ARM: Fix pfn_valid() for sparse memory

On OMAP platforms, some people want to declare to segment up the memory
between the kernel and a separate application such that there is a hole
in the middle of the memory as far as Linux is concerned.  However,
they want to be able to mmap() the hole.

This currently causes problems, because update_mmu_cache() thinks that
there are valid struct pages for the "hole".  Fix this by making
pfn_valid() slightly more expensive, by checking whether the PFN is
contained within the meminfo array.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Khasim Syed Mohammed <khasim@ti.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 3a7279c1ce5e..ea36186f32c3 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -15,6 +15,7 @@
 #include <linux/mman.h>
 #include <linux/nodemask.h>
 #include <linux/initrd.h>
+#include <linux/sort.h>
 #include <linux/highmem.h>
 
 #include <asm/mach-types.h>
@@ -349,12 +350,43 @@ static void __init bootmem_free_node(int node, struct meminfo *mi)
         free_area_init_node(node, zone_size, min, zhole_size);
 }
 
+#ifndef CONFIG_SPARSEMEM
+int pfn_valid(unsigned long pfn)
+{
+        struct meminfo *mi = &meminfo;
+        unsigned int left = 0, right = mi->nr_banks;
+
+        do {
+                unsigned int mid = (right + left) / 2;
+                struct membank *bank = &mi->bank[mid];
+
+                if (pfn < bank_pfn_start(bank))
+                        right = mid;
+                else if (pfn >= bank_pfn_end(bank))
+                        left = mid + 1;
+                else
+                        return 1;
+        } while (left < right);
+        return 0;
+}
+EXPORT_SYMBOL(pfn_valid);
+#endif
+
+static int __init meminfo_cmp(const void *_a, const void *_b)
+{
+        const struct membank *a = _a, *b = _b;
+        long cmp = bank_pfn_start(a) - bank_pfn_start(b);
+        return cmp < 0 ? -1 : cmp > 0 ? 1 : 0;
+}
+
 void __init bootmem_init(void)
 {
         struct meminfo *mi = &meminfo;
         unsigned long min, max_low, max_high;
         int node, initrd_node;
 
+        sort(&mi->bank, mi->nr_banks, sizeof(mi->bank[0]), meminfo_cmp, NULL);
+
         /*
          * Locate which node contains the ramdisk image, if any.
          */