From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39042) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alvN9-0002ff-1n for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:28:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alvN8-0001W4-4Q for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:28:06 -0400 Received: from mail.avalus.com ([2001:41c8:10:1dd::10]:51630) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alvN7-0001Vr-UB for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:28:06 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) From: Alex Bligh In-Reply-To: <20160401083522.GC25514@grep.be> Date: Fri, 1 Apr 2016 10:28:03 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: <2073BBC6-CD9E-427D-831C-05E9B4599A4B@alex.org.uk> References: <1459465399-56203-1-git-send-email-alex@alex.org.uk> <20160401083522.GC25514@grep.be> Subject: Re: [Qemu-devel] [Nbd] [PATCH] Improve documentation of FUA and FLUSH List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wouter Verhelst Cc: "nbd-general@lists.sourceforge.net" , "qemu-devel@nongnu.org" , Alex Bligh On 1 Apr 2016, at 09:35, Wouter Verhelst wrote: >> +* All write commands (that includes both `NBD_CMD_WRITE` and >> + `NBD_CMD_TRIM`) that the server completes (i.e. replies to) >> + prior to processing to a `NBD_CMD_FLUSH` MUST be written to = non-volatile >> + storage prior to replying to that `NBD_CMD_FLUSH`. The server = SHOULD ensure >> + that all write command received prior to processing the = `NBD_CMD_FLUSH` >> + (whether they are replied to or not) are written to non-volatile >> + storage prior to processing an `NBD_CMD_FLUSH`; note this is a >> + stronger condition than the previous 'MUST' condition. This >=20 > This seems to make little sense. Are you saying that suddenly now > sending a reply for FLUSH with outstanding writes is wrong? If not, = the > above should be clarified. The MUST sentence does not cover that situation as it only refers to completed writes. The SHOULD sentence says that's a 'SHOULD NOT' situation in respect of writes that have PROCESSED (i.e actioned) whether or not they have been replied to. Of course the client has no way of knowing whether they have been PROCESSED without a reply. Personally I think the SHOULD clause is pretty pointless and is unnecessary, but that's where the conversation got to n years ago I believe. Happy to delete the last sentence if that's wrong. --=20 Alex Bligh