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 10:19:04 -0400 Message-ID: <20090407141904.GD31725@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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jens Axboe , Linux Kernel Developers List , Ext4 Developers List , jack@suse.cz To: Andrew Morton Return-path: Received: from THUNK.ORG ([69.25.196.29]:44884 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752278AbZDGOTW (ORCPT ); Tue, 7 Apr 2009 10:19:22 -0400 Content-Disposition: inline In-Reply-To: <20090407002313.fcdd1da0.akpm@linux-foundation.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Apr 07, 2009 at 12:23:13AM -0700, Andrew Morton wrote: > > I think the number of different greps which was needed to find all the > above was excessive. Too many levels of wrappers and helpers. This is true not only for the block I/O code, it's true also for the page writeback code --- have you ever tried creating a call tree that traces all of the descendents of sync_inode()? One of these days when I have a spare week (hah!), I'd love to create a huge chart of all of the callers into the various wrapper functions of the page writeback paths, figure out who needs what, and then collapse the rest. > > It looks like a good candidate for WRITE_SYNC_PLUG instead, Yeah, what we'll need to do now that we have the difference between WRITE_SYNC and WRITE_SYNC_PLUG is to have a way of signalling (probably via yet another wbc flag) that we want WRITE_SYNC_PLUG and not WRITE_SYNC, and that the top-level caller of this whole mess will be responsible for issuing the unplug. I'll try to get something whipped up. - Ted