From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51484) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1adYm7-0000Me-3x for qemu-devel@nongnu.org; Wed, 09 Mar 2016 02:43:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1adYm6-00032f-BV for qemu-devel@nongnu.org; Wed, 09 Mar 2016 02:43:19 -0500 Sender: Paolo Bonzini References: <1455645388-32401-1-git-send-email-pbonzini@redhat.com> <1455645388-32401-7-git-send-email-pbonzini@redhat.com> <20160309033504.GE17947@ad.usersys.redhat.com> From: Paolo Bonzini Message-ID: <56DFD40D.4040109@redhat.com> Date: Wed, 9 Mar 2016 08:43:09 +0100 MIME-Version: 1.0 In-Reply-To: <20160309033504.GE17947@ad.usersys.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 06/16] block: add BDS field to count in-flight requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, stefanha@redhat.com On 09/03/2016 04:35, Fam Zheng wrote: >> > enum BdrvTrackedRequestType { >> > BDRV_TRACKED_READ, >> > BDRV_TRACKED_WRITE, >> > - BDRV_TRACKED_FLUSH, >> > - BDRV_TRACKED_IOCTL, >> > BDRV_TRACKED_DISCARD, > Okay, so flush and ioctl are not needed, but why is discard different? Discard can modify the contents of the device, so I think it's safer to serialize it against RMW and copy-on-read operations. Paolo