Messages in this thread | | | Subject | Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements | From | Alex Bligh <> | Date | Thu, 15 Sep 2016 12:46:07 +0100 |
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> On 15 Sep 2016, at 12:40, Christoph Hellwig <hch@infradead.org> wrote: > > On Thu, Sep 15, 2016 at 01:29:36PM +0200, Wouter Verhelst wrote: >> Yes, and that is why I was asking about this. If the write barriers >> are expected to be shared across connections, we have a problem. If, >> however, they are not, then it doesn't matter that the commands may be >> processed out of order. > > There is no such thing as a write barrier in the Linux kernel. We'd > much prefer protocols not to introduce any pointless synchronization > if we can avoid it.
I suspect the issue is terminological.
Essentially NBD does supports FLUSH/FUA like this:
https://www.kernel.org/doc/Documentation/block/writeback_cache_control.txt
IE supports the same FLUSH/FUA primitives as other block drivers (AIUI).
Link to protocol (per last email) here:
https://github.com/yoe/nbd/blob/master/doc/proto.md#ordering-of-messages-and-writes
-- Alex Bligh
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