Messages in this thread | | | Date | Thu, 6 Jun 2019 12:27:40 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH V2 4/4] arm64/mm: Drop local variable vm_fault_t from __do_page_fault() |
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On Thu, Jun 06, 2019 at 10:24:01AM +0530, Anshuman Khandual wrote: > On 06/04/2019 08:26 PM, Catalin Marinas wrote: > > On Mon, Jun 03, 2019 at 12:11:25PM +0530, Anshuman Khandual wrote: > >> 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.
Not bothered really. You can leave them as in your proposal (I was just seeing the VM_GROWSDOWN check tightly coupled with the expand_stack(), it's fine either way).
-- Catalin
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