From: Andreas Dilger Subject: Re: delayed allocatiou result in Oops Date: Tue, 19 Jun 2007 15:50:05 -0600 Message-ID: <20070619215005.GU5181@schatzie.adilger.int> References: <20070614072352.GA6517@localhost.sw.ru> <4672202C.4080304@clusterfs.com> <1181949368.3808.7.camel@dyn9047017103.beaverton.ibm.com> <20070616081426.GB14349@localhost.sw.ru> <1182214878.3711.21.camel@dyn9047017103.beaverton.ibm.com> <46778186.9030306@clusterfs.com> <20070619091628.GB20172@localhost.sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Alex Tomas , cmm@us.ibm.com, linux-ext4@vger.kernel.org To: Dmitry Monakhov Return-path: Received: from mail.clusterfs.com ([206.168.112.78]:53845 "EHLO mail.clusterfs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751779AbXFSVuI (ORCPT ); Tue, 19 Jun 2007 17:50:08 -0400 Content-Disposition: inline In-Reply-To: <20070619091628.GB20172@localhost.sw.ru> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Jun 19, 2007 13:16 +0400, Dmitry Monakhov wrote: > But whole approach based on using PagePrivate bit and page->private > ptr for special purposes is realy dengerous, and imho wrong, > because avery fs-related code assume that page->private points to > page_buffers. This is actually a misconception. page->private can be anything. While many fs helper routines use page->private as buffers, that only happens when the fs itself causes those helper routines to be called. Lustre, for example, has no buffer heads on the clients, and uses page->private to track RPC batching information and data checksums. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.