Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753267Ab3EUURJ (ORCPT ); Tue, 21 May 2013 16:17:09 -0400 Received: from mail-gg0-f171.google.com ([209.85.161.171]:60013 "EHLO mail-gg0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751960Ab3EUURH (ORCPT ); Tue, 21 May 2013 16:17:07 -0400 Message-ID: <519BD640.4040102@gmail.com> Date: Tue, 21 May 2013 16:17:04 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Karel Zak CC: KOSAKI Motohiro , Rafael Aquini , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hughd@google.com, shli@kernel.org, jmoyer@redhat.com, riel@redhat.com, lwoodman@redhat.com, mgorman@suse.de Subject: Re: [RFC PATCH 02/02] swapon: add "cluster-discard" support References: <398ace0dd3ca1283372b3aad3fceeee59f6897d7.1369084886.git.aquini@redhat.com> <519AC7B3.5060902@gmail.com> <20130521102648.GB11774@x2.net.home> In-Reply-To: <20130521102648.GB11774@x2.net.home> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1687 Lines: 41 (5/21/13 6:26 AM), Karel Zak wrote: > On Mon, May 20, 2013 at 09:02:43PM -0400, KOSAKI Motohiro wrote: >>> - if (fl_discard) >>> + if (fl_discard) { >>> flags |= SWAP_FLAG_DISCARD; >>> + if (fl_discard > 1) >>> + flags |= SWAP_FLAG_DISCARD_CLUSTER; >> >> This is not enough, IMHO. When running this code on old kernel, swapon() return EINVAL. >> At that time, we should fall back swapon(0x10000). > > Hmm.. currently we don't use any fallback for any swap flag (e.g. > 0x10000) for compatibility with old kernels. Maybe it's better to > keep it simple and stupid and return an error message than introduce > any super-smart semantic to hide incompatible fstab configuration. Hm. If so, I'd propose to revert the following change. > .B "\-d, \-\-discard" >-Discard freed swap pages before they are reused, if the swap >-device supports the discard or trim operation. This may improve >-performance on some Solid State Devices, but often it does not. >+Enables swap discards, if the swap device supports that, and performs >+a batch discard operation for the swap device at swapon time. And instead, I suggest to make --discard-on-swapon like the following. (better name idea is welcome) +--discard-on-swapon +Enables swap discards, if the swap device supports that, and performs +a batch discard operation for the swap device at swapon time. I mean, preserving flags semantics removes the reason we need make a fallback. -- 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/