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Date: Wed, 12 Sep 2012 11:58:24 -0700
From: Tejun Heo <tj@kernel.org>
To: NeilBrown <neilb@suse.de>, Kent Overstreet <koverstreet@google.com>,
        Jens Axboe <axboe@kernel.dk>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Vivek Goyal <vgoyal@redhat.com>, drbd-dev@lists.linbit.com
Subject: Re: [Drbd-dev] FLUSH/FUA documentation & code discrepancy
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Hello,

On Tue, Sep 11, 2012 at 10:25:01AM +0200, Lars Ellenberg wrote:
> Or do we have a better place to document write ordering requirements?
> 
> "To enforce write-after-write dependencies, you *have* to drain the
> queue (do we have a generic interface available for that?),
> or at least wait for the completion of all the requests you
> (potentially) depend upon, before even submitting the dependent request.
> 
> Additionally, to avoid integrity issues due to volatile caches,
> you need to use FLUSH/FUA as appropriate."

I think it would be best to note the lack of any ordering guarantee in
the comment of bio_submit()?  Any one interested in submitting a
patch?

Thanks.

-- 
tejun