[PATCH v4 0/8] Support for Open-Channel SSDs

[Christoph Hellwig]

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.