Commit 1d5e4640 authored Apr 27, 2021 by Vladimir Isaev Committed by Vineet Gupta May 10, 2021

ARC: mm: Use max_high_pfn as a HIGHMEM zone border



Commit 4af22ded ("arc: fix memory initialization for systems
with two memory banks") fixed highmem, but for the PAE case it causes
bug messages:

| BUG: Bad page state in process swapper  pfn:80000
| page:(ptrval) refcount:0 mapcount:1 mapping:00000000 index:0x0 pfn:0x80000 flags: 0x0()
| raw: 00000000 00000100 00000122 00000000 00000000 00000000 00000000 00000000
| raw: 00000000
| page dumped because: nonzero mapcount
| Modules linked in:
| CPU: 0 PID: 0 Comm: swapper Not tainted 5.12.0-rc5-00003-g1e43c377a79f #1

This is because the fix expects highmem to be always less than
lowmem and uses min_low_pfn as an upper zone border for highmem.

max_high_pfn should be ok for both highmem and highmem+PAE cases.

Fixes: 4af22ded ("arc: fix memory initialization for systems with two memory banks")
Signed-off-by: Vladimir Isaev <isaev@synopsys.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: stable@vger.kernel.org  #5.8 onwards
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

parent c5f756d8

arch/arc/mm/init.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -157,7 +157,16 @@ void __init setup_arch_memory(void)
		min_high_pfn = PFN_DOWN(high_mem_start);
		max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz);

		max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn;
		/*
		* max_high_pfn should be ok here for both HIGHMEM and HIGHMEM+PAE.
		* For HIGHMEM without PAE max_high_pfn should be less than
		* min_low_pfn to guarantee that these two regions don't overlap.
		* For PAE case highmem is greater than lowmem, so it is natural
		* to use max_high_pfn.
		*
		* In both cases, holes should be handled by pfn_valid().
		*/
		max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn;

		high_memory = (void *)(min_high_pfn << PAGE_SHIFT);