powerpc/mm: Drop PTE_ATOMIC_UPDATES from pmd_hugepage_update()

pmd_hugepage_update() is inside #ifdef CONFIG_TRANSPARENT_HUGEPAGE. THP
can only be enabled if PPC_BOOK3S_64=y && PPC_64K_PAGES=y, aka. hash64.

On hash64 we always define PTE_ATOMIC_UPDATES to 1, meaning the #ifdef
in pmd_hugepage_update() is unnecessary, so drop it.

That is also the only use of PTE_ATOMIC_UPDATES in any of the hash code,
meaning we no longer need to #define it at all in the hash headers.

Note it's still #defined and used in the nohash code.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/32/hash.h

@@ -39,8 +39,5 @@
 #define _PMD_PRESENT_MASK (PAGE_MASK)
 #define _PMD_BAD	(~PAGE_MASK)
 
-/* Hash table based platforms need atomic updates of the linux PTE */
-#define PTE_ATOMIC_UPDATES	1
-
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_BOOK3S_32_HASH_H */

arch/powerpc/include/asm/book3s/64/hash.h

@@ -127,8 +127,6 @@
 #define _PTEIDX_SECONDARY	0x8
 #define _PTEIDX_GROUP_IX	0x7
 
-/* Hash table based platforms need atomic updates of the linux PTE */
-#define PTE_ATOMIC_UPDATES	1
 #define _PTE_NONE_MASK	_PAGE_HPTEFLAGS
 /*
  * The mask convered by the RPN must be a ULL on 32-bit platforms with

arch/powerpc/mm/pgtable_64.c

@@ -522,7 +522,6 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	assert_spin_locked(&mm->page_table_lock);
 #endif
 
-#ifdef PTE_ATOMIC_UPDATES
 	__asm__ __volatile__(
 	"1:	ldarx	%0,0,%3\n\
 		andi.	%1,%0,%6\n\
@@ -534,10 +533,7 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	: "=&r" (old), "=&r" (tmp), "=m" (*pmdp)
 	: "r" (pmdp), "r" (clr), "m" (*pmdp), "i" (_PAGE_BUSY), "r" (set)
 	: "cc" );
-#else
-	old = pmd_val(*pmdp);
-	*pmdp = __pmd((old & ~clr) | set);
-#endif
+
 	trace_hugepage_update(addr, old, clr, set);
 	if (old & _PAGE_HASHPTE)
 		hpte_do_hugepage_flush(mm, addr, pmdp, old);