Re: [PATCH V2 4/4] arm64/mm: Drop local variable vm_fault_t from __do_page_fault()

[Catalin Marinas]

On Mon, Jun 03, 2019 at 12:11:25PM +0530, Anshuman Khandual wrote:
> __do_page_fault() is over complicated with multiple goto statements. This
> cleans up the code flow and while there drops local variable vm_fault_t.

I'd change the subject as well here to something like refactor or
simplify __do_page_fault().

> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 4bb65f3..41fa905 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -397,37 +397,29 @@ static void do_bad_area(unsigned long addr, unsigned 
> int esr, struct pt_regs *re
>  static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr,
>                          unsigned int mm_flags, unsigned long vm_flags)
>  {
> -     struct vm_area_struct *vma;
> -     vm_fault_t fault;
> +     struct vm_area_struct *vma = find_vma(mm, addr);
>  
> -     vma = find_vma(mm, addr);
> -     fault = VM_FAULT_BADMAP;
>       if (unlikely(!vma))
> -             goto out;
> -     if (unlikely(vma->vm_start > addr))
> -             goto check_stack;
> +             return VM_FAULT_BADMAP;
>  
>       /*
>        * Ok, we have a good vm_area for this memory access, so we can handle
>        * it.
>        */
> -good_area:
> +     if (unlikely(vma->vm_start > addr)) {
> +             if (!(vma->vm_flags & VM_GROWSDOWN))
> +                     return VM_FAULT_BADMAP;
> +             if (expand_stack(vma, addr))
> +                     return VM_FAULT_BADMAP;
> +     }

You could have a single return here:

        if (unlikely(vma->vm_start > addr) &&
            (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, addr)))
                return VM_FAULT_BADMAP;

Not sure it's any clearer though.

-- 
Catalin