x86_64: extract helper function from e820_register_active_regions

The logic in e820_find_active_regions() for determining the true active
regions for an e820 entry given a range of PFN's is needed for
e820_hole_size() as well.

e820_hole_size() is called from the NUMA emulation code to determine the
reserved area within an address range on a per-node basis.  Its logic should
duplicate that of finding active regions in an e820 entry because these are
the only true ranges we may register anyway.

[akpm@linux-foundation.org: cleanup]
Cc: Mel Gorman <mel@csn.ul.ie>
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, 48 insertions, 34 deletions

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 13c6c37610e0..2570643ba1c5 100644
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -289,47 +289,61 @@ void __init e820_mark_nosave_regions(void)
         }
 }
 
-/* Walk the e820 map and register active regions within a node */
-void __init
-e820_register_active_regions(int nid, unsigned long start_pfn,
-                                                        unsigned long end_pfn)
+/*
+ * Finds an active region in the address range from start_pfn to end_pfn and
+ * returns its range in ei_startpfn and ei_endpfn for the e820 entry.
+ */
+static int __init e820_find_active_region(const struct e820entry *ei,
+                                          unsigned long start_pfn,
+                                          unsigned long end_pfn,
+                                          unsigned long *ei_startpfn,
+                                          unsigned long *ei_endpfn)
 {
-        int i;
-        unsigned long ei_startpfn, ei_endpfn;
-        for (i = 0; i < e820.nr_map; i++) {
-                struct e820entry *ei = &e820.map[i];
-                ei_startpfn = round_up(ei->addr, PAGE_SIZE) >> PAGE_SHIFT;
-                ei_endpfn = round_down(ei->addr + ei->size, PAGE_SIZE)
-                                                                >> PAGE_SHIFT;
+        *ei_startpfn = round_up(ei->addr, PAGE_SIZE) >> PAGE_SHIFT;
+        *ei_endpfn = round_down(ei->addr + ei->size, PAGE_SIZE) >> PAGE_SHIFT;
 
-                /* Skip map entries smaller than a page */
-                if (ei_startpfn >= ei_endpfn)
-                        continue;
+        /* Skip map entries smaller than a page */
+        if (*ei_startpfn >= *ei_endpfn)
+                return 0;
 
-                /* Check if end_pfn_map should be updated */
-                if (ei->type != E820_RAM && ei_endpfn > end_pfn_map)
-                        end_pfn_map = ei_endpfn;
+        /* Check if end_pfn_map should be updated */
+        if (ei->type != E820_RAM && *ei_endpfn > end_pfn_map)
+                end_pfn_map = *ei_endpfn;
 
-                /* Skip if map is outside the node */
-                if (ei->type != E820_RAM ||
-                                ei_endpfn <= start_pfn ||
-                                ei_startpfn >= end_pfn)
-                        continue;
+        /* Skip if map is outside the node */
+        if (ei->type != E820_RAM || *ei_endpfn <= start_pfn ||
+                                    *ei_startpfn >= end_pfn)
+                return 0;
 
-                /* Check for overlaps */
-                if (ei_startpfn < start_pfn)
-                        ei_startpfn = start_pfn;
-                if (ei_endpfn > end_pfn)
-                        ei_endpfn = end_pfn;
+        /* Check for overlaps */
+        if (*ei_startpfn < start_pfn)
+                *ei_startpfn = start_pfn;
+        if (*ei_endpfn > end_pfn)
+                *ei_endpfn = end_pfn;
 
-                /* Obey end_user_pfn to save on memmap */
-                if (ei_startpfn >= end_user_pfn)
-                        continue;
-                if (ei_endpfn > end_user_pfn)
-                        ei_endpfn = end_user_pfn;
+        /* Obey end_user_pfn to save on memmap */
+        if (*ei_startpfn >= end_user_pfn)
+                return 0;
+        if (*ei_endpfn > end_user_pfn)
+                *ei_endpfn = end_user_pfn;
 
-                add_active_range(nid, ei_startpfn, ei_endpfn);
-        }
+        return 1;
+}
+
+/* Walk the e820 map and register active regions within a node */
+void __init
+e820_register_active_regions(int nid, unsigned long start_pfn,
+                                                        unsigned long end_pfn)
+{
+        unsigned long ei_startpfn;
+        unsigned long ei_endpfn;
+        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))
+                        add_active_range(nid, ei_startpfn, ei_endpfn);
 }
 
 /*