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- From: Tobias Wolf <dev-NTEO@vplace.de>
- Subject: mm: Fix alloc_node_mem_map with ARCH_PFN_OFFSET calculation
- An rt288x (ralink) based router (Belkin F5D8235 v1) does not boot with any
- kernel beyond version 4.3 resulting in:
- BUG: Bad page state in process swapper pfn:086ac
- bisect resulted in:
- a1c34a3bf00af2cede839879502e12dc68491ad5 is the first bad commit
- commit a1c34a3bf00af2cede839879502e12dc68491ad5
- Author: Laura Abbott <laura@labbott.name>
- Date: Thu Nov 5 18:48:46 2015 -0800
- mm: Don't offset memmap for flatmem
- Srinivas Kandagatla reported bad page messages when trying to remove the
- bottom 2MB on an ARM based IFC6410 board
- BUG: Bad page state in process swapper pfn:fffa8
- page:ef7fb500 count:0 mapcount:0 mapping: (null) index:0x0
- flags: 0x96640253(locked|error|dirty|active|arch_1|reclaim|mlocked)
- page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
- bad because of flags:
- flags: 0x200041(locked|active|mlocked)
- Modules linked in:
- CPU: 0 PID: 0 Comm: swapper Not tainted 3.19.0-rc3-00007-g412f9ba-dirty
- #816
- Hardware name: Qualcomm (Flattened Device Tree)
- unwind_backtrace
- show_stack
- dump_stack
- bad_page
- free_pages_prepare
- free_hot_cold_page
- __free_pages
- free_highmem_page
- mem_init
- start_kernel
- Disabling lock debugging due to kernel taint
- [...]
- :040000 040000 2de013c372345fd471cd58f0553c9b38b0ef1cc4
- 0a8156f848733dfa21e16c196dfb6c0a76290709 M mm
- This fix for ARM does not account ARCH_PFN_OFFSET for mem_map as later used by
- page_to_pfn anymore.
- The following output was generated with two hacked in printk statements:
- printk("before %p vs. %p or %p\n", mem_map, mem_map - offset, mem_map -
- (pgdat->node_start_pfn - ARCH_PFN_OFFSET));
- if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
- mem_map -= offset + (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
- printk("after %p\n", mem_map);
- Output:
- [ 0.000000] before 8861b280 vs. 8861b280 or 8851b280
- [ 0.000000] after 8851b280
- As seen in the first line mem_map with subtraction of offset does not equal the
- mem_map after subtraction of ARCH_PFN_OFFSET.
- After adding the offset of ARCH_PFN_OFFSET as well to mem_map as the
- previously calculated offset is zero for the named platform it is able to boot
- 4.4 and 4.9-rc7 again.
- Signed-off-by: Tobias Wolf <dev-NTEO@vplace.de>
- ---
- --- a/mm/page_alloc.c
- +++ b/mm/page_alloc.c
- @@ -6146,7 +6146,7 @@ static void __ref alloc_node_mem_map(str
- mem_map = NODE_DATA(0)->node_mem_map;
- #if defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) || defined(CONFIG_FLATMEM)
- if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
- - mem_map -= offset;
- + mem_map -= offset + (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
- #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
- }
- #endif
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