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 S1755397Ab1KXDCp (ORCPT <rfc822;w@1wt.eu>);
	Wed, 23 Nov 2011 22:02:45 -0500
Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:40586 "EHLO
	fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750985Ab1KXDCo (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 23 Nov 2011 22:02:44 -0500
X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1
Date: Thu, 24 Nov 2011 12:01:26 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Cong Wang <amwang@redhat.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: <20111124120126.9361b2c9.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <CAHGf_=oD0Coc=k5kAAQoP=GqK+nc0jd3qq3TmLZaitSjH-ZPmQ@mail.gmail.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>
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=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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.

Thanks,
-kame