Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753441AbaBCVlF (ORCPT ); Mon, 3 Feb 2014 16:41:05 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46770 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751912AbaBCVlC (ORCPT ); Mon, 3 Feb 2014 16:41:02 -0500 Date: Mon, 3 Feb 2014 13:41:01 -0800 From: Andrew Morton To: Ryusuke Konishi Cc: LKML , linux-nilfs , Andreas Rohner Subject: Re: [PATCH 4/4] nilfs2: implementation of NILFS_IOCTL_SET_SUINFO ioctl Message-Id: <20140203134101.c56b916544e2475f63227339@linux-foundation.org> In-Reply-To: <1391446244-1435-5-git-send-email-konishi.ryusuke@lab.ntt.co.jp> References: <1391446244-1435-1-git-send-email-konishi.ryusuke@lab.ntt.co.jp> <1391446244-1435-5-git-send-email-konishi.ryusuke@lab.ntt.co.jp> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 4 Feb 2014 01:50:44 +0900 Ryusuke Konishi wrote: > With this ioctl the segment usage entries in the SUFILE can be > updated from userspace. > > This is useful, because it allows the userspace GC to modify and update > segment usage entries for specific segments, which enables it to avoid > unnecessary write operations. > > If a segment needs to be cleaned, but there is no or very little > reclaimable space in it, the cleaning operation basically degrades to > a useless moving operation. In the end the only thing that changes is > the location of the data and a timestamp in the segment usage > information. With this ioctl the GC can skip the cleaning and update > the segment usage entries directly instead. > > This is basically a shortcut to cleaning the segment. It is still > necessary to read the segment summary information, but the writing of > the live blocks can be skipped if it's not worth it. Documentation/filesystems/nilfs2.txt should be updated to document the new ioctl. Which we're in there, please check that the ioctl documentation is otherwise complete and up-to-date. These things have a tendency to bitrot. -- 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/