linux-kernel - [PATCH v2 0/7] mm: Rework hmm to use devm_memremap

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Date:   Tue, 22 May 2018 22:10:17 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     stable@...r.kernel.org, Logan Gunthorpe <logang@...tatee.com>,
        Christoph Hellwig <hch@....de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/7] mm: Rework hmm to use devm_memremap_pages

Changes since v1: [1]
* Kill support for mapping System RAM as a nop. No one uses this
  functionality and it is broken relative to percpu_ref management.

* Fix percpu_ref teardown. Given that devm_memremap_pages() has strict
  assumptions about when the percpu_ref is killed, give it
  responsibility to make the live-dead transition explicitly. (Logan)

* Split the patch that adds HMM support to devm_memremap_pages() from
  the patch that converts HMM to use devm_memremap_pages(). This caught
  an incomplete conversion in v1. (Logan)

* Collect Christoph's reviewed-by.

[1]: https://lkml.org/lkml/2018/5/21/1109

---

Hi Andrew, here's v2 to replace the 5 currently in mm. The first and
last patch did not change.

For maintainability, as ZONE_DEVICE continues to attract new users,
it is useful to keep all users consolidated on devm_memremap_pages() as
the interface for create "device pages".

The devm_memremap_pages() implementation was recently reworked to make
it more generic for arbitrary users, like the proposed peer-to-peer
PCI-E enabling. HMM pre-dated this rework and opted to duplicate
devm_memremap_pages() as hmm_devmem_pages_create().

Rework HMM to be a consumer of devm_memremap_pages() directly and fix up
the licensing on the exports given the deep dependencies on the mm.

Patches based on v4.17-rc6 where there are no upstream consumers of the
HMM functionality.

---

Dan Williams (7):
      mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL
      mm, devm_memremap_pages: Kill mapping "System RAM" support
      mm, devm_memremap_pages: Fix shutdown handling
      mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support
      mm, hmm: Use devm semantics for hmm_devmem_{add,remove}
      mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()
      mm, hmm: Mark hmm_devmem_{add,add_resource} EXPORT_SYMBOL_GPL

 Documentation/vm/hmm.txt          |    1 
 drivers/dax/pmem.c                |   10 -
 drivers/nvdimm/pmem.c             |   18 +-
 include/linux/hmm.h               |    4 
 include/linux/memremap.h          |    7 +
 kernel/memremap.c                 |   85 +++++++---
 mm/hmm.c                          |  307 +++++--------------------------------
 tools/testing/nvdimm/test/iomap.c |   21 ++-
 8 files changed, 130 insertions(+), 323 deletions(-)