From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753305Ab1KXEZD (ORCPT <rfc822;w@1wt.eu>);
	Wed, 23 Nov 2011 23:25:03 -0500
Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:59024 "EHLO
	fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752030Ab1KXEZB (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 23 Nov 2011 23:25:01 -0500
X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1
Date: Thu, 24 Nov 2011 13:23:49 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Cong Wang <amwang@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        Pekka Enberg <penberg@kernel.org>, Christoph Hellwig <hch@lst.de>,
        Hugh Dickins <hughd@google.com>, Dave Hansen <dave@linux.vnet.ibm.com>,
        Lennart Poettering <lennart@poettering.net>,
        Kay Sievers <kay.sievers@vrfy.org>, linux-mm@kvack.org
Subject: Re: [V3 PATCH 1/2] tmpfs: add fallocate support
Message-Id: <20111124132349.ca862c9e.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <4ECDB87A.90106@redhat.com>
References: <1322038412-29013-1-git-send-email-amwang@redhat.com>
	<20111124105245.b252c65f.kamezawa.hiroyu@jp.fujitsu.com>
	<CAHGf_=oD0Coc=k5kAAQoP=GqK+nc0jd3qq3TmLZaitSjH-ZPmQ@mail.gmail.com>
	<20111124120126.9361b2c9.kamezawa.hiroyu@jp.fujitsu.com>
	<4ECDB87A.90106@redhat.com>
Organization: FUJITSU Co. LTD.
X-Mailer: Sylpheed 3.1.1 (GTK+ 2.10.14; i686-pc-mingw32)
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-2022-JP
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 24 Nov 2011 11:22:34 +0800
Cong Wang <amwang@redhat.com> wrote:

> 于 2011年11月24日 11:01, KAMEZAWA Hiroyuki 写道:
> > On Wed, 23 Nov 2011 21:46:39 -0500
> > KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>  wrote:
> >
> >>>> +     while (index<  end) {
> >>>> +             ret = shmem_getpage(inode, index,&page, SGP_WRITE, NULL);
> >>>
> >>> If the 'page' for index exists before this call, this will return the page without
> >>> allocaton.
> >>>
> >>> Then, the page may not be zero-cleared. I think the page should be zero-cleared.
> >>
> >> No. fallocate shouldn't destroy existing data. It only ensure
> >> subsequent file access don't make ENOSPC error.
> >>
> >        FALLOC_FL_KEEP_SIZE
> >                This flag allocates and initializes to zero the disk  space
> >                within the range specified by offset and len. ....
> >
> > just manual is unclear ? it seems that the range [offset, offset+len) is
> > zero cleared after the call.
> 
> I think we should fix the man page, because at least ext4 doesn't clear
> the original contents,
> 
> % echo hi > /tmp/foobar
> % fallocate -n -l 1 -o 10 /tmp/foobar
> % hexdump -Cv /tmp/foobar
> 00000000  68 69 0a                                          |hi.|
> 00000003
> 

thank you for checking. So, at failure path, original data should not be
cleared, either.

Thanks,
-Kame