From: Mike Snitzer Subject: Re: [PATCH 3/3] block: reimplement FLUSH/FUA to support merge Date: Fri, 21 Jan 2011 19:49:55 -0500 Message-ID: <20110122004955.GA17792@redhat.com> References: <1295625598-15203-1-git-send-email-tj@kernel.org> <1295625598-15203-4-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: axboe@kernel.dk, tytso@mit.edu, djwong@us.ibm.com, shli@kernel.org, neilb@suse.de, adilger.kernel@dilger.ca, jack@suse.cz, linux-kernel@vger.kernel.org, kmannth@us.ibm.com, cmm@us.ibm.com, linux-ext4@vger.kernel.org, rwheeler@redhat.com, hch@lst.de, josef@redhat.com To: Tejun Heo Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33021 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750766Ab1AVAuy (ORCPT ); Fri, 21 Jan 2011 19:50:54 -0500 Content-Disposition: inline In-Reply-To: <1295625598-15203-4-git-send-email-tj@kernel.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Jan 21 2011 at 10:59am -0500, Tejun Heo wrote: > diff --git a/block/blk-flush.c b/block/blk-flush.c > index 8592869..cd73e93 100644 > --- a/block/blk-flush.c > +++ b/block/blk-flush.c > @@ -1,6 +1,69 @@ > /* > * Functions to sequence FLUSH and FUA writes. > + * > + * Copyright (C) 2011 Max Planck Institute for Gravitational Physics > + * Copyright (C) 2011 Tejun Heo > + * > + * This file is released under the GPLv2. > + * > + * REQ_{FLUSH|FUA} requests are decomposed to sequences consisted of three > + * optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request > + * properties and hardware capability. > + * > + * If a request doesn't have data, only REQ_FLUSH makes sense, which > + * indicates a simple flush request. If there is data, REQ_FLUSH indicates > + * that the device cache should be flushed before the data is executed, and > + * REQ_FUA means that the data must be on non-volatile media on request > + * completion. > + * > + * If the device doesn't have writeback cache, FLUSH and FUA don't make any > + * difference. The requests are either completed immediately if there's no > + * data or executed as normal requests otherwise. For devices without a writeback cache, I'm not seeing where pure flushes are completed immediately. But I do see where data is processed directly in blk_insert_flush(). > -struct request *blk_do_flush(struct request_queue *q, struct request *rq) > +/** > + * blk_abort_flush - @q is being aborted, abort flush requests ^^^^^^^^^^^^^^^ Small comment nit, s/blk_abort_flush/blk_abort_flushes/ > + * @q: request_queue being aborted > + * > + * To be called from elv_abort_queue(). @q is being aborted. Prepare all > + * FLUSH/FUA requests for abortion. > + * > + * CONTEXT: > + * spin_lock_irq(q->queue_lock) > + */ > +void blk_abort_flushes(struct request_queue *q)