Date: Wed, 10 Dec 2014 13:42:24 +0000
From: Joe Thornber <thornber@redhat.com>
To: Akira Hayakawa <ruby.wktk@gmail.com>
Cc: ejt@redhat.com, dm-devel@redhat.com, gregkh@linuxfoundation.org,
        snitzer@redhat.com, agk@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [dm-devel] [PATCH] staging: writeboost: Add dm-writeboost
Message-ID: <20141210134223.GE21108@debian>
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	dm-devel@redhat.com, gregkh@linuxfoundation.org, snitzer@redhat.com,
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On Wed, Dec 10, 2014 at 10:31:31PM +0900, Akira Hayakawa wrote:
> Joe,
> 
> > So you copy the bio payload to a different block of ram and then
> > complete the bio?  Or does the rambuf refer to the bio payload
> > directly?
> Good question.
> The answer is, copy the data (got by bio_data(bio)) to rambuf once
> and ack if it's not barrier things.
> It would be nice if data in rambuf points to bio payload but it now copies
> because bio payload can be reused after completion. Am I right?
> Is there a way of eliminate memory copying?

You *have* to eliminate this memory copying.  Remap the bios to the
relevant portion of your log, and don't complete them until you log
chunk is coherent.
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