arm64 fix for -rc7

- Fix pte_same() to avoid getting stuck on write fault
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fix from Will Deacon:
 "Fix pte_same() to avoid getting stuck on write fault.

  This single arm64 fix is a revert of 747a70e60b ("arm64: Fix
  copy-on-write referencing in HugeTLB"), not because that patch was
  wrong, but because it was broken by aa57157be6 ("arm64: Ensure
  VM_WRITE|VM_SHARED ptes are clean by default") which we merged in
  -rc6.

  We spotted the issue in Android (AOSP), where one of the JIT threads
  gets stuck on a write fault during boot because the faulting pte is
  marked as PTE_DIRTY | PTE_WRITE | PTE_RDONLY and the fault handler
  decides that there's nothing to do thanks to pte_same() masking out
  PTE_RDONLY.

  Thanks to John Stultz for reporting this and testing this so quickly,
  and to Steve Capper for confirming that the HugeTLB tests continue to
  pass"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Do not mask out PTE_RDONLY in pte_same()

arch/arm64/include/asm/pgtable.h

@@ -283,23 +283,6 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 	set_pte(ptep, pte);
 }
 
-#define __HAVE_ARCH_PTE_SAME
-static inline int pte_same(pte_t pte_a, pte_t pte_b)
-{
-	pteval_t lhs, rhs;
-
-	lhs = pte_val(pte_a);
-	rhs = pte_val(pte_b);
-
-	if (pte_present(pte_a))
-		lhs &= ~PTE_RDONLY;
-
-	if (pte_present(pte_b))
-		rhs &= ~PTE_RDONLY;
-
-	return (lhs == rhs);
-}
-
 /*
  * Huge pte definitions.
  */