From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] block: fix DISCARD_BARRIER requests Date: Thu, 17 Jun 2010 10:10:18 +0200 Message-ID: <4C19D86A.5030709@kernel.dk> References: <20100617075432.GA22407@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, Chris Mason To: Christoph Hellwig Return-path: Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:59403 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756906Ab0FQIKT (ORCPT ); Thu, 17 Jun 2010 04:10:19 -0400 In-Reply-To: <20100617075432.GA22407@lst.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2010-06-17 09:54, Christoph Hellwig wrote: > Filesystems assume that DISCARD_BARRIER are full barriers, so that they > don't have to track in-progress discard operation when submitting new I/O. > But currently we only treat them as elevator barriers, which don't > actually do the nessecary queue drains. > > Also remove the unlikely around both the DISCARD and BARRIER requests - > the happen far too often for a static mispredict. Thanks, applied. There was a recent problem report on btrfs using discard, could possibly explain it if Chris assumed it was a full barrier. -- Jens Axboe