Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdim...

Pull memremap fix from Dan Williams:
 "The new memremap() api introduced in the 4.3 cycle to unify/replace
  ioremap_cache() and ioremap_wt() is mishandling the highmem case.
  This patch has received a build success notification from a
  0day-kbuild-robot run and has received an ack from Ard"

From the commit message:
 "The impact of this bug is low for now since the pmem driver is the
  only user of memremap(), but this is important to fix before more
  conversions to memremap arrive in 4.4"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  memremap: fix highmem support

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 72b0c66628b6b3db589ad0cd6ed6533edb68a9ea..9d6b55587eaa59a25c38776e43aeff51ba682c40 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
 }
 #endif
 
+static void *try_ram_remap(resource_size_t offset, size_t size)
+{
+       struct page *page = pfn_to_page(offset >> PAGE_SHIFT);
+
+       /* In the simple case just return the existing linear address */
+       if (!PageHighMem(page))
+               return __va(offset);
+       return NULL; /* fallback to ioremap_cache */
+}
+
 /**
  * memremap() - remap an iomem_resource as cacheable memory
  * @offset: iomem resource start address
@@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
                 * the requested range is potentially in "System RAM"
                 */
                if (is_ram == REGION_INTERSECTS)
-                       addr = __va(offset);
-               else
+                       addr = try_ram_remap(offset, size);
+               if (!addr)
                        addr = ioremap_cache(offset, size);
        }