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

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