From: Amir Goldstein Subject: Re: ext4: Fix 32bit overflow in ext4_ext_find_goal() Date: Mon, 3 Jan 2011 09:02:56 +0200 Message-ID: References: <4D05B132.3060402@sx.jp.nec.com> <20110102214031.GA10889@thunk.org> <20110103041157.GE11955@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Andreas Dilger , Kazuya Mio , ext4 To: "Ted Ts'o" Return-path: Received: from mail-qy0-f181.google.com ([209.85.216.181]:48697 "EHLO mail-qy0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198Ab1ACHC4 convert rfc822-to-8bit (ORCPT ); Mon, 3 Jan 2011 02:02:56 -0500 Received: by qyk12 with SMTP id 12so14735917qyk.19 for ; Sun, 02 Jan 2011 23:02:56 -0800 (PST) In-Reply-To: <20110103041157.GE11955@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Jan 3, 2011 at 6:11 AM, Ted Ts'o wrote: > On Sun, Jan 02, 2011 at 08:35:39PM -0700, Andreas Dilger wrote: >> It was written that way because HPC applications writing to a shared >> file normally write to an offset of task_num * task_data_size so >> they do not overlap, and end up with a dense file. Similarly, >> bittorrent and parallel FTP clients will write dense files after >> seeking randomly around the file, and database files often end up >> dense as well. >> >> I'd rather fix the relatively few applications that expect >> permanently sparse files to use fadvise() to notify the kernel of >> this. > > Agreed, and I'm not sure there are enough applications that expect > permanently sparse files that's worth adding a new fadvise(). =A0But = if > we do add a new fadvise(), the default should clearly be the current > behavior. > > If someone knows of use cases where permanently sparse files are > common, please let us know! > Well, there's e2image of course, but using the qcow2 format is a better solution than fadvise in this case. Also, I believe that if one chooses to use VM with raw image format, it is mostly for the purpose or read performance, which implies that the image was fallocate'd. Am I wrong about this? Amir. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html