arm, arm64: move free_unused_memmap() to generic mm

ARM and ARM64 free unused parts of the memory map just before the
initialization of the page allocator. To allow holes in the memory map both
architectures overload pfn_valid() and define HAVE_ARCH_PFN_VALID.

Allowing holes in the memory map for FLATMEM may be useful for small
machines, such as ARC and m68k and will enable those architectures to cease
using DISCONTIGMEM and still support more than one memory bank.

Move the functions that free unused memory map to generic mm and enable
them in case HAVE_ARCH_PFN_VALID=y.

Link: https://lkml.kernel.org/r/20201101170454.9567-10-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Meelis Roos <mroos@linux.ee>
Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 1 insertions, 81 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 353c3979a2d5..03602e8fe16d 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -69,6 +69,7 @@ config ARM
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
+	select HAVE_ARCH_PFN_VALID
 	select HAVE_ARCH_SECCOMP
 	select HAVE_ARCH_SECCOMP_FILTER if AEABI && !OABI_COMPAT
 	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
@@ -1489,9 +1490,6 @@ config ARCH_SPARSEMEM_ENABLE
 	bool
 	select SPARSEMEM_STATIC if SPARSEMEM
 
-config HAVE_ARCH_PFN_VALID
-	def_bool y
-
 config HIGHMEM
 	bool "High Memory Support"
 	depends on MMU
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index c23dbf8bebee..db623d7c30de 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -267,83 +267,6 @@ static inline void poison_init_mem(void *s, size_t count)
 		*p++ = 0xe7fddef0;
 }
 
-static inline void __init
-free_memmap(unsigned long start_pfn, unsigned long end_pfn)
-{
-	struct page *start_pg, *end_pg;
-	phys_addr_t pg, pgend;
-
-	/*
-	 * 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 - 1) + 1;
-
-	/*
-	 * Convert to physical addresses, and
-	 * round start upwards and end downwards.
-	 */
-	pg = PAGE_ALIGN(__pa(start_pg));
-	pgend = __pa(end_pg) & PAGE_MASK;
-
-	/*
-	 * If there are free pages between these,
-	 * free the section of the memmap array.
-	 */
-	if (pg < pgend)
-		memblock_free_early(pg, pgend - pg);
-}
-
-/*
- * The mem_map array can get very big.  Free the unused area of the memory map.
- */
-static void __init free_unused_memmap(void)
-{
-	unsigned long start, end, prev_end = 0;
-	int i;
-
-	/*
-	 * This relies on each bank being in address order.
-	 * The banks are sorted previously in bootmem_init().
-	 */
-	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, NULL) {
-#ifdef CONFIG_SPARSEMEM
-		/*
-		 * Take care not to free memmap entries that don't exist
-		 * due to SPARSEMEM sections which aren't present.
-		 */
-		start = min(start,
-				 ALIGN(prev_end, PAGES_PER_SECTION));
-#else
-		/*
-		 * Align down here since the VM subsystem insists that the
-		 * memmap entries are valid from the bank start aligned to
-		 * MAX_ORDER_NR_PAGES.
-		 */
-		start = round_down(start, MAX_ORDER_NR_PAGES);
-#endif
-		/*
-		 * If we had a previous bank, and there is a space
-		 * between the current bank and the previous, free it.
-		 */
-		if (prev_end && prev_end < start)
-			free_memmap(prev_end, start);
-
-		/*
-		 * Align up here since the VM subsystem insists that the
-		 * memmap entries are valid from the bank end aligned to
-		 * MAX_ORDER_NR_PAGES.
-		 */
-		prev_end = ALIGN(end, MAX_ORDER_NR_PAGES);
-	}
-
-#ifdef CONFIG_SPARSEMEM
-	if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
-		free_memmap(prev_end,
-			    ALIGN(prev_end, PAGES_PER_SECTION));
-#endif
-}
-
 static void __init free_highpages(void)
 {
 #ifdef CONFIG_HIGHMEM
@@ -385,7 +308,6 @@ void __init mem_init(void)
 	set_max_mapnr(pfn_to_page(max_pfn) - mem_map);
 
 	/* this will put all unused low memory onto the freelists */
-	free_unused_memmap();
 	memblock_free_all();
 
 #ifdef CONFIG_SA1111