From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Thu, 26 Jun 2008 00:45:40 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m5Q7jbgv003159 for ; Thu, 26 Jun 2008 00:45:37 -0700 Received: from bombadil.infradead.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 7ECCB2832D3 for ; Thu, 26 Jun 2008 00:46:38 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org [18.85.46.34]) by cuda.sgi.com with ESMTP id EZOzfq18SKzROMMH for ; Thu, 26 Jun 2008 00:46:38 -0700 (PDT) Date: Thu, 26 Jun 2008 03:46:36 -0400 From: Christoph Hellwig Subject: Re: [PATCH 1/6] Extend completions to provide XFS object flush requirements Message-ID: <20080626074636.GB7064@infradead.org> References: <1214455277-6387-1-git-send-email-david@fromorbit.com> <1214455277-6387-2-git-send-email-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1214455277-6387-2-git-send-email-david@fromorbit.com> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Dave Chinner Cc: xfs@oss.sgi.com, matthew@wil.cx, linux-kernel@vger.kernel.org On Thu, Jun 26, 2008 at 02:41:12PM +1000, Dave Chinner wrote: > XFS object flushing doesn't quite match existing completion semantics. It > mixed exclusive access with completion. That is, we need to mark an object as > being flushed before flushing it to disk, and then block any other attempt to > flush it until the completion occurs. > > To do this we introduce: > > void init_completion_flush(struct completion *x) > which initialises x->done = 1 > > void completion_flush_start(struct completion *x) > which blocks if done == 0, otherwise decrements done to zero and > allows the caller to continue. > > bool completion_flush_start_nowait(struct completion *x) > returns a failure status if done == 0, otherwise decrements done > to zero and returns a "flush started" status. This is provided > to allow flushing to begin safely while holding object locks in > inverted order. > > This replaces the use of semaphores for providing this exclusion > and completion mechanism. Given that the only API call shared with normal completions is complete() I'd rather make this a primitive of it's own, even if internally implemented as completions. Also please add kerneldoc comments for all new APIs eported to modules.