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From: Logan Gunthorpe <logang@deltatee.com>
To: Dan Williams <dan.j.williams@intel.com>, akpm@linux-foundation.org
Cc: "Michal Hocko" <mhocko@suse.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Christoph Hellwig" <hch@lst.de>,
	alexander.h.duyck@intel.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/7] mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL
Date: Thu, 13 Sep 2018 10:25:58 -0600
Message-ID: <f011859e-eab3-acea-9498-246f791922ff@deltatee.com> (raw)
In-Reply-To: <153680532635.453305.11297363695024516117.stgit@dwillia2-desk3.amr.corp.intel.com>



On 12/09/18 08:22 PM, Dan Williams wrote:
> devm_memremap_pages() is a facility that can create struct page entries
> for any arbitrary range and give drivers the ability to subvert core
> aspects of page management.
> 
> Specifically the facility is tightly integrated with the kernel's memory
> hotplug functionality. It injects an altmap argument deep into the
> architecture specific vmemmap implementation to allow allocating from
> specific reserved pages, and it has Linux specific assumptions about
> page structure reference counting relative to get_user_pages() and
> get_user_pages_fast(). It was an oversight and a mistake that this was
> not marked EXPORT_SYMBOL_GPL from the outset.
> 
> Again, devm_memremap_pagex() exposes and relies upon core kernel
> internal assumptions and will continue to evolve along with 'struct
> page', memory hotplug, and support for new memory types / topologies.
> Only an in-kernel GPL-only driver is expected to keep up with this
> ongoing evolution. This interface, and functionality derived from this
> interface, is not suitable for kernel-external drivers.
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>

Mostly to say that I agree with you and Christoph on this debate and
that the change to GPL does not affect my P2PDMA work.

Logan

  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-13  2:22 [PATCH v5 0/7] mm: Merge hmm into devm_memremap_pages, mark GPL-only Dan Williams
2018-09-13  2:22 ` [PATCH v5 1/7] mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL Dan Williams
2018-09-13 16:25   ` Logan Gunthorpe [this message]
2018-09-13  2:22 ` [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support Dan Williams
2018-09-13 16:10   ` Logan Gunthorpe
2018-09-14 13:14   ` Christoph Hellwig
2018-09-14 17:40     ` Dan Williams
2018-09-18 20:28   ` Jerome Glisse
2018-09-13  2:22 ` [PATCH v5 3/7] mm, devm_memremap_pages: Fix shutdown handling Dan Williams
2018-09-14 13:16   ` Christoph Hellwig
2018-09-14 17:25     ` Dan Williams
2018-09-18 20:28   ` Jerome Glisse
2018-09-13  2:22 ` [PATCH v5 4/7] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support Dan Williams
2018-09-14 13:18   ` Christoph Hellwig
2018-09-18 20:34   ` Jerome Glisse
2018-09-13  2:22 ` [PATCH v5 5/7] mm, hmm: Use devm semantics for hmm_devmem_{add, remove} Dan Williams
2018-09-14 13:18   ` Christoph Hellwig
2018-09-14 14:16     ` Jerome Glisse
2018-09-18 20:34   ` Jerome Glisse
2018-09-13  2:22 ` [PATCH v5 6/7] mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages() Dan Williams
2018-09-18 20:35   ` Jerome Glisse
2018-09-19  1:24   ` Balbir Singh
2018-09-13  2:22 ` [PATCH v5 7/7] mm, hmm: Mark hmm_devmem_{add, add_resource} EXPORT_SYMBOL_GPL Dan Williams

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