Kukjin reported oops happen while he change min_free_kbytes http://www.spinics.net/lists/arm-kernel/msg92894.html It happen by memory map on sparsemem. The system has a memory map following as. section 0 section 1 section 2 0x20000000-0x25000000, 0x40000000-0x50000000, 0x50000000-0x58000000 SECTION_SIZE_BITS 28(256M) It means section 0 is an incompletely filled section. Nontheless, current pfn_valid of sparsemem checks pfn loosely. It checks only mem_section's validation but ARM can free mem_map on hole to save memory space. So in above case, pfn on 0x25000000 can pass pfn_valid's validation check. It's not what we want. We can match section size to smallest valid size.(ex, above case, 16M) But Russell doesn't like it due to mem_section's memory overhead with different configuration(ex, 512K section). I tried to add valid pfn range in mem_section but everyone doesn't like it due to size overhead. This patch is suggested by KAMEZAWA-san. I just fixed compile error and change some naming. This patch registers address of mem_section to memmap itself's page struct's pg->private field. This means the page is used for memmap of the section. Otherwise, the page is used for other purpose and memmap has a hole. This patch is based on mmotm-2010-07-01-12-19. Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Reported-by: Kukjin Kim <kgene.kim@xxxxxxxxxxx> --- arch/arm/mm/init.c | 9 ++++++++- include/linux/mmzone.h | 21 ++++++++++++++++++++- mm/Kconfig | 5 +++++ mm/sparse.c | 41 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 74 insertions(+), 2 deletions(-) diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index cfe4c5e..4586f40 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c @@ -234,6 +234,11 @@ static void __init arm_bootmem_free(struct meminfo *mi) arch_adjust_zones(zone_size, zhole_size); free_area_init_node(0, zone_size, min, zhole_size); + + for_each_bank(i, mi) { + mark_memmap_hole(bank_pfn_start(&mi->bank[i]), + bank_pfn_end(&mi->bank[i]), true); + } } #ifndef CONFIG_SPARSEMEM @@ -386,8 +391,10 @@ free_memmap(unsigned long start_pfn, unsigned long end_pfn) * If there are free pages between these, * free the section of the memmap array. */ - if (pg < pgend) + if (pg < pgend) { + mark_memmap_hole(pg >> PAGE_SHIFT, pgend >> PAGE_SHIFT, false); free_bootmem(pg, pgend - pg); + } } /* diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 9ed9c45..2ed9728 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -15,6 +15,7 @@ #include <linux/seqlock.h> #include <linux/nodemask.h> #include <linux/pageblock-flags.h> +#include <linux/mm_types.h> #include <generated/bounds.h> #include <asm/atomic.h> #include <asm/page.h> @@ -1047,11 +1048,29 @@ static inline struct mem_section *__pfn_to_section(unsigned long pfn) return __nr_to_section(pfn_to_section_nr(pfn)); } +void mark_memmap_hole(unsigned long start, unsigned long end, bool valid); + +#ifdef CONFIG_SPARSEMEM_HAS_HOLE +static inline int page_valid(struct mem_section *ms, unsigned long pfn) +{ + struct page *page = pfn_to_page(pfn); + struct page *__pg = virt_to_page(page); + return __pg->private == (unsigned long)ms; +} +#else +static inline int page_valid(struct mem_section *ms, unsigned long pfn) +{ + return 1; +} +#endif + static inline int pfn_valid(unsigned long pfn) { + struct mem_section *ms; if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) return 0; - return valid_section(__nr_to_section(pfn_to_section_nr(pfn))); + ms = __nr_to_section(pfn_to_section_nr(pfn)); + return valid_section(ms) && page_valid(ms, pfn); } static inline int pfn_present(unsigned long pfn) diff --git a/mm/Kconfig b/mm/Kconfig index 527136b..959ac1d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -128,6 +128,11 @@ config SPARSEMEM_VMEMMAP pfn_to_page and page_to_pfn operations. This is the most efficient option when sufficient kernel resources are available. +config SPARSEMEM_HAS_HOLE + bool "allow holes in sparsemem's memmap" + depends on ARM && SPARSEMEM && !SPARSEMEM_VMEMMAP + default n + # eventually, we can have this option just 'select SPARSEMEM' config MEMORY_HOTPLUG bool "Allow for memory hot-add" diff --git a/mm/sparse.c b/mm/sparse.c index 95ac219..76d5012 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -615,6 +615,47 @@ void __init sparse_init(void) free_bootmem(__pa(usemap_map), size); } +#ifdef CONFIG_SPARSEMEM_HAS_HOLE +/* + * Fill memmap's pg->private with a pointer to mem_section. + * pfn_valid() will check this later. (see include/linux/mmzone.h) + * Evenry arch should call + * mark_memmap_hole(start, end, true) # for all allocated mem_map + * and, after that, + * mark_memmap_hole(start, end, false) # for all holes in mem_map. + * please see usage in ARM. + */ +void mark_memmap_hole(unsigned long start, unsigned long end, bool valid) +{ + struct mem_section *ms; + unsigned long pos, next; + struct page *pg; + void *memmap, *mapend; + + for (pos = start; pos < end; pos = next) { + next = (pos + PAGES_PER_SECTION) & PAGE_SECTION_MASK; + ms = __pfn_to_section(pos); + if (!valid_section(ms)) + continue; + + for (memmap = (void*)pfn_to_page(pos), + /* The last page in section */ + mapend = pfn_to_page(next-1); + memmap < mapend; memmap += PAGE_SIZE) { + pg = virt_to_page(memmap); + if (valid) + pg->private = (unsigned long)ms; + else + pg->private = 0; + } + } +} +#else +void mark_memmap_hole(unsigned long start, unsigned long end, bool valid) +{ +} +#endif + #ifdef CONFIG_MEMORY_HOTPLUG #ifdef CONFIG_SPARSEMEM_VMEMMAP static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid, -- 1.7.0.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . 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