linux-kernel - Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory

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Message-ID: <8ed955f8-55c9-a2bd-1d58-90bf1dcfa055@deltatee.com>
Date:   Thu, 1 Mar 2018 14:15:01 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     Benjamin Herrenschmidt <benh@....ibm.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Oliver OHalloran <oliveroh@....ibm.com>
Subject: Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory



On 01/03/18 02:10 PM, Jerome Glisse wrote:
> It seems people miss-understand HMM :( you do not have to use all of
> its features. If all you care about is having struct page then just
> use that for instance in your case only use those following 3 functions:
> 
> hmm_devmem_add() or hmm_devmem_add_resource() and hmm_devmem_remove()
> for cleanup.

To what benefit over just using devm_memremap_pages()? If I'm using the 
hmm interface and disabling all the features, I don't see the point. 
We've also cleaned up the devm_memremap_pages() interface to be more 
usefully generic in such a way that I'd hope HMM starts using it too and 
gets rid of the code duplication.

Logan