Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753435AbbDTVle (ORCPT ); Mon, 20 Apr 2015 17:41:34 -0400 Received: from mail-ig0-f182.google.com ([209.85.213.182]:38421 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751607AbbDTVlc (ORCPT ); Mon, 20 Apr 2015 17:41:32 -0400 MIME-Version: 1.0 In-Reply-To: <20150420213247.GN889@ZenIV.linux.org.uk> References: <20150420181222.GK889@ZenIV.linux.org.uk> <1429553588-24764-16-git-send-email-viro@ZenIV.linux.org.uk> <20150420213247.GN889@ZenIV.linux.org.uk> Date: Mon, 20 Apr 2015 14:41:31 -0700 X-Google-Sender-Auth: Cxc9s94bdcDOV64wiZlOP4Q5XDg Message-ID: Subject: Re: [PATCH 16/24] link_path_walk: kill the recursion From: Linus Torvalds To: Al Viro Cc: Neil Brown , Linux Kernel Mailing List , linux-fsdevel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 800 Lines: 19 On Mon, Apr 20, 2015 at 2:32 PM, Al Viro wrote: > > A kilobyte would suffice for 32 levels. _IF_ we go for "lift the restrictions > on nesting completely", sure, we want to switch to (on-demand) dynamic > allocation. And no, we will *never* lift the recursion limit. Not for 1kB, not for 1MB. Never. Because it's a latency and DoS issue too. We need to react well to true loops, but also to "very deep" non-loops. It's not about memory use, it's about users triggering unreasonable CPU resources. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/