From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753742AbZIQPZK (ORCPT ); Thu, 17 Sep 2009 11:25:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753445AbZIQPZJ (ORCPT ); Thu, 17 Sep 2009 11:25:09 -0400 Received: from cantor2.suse.de ([195.135.220.15]:50877 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753175AbZIQPZI (ORCPT ); Thu, 17 Sep 2009 11:25:08 -0400 Date: Thu, 17 Sep 2009 17:25:10 +0200 From: Jan Kara To: Boaz Harrosh Cc: Jan Kara , Nick Piggin , linux-fsdevel@vger.kernel.org, LKML , pbadari@us.ibm.com, Andrew Morton Subject: Re: Is nobh code still useful? Message-ID: <20090917152510.GC13660@duck.suse.cz> References: <20090917135627.GB13660@duck.suse.cz> <4AB2519F.8020409@panasas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AB2519F.8020409@panasas.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 17-09-09 18:11:27, Boaz Harrosh wrote: > On 09/17/2009 04:56 PM, Jan Kara wrote: > > Hi, > > > > during my page_mkwrite() work, I've looked at who uses nobh_ versions of > > various functions in fs/buffer.c. It seems only ext2 and jfs use them. ext3 > > uses them only from writepage() (which means we needn't attach buffers to a > > page when it was written via mmap in writeback mode) and ext4 tries to use > > them but in fact it's nop because it always attaches buffers to the page > > earlier. So it's not really widely used, there's quite some code to support > > it (including one page flag), and it also slightly complicates my > > page_mkwrite() fixes. > > So I wanted to ask does somebody actually remember what it is good for? > > Buffer heads obviously consume some memory so was that the reason? OTOH we > > have to map the page whenever we write to it or send it to disk via > > writepage(). > > > > Honza > > I'm currently using nobh_truncate_page() in fs/exofs/inode.c::exofs_truncate(). > > Though, I suspect that once I do the conversion to Nick's: > "[patch 00/11] new truncate sequence" > and it is submitted, that use will disappear. Yeah, actually with page_mkwrite patches I've just sent, this would definitely go away so this isn't a use I'm too much worried about ;). But thanks for info anyway. Honza -- Jan Kara SUSE Labs, CR