From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: mm/sparsemem: introduce a SECTION_IS_EARLY flag In preparation for sub-section hotplug, track whether a given section was created during early memory initialization, or later via memory hotplug. This distinction is needed to maintain the coarse expectation that pfn_valid() returns true for any pfn within a given section even if that section has pages that are reserved from the page allocator. For example one of the of goals of subsection hotplug is to support cases where the system physical memory layout collides System RAM and PMEM within a section. Several pfn_valid() users expect to just check if a section is valid, but they are not careful to check if the given pfn is within a "System RAM" boundary and instead expect pgdat information to further validate the pfn. Rather than unwind those paths to make their pfn_valid() queries more precise a follow on patch uses the SECTION_IS_EARLY flag to maintain the traditional expectation that pfn_valid() returns true for all early sections. Link: https://lore.kernel.org/lkml/1560366952-10660-1-git-send-email-cai@xxxxxx/ Link: http://lkml.kernel.org/r/156092350358.979959.5817209875548072819.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reported-by: Qian Cai <cai@xxxxxx> Tested-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> [ppc64] Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Jane Chu <jane.chu@xxxxxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Toshi Kani <toshi.kani@xxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mmzone.h | 8 +++++++- mm/sparse.c | 20 +++++++++----------- 2 files changed, 16 insertions(+), 12 deletions(-) --- a/include/linux/mmzone.h~mm-sparsemem-introduce-a-section_is_early-flag +++ a/include/linux/mmzone.h @@ -1260,7 +1260,8 @@ extern size_t mem_section_usage_size(voi #define SECTION_MARKED_PRESENT (1UL<<0) #define SECTION_HAS_MEM_MAP (1UL<<1) #define SECTION_IS_ONLINE (1UL<<2) -#define SECTION_MAP_LAST_BIT (1UL<<3) +#define SECTION_IS_EARLY (1UL<<3) +#define SECTION_MAP_LAST_BIT (1UL<<4) #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) #define SECTION_NID_SHIFT 3 @@ -1286,6 +1287,11 @@ static inline int valid_section(struct m return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP)); } +static inline int early_section(struct mem_section *section) +{ + return (section && (section->section_mem_map & SECTION_IS_EARLY)); +} + static inline int valid_section_nr(unsigned long nr) { return valid_section(__nr_to_section(nr)); --- a/mm/sparse.c~mm-sparsemem-introduce-a-section_is_early-flag +++ a/mm/sparse.c @@ -288,11 +288,11 @@ struct page *sparse_decode_mem_map(unsig static void __meminit sparse_init_one_section(struct mem_section *ms, unsigned long pnum, struct page *mem_map, - struct mem_section_usage *usage) + struct mem_section_usage *usage, unsigned long flags) { ms->section_mem_map &= ~SECTION_MAP_MASK; - ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) | - SECTION_HAS_MEM_MAP; + ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) + | SECTION_HAS_MEM_MAP | flags; ms->usage = usage; } @@ -497,7 +497,8 @@ static void __init sparse_init_nid(int n goto failed; } check_usemap_section_nr(nid, usage); - sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage); + sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage, + SECTION_IS_EARLY); usage = (void *) usage + mem_section_usage_size(); } sparse_buffer_fini(); @@ -732,7 +733,7 @@ int __meminit sparse_add_one_section(int set_section_nid(section_nr, nid); section_mark_present(ms); - sparse_init_one_section(ms, section_nr, memmap, usage); + sparse_init_one_section(ms, section_nr, memmap, usage, 0); out: if (ret < 0) { @@ -772,19 +773,16 @@ static inline void clear_hwpoisoned_page } #endif -static void free_section_usage(struct page *memmap, +static void free_section_usage(struct mem_section *ms, struct page *memmap, struct mem_section_usage *usage, struct vmem_altmap *altmap) { - struct page *usage_page; - if (!usage) return; - usage_page = virt_to_page(usage); /* * Check to see if allocation came from hot-plug-add */ - if (PageSlab(usage_page) || PageCompound(usage_page)) { + if (!early_section(ms)) { kfree(usage); if (memmap) __kfree_section_memmap(memmap, altmap); @@ -816,6 +814,6 @@ void sparse_remove_one_section(struct me clear_hwpoisoned_pages(memmap + map_offset, PAGES_PER_SECTION - map_offset); - free_section_usage(memmap, usage, altmap); + free_section_usage(ms, memmap, usage, altmap); } #endif /* CONFIG_MEMORY_HOTPLUG */ _
