f2fs: add f2fs_readonly()

Introduce a simple macro function for readability.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9182b27..6594ce1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -887,6 +887,11 @@
 	return 0;
 }
 
+static inline int f2fs_readonly(struct super_block *sb)
+{
+	return sb->s_flags & MS_RDONLY;
+}
+
 /*
  * file.c
  */
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 9937ba1..316bcfe 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -114,7 +114,7 @@
 		.for_reclaim = 0,
 	};
 
-	if (inode->i_sb->s_flags & MS_RDONLY)
+	if (f2fs_readonly(inode->i_sb))
 		return 0;
 
 	trace_f2fs_sync_file_enter(inode);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 8555f7d..3ac305d 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -170,7 +170,7 @@
 {
 	int err;
 
-	if (sb->s_flags & MS_RDONLY)
+	if (f2fs_readonly(sb))
 		return 0;
 
 	err = f2fs_sync_fs(sb, 1);