ocfs2: Fix NULL pointer deref when writing local dquot

commit_dqblk() can write quota info to global file. That is actually a bad
thing to do because if we are just modifying local quota file, we are not
prepared (do not hold proper locks, do not have transaction credits) to do
a modification of the global quota file. So do not use commit_dqblk() and
instead call our writing function directly.

Acked-by: Joel Becker <Joel.Becker@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
index 778947f..551a6bf 100644
--- a/fs/ocfs2/quota_local.c
+++ b/fs/ocfs2/quota_local.c
@@ -892,7 +892,7 @@
 }
 
 /* Write dquot to local quota file */
-static int ocfs2_local_write_dquot(struct dquot *dquot)
+int ocfs2_local_write_dquot(struct dquot *dquot)
 {
 	struct super_block *sb = dquot->dq_sb;
 	struct ocfs2_dquot *od = OCFS2_DQUOT(dquot);
@@ -1309,7 +1309,6 @@
 	.read_file_info		= ocfs2_local_read_info,
 	.write_file_info	= ocfs2_global_write_info,
 	.free_file_info		= ocfs2_local_free_info,
-	.commit_dqblk		= ocfs2_local_write_dquot,
 };
 
 struct quota_format_type ocfs2_quota_format = {