quota: make dquot_quota_sync return errors from ->sync_fs

Strangely, dquot_quota_sync ignores the return code from the ->sync_fs
call, which means that quotacalls like Q_SYNC never see the error. This
doesn't seem right, so fix that.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Jan Kara <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: Christian Brauner <[e-mail]>

fs/quota/dquot.c

···
 	/* This is not very clever (and fast) but currently I don't know about
 	 * any other simple way of getting quota data to disk and we must get
 	 * them there for userspace to be visible... */
-	if (sb->s_op->sync_fs)
-		sb->s_op->sync_fs(sb, 1);
-	sync_blockdev(sb->s_bdev);
+	if (sb->s_op->sync_fs) {
+		ret = sb->s_op->sync_fs(sb, 1);
+		if (ret)
+			return ret;
+	}
+	ret = sync_blockdev(sb->s_bdev);
+	if (ret)
+		return ret;
 
 	/*
 	 * Now when everything is written we can discard the pagecache so