linux-kernel - [PATCH v4 7/8] mm, hmm: Mark hmm_devmem_{add, add_resource} EXPORT_SYMBOL

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Message-ID: <153128611419.2928.14858876648286345508.stgit@dwillia2-desk3.amr.corp.intel.com>
Date:   Tue, 10 Jul 2018 22:15:14 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Christoph Hellwig <hch@....de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 7/8] mm, hmm: Mark hmm_devmem_{add,
 add_resource} EXPORT_SYMBOL_GPL

The routines hmm_devmem_add(), and hmm_devmem_add_resource() duplicated
devm_memremap_pages() and are now simple now wrappers around the core
facility to inject a dev_pagemap instance into the global pgmap_radix
and hook page-idle events. The devm_memremap_pages() interface is base
infrastructure for HMM. HMM has more and deeper ties into the kernel
memory management implementation than base ZONE_DEVICE which is itself a
EXPORT_SYMBOL_GPL facility.

Originally, the HMM page structure creation routines copied the
devm_memremap_pages() code and reused ZONE_DEVICE. A cleanup to unify
the implementations was discussed during the initial review:
http://lkml.iu.edu/hypermail/linux/kernel/1701.2/00812.html
Recent work to extend devm_memremap_pages() for the peer-to-peer-DMA
facility enabled this cleanup to move forward.

In addition to the integration with devm_memremap_pages() HMM depends on
other GPL-only symbols:

    mmu_notifier_unregister_no_release
    percpu_ref
    region_intersects
    __class_create

It goes further to consume / indirectly expose functionality that is not
exported to any other driver:

    alloc_pages_vma
    walk_page_range

HMM depends upon and extends deep core-kernel fundamentals. Mark its
main entry points EXPORT_SYMBOL_GPL().

Cc: "Jérôme Glisse" <jglisse@...hat.com>
Cc: Logan Gunthorpe <logang@...tatee.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 mm/hmm.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index c5a6e61ee302..0af3220ffcba 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1055,7 +1055,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 		return result;
 	return devmem;
 }
-EXPORT_SYMBOL(hmm_devmem_add);
+EXPORT_SYMBOL_GPL(hmm_devmem_add);

 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 					   struct device *device,
@@ -1109,7 +1109,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 		return result;
 	return devmem;
 }
-EXPORT_SYMBOL(hmm_devmem_add_resource);
+EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);

 /*
  * A device driver that wants to handle multiple devices memory through a