f2fs: add f2fs_readonly()

Introduce a simple macro function for readability.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/f2fs.h

@@ -887,6 +887,11 @@ static inline int cond_clear_inode_flag(struct f2fs_inode_info *fi, int flag)
 	return 0;
 }
 
+static inline int f2fs_readonly(struct super_block *sb)
+{
+	return sb->s_flags & MS_RDONLY;
+}
+
 /*
  * file.c
  */

fs/f2fs/file.c

@@ -114,7 +114,7 @@ int f2fs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 		.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);

fs/f2fs/super.c

@@ -170,7 +170,7 @@ static int f2fs_freeze(struct super_block *sb)
 {
 	int err;
 
-	if (sb->s_flags & MS_RDONLY)
+	if (f2fs_readonly(sb))
 		return 0;
 
 	err = f2fs_sync_fs(sb, 1);