Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752386Ab2HGIsh (ORCPT ); Tue, 7 Aug 2012 04:48:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62047 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225Ab2HGIse (ORCPT ); Tue, 7 Aug 2012 04:48:34 -0400 Message-ID: <5020D6E5.3060504@redhat.com> Date: Tue, 07 Aug 2012 16:50:45 +0800 From: Asias He User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Christoph Hellwig CC: linux-kernel@vger.kernel.org, Rusty Russell , Jens Axboe , Tejun Heo , Shaohua Li , "Michael S. Tsirkin" , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path References: <1343888757-25723-1-git-send-email-asias@redhat.com> <1343888757-25723-5-git-send-email-asias@redhat.com> <20120802062742.GA23573@lst.de> <501A2178.3000906@redhat.com> <20120806151731.GA23220@lst.de> In-Reply-To: <20120806151731.GA23220@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 34 On 08/06/2012 11:17 PM, Christoph Hellwig wrote: > On Thu, Aug 02, 2012 at 02:43:04PM +0800, Asias He wrote: >>> Even if it has a payload waiting is highly suboptimal and it should >>> use a non-blocking sequencing like it is done in the request layer. >> >> So, for REQ_FLUSH, what we need is that send out the VIRTIO_BLK_T_FLUSH and >> not to wait. > > If it's REQ_FLUSH without data a VIRTIO_BLK_T_FLUSH should be sent out only, > if it's a REQ_FLUSH that has data a VIRTIO_BLK_T_FLUSH should be sent out, > but instead of waiting for it to finish the I/O completion handler should > then submit the actual write. > >> We still need to wait until the actual write is finished here? >> Like, >> >> REQ_FUA is emulated by: >> 1. Send the actual write >> 2. Wait until the actual write is finished >> 3. Send VIRTIO_BLK_T_FLUSH to device >> 4. Signal the end of the write to upper layer > > Remove step 2 and run step 3 from the I/O completion handler. > Thanks for the explanation. V6 is in flight. -- Asias -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/