ocfs2: rollback transaction in ocfs2_group_add()

If ocfs2_journal_access_di() fails, group->bg_next_group should rollback.
Otherwise, there would be a inconsistency between group_bh and main_bm_bh.

Signed-off-by: Younger Liu <younger.liu@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Acked-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/resize.c

@@ -469,6 +469,7 @@ int ocfs2_group_add(struct inode *inode, struct ocfs2_new_group_input *input)
 	struct ocfs2_chain_list *cl;
 	struct ocfs2_chain_rec *cr;
 	u16 cl_bpc;
+	u64 bg_ptr;
 
 	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
 		return -EROFS;
@@ -538,12 +539,14 @@ int ocfs2_group_add(struct inode *inode, struct ocfs2_new_group_input *input)
 	}
 
 	group = (struct ocfs2_group_desc *)group_bh->b_data;
+	bg_ptr = le64_to_cpu(group->bg_next_group);
 	group->bg_next_group = cr->c_blkno;
 	ocfs2_journal_dirty(handle, group_bh);
 
 	ret = ocfs2_journal_access_di(handle, INODE_CACHE(main_bm_inode),
 				      main_bm_bh, OCFS2_JOURNAL_ACCESS_WRITE);
 	if (ret < 0) {
+		group->bg_next_group = cpu_to_le64(bg_ptr);
 		mlog_errno(ret);
 		goto out_commit;
 	}