f2fs: use atomic_t to record hit ratio info of extent cache

Variables for recording extent cache ratio info were updated without
protection, this patch tries to alter them to atomic_t type for more
accurate stat.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 2aeaf4e..bc215fd 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -33,8 +33,8 @@
 	int i;
 
 	/* validation check of the segment numbers */
-	si->hit_ext = sbi->read_hit_ext;
-	si->total_ext = sbi->total_hit_ext;
+	si->hit_ext = atomic_read(&sbi->read_hit_ext);
+	si->total_ext = atomic_read(&sbi->total_hit_ext);
 	si->ext_tree = sbi->total_ext_tree;
 	si->ext_node = atomic_read(&sbi->total_ext_node);
 	si->ndirty_node = get_pages(sbi, F2FS_DIRTY_NODES);
@@ -369,6 +369,9 @@
 	si->sbi = sbi;
 	sbi->stat_info = si;
 
+	atomic_set(&sbi->total_hit_ext, 0);
+	atomic_set(&sbi->read_hit_ext, 0);
+
 	atomic_set(&sbi->inline_xattr, 0);
 	atomic_set(&sbi->inline_inode, 0);
 	atomic_set(&sbi->inline_dir, 0);