ARM: 6890/1: memmap: only free allocated memmap entries when using SPARSEMEM (9af386c8) · Commits · 戴 / test

The SPARSEMEM code allocates memmap entries only for sections which are present (i.e. those which contain some valid memory). The membank checks in free_unused_memmap do not take this into account and can incorrectly attempt to free memory which is not allocated, resulting in a BUG() in the bootmem code. However, if memory is configured as follows: |<----section---->|<----hole---->|<----section---->| +--------+--------+--------------+--------+--------+ | bank 0 | unused | | bank 1 | unused | +--------+--------+--------------+--------+--------+ where a bank only occupies part of a section, the memmap allocated for the remainder of the section *can* be freed. This patch modifies the checks in free_unused_memmap so that only valid memmap entries are considered for removal. Acked-by:

Catalin Marinas <catalin.marinas@arm.com> Signed-off-by:

Will Deacon <will.deacon@arm.com> Signed-off-by:

Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/init.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -392,7 +392,7 @@ free_memmap(unsigned long start_pfn, unsigned long end_pfn)
		* Convert start_pfn/end_pfn to a struct page pointer.
		*/
		start_pg = pfn_to_page(start_pfn - 1) + 1;
		end_pg = pfn_to_page(end_pfn);
		end_pg = pfn_to_page(end_pfn - 1) + 1;

		/*
		* Convert to physical addresses, and
		@@ -426,6 +426,14 @@ static void __init free_unused_memmap(struct meminfo *mi)

		bank_start = bank_pfn_start(bank);

		#ifdef CONFIG_SPARSEMEM
		/*
		* Take care not to free memmap entries that don't exist
		* due to SPARSEMEM sections which aren't present.
		*/
		bank_start = min(bank_start,
		ALIGN(prev_bank_end, PAGES_PER_SECTION));
		#endif
		/*
		* If we had a previous bank, and there is a space
		* between the current bank and the previous, free it.
		@@ -440,6 +448,12 @@ static void __init free_unused_memmap(struct meminfo *mi)
		*/
		prev_bank_end = ALIGN(bank_pfn_end(bank), MAX_ORDER_NR_PAGES);
		}

		#ifdef CONFIG_SPARSEMEM
		if (!IS_ALIGNED(prev_bank_end, PAGES_PER_SECTION))
		free_memmap(prev_bank_end,
		ALIGN(prev_bank_end, PAGES_PER_SECTION));
		#endif
		}

		static void __init free_highpages(void)

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