From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48116) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alw2e-0007dh-CC for qemu-devel@nongnu.org; Fri, 01 Apr 2016 06:11:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alw2Z-0003Qn-Du for qemu-devel@nongnu.org; Fri, 01 Apr 2016 06:11:00 -0400 Received: from barbershop.grep.be ([89.106.240.122]:54387) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alw2Z-0003Qa-8i for qemu-devel@nongnu.org; Fri, 01 Apr 2016 06:10:55 -0400 Date: Fri, 1 Apr 2016 12:10:19 +0200 From: Wouter Verhelst Message-ID: <20160401101019.GL25514@grep.be> References: <1459465399-56203-1-git-send-email-alex@alex.org.uk> <20160401083522.GC25514@grep.be> <2073BBC6-CD9E-427D-831C-05E9B4599A4B@alex.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2073BBC6-CD9E-427D-831C-05E9B4599A4B@alex.org.uk> 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: Alex Bligh Cc: "nbd-general@lists.sourceforge.net" , "qemu-devel@nongnu.org" On Fri, Apr 01, 2016 at 10:28:03AM +0100, Alex Bligh wrote: > > 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 > > > > 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. I'm still not sure what it's supposed to mean, though. Clearly, you should at the very least reword it, if not... > Happy to delete the last sentence if that's wrong. ... remove it instead. -- < ron> I mean, the main *practical* problem with C++, is there's like a dozen people in the world who think they really understand all of its rules, and pretty much all of them are just lying to themselves too. -- #debian-devel, OFTC, 2016-02-12