Messages in this thread | | | Subject | Re: [PATCH V2 4/4] arm64/mm: Drop local variable vm_fault_t from __do_page_fault() | From | Anshuman Khandual <> | Date | Thu, 6 Jun 2019 10:24:01 +0530 |
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On 06/04/2019 08:26 PM, Catalin Marinas wrote: > 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().
Sure.
> >> 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. >
TBH the proposed one seems clearer as it separates effect (vma->vm_start > addr) from required permission check (vma->vm_flags & VM_GROWSDOWN) and required action (expand_stack(vma, addr)). But I am happy to change as you have mentioned if that is preferred.
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