Re: [PATCH v1 1/2] mm: huge_memory: add vma_thp_disabled() and thp_disabled_by_hw()

[Ryan Roberts <ryan.roberts@arm.com>]

On 11/10/2024 11:24, David Hildenbrand wrote:
> From: Kefeng Wang <wangkefeng.wang@huawei.com>
> 
> Add vma_thp_disabled() and thp_disabled_by_hw() helpers to be shared by
> shmem_allowable_huge_orders() and __thp_vma_allowable_orders().
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> [ rename to vma_thp_disabled(), split out thp_disabled_by_hw() ]
> Signed-off-by: David Hildenbrand <david@redhat.com>

Looks like a nice tidy up on its own:

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>

> ---
>  include/linux/huge_mm.h | 18 ++++++++++++++++++
>  mm/huge_memory.c        | 13 +------------
>  mm/shmem.c              |  7 +------
>  3 files changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 67d0ab3c3bba..ef5b80e48599 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -322,6 +322,24 @@ struct thpsize {
>  	(transparent_hugepage_flags &					\
>  	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
>  
> +static inline bool vma_thp_disabled(struct vm_area_struct *vma,
> +		unsigned long vm_flags)
> +{
> +	/*
> +	 * Explicitly disabled through madvise or prctl, or some
> +	 * architectures may disable THP for some mappings, for
> +	 * example, s390 kvm.
> +	 */
> +	return (vm_flags & VM_NOHUGEPAGE) ||
> +	       test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags);
> +}
> +
> +static inline bool thp_disabled_by_hw(void)
> +{
> +	/* If the hardware/firmware marked hugepage support disabled. */
> +	return transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED);
> +}
> +
>  unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
>  		unsigned long len, unsigned long pgoff, unsigned long flags);
>  unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 87b49ecc7b1e..2fb328880b50 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -109,18 +109,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
>  	if (!vma->vm_mm)		/* vdso */
>  		return 0;
>  
> -	/*
> -	 * Explicitly disabled through madvise or prctl, or some
> -	 * architectures may disable THP for some mappings, for
> -	 * example, s390 kvm.
> -	 * */
> -	if ((vm_flags & VM_NOHUGEPAGE) ||
> -	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
> -		return 0;
> -	/*
> -	 * If the hardware/firmware marked hugepage support disabled.
> -	 */
> -	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
> +	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))
>  		return 0;
>  
>  	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4f11b5506363..c5adb987b23c 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1664,12 +1664,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
>  	loff_t i_size;
>  	int order;
>  
> -	if (vma && ((vm_flags & VM_NOHUGEPAGE) ||
> -	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
> -		return 0;
> -
> -	/* If the hardware/firmware marked hugepage support disabled. */
> -	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
> +	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags)))
>  		return 0;
>  
>  	global_huge = shmem_huge_global_enabled(inode, index, write_end,