Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755838Ab0AFNmN (ORCPT ); Wed, 6 Jan 2010 08:42:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755604Ab0AFNmM (ORCPT ); Wed, 6 Jan 2010 08:42:12 -0500 Received: from mail-yx0-f188.google.com ([209.85.210.188]:43534 "EHLO mail-yx0-f188.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755534Ab0AFNmJ (ORCPT ); Wed, 6 Jan 2010 08:42:09 -0500 Message-ID: <4B4492B2.1040107@vflare.org> Date: Wed, 06 Jan 2010 19:10:02 +0530 From: Nitin Gupta Reply-To: ngupta@vflare.org User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-3.fc11 Thunderbird/3.0 MIME-Version: 1.0 To: Hugh Dickins CC: Pekka Enberg , Al Viro , Christoph Hellwig , Jens Axboe , Andi Kleen , Andrew Morton , linux-kernel Subject: Re: [PATCH 1/2] [mmotm] Add swap slot free callback to block_device_operations References: <1262661514-4148-1-git-send-email-ngupta@vflare.org> In-Reply-To: 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: 1784 Lines: 50 On 01/05/2010 04:28 PM, Hugh Dickins wrote: > On Tue, 5 Jan 2010, Nitin Gupta wrote: > >> This callback is required when RAM based devices are >> used as swap disks. One such device is ramzswap[1] which >> is used as compressed in-memory swap disk. For such >> devices, we need a callback as soon as a swap slot is no >> longer used to allow freeing memory allocated for this >> slot. Without this callback, stale data can quickly >> accumulate in memory defeating the whole purpose of >> such devices. >> >> Another user of this callback will be "preswap" as >> introduced by "Transcendent Memory" patches: >> http://lwn.net/Articles/367286/ >> (I intend to integrade preswap with ramzswap). >> >> [1] ramzswap: http://code.google.com/p/compcache/ >> >> Signed-off-by: Nitin Gupta > > Yes, thanks for your patience in putting this together: > I much prefer this version to all the other ways considered. > > (Though you should later add a comment, pointing out that this > callback is with swap_lock and often page table lock also held.) > I will send another patch for this. > We know that's unsatisfactory, but it is the nature of swap: > cutting some corners to get the job done without allocating > more memory. Having tried myself to do proper discard at > swap_free time, I know that is hard: and I believe you've > made the right decision to do it in this way for ramzswap. > > Acked-by: Hugh Dickins > Thanks for the review. So, is this now going in mmotm tree? Nitin -- 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/