mm, devm_memremap_pages: kill mapping "System RAM" support

commit 06489cfbd915ff36c8e36df27f1c2dc60f97ca56 upstream.

Given the fact that devm_memremap_pages() requires a percpu_ref that is
torn down by devm_memremap_pages_release() the current support for mapping
RAM is broken.

Support for remapping "System RAM" has been broken since the beginning and
there is no existing user of this this code path, so just kill the support
and make it an explicit error.

This cleanup also simplifies a follow-on patch to fix the error path when
setting a devm release action for devm_memremap_pages_release() fails.

Link: http://lkml.kernel.org/r/154275557997.76910.14689813630968180480.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: "Jérôme Glisse" <jglisse@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 71d28a5dbfc2ddcb9d5b84157bdcfa9c9e1fad46..1be42f9b3e006e9b3497f0f0935b448fc5d6849d 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -171,15 +171,12 @@ void *devm_memremap_pages(struct device *dev, struct resource *res)
        struct page_map *page_map;
        int error, nid;
 
-       if (is_ram == REGION_MIXED) {
-               WARN_ONCE(1, "%s attempted on mixed region %pr\n",
-                               __func__, res);
+       if (is_ram != REGION_DISJOINT) {
+               WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
+                               is_ram == REGION_MIXED ? "mixed" : "ram", res);
                return ERR_PTR(-ENXIO);
        }
 
-       if (is_ram == REGION_INTERSECTS)
-               return __va(res->start);
-
        page_map = devres_alloc_node(devm_memremap_pages_release,
                        sizeof(*page_map), GFP_KERNEL, dev_to_node(dev));
        if (!page_map)