[PATCH] sparsemem base: teach discontig about sparse ranges

discontig.c has some assumptions that mem_map[]s inside of a node are
contiguous.  Teach it to make sure that each region that it's bringing online
is actually made up of valid ranges of ram.

Written-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/i386/mm/discontig.c b/arch/i386/mm/discontig.c
index dcc71f969b01..088ca4722183 100644
--- a/arch/i386/mm/discontig.c
+++ b/arch/i386/mm/discontig.c
@@ -216,6 +216,7 @@ static unsigned long calculate_numa_remap_pages(void)
 {
         int nid;
         unsigned long size, reserve_pages = 0;
+        unsigned long pfn;
 
         for_each_online_node(nid) {
                 /*
@@ -234,6 +235,19 @@ static unsigned long calculate_numa_remap_pages(void)
                 size = (size + LARGE_PAGE_BYTES - 1) / LARGE_PAGE_BYTES;
                 /* now the roundup is correct, convert to PAGE_SIZE pages */
                 size = size * PTRS_PER_PTE;
+
+                /*
+                 * Validate the region we are allocating only contains valid
+                 * pages.
+                 */
+                for (pfn = node_end_pfn[nid] - size;
+                     pfn < node_end_pfn[nid]; pfn++)
+                        if (!page_is_ram(pfn))
+                                break;
+
+                if (pfn != node_end_pfn[nid])
+                        size = 0;
+
                 printk("Reserving %ld pages of KVA for lmem_map of node %d\n",
                                 size, nid);
                 node_remap_size[nid] = size;