From: Theodore Tso Subject: Re: [PATCH 1/3] block_write_full_page: Use synchronous writes for WBC_SYNC_ALL writebacks Date: Tue, 7 Apr 2009 17:44:21 -0400 Message-ID: <20090407214421.GA7031@mit.edu> References: <1238185471-31152-1-git-send-email-tytso@mit.edu> <1238185471-31152-2-git-send-email-tytso@mit.edu> <20090406232141.ebdb426a.akpm@linux-foundation.org> <20090406235052.1ea47513.akpm@linux-foundation.org> <20090407070835.GM5178@kernel.dk> <20090407002313.fcdd1da0.akpm@linux-foundation.org> <20090407075732.GO5178@kernel.dk> <20090407190913.GA31723@mit.edu> <20090407193239.GE5178@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Linux Kernel Developers List , Ext4 Developers List , jack@suse.cz To: Jens Axboe Return-path: Received: from THUNK.ORG ([69.25.196.29]:49595 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756161AbZDGVoe (ORCPT ); Tue, 7 Apr 2009 17:44:34 -0400 Content-Disposition: inline In-Reply-To: <20090407193239.GE5178@kernel.dk> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Apr 07, 2009 at 09:32:39PM +0200, Jens Axboe wrote: > > This should be all you need, forget the below. The manual unplugging > only really makes sense for very select situations, since it'll be done > when someone waits on the buffer anyway. Thanks, ok; I missed the "sync_buffer" in the call to wait_on_bit() in __wait_on_buffer(). It also wasn't obvious to me that wait_on_writeback_range() ultimately ends up calling aops->sync_page which for filemap.c will call blk_run_backing_dev() --- and that blk_run_*() results in the right device queue getting unplugged. So this would be a nice thing to get documented in Documentation/biodoc.txt. - Ted