From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 17/18] writeback: fix dirtied pages accounting on redirty Date: Wed, 7 Sep 2011 08:56:35 +0200 Message-ID: <20110907065635.GA12619@lst.de> References: <20110904015305.367445271@intel.com> <20110904020916.841463184@intel.com> <1315325936.14232.22.camel@twins> <20110907002222.GF31945@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , Wu Fengguang , linux-fsdevel@vger.kernel.org, Andrew Morton , Christoph Hellwig , Dave Chinner , Greg Thelen , Minchan Kim , Vivek Goyal , Andrea Righi , linux-mm , LKML To: Jan Kara Return-path: Content-Disposition: inline In-Reply-To: <20110907002222.GF31945@quack.suse.cz> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Sep 07, 2011 at 02:22:22AM +0200, Jan Kara wrote: > > So wtf is ext4 doing? Shouldn't a page stay dirty until its written out? > > > > That is, should we really frob around this behaviour or fix ext4 because > > its on crack? > Fengguang, could you please verify your findings with recent kernel? I > believe ext4 got fixed in this regard some time ago already (and yes, old > delalloc writeback code in ext4 was terrible). The pattern we do in writeback is: in pageout / write_cache_pages: lock_page(); clear_page_dirty_for_io(); in ->writepage: set_page_writeback(); unlock_page(); end_page_writeback(); So whenever ->writepage decides it doesn't want to write things back we have to redirty pages. We have this happen quite a bit in every filesystem, but ext4 hits it a lot more than usual because it refuses to write out delalloc pages from plain ->writepage and only allows ->writepages to do it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org