quota: Remove BUG_ON from dqget()

dqget() checks whether dquot->dq_sb is set when returning it using
BUG_ON. Firstly this doesn't work as an invalidation check for quite
some time (we release dquot with dq_sb set these days), secondly using
BUG_ON is quite harsh. Use WARN_ON_ONCE and check whether dquot is still
hashed instead.

Signed-off-by: Jan Kara <[email protected]>

Author: jankara

fs/quota/dquot.c

@@ -984,9 +984,8 @@ struct dquot *dqget(struct super_block *sb, struct kqid qid)
 	 * smp_mb__before_atomic() in dquot_acquire().
 	 */
 	smp_rmb();
-#ifdef CONFIG_QUOTA_DEBUG
-	BUG_ON(!dquot->dq_sb);	/* Has somebody invalidated entry under us? */
-#endif
+	/* Has somebody invalidated entry under us? */
+	WARN_ON_ONCE(hlist_unhashed(&dquot->dq_hash));
 out:
 	if (empty)
 		do_destroy_dquot(empty);