x86_64: fix e820_hole_size based on address ranges

e820_hole_size() now uses the newly extracted helper function,
e820_find_active_region(), to determine the size of usable RAM in a range of
PFN's.

This was previously broken because of two reasons:

 - The start and end PFN's of each e820 entry were not properly rounded
   prior to excluding those entries in the range, and

 - Entries smaller than a page were not properly excluded from being
   accumulated.

This resulted in emulated nodes being incorrectly mapped to ranges that
were completely reserved and not candidates for being registered as
active ranges.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 31 deletions

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 2570643ba1c5..62e051bab3b2 100644
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -194,37 +194,6 @@ unsigned long __init e820_end_of_ram(void)
 }
 
 /*
- * Find the hole size in the range.
- */
-unsigned long __init e820_hole_size(unsigned long start, unsigned long end)
-{
-        unsigned long ram = 0;
-        int i;
-
-        for (i = 0; i < e820.nr_map; i++) {
-                struct e820entry *ei = &e820.map[i];
-                unsigned long last, addr;
-
-                if (ei->type != E820_RAM ||
-                    ei->addr+ei->size <= start ||
-                    ei->addr >= end)
-                        continue;
-
-                addr = round_up(ei->addr, PAGE_SIZE);
-                if (addr < start)
-                        addr = start;
-
-                last = round_down(ei->addr + ei->size, PAGE_SIZE);
-                if (last >= end)
-                        last = end;
-
-                if (last > addr)
-                        ram += last - addr;
-        }
-        return ((end - start) - ram);
-}
-
-/*
  * Mark e820 reserved areas as busy for the resource manager.
  */
 void __init e820_reserve_resources(void)
@@ -364,6 +333,29 @@ void __init add_memory_region(unsigned long start, unsigned long size, int type)
         e820.nr_map++;
 }
 
+/*
+ * Find the hole size (in bytes) in the memory range.
+ * @start: starting address of the memory range to scan
+ * @end: ending address of the memory range to scan
+ */
+unsigned long __init e820_hole_size(unsigned long start, unsigned long end)
+{
+        unsigned long start_pfn = start >> PAGE_SHIFT;
+        unsigned long end_pfn = end >> PAGE_SHIFT;
+        unsigned long ei_startpfn;
+        unsigned long ei_endpfn;
+        unsigned long ram = 0;
+        int i;
+
+        for (i = 0; i < e820.nr_map; i++) {
+                if (e820_find_active_region(&e820.map[i],
+                                            start_pfn, end_pfn,
+                                            &ei_startpfn, &ei_endpfn))
+                        ram += ei_endpfn - ei_startpfn;
+        }
+        return end - start - (ram << PAGE_SHIFT);
+}
+
 void __init e820_print_map(char *who)
 {
         int i;