mm: wrap follow_pte() using __cond_lock()

The follow_pte() conditionally grabs *@ptlp in case of returning 0.
Rename and wrap it using __cond_lock() removes following warnings:

 mm/memory.c:2337:9: warning: context imbalance in 'do_wp_page' - unexpected unlock
 mm/memory.c:3142:19: warning: context imbalance in 'handle_mm_fault' - different lock contexts for basic block

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>

1 files changed, 12 insertions, 1 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 01bdf9dbbfac..861f7982dd54 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3351,7 +3351,7 @@ int in_gate_area_no_task(unsigned long addr)
 
 #endif  /* __HAVE_ARCH_GATE_AREA */
 
-static int follow_pte(struct mm_struct *mm, unsigned long address,
+static int __follow_pte(struct mm_struct *mm, unsigned long address,
                 pte_t **ptepp, spinlock_t **ptlp)
 {
         pgd_t *pgd;
@@ -3388,6 +3388,17 @@ out:
         return -EINVAL;
 }
 
+static inline int follow_pte(struct mm_struct *mm, unsigned long address,
+                             pte_t **ptepp, spinlock_t **ptlp)
+{
+        int res;
+
+        /* (void) is needed to make gcc happy */
+        (void) __cond_lock(*ptlp,
+                           !(res = __follow_pte(mm, address, ptepp, ptlp)));
+        return res;
+}
+
 /**
  * follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping