Revert "kernel: Fix alloc_node_mem_map with ARCH_PFN_OFFSET"

The boot hang issue on ralink rt288x has been fixed in Linux upstream
commit 7f028bff8a8e ("MIPS: ralink: rt288x: select MIPS_AUTO_PFN_OFFSET")
Link: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7f028bff8a8e55a783eeb12e50bb3f5f18804459



This reverts commit b3c5db79.

Signed-off-by: Shiji Yang <yangshiji66@qq.com>
Link: https://github.com/openwrt/openwrt/pull/17498


Signed-off-by: Robert Marko <robimarko@gmail.com>

target/linux/generic/pending-6.6/120-Fix-alloc_node_mem_map-with-ARCH_PFN_OFFSET-calcu.patch

-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/mm_init.c
-+++ b/mm/mm_init.c
-@@ -1673,7 +1673,7 @@ static void __init alloc_node_mem_map(st
- 	if (pgdat == NODE_DATA(0)) {
- 		mem_map = NODE_DATA(0)->node_mem_map;
- 		if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
--			mem_map -= offset;
-+			mem_map -= offset + (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
- 	}
- #endif
- }