JFS: Add write_super_lockfs() and unlock_fs() for snapshot.

Submitted by Steve Best.

fs/jfs/super.c

@@ -377,6 +377,31 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 	return -EINVAL;
 }
 
+static void jfs_write_super_lockfs(struct super_block *sb)
+{
+	struct jfs_sb_info *sbi = JFS_SBI(sb);
+	log_t *log = sbi->log;
+
+	if (!(sb->s_flags & MS_RDONLY)) {
+		txQuiesce(sb);
+		lmLogShutdown(log);
+	}
+}
+
+static void jfs_unlockfs(struct super_block *sb)
+{
+	struct jfs_sb_info *sbi = JFS_SBI(sb);
+	log_t *log = sbi->log;
+	int rc = 0;
+
+	if (!(sb->s_flags & MS_RDONLY)) {
+		if ((rc = lmLogInit(log)))
+			jERROR(1,
+			       ("jfs_unlock failed with return code %d\n", rc));
+		else
+			txResume(sb);
+	}
+}
 static struct super_block *jfs_get_sb(struct file_system_type *fs_type,
 		int flags, char *dev_name, void *data)
 {
@@ -390,6 +415,8 @@ static struct super_operations jfs_super_operations = {
 	.write_inode	= jfs_write_inode,
 	.delete_inode	= jfs_delete_inode,
 	.put_super	= jfs_put_super,
+	.write_super_lockfs = jfs_write_super_lockfs,
+	.unlockfs       = jfs_unlockfs,
 	.statfs		= jfs_statfs,
 	.remount_fs	= jfs_remount,
 };