x86/mm: Initialize high mem before free_all_bootmem()

Patch fixes a boot crash with pagealloc debugging enabled:

  Initializing HighMem for node 0 (000377fe:0003fff0)
  BUG: unable to handle kernel paging request at f6fefe80
  IP: [<c1621ab5>] find_range_array+0x5e/0x69
  [...]
  Call Trace:
   [<c1622064>] __get_free_all_memory_range+0x39/0xb4
   [<c1620dd0>] add_highpages_with_active_regions+0x18/0x9b
   [<c1621a2e>] set_highmem_pages_init+0x70/0x90
   [<c162122b>] mem_init+0x50/0x21b
   [<c16155bd>] start_kernel+0x1bf/0x31c
   [<c1615065>] i386_start_kernel+0x65/0x67

The crash happens when memblock wants to allocate big area for
temporary "struct range" array and reuses pages from top of low
memory, which were already passed to the buddy allocator.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: linux-mm@kvack.org
Cc: Mel Gorman <mgorman@suse.de>
Link: http://lkml.kernel.org/r/20111206080833.GB3105@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 3bebaed5021c1e1bc606cb8c30219c23acbc7990..a2fecb1611cc9af7c420e8ef624152c439252290 100644 (file)
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -744,6 +744,17 @@ void __init mem_init(void)
 #ifdef CONFIG_FLATMEM
        BUG_ON(!mem_map);
 #endif
+       /*
+        * With CONFIG_DEBUG_PAGEALLOC initialization of highmem pages has to
+        * be done before free_all_bootmem(). Memblock use free low memory for
+        * temporary data (see find_range_array()) and for this purpose can use
+        * pages that was already passed to the buddy allocator, hence marked as
+        * not accessible in the page tables when compiled with
+        * CONFIG_DEBUG_PAGEALLOC. Otherwise order of initialization is not
+        * important here.
+        */
+       set_highmem_pages_init();
+
        /* this will put all low memory onto the freelists */
        totalram_pages += free_all_bootmem();
 
@@ -755,8 +766,6 @@ void __init mem_init(void)
                if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
                        reservedpages++;
 
-       set_highmem_pages_init();
-
        codesize =  (unsigned long) &_etext - (unsigned long) &_text;
        datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
        initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;