91,21 @@ int ptep_clear_flush_young(struct vm_area_struct *vma,
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
> -int pmdp_clear_flush_young(struct vm_area_struct *vma,
> -			   unsigned long address, pmd_t *pmdp);
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
> +				  unsigned long address, pmd_t *pmdp);
> +#else
> +/*
> + * Despite relevant to THP only, this API is called from generic rmap code
> + * under PageTransHuge(), hence needs a dummy implementation for !THP
> + */
> +static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
> +					 unsigned long address, pmd_t *pmdp)
> +{
> +	BUILD_BUG();
> +	return 0;
> +}
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
> @@ -175,11 +198,11 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
>  	pmd_t old_pmd = *pmdp;
>  	set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
>  }
> -#else /* CONFIG_TRANSPARENT_HUGEPAGE */
> +#else
>  static inline void pmdp_set_wrprotect(struct mm_struct *mm,
>  				      unsigned long address, pmd_t *pmdp)
>  {
> -	BUG();
> +	BUILD_BUG();
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
> @@ -248,7 +271,7 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
>  #else /* CONFIG_TRANSPARENT_HUGEPAGE */
>  static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
>  {
> -	BUG();
> +	BUILD_BUG();
>  	return 0;
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
> index 48851894e699..c9c59bb75a17 100644
> --- a/mm/pgtable-generic.c
> +++ b/mm/pgtable-generic.c
> @@ -82,12 +82,13 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
>  }
>  #endif
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +
>  #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
>  int pmdp_set_access_flags(struct vm_area_struct *vma,
>  			  unsigned long address, pmd_t *pmdp,
>  			  pmd_t entry, int dirty)
>  {
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	int changed = !pmd_same(*pmdp, entry);
>  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
>  	if (changed) {
> @@ -95,10 +96,6 @@ int pmdp_set_access_flags(struct vm_area_struct *vma,
>  		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>  	}
>  	return changed;
> -#else /* CONFIG_TRANSPARENT_HUGEPAGE */
> -	BUG();
> -	return 0;
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  }
>  #endif
>  
> @@ -107,11 +104,7 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
>  			   unsigned long address, pmd_t *pmdp)
>  {
>  	int young;
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> -#else
> -	BUG();
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  	young = pmdp_test_and_clear_young(vma, address, pmdp);
>  	if (young)
>  		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
> @@ -120,7 +113,6 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,
>  			    pmd_t *pmdp)
>  {
> @@ -131,11 +123,9 @@ pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,
>  	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>  	return pmd;
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
>  			  pmd_t *pmdp)
>  {
> @@ -145,11 +135,9 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
>  	/* tlb flush only to serialize against gup-fast */
>  	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
>  				pgtable_t pgtable)
>  {
> @@ -162,11 +150,9 @@ void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
>  		list_add(&pgtable->lru, &pmd_huge_pte(mm, pmdp)->lru);
>  	pmd_huge_pte(mm, pmdp) = pgtable;
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  /* no "address" argument so destroys page coloring of some arch */
>  pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
>  {
> @@ -185,11 +171,9 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
>  	}
>  	return pgtable;
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_INVALIDATE
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
>  		     pmd_t *pmdp)
>  {
> @@ -197,11 +181,9 @@ void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
>  	set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry));
>  	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef pmdp_collapse_flush
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
>  			  pmd_t *pmdp)
>  {
> @@ -217,5 +199,5 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
>  	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>  	return pmd;
>  }
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> 

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