mm: fix mixed zone detection in devm_memremap_pages

The check for whether we overlap "System RAM" needs to be done at
section granularity.  For example a system with the following mapping:

    100000000-37bffffff : System RAM
    37c000000-837ffffff : Persistent Memory

...is unable to use devm_memremap_pages() as it would result in two
zones colliding within a given section.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 778191e3e887..60baf4d3401e 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -270,13 +270,16 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
 void *devm_memremap_pages(struct device *dev, struct resource *res,
                 struct percpu_ref *ref, struct vmem_altmap *altmap)
 {
-        int is_ram = region_intersects(res->start, resource_size(res),
-                        "System RAM");
         resource_size_t key, align_start, align_size, align_end;
         struct dev_pagemap *pgmap;
         struct page_map *page_map;
+        int error, nid, is_ram;
         unsigned long pfn;
-        int error, nid;
+
+        align_start = res->start & ~(SECTION_SIZE - 1);
+        align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
+                - align_start;
+        is_ram = region_intersects(align_start, align_size, "System RAM");
 
         if (is_ram == REGION_MIXED) {
                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
@@ -314,8 +317,6 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 
         mutex_lock(&pgmap_lock);
         error = 0;
-        align_start = res->start & ~(SECTION_SIZE - 1);
-        align_size = ALIGN(resource_size(res), SECTION_SIZE);
         align_end = align_start + align_size - 1;
         for (key = align_start; key <= align_end; key += SECTION_SIZE) {
                 struct dev_pagemap *dup;