To: Dan Williams <dan.j.williams@intel.com>,
        Jerome Glisse <jglisse@redhat.com>
References: <20170418164557.GA7181@obsidianresearch.com>
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Cc: Jens Axboe <axboe@kernel.dk>, Keith Busch <keith.busch@intel.com>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-rdma@vger.kernel.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Steve Wise <swise@opengridcomputing.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-nvme@lists.infradead.org,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
        Bjorn Helgaas <helgaas@kernel.org>, linux-pci@vger.kernel.org,
        linux-nvdimm <linux-nvdimm@ml01.01.org>,
        Max Gurtovoy <maxg@mellanox.com>,
        linux-scsi <linux-scsi@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
From: Logan Gunthorpe <logang@deltatee.com>
Message-ID: <99a22044-8f15-f381-19ee-e239e9d2da29@deltatee.com>
Date: Wed, 19 Apr 2017 12:19:32 -0600
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On 19/04/17 12:11 PM, Logan Gunthorpe wrote:
> 
> 
> On 19/04/17 11:41 AM, Dan Williams wrote:
>> No, not quite ;-). I still don't think we should require the non-HMM
>> to pass NULL for all the HMM arguments. What I like about Logan's
>> proposal is to have a separate create and register steps dev_pagemap.
>> That way call paths that don't care about HMM specifics can just turn
>> around and register the vanilla dev_pagemap.
> 
> Would you necessarily even need a create step? I was thinking more along
> the lines that struct dev_pagemap _could_ just be a member in another
> structure. The caller would set the attributes they needed and pass it
> to devm_memremap. (Similar to how we commonly do things with struct
> device, et al). Potentially, that could also get rid of the need for the
> *data pointer HMM is using to get back the struct hmm_devmem seeing
> container_of could be used instead.

Also, now that I've thought about it a little more, it _may_ be that
many or all of the hmm specific fields in dev_pagemap could move to a
containing struct too...

Logan