Date: Tue, 9 Jun 2015 00:46:43 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Matias Bj??rling <m@bjorling.me>
Cc: hch@infradead.org, axboe@fb.com, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        Stephen.Bates@pmcs.com, keith.busch@intel.com, javier@lightnvm.io
Subject: Re: [PATCH v4 0/8] Support for Open-Channel SSDs
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Hi Matias,

I've been looking over this and I really think it needs a fundamental
rearchitecture still.  The design of using a separate stacking
block device and all kinds of private hooks does not look very
maintainable.

Here is my counter suggestion:

 - the stacking block device goes away
 - the nvm_target_type make_rq and prep_rq callbacks are combined
   into one and called from the nvme/null_blk ->queue_rq method
   early on to prepare the FTL state.  The drivers that are LightNVM
   enabled reserve a pointer to it in their per request data, which
   the unprep_rq callback is called on durign I/O completion.
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