From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o59L7qjV032559 for ; Wed, 9 Jun 2010 16:07:52 -0500 Received: from smtp1.linux-foundation.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 092231591969 for ; Wed, 9 Jun 2010 14:13:25 -0700 (PDT) Received: from smtp1.linux-foundation.org (smtp1.linux-foundation.org [140.211.169.13]) by cuda.sgi.com with ESMTP id VqIGzDJB85EnA6MM for ; Wed, 09 Jun 2010 14:13:25 -0700 (PDT) Date: Wed, 9 Jun 2010 14:09:42 -0700 From: Andrew Morton Subject: Re: [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages Message-Id: <20100609140942.6799c84a.akpm@linux-foundation.org> In-Reply-To: <1276043840-1946-2-git-send-email-david@fromorbit.com> References: <1276043840-1946-1-git-send-email-david@fromorbit.com> <1276043840-1946-2-git-send-email-david@fromorbit.com> Mime-Version: 1.0 List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: linux-fsdevel@vger.kernel.org, stable@kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com On Wed, 9 Jun 2010 10:37:18 +1000 Dave Chinner wrote: > From: Dave Chinner > > If a filesystem writes more than one page in ->writepage, write_cache_pages > fails to notice this and continues to attempt writeback when wbc->nr_to_write > has gone negative - this trace was captured from XFS: > > > wbc_writeback_start: towrt=1024 > wbc_writepage: towrt=1024 > wbc_writepage: towrt=0 > wbc_writepage: towrt=-1 > wbc_writepage: towrt=-5 > wbc_writepage: towrt=-21 > wbc_writepage: towrt=-85 > > This has adverse effects on filesystem writeback behaviour. write_cache_pages() > needs to terminate after a certain number of pages are written, not after a > certain number of calls to ->writepage are made. This is a regression > introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add > no_nrwrite_index_update writeback control flag"), but cannot be reverted > directly due to subsequent bug fixes that have gone in on top of it. Might be needed in -stable. Unfortunately the most important piece of information which is needed to make that decision was cunningly hidden from us behind the vague-to-the-point-of-uselessness term "adverse effects". _what_ "adverse effects"?? _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs