Re: [PATCH v2 09/13] arch, mm: set max_mapnr when allocating memory map for FLATMEM

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 13/03/2025 à 14:49, Mike Rapoport a écrit :
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> max_mapnr is essentially the size of the memory map for systems that use
> FLATMEM. There is no reason to calculate it in each and every architecture
> when it's anyway calculated in alloc_node_mem_map().
> 
> Drop setting of max_mapnr from architecture code and set it once in
> alloc_node_mem_map().

As far as I can see alloc_node_mem_map() is called quite late.

I fear that it will regress commit daa9ada2093e ("powerpc/mm: Fix boot 
crash with FLATMEM")

Can you check ?

Christophe

> 
> While on it, move definition of mem_map and max_mapnr to mm/mm_init.c so
> there won't be two copies for MMU and !MMU variants.
> 
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>	# x86
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>   arch/alpha/mm/init.c               |  1 -
>   arch/arc/mm/init.c                 |  5 -----
>   arch/arm/mm/init.c                 |  2 --
>   arch/csky/mm/init.c                |  4 ----
>   arch/loongarch/mm/init.c           |  1 -
>   arch/microblaze/mm/init.c          |  4 ----
>   arch/mips/mm/init.c                |  8 --------
>   arch/nios2/kernel/setup.c          |  1 -
>   arch/nios2/mm/init.c               |  2 +-
>   arch/openrisc/mm/init.c            |  1 -
>   arch/parisc/mm/init.c              |  1 -
>   arch/powerpc/kernel/setup-common.c |  2 --
>   arch/riscv/mm/init.c               |  1 -
>   arch/s390/mm/init.c                |  1 -
>   arch/sh/mm/init.c                  |  1 -
>   arch/sparc/mm/init_32.c            |  1 -
>   arch/um/include/shared/mem_user.h  |  1 -
>   arch/um/kernel/physmem.c           | 12 ------------
>   arch/um/kernel/um_arch.c           |  1 -
>   arch/x86/mm/init_32.c              |  3 ---
>   arch/xtensa/mm/init.c              |  1 -
>   include/asm-generic/memory_model.h |  5 +++--
>   include/linux/mm.h                 | 11 -----------
>   mm/memory.c                        |  8 --------
>   mm/mm_init.c                       | 25 +++++++++++++++++--------
>   mm/nommu.c                         |  4 ----
>   26 files changed, 21 insertions(+), 86 deletions(-)
> 
> diff --git a/arch/alpha/mm/init.c b/arch/alpha/mm/init.c
> index 61c2198b1359..ec0eeae9c653 100644
> --- a/arch/alpha/mm/init.c
> +++ b/arch/alpha/mm/init.c
> @@ -276,7 +276,6 @@ srm_paging_stop (void)
>   void __init
>   mem_init(void)
>   {
> -	set_max_mapnr(max_low_pfn);
>   	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
>   	memblock_free_all();
>   }
> diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
> index 6a71b23f1383..7ef883d58dc1 100644
> --- a/arch/arc/mm/init.c
> +++ b/arch/arc/mm/init.c
> @@ -154,11 +154,6 @@ void __init setup_arch_memory(void)
>   
>   	arch_pfn_offset = min(min_low_pfn, min_high_pfn);
>   	kmap_init();
> -
> -#else /* CONFIG_HIGHMEM */
> -	/* pfn_valid() uses this when FLATMEM=y and HIGHMEM=n */
> -	max_mapnr = max_low_pfn - min_low_pfn;
> -
>   #endif /* CONFIG_HIGHMEM */
>   
>   	free_area_init(max_zone_pfn);
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 9aec1cb2386f..d4bcc745a044 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -275,8 +275,6 @@ void __init mem_init(void)
>   	swiotlb_init(max_pfn > arm_dma_pfn_limit, SWIOTLB_VERBOSE);
>   #endif
>   
> -	set_max_mapnr(pfn_to_page(max_pfn) - mem_map);
> -
>   #ifdef CONFIG_SA1111
>   	/* now that our DMA memory is actually so designated, we can free it */
>   	memblock_phys_free(PHYS_OFFSET, __pa(swapper_pg_dir) - PHYS_OFFSET);
> diff --git a/arch/csky/mm/init.c b/arch/csky/mm/init.c
> index ab51acbc19b2..ba6694d6170a 100644
> --- a/arch/csky/mm/init.c
> +++ b/arch/csky/mm/init.c
> @@ -46,10 +46,6 @@ void __init mem_init(void)
>   {
>   #ifdef CONFIG_HIGHMEM
>   	unsigned long tmp;
> -
> -	set_max_mapnr(highend_pfn - ARCH_PFN_OFFSET);
> -#else
> -	set_max_mapnr(max_low_pfn - ARCH_PFN_OFFSET);
>   #endif
>   	high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
>   
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index ca5aa5f46a9f..00449df50db1 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -78,7 +78,6 @@ void __init paging_init(void)
>   
>   void __init mem_init(void)
>   {
> -	max_mapnr = max_low_pfn;
>   	high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
>   
>   	memblock_free_all();
> diff --git a/arch/microblaze/mm/init.c b/arch/microblaze/mm/init.c
> index 4520c5741579..857cd2b44bcf 100644
> --- a/arch/microblaze/mm/init.c
> +++ b/arch/microblaze/mm/init.c
> @@ -104,17 +104,13 @@ void __init setup_memory(void)
>   	 *
>   	 * min_low_pfn - the first page (mm/bootmem.c - node_boot_start)
>   	 * max_low_pfn
> -	 * max_mapnr - the first unused page (mm/bootmem.c - node_low_pfn)
>   	 */
>   
>   	/* memory start is from the kernel end (aligned) to higher addr */
>   	min_low_pfn = memory_start >> PAGE_SHIFT; /* minimum for allocation */
> -	/* RAM is assumed contiguous */
> -	max_mapnr = memory_size >> PAGE_SHIFT;
>   	max_low_pfn = ((u64)memory_start + (u64)lowmem_size) >> PAGE_SHIFT;
>   	max_pfn = ((u64)memory_start + (u64)memory_size) >> PAGE_SHIFT;
>   
> -	pr_info("%s: max_mapnr: %#lx\n", __func__, max_mapnr);
>   	pr_info("%s: min_low_pfn: %#lx\n", __func__, min_low_pfn);
>   	pr_info("%s: max_low_pfn: %#lx\n", __func__, max_low_pfn);
>   	pr_info("%s: max_pfn: %#lx\n", __func__, max_pfn);
> diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
> index 820e35a59d4d..eb61a73520a0 100644
> --- a/arch/mips/mm/init.c
> +++ b/arch/mips/mm/init.c
> @@ -415,15 +415,7 @@ void __init paging_init(void)
>   		       " %ldk highmem ignored\n",
>   		       (highend_pfn - max_low_pfn) << (PAGE_SHIFT - 10));
>   		max_zone_pfns[ZONE_HIGHMEM] = max_low_pfn;
> -
> -		max_mapnr = max_low_pfn;
> -	} else if (highend_pfn) {
> -		max_mapnr = highend_pfn;
> -	} else {
> -		max_mapnr = max_low_pfn;
>   	}
> -#else
> -	max_mapnr = max_low_pfn;
>   #endif
>   	high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
>   
> diff --git a/arch/nios2/kernel/setup.c b/arch/nios2/kernel/setup.c
> index a4cffbfc1399..2a40150142c3 100644
> --- a/arch/nios2/kernel/setup.c
> +++ b/arch/nios2/kernel/setup.c
> @@ -158,7 +158,6 @@ void __init setup_arch(char **cmdline_p)
>   	*cmdline_p = boot_command_line;
>   
>   	find_limits(&min_low_pfn, &max_low_pfn, &max_pfn);
> -	max_mapnr = max_low_pfn;
>   
>   	memblock_reserve(__pa_symbol(_stext), _end - _stext);
>   #ifdef CONFIG_BLK_DEV_INITRD
> diff --git a/arch/nios2/mm/init.c b/arch/nios2/mm/init.c
> index aa692ad30044..3cafa87ead9e 100644
> --- a/arch/nios2/mm/init.c
> +++ b/arch/nios2/mm/init.c
> @@ -51,7 +51,7 @@ void __init paging_init(void)
>   	pagetable_init();
>   	pgd_current = swapper_pg_dir;
>   
> -	max_zone_pfn[ZONE_NORMAL] = max_mapnr;
> +	max_zone_pfn[ZONE_NORMAL] = max_low_pfn;
>   
>   	/* pass the memory from the bootmem allocator to the main allocator */
>   	free_area_init(max_zone_pfn);
> diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
> index d0cb1a0126f9..9093c336e158 100644
> --- a/arch/openrisc/mm/init.c
> +++ b/arch/openrisc/mm/init.c
> @@ -193,7 +193,6 @@ void __init mem_init(void)
>   {
>   	BUG_ON(!mem_map);
>   
> -	max_mapnr = max_low_pfn;
>   	high_memory = (void *)__va(max_low_pfn * PAGE_SIZE);
>   
>   	/* clear the zero-page */
> diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
> index 61c0a2477072..2cdfc0b1195c 100644
> --- a/arch/parisc/mm/init.c
> +++ b/arch/parisc/mm/init.c
> @@ -563,7 +563,6 @@ void __init mem_init(void)
>   #endif
>   
>   	high_memory = __va((max_pfn << PAGE_SHIFT));
> -	set_max_mapnr(max_low_pfn);
>   	memblock_free_all();
>   
>   #ifdef CONFIG_PA11
> diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
> index a08b0ede4e64..68d47c53876c 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -957,8 +957,6 @@ void __init setup_arch(char **cmdline_p)
>   
>   	/* Parse memory topology */
>   	mem_topology_setup();
> -	/* Set max_mapnr before paging_init() */
> -	set_max_mapnr(max_pfn);
>   	high_memory = (void *)__va(max_low_pfn * PAGE_SIZE);
>   
>   	/*
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 15b2eda4c364..157c9ca51541 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -298,7 +298,6 @@ static void __init setup_bootmem(void)
>   	high_memory = (void *)(__va(PFN_PHYS(max_low_pfn)));
>   
>   	dma32_phys_limit = min(4UL * SZ_1G, (unsigned long)PFN_PHYS(max_low_pfn));
> -	set_max_mapnr(max_low_pfn - ARCH_PFN_OFFSET);
>   
>   	reserve_initrd_mem();
>   
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index f8333feb6a7e..36fed6dffb38 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -159,7 +159,6 @@ void __init mem_init(void)
>   	cpumask_set_cpu(0, &init_mm.context.cpu_attach_mask);
>   	cpumask_set_cpu(0, mm_cpumask(&init_mm));
>   
> -	set_max_mapnr(max_low_pfn);
>           high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
>   
>   	pv_init();
> diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
> index 289a2fecebef..72aea5cd1b85 100644
> --- a/arch/sh/mm/init.c
> +++ b/arch/sh/mm/init.c
> @@ -290,7 +290,6 @@ void __init paging_init(void)
>   	 */
>   	max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
>   	min_low_pfn = __MEMORY_START >> PAGE_SHIFT;
> -	set_max_mapnr(max_low_pfn - min_low_pfn);
>   
>   	nodes_clear(node_online_map);
>   
> diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
> index d96a14ffceeb..6b58da14edc6 100644
> --- a/arch/sparc/mm/init_32.c
> +++ b/arch/sparc/mm/init_32.c
> @@ -275,7 +275,6 @@ void __init mem_init(void)
>   
>   	taint_real_pages();
>   
> -	max_mapnr = last_valid_pfn - pfn_base;
>   	high_memory = __va(max_low_pfn << PAGE_SHIFT);
>   	memblock_free_all();
>   
> diff --git a/arch/um/include/shared/mem_user.h b/arch/um/include/shared/mem_user.h
> index adfa08062f88..d4727efcf23d 100644
> --- a/arch/um/include/shared/mem_user.h
> +++ b/arch/um/include/shared/mem_user.h
> @@ -47,7 +47,6 @@ extern int iomem_size;
>   #define ROUND_4M(n) ((((unsigned long) (n)) + (1 << 22)) & ~((1 << 22) - 1))
>   
>   extern unsigned long find_iomem(char *driver, unsigned long *len_out);
> -extern void mem_total_pages(unsigned long physmem, unsigned long iomem);
>   extern void setup_physmem(unsigned long start, unsigned long usable,
>   			  unsigned long len);
>   extern void map_memory(unsigned long virt, unsigned long phys,
> diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
> index a74f17b033c4..af02b5f9911d 100644
> --- a/arch/um/kernel/physmem.c
> +++ b/arch/um/kernel/physmem.c
> @@ -22,18 +22,6 @@ static int physmem_fd = -1;
>   unsigned long high_physmem;
>   EXPORT_SYMBOL(high_physmem);
>   
> -void __init mem_total_pages(unsigned long physmem, unsigned long iomem)
> -{
> -	unsigned long phys_pages, iomem_pages, total_pages;
> -
> -	phys_pages  = physmem >> PAGE_SHIFT;
> -	iomem_pages = iomem   >> PAGE_SHIFT;
> -
> -	total_pages = phys_pages + iomem_pages;
> -
> -	max_mapnr = total_pages;
> -}
> -
>   void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
>   		int r, int w, int x)
>   {
> diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
> index 79ea97d4797e..6414cbf00572 100644
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -419,7 +419,6 @@ void __init setup_arch(char **cmdline_p)
>   
>   	stack_protections((unsigned long) init_task.stack);
>   	setup_physmem(uml_physmem, uml_reserved, physmem_size);
> -	mem_total_pages(physmem_size, iomem_size);
>   	uml_dtb_init();
>   	read_initrd();
>   
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index ac41b1e0940d..6d2f8cb9451e 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -650,9 +650,6 @@ void __init initmem_init(void)
>   
>   	memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
>   
> -#ifdef CONFIG_FLATMEM
> -	max_mapnr = IS_ENABLED(CONFIG_HIGHMEM) ? highend_pfn : max_low_pfn;
> -#endif
>   	__vmalloc_start_set = true;
>   
>   	printk(KERN_NOTICE "%ldMB LOWMEM available.\n",
> diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
> index 01577d33e602..9f1b0d5fccc7 100644
> --- a/arch/xtensa/mm/init.c
> +++ b/arch/xtensa/mm/init.c
> @@ -164,7 +164,6 @@ void __init mem_init(void)
>   {
>   	free_highpages();
>   
> -	max_mapnr = max_pfn - ARCH_PFN_OFFSET;
>   	high_memory = (void *)__va(max_low_pfn << PAGE_SHIFT);
>   
>   	memblock_free_all();
> diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
> index 6d1fb6162ac1..a3b5029aebbd 100644
> --- a/include/asm-generic/memory_model.h
> +++ b/include/asm-generic/memory_model.h
> @@ -19,11 +19,12 @@
>   #define __page_to_pfn(page)	((unsigned long)((page) - mem_map) + \
>   				 ARCH_PFN_OFFSET)
>   
> +/* avoid <linux/mm.h> include hell */
> +extern unsigned long max_mapnr;
> +
>   #ifndef pfn_valid
>   static inline int pfn_valid(unsigned long pfn)
>   {
> -	/* avoid <linux/mm.h> include hell */
> -	extern unsigned long max_mapnr;
>   	unsigned long pfn_offset = ARCH_PFN_OFFSET;
>   
>   	return pfn >= pfn_offset && (pfn - pfn_offset) < max_mapnr;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7b1068ddcbb7..fdf20503850e 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -45,17 +45,6 @@ extern int sysctl_page_lock_unfairness;
>   void mm_core_init(void);
>   void init_mm_internals(void);
>   
> -#ifndef CONFIG_NUMA		/* Don't use mapnrs, do it properly */
> -extern unsigned long max_mapnr;
> -
> -static inline void set_max_mapnr(unsigned long limit)
> -{
> -	max_mapnr = limit;
> -}
> -#else
> -static inline void set_max_mapnr(unsigned long limit) { }
> -#endif
> -
>   extern atomic_long_t _totalram_pages;
>   static inline unsigned long totalram_pages(void)
>   {
> diff --git a/mm/memory.c b/mm/memory.c
> index b4d3d4893267..126fdd3001e3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -95,14 +95,6 @@
>   #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
>   #endif
>   
> -#ifndef CONFIG_NUMA
> -unsigned long max_mapnr;
> -EXPORT_SYMBOL(max_mapnr);
> -
> -struct page *mem_map;
> -EXPORT_SYMBOL(mem_map);
> -#endif
> -
>   static vm_fault_t do_fault(struct vm_fault *vmf);
>   static vm_fault_t do_anonymous_page(struct vm_fault *vmf);
>   static bool vmf_pte_changed(struct vm_fault *vmf);
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 2630cc30147e..50a93714e1c6 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -36,6 +36,14 @@
>   
>   #include <asm/setup.h>
>   
> +#ifndef CONFIG_NUMA
> +unsigned long max_mapnr;
> +EXPORT_SYMBOL(max_mapnr);
> +
> +struct page *mem_map;
> +EXPORT_SYMBOL(mem_map);
> +#endif
> +
>   #ifdef CONFIG_DEBUG_MEMORY_INIT
>   int __meminitdata mminit_loglevel;
>   
> @@ -1617,7 +1625,7 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat)
>   	start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
>   	offset = pgdat->node_start_pfn - start;
>   	/*
> -		 * The zone's endpoints aren't required to be MAX_PAGE_ORDER
> +	 * The zone's endpoints aren't required to be MAX_PAGE_ORDER
>   	 * aligned but the node_mem_map endpoints must be in order
>   	 * for the buddy allocator to function correctly.
>   	 */
> @@ -1633,14 +1641,15 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat)
>   	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
>   		 __func__, pgdat->node_id, (unsigned long)pgdat,
>   		 (unsigned long)pgdat->node_mem_map);
> -#ifndef CONFIG_NUMA
> +
>   	/* the global mem_map is just set as node 0's */
> -	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;
> -	}
> -#endif
> +	WARN_ON(pgdat != NODE_DATA(0));
> +
> +	mem_map = pgdat->node_mem_map;
> +	if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
> +		mem_map -= offset;
> +
> +	max_mapnr = end - start;
>   }
>   #else
>   static inline void alloc_node_mem_map(struct pglist_data *pgdat) { }
> diff --git a/mm/nommu.c b/mm/nommu.c
> index baa79abdaf03..f0209dd26dfa 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -44,16 +44,12 @@
>   
>   void *high_memory;
>   EXPORT_SYMBOL(high_memory);
> -struct page *mem_map;
> -unsigned long max_mapnr;
> -EXPORT_SYMBOL(max_mapnr);
>   unsigned long highest_memmap_pfn;
>   int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
>   int heap_stack_gap = 0;
>   
>   atomic_long_t mmap_pages_allocated;
>   
> -EXPORT_SYMBOL(mem_map);
>   
>   /* list of mapped, potentially shareable regions */
>   static struct kmem_cache *vm_region_jar;