ocfs2: Fix lock inversion in quotas during umount

We cannot cancel delayed work from ocfs2_local_free_info because that is called
with dqonoff_mutex held and the work it cancels requires dqonoff_mutex to
finish. Cancel the work before acquiring dqonoff_mutex.

Acked-by: Joel Becker <Joel.Becker@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ocfs2/quota_local.c

@@ -816,10 +816,6 @@ static int ocfs2_local_free_info(struct super_block *sb, int type)
 	int mark_clean = 1, len;
 	int status;
 
-	/* At this point we know there are no more dquots and thus
-	 * even if there's some sync in the pdflush queue, it won't
-	 * find any dquots and return without doing anything */
-	cancel_delayed_work_sync(&oinfo->dqi_sync_work);
 	iput(oinfo->dqi_gqinode);
 	ocfs2_simple_drop_lockres(OCFS2_SB(sb), &oinfo->dqi_gqlock);
 	ocfs2_lock_res_free(&oinfo->dqi_gqlock);

fs/ocfs2/super.c

@@ -938,12 +938,16 @@ static void ocfs2_disable_quotas(struct ocfs2_super *osb)
 	int type;
 	struct inode *inode;
 	struct super_block *sb = osb->sb;
+	struct ocfs2_mem_dqinfo *oinfo;
 
 	/* We mostly ignore errors in this function because there's not much
 	 * we can do when we see them */
 	for (type = 0; type < MAXQUOTAS; type++) {
 		if (!sb_has_quota_loaded(sb, type))
 			continue;
+		/* Cancel periodic syncing before we grab dqonoff_mutex */
+		oinfo = sb_dqinfo(sb, type)->dqi_priv;
+		cancel_delayed_work_sync(&oinfo->dqi_sync_work);
 		inode = igrab(sb->s_dquot.files[type]);
 		/* Turn off quotas. This will remove all dquot structures from
 		 * memory and so they will be automatically synced to global