target/linux/generic/pending-4.14/120-Fix-alloc_node_mem_map-with-ARCH_PFN_OFFSET-calcu.patch

   1 From: Tobias Wolf <dev-NTEO@vplace.de>
   2 Subject: mm: Fix alloc_node_mem_map with ARCH_PFN_OFFSET calculation
   3
   4 An rt288x (ralink) based router (Belkin F5D8235 v1) does not boot with any
   5 kernel beyond version 4.3 resulting in:
   6
   7 BUG: Bad page state in process swapper  pfn:086ac
   8
   9 bisect resulted in:
  10
  11 a1c34a3bf00af2cede839879502e12dc68491ad5 is the first bad commit
  12 commit a1c34a3bf00af2cede839879502e12dc68491ad5
  13 Author: Laura Abbott <laura@labbott.name>
  14 Date:   Thu Nov 5 18:48:46 2015 -0800
  15
  16     mm: Don't offset memmap for flatmem
  17
  18     Srinivas Kandagatla reported bad page messages when trying to remove the
  19     bottom 2MB on an ARM based IFC6410 board
  20
  21       BUG: Bad page state in process swapper  pfn:fffa8
  22       page:ef7fb500 count:0 mapcount:0 mapping:  (null) index:0x0
  23       flags: 0x96640253(locked|error|dirty|active|arch_1|reclaim|mlocked)
  24       page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
  25       bad because of flags:
  26       flags: 0x200041(locked|active|mlocked)
  27       Modules linked in:
  28       CPU: 0 PID: 0 Comm: swapper Not tainted 3.19.0-rc3-00007-g412f9ba-dirty
  29 #816
  30       Hardware name: Qualcomm (Flattened Device Tree)
  31         unwind_backtrace
  32         show_stack
  33         dump_stack
  34         bad_page
  35         free_pages_prepare
  36         free_hot_cold_page
  37         __free_pages
  38         free_highmem_page
  39         mem_init
  40         start_kernel
  41       Disabling lock debugging due to kernel taint
  42     [...]
  43 :040000 040000 2de013c372345fd471cd58f0553c9b38b0ef1cc4
  44 0a8156f848733dfa21e16c196dfb6c0a76290709 M      mm
  45
  46 This fix for ARM does not account ARCH_PFN_OFFSET for mem_map as later used by
  47 page_to_pfn anymore.
  48
  49 The following output was generated with two hacked in printk statements:
  50
  51 printk("before %p vs. %p or %p\n", mem_map, mem_map - offset, mem_map -
  52 (pgdat->node_start_pfn - ARCH_PFN_OFFSET));
  53                 if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
  54                         mem_map -= offset + (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
  55 printk("after %p\n", mem_map);
  56
  57 Output:
  58
  59 [    0.000000] before 8861b280 vs. 8861b280 or 8851b280
  60 [    0.000000] after 8851b280
  61
  62 As seen in the first line mem_map with subtraction of offset does not equal the
  63 mem_map after subtraction of ARCH_PFN_OFFSET.
  64
  65 After adding the offset of ARCH_PFN_OFFSET as well to mem_map as the
  66 previously calculated offset is zero for the named platform it is able to boot
  67 4.4 and 4.9-rc7 again.
  68
  69 Signed-off-by: Tobias Wolf <dev-NTEO@vplace.de>
  70 ---
  71
  72 --- a/mm/page_alloc.c
  73 +++ b/mm/page_alloc.c
  74 @@ -6153,7 +6153,7 @@ static void __ref alloc_node_mem_map(str
  75                 mem_map = NODE_DATA(0)->node_mem_map;
  76  #if defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) || defined(CONFIG_FLATMEM)
  77                 if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
  78 -                       mem_map -= offset;
  79 +                       mem_map -= offset + (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
  80  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  81         }
  82  #endif