mm, devm_memremap_pages: kill mapping "System RAM" support

BugLink: https://bugs.launchpad.net/bugs/1837477
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>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/kernel/memremap.c b/kernel/memremap.c
index ddb00e6401a20c3df460345c723dcd6947bfe292..e1b8ffcdada6a379e73c24a51d09ce8caed656f4 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -379,15 +379,12 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
        is_ram = region_intersects(align_start, align_size,
                IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 
-       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);
-
        if (!ref)
                return ERR_PTR(-EINVAL);