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>

diff --git a/mm/memory.c b/mm/memory.c
index 01bdf9dbbfac774380b2d25336c52b5822359b08..861f7982dd54db7bfad268386185fe1829db01bd 100644 (file)
--- 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