mm: wrap get_locked_pte() using __cond_lock()

The get_locked_pte() conditionally grabs 'ptl' in case of returning
non-NULL.  This leads sparse to complain about context imbalance.  Rename
and wrap it using __cond_lock() to make sparse happy.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1034,7 +1034,15 @@ extern void unregister_shrinker(struct shrinker *);
 
 int vma_wants_writenotify(struct vm_area_struct *vma);
 
-extern pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl);
+extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
+			       spinlock_t **ptl);
+static inline pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
+				    spinlock_t **ptl)
+{
+	pte_t *ptep;
+	__cond_lock(*ptl, ptep = __get_locked_pte(mm, addr, ptl));
+	return ptep;
+}
 
 #ifdef __PAGETABLE_PUD_FOLDED
 static inline int __pud_alloc(struct mm_struct *mm, pgd_t *pgd,

mm/memory.c

@@ -1591,7 +1591,7 @@ struct page *get_dump_page(unsigned long addr)
 }
 #endif /* CONFIG_ELF_CORE */
 
-pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
+pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
 			spinlock_t **ptl)
 {
 	pgd_t * pgd = pgd_offset(mm, addr);