1 files changed, 18 insertions, 4 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index 24e9e60c1459..2d5be5d9bf5f 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -304,7 +304,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
                 void *arg, int (*func)(unsigned long, unsigned long, void *))
 {
         struct resource res;
-        unsigned long pfn, len;
+        unsigned long pfn, end_pfn;
         u64 orig_end;
         int ret = -1;
 
@@ -314,9 +314,10 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
         orig_end = res.end;
         while ((res.start < res.end) &&
                 (find_next_system_ram(&res, "System RAM") >= 0)) {
-                pfn = (unsigned long)(res.start >> PAGE_SHIFT);
-                len = (unsigned long)((res.end + 1 - res.start) >> PAGE_SHIFT);
-                ret = (*func)(pfn, len, arg);
+                pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
+                end_pfn = (res.end + 1) >> PAGE_SHIFT;
+                if (end_pfn > pfn)
+                        ret = (*func)(pfn, end_pfn - pfn, arg);
                 if (ret)
                         break;
                 res.start = res.end + 1;
@@ -327,6 +328,19 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 
 #endif
 
+static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg)
+{
+        return 1;
+}
+/*
+ * This generic page_is_ram() returns true if specified address is
+ * registered as "System RAM" in iomem_resource list.
+ */
+int __weak page_is_ram(unsigned long pfn)
+{
+        return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
+}
+
 /*
  * Find empty slot in the resource tree given range and alignment.
  */