Re: [Nbd] Is NBD_CMD_FLAG_FUA valid during NBD_CMD_FLUSH?
- To: Eric Blake <eblake@...696...>
- Cc: "nbd-general@lists.sourceforge.net" <nbd-general@lists.sourceforge.net>, Wouter Verhelst <w@...112...>, "qemu-devel@...530..." <qemu-devel@...530...>
- Subject: Re: [Nbd] Is NBD_CMD_FLAG_FUA valid during NBD_CMD_FLUSH?
- From: Alex Bligh <alex@...872...>
- Date: Fri, 1 Apr 2016 16:12:47 +0100
- Message-id: <BBDA394F-F2D2-49A1-9AA1-4B1401458587@...872...>
- In-reply-to: <56FE8EF8.3080603@...696...>
- References: <56FD7B7E.4060004@...696...> <64B326DA-CDF4-4537-B38A-46E7B57C319C@...872...> <56FD8069.7020101@...696...> <FC6D7B08-B1C0-4ED7-ABD0-FE409C43782C@...872...> <56FD89D0.5050408@...696...> <20160401082715.GB25514@...3...> <56FE82B3.4010205@...696...> <33E7C614-E8C4-48FF-84BE-7F2418C65D22@...872...> <56FE8EF8.3080603@...696...>
On 1 Apr 2016, at 16:08, Eric Blake <eblake@...696...> wrote:
> But yes, I'm favoring a) as well, for the simplicity factor. There's
> still the issue that if we document a behavior, a new client talking to
> an older server can't reliably tell if the behavior will be guaranteed.
Existing clients should not be sending FUA on anything other than
NBD_CMD_WRITE *and* relying on the behaviour, as the behaviour is
not documented (hence this discussion). Therefore it shouldn't
break anything. I also think it won't break anything in practice
as qemu doesn't use FUA on write and the kernel doesn't use FUA
at all; I realise that is not an exhaustive list.
--
Alex Bligh
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