// SPDX-License-Identifier: GPL-2.0

  /*
   * sparse memory mappings.
   */

  #include <linux/mm.h>

  #include <linux/slab.h>

  #include <linux/mmzone.h>

  #include <linux/memblock.h>

  #include <linux/compiler.h>

  #include <linux/highmem.h>

  #include <linux/export.h>

  #include <linux/spinlock.h>

  #include <linux/vmalloc.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  #include "internal.h"

  #include <asm/dma.h>
  
  /*
   * Permanent SPARSEMEM data:
   *
   * 1) mem_section	- memory sections, mem_map's for valid memory
   */

  #ifdef CONFIG_SPARSEMEM_EXTREME

  struct mem_section **mem_section;

  #else
  struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]

  	____cacheline_internodealigned_in_smp;

  #endif
  EXPORT_SYMBOL(mem_section);

  #ifdef NODE_NOT_IN_PAGE_FLAGS
  /*
   * If we did not store the node number in the page then we have to
   * do a lookup in the section_to_node_table in order to find which
   * node the page belongs to.
   */
  #if MAX_NUMNODES <= 256
  static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
  #else
  static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
  #endif

  int page_to_nid(const struct page *page)

  {
  	return section_to_node_table[page_to_section(page)];
  }
  EXPORT_SYMBOL(page_to_nid);

  
  static void set_section_nid(unsigned long section_nr, int nid)
  {
  	section_to_node_table[section_nr] = nid;
  }
  #else /* !NODE_NOT_IN_PAGE_FLAGS */
  static inline void set_section_nid(unsigned long section_nr, int nid)
  {
  }

  #endif

  #ifdef CONFIG_SPARSEMEM_EXTREME

  static noinline struct mem_section __ref *sparse_index_alloc(int nid)

  {
  	struct mem_section *section = NULL;
  	unsigned long array_size = SECTIONS_PER_ROOT *
  				   sizeof(struct mem_section);

  	if (slab_is_available()) {

  		section = kzalloc_node(array_size, GFP_KERNEL, nid);

  	} else {

  		section = memblock_alloc_node(array_size, SMP_CACHE_BYTES,
  					      nid);

  		if (!section)
  			panic("%s: Failed to allocate %lu bytes nid=%d
  ",
  			      __func__, array_size, nid);
  	}

  
  	return section;

  }

  static int __meminit sparse_index_init(unsigned long section_nr, int nid)

  {

  	unsigned long root = SECTION_NR_TO_ROOT(section_nr);
  	struct mem_section *section;

  	/*
  	 * An existing section is possible in the sub-section hotplug
  	 * case. First hot-add instantiates, follow-on hot-add reuses
  	 * the existing section.
  	 *
  	 * The mem_hotplug_lock resolves the apparent race below.
  	 */

  	if (mem_section[root])

  		return 0;

  	section = sparse_index_alloc(nid);

  	if (!section)
  		return -ENOMEM;

  
  	mem_section[root] = section;

  	return 0;

  }
  #else /* !SPARSEMEM_EXTREME */
  static inline int sparse_index_init(unsigned long section_nr, int nid)
  {
  	return 0;

  }

  #endif

  #ifdef CONFIG_SPARSEMEM_EXTREME

  unsigned long __section_nr(struct mem_section *ms)

  {
  	unsigned long root_nr;

  	struct mem_section *root = NULL;

  	for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
  		root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);

  		if (!root)
  			continue;
  
  		if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
  		     break;
  	}

  	VM_BUG_ON(!root);

  	return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
  }

  #else

  unsigned long __section_nr(struct mem_section *ms)

  {

  	return (unsigned long)(ms - mem_section[0]);

  }
  #endif

  /*
   * During early boot, before section_mem_map is used for an actual
   * mem_map, we use section_mem_map to store the section's NUMA
   * node.  This keeps us from having to use another data structure.  The
   * node information is cleared just before we store the real mem_map.
   */
  static inline unsigned long sparse_encode_early_nid(int nid)
  {
  	return (nid << SECTION_NID_SHIFT);
  }
  
  static inline int sparse_early_nid(struct mem_section *section)
  {
  	return (section->section_mem_map >> SECTION_NID_SHIFT);
  }

  /* Validate the physical addressing limitations of the model */
  void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
  						unsigned long *end_pfn)

  {

  	unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);

  	/*
  	 * Sanity checks - do not allow an architecture to pass
  	 * in larger pfns than the maximum scope of sparsemem:
  	 */

  	if (*start_pfn > max_sparsemem_pfn) {
  		mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
  			"Start of range %lu -> %lu exceeds SPARSEMEM max %lu
  ",
  			*start_pfn, *end_pfn, max_sparsemem_pfn);
  		WARN_ON_ONCE(1);
  		*start_pfn = max_sparsemem_pfn;
  		*end_pfn = max_sparsemem_pfn;

  	} else if (*end_pfn > max_sparsemem_pfn) {

  		mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
  			"End of range %lu -> %lu exceeds SPARSEMEM max %lu
  ",
  			*start_pfn, *end_pfn, max_sparsemem_pfn);
  		WARN_ON_ONCE(1);
  		*end_pfn = max_sparsemem_pfn;
  	}
  }

  /*
   * There are a number of times that we loop over NR_MEM_SECTIONS,
   * looking for section_present() on each.  But, when we have very
   * large physical address spaces, NR_MEM_SECTIONS can also be
   * very large which makes the loops quite long.
   *
   * Keeping track of this gives us an easy way to break out of
   * those loops early.
   */

  unsigned long __highest_present_section_nr;

  static void section_mark_present(struct mem_section *ms)
  {

  	unsigned long section_nr = __section_nr(ms);

  
  	if (section_nr > __highest_present_section_nr)
  		__highest_present_section_nr = section_nr;
  
  	ms->section_mem_map |= SECTION_MARKED_PRESENT;
  }

  #define for_each_present_section_nr(start, section_nr)		\
  	for (section_nr = next_present_section_nr(start-1);	\

  	     ((section_nr != -1) &&				\

  	      (section_nr <= __highest_present_section_nr));	\
  	     section_nr = next_present_section_nr(section_nr))

  static inline unsigned long first_present_section_nr(void)
  {
  	return next_present_section_nr(-1);
  }

  #ifdef CONFIG_SPARSEMEM_VMEMMAP

  static void subsection_mask_set(unsigned long *map, unsigned long pfn,

  		unsigned long nr_pages)
  {
  	int idx = subsection_map_index(pfn);
  	int end = subsection_map_index(pfn + nr_pages - 1);
  
  	bitmap_set(map, idx, end - idx + 1);
  }
  
  void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
  {
  	int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);

  	unsigned long nr, start_sec = pfn_to_section_nr(pfn);

  
  	if (!nr_pages)
  		return;

  	for (nr = start_sec; nr <= end_sec; nr++) {

  		struct mem_section *ms;
  		unsigned long pfns;
  
  		pfns = min(nr_pages, PAGES_PER_SECTION
  				- (pfn & ~PAGE_SECTION_MASK));

  		ms = __nr_to_section(nr);

  		subsection_mask_set(ms->usage->subsection_map, pfn, pfns);

  		pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)
  ", __func__, nr,

  				pfns, subsection_map_index(pfn),
  				subsection_map_index(pfn + pfns - 1));
  
  		pfn += pfns;
  		nr_pages -= pfns;
  	}
  }

  #else
  void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
  {
  }
  #endif

  /* Record a memory area against a node. */

  static void __init memory_present(int nid, unsigned long start, unsigned long end)

  {
  	unsigned long pfn;

  #ifdef CONFIG_SPARSEMEM_EXTREME
  	if (unlikely(!mem_section)) {
  		unsigned long size, align;

  		size = sizeof(struct mem_section*) * NR_SECTION_ROOTS;

  		align = 1 << (INTERNODE_CACHE_SHIFT);

  		mem_section = memblock_alloc(size, align);

  		if (!mem_section)
  			panic("%s: Failed to allocate %lu bytes align=0x%lx
  ",
  			      __func__, size, align);

  	}
  #endif

  	start &= PAGE_SECTION_MASK;

  	mminit_validate_memmodel_limits(&start, &end);

  	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
  		unsigned long section = pfn_to_section_nr(pfn);

  		struct mem_section *ms;
  
  		sparse_index_init(section, nid);

  		set_section_nid(section, nid);

  
  		ms = __nr_to_section(section);

  		if (!ms->section_mem_map) {

  			ms->section_mem_map = sparse_encode_early_nid(nid) |
  							SECTION_IS_ONLINE;

  			section_mark_present(ms);
  		}

  	}
  }
  
  /*

   * Mark all memblocks as present using memory_present().
   * This is a convenience function that is useful to mark all of the systems
   * memory as present during initialization.

   */

  static void __init memblocks_present(void)

  {

  	unsigned long start, end;
  	int i, nid;

  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
  		memory_present(nid, start, end);

  }
  
  /*

   * Subtle, we encode the real pfn into the mem_map such that
   * the identity pfn - section_mem_map will return the actual
   * physical page frame number.
   */
  static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
  {

  	unsigned long coded_mem_map =
  		(unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
  	BUILD_BUG_ON(SECTION_MAP_LAST_BIT > (1UL<<PFN_SECTION_SHIFT));
  	BUG_ON(coded_mem_map & ~SECTION_MAP_MASK);
  	return coded_mem_map;

  }

  #ifdef CONFIG_MEMORY_HOTPLUG

  /*

   * Decode mem_map from the coded memmap

   */

  struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
  {

  	/* mask off the extra low bits of information */
  	coded_mem_map &= SECTION_MAP_MASK;

  	return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
  }

  #endif /* CONFIG_MEMORY_HOTPLUG */

  static void __meminit sparse_init_one_section(struct mem_section *ms,

  		unsigned long pnum, struct page *mem_map,

  		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 | flags;

  	ms->usage = usage;

  }

  static unsigned long usemap_size(void)

  {

  	return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);

  }

  size_t mem_section_usage_size(void)

  {

  	return sizeof(struct mem_section_usage) + usemap_size();

  }

  #ifdef CONFIG_MEMORY_HOTREMOVE

  static struct mem_section_usage * __init

  sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,

  					 unsigned long size)

  {

  	struct mem_section_usage *usage;

  	unsigned long goal, limit;

  	int nid;

  	/*
  	 * A page may contain usemaps for other sections preventing the
  	 * page being freed and making a section unremovable while

  	 * other sections referencing the usemap remain active. Similarly,

  	 * a pgdat can prevent a section being removed. If section A
  	 * contains a pgdat and section B contains the usemap, both
  	 * sections become inter-dependent. This allocates usemaps
  	 * from the same section as the pgdat where possible to avoid
  	 * this problem.
  	 */

  	goal = __pa(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);

  	limit = goal + (1UL << PA_SECTION_SHIFT);
  	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
  again:

  	usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid);
  	if (!usage && limit) {

  		limit = 0;
  		goto again;
  	}

  	return usage;

  }

  static void __init check_usemap_section_nr(int nid,
  		struct mem_section_usage *usage)

  {
  	unsigned long usemap_snr, pgdat_snr;

  	static unsigned long old_usemap_snr;
  	static unsigned long old_pgdat_snr;

  	struct pglist_data *pgdat = NODE_DATA(nid);
  	int usemap_nid;

  	/* First call */
  	if (!old_usemap_snr) {
  		old_usemap_snr = NR_MEM_SECTIONS;
  		old_pgdat_snr = NR_MEM_SECTIONS;
  	}

  	usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT);

  	pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
  	if (usemap_snr == pgdat_snr)
  		return;
  
  	if (old_usemap_snr == usemap_snr && old_pgdat_snr == pgdat_snr)
  		/* skip redundant message */
  		return;
  
  	old_usemap_snr = usemap_snr;
  	old_pgdat_snr = pgdat_snr;
  
  	usemap_nid = sparse_early_nid(__nr_to_section(usemap_snr));
  	if (usemap_nid != nid) {

  		pr_info("node %d must be removed before remove section %ld
  ",
  			nid, usemap_snr);

  		return;
  	}
  	/*
  	 * There is a circular dependency.
  	 * Some platforms allow un-removable section because they will just
  	 * gather other removable sections for dynamic partitioning.
  	 * Just notify un-removable section's number here.
  	 */

  	pr_info("Section %ld and %ld (node %d) have a circular dependency on usemap and pgdat allocations
  ",
  		usemap_snr, pgdat_snr, nid);

  }
  #else

  static struct mem_section_usage * __init

  sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,

  					 unsigned long size)

  {

  	return memblock_alloc_node(size, SMP_CACHE_BYTES, pgdat->node_id);

  }

  static void __init check_usemap_section_nr(int nid,
  		struct mem_section_usage *usage)

  {
  }
  #endif /* CONFIG_MEMORY_HOTREMOVE */

  #ifdef CONFIG_SPARSEMEM_VMEMMAP

  static unsigned long __init section_map_size(void)

  {
  	return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
  }
  
  #else

  static unsigned long __init section_map_size(void)

  {
  	return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
  }

  struct page __init *__populate_section_memmap(unsigned long pfn,
  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)

  {

  	unsigned long size = section_map_size();
  	struct page *map = sparse_buffer_alloc(size);

  	phys_addr_t addr = __pa(MAX_DMA_ADDRESS);

  
  	if (map)
  		return map;

  	map = memblock_alloc_try_nid_raw(size, size, addr,

  					  MEMBLOCK_ALLOC_ACCESSIBLE, nid);

  	if (!map)
  		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa
  ",
  		      __func__, size, PAGE_SIZE, nid, &addr);

  	return map;
  }
  #endif /* !CONFIG_SPARSEMEM_VMEMMAP */

  static void *sparsemap_buf __meminitdata;
  static void *sparsemap_buf_end __meminitdata;

  static inline void __meminit sparse_buffer_free(unsigned long size)
  {
  	WARN_ON(!sparsemap_buf || size == 0);
  	memblock_free_early(__pa(sparsemap_buf), size);
  }

  static void __init sparse_buffer_init(unsigned long size, int nid)

  {

  	phys_addr_t addr = __pa(MAX_DMA_ADDRESS);

  	WARN_ON(sparsemap_buf);	/* forgot to call sparse_buffer_fini()? */

  	/*
  	 * Pre-allocated buffer is mainly used by __populate_section_memmap
  	 * and we want it to be properly aligned to the section size - this is
  	 * especially the case for VMEMMAP which maps memmap to PMDs
  	 */

  	sparsemap_buf = memblock_alloc_exact_nid_raw(size, section_map_size(),

  					addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid);

  	sparsemap_buf_end = sparsemap_buf + size;
  }

  static void __init sparse_buffer_fini(void)

  {
  	unsigned long size = sparsemap_buf_end - sparsemap_buf;
  
  	if (sparsemap_buf && size > 0)

  		sparse_buffer_free(size);

  	sparsemap_buf = NULL;
  }
  
  void * __meminit sparse_buffer_alloc(unsigned long size)
  {
  	void *ptr = NULL;
  
  	if (sparsemap_buf) {

  		ptr = (void *) roundup((unsigned long)sparsemap_buf, size);

  		if (ptr + size > sparsemap_buf_end)
  			ptr = NULL;

  		else {
  			/* Free redundant aligned space */
  			if ((unsigned long)(ptr - sparsemap_buf) > 0)
  				sparse_buffer_free((unsigned long)(ptr - sparsemap_buf));

  			sparsemap_buf = ptr + size;

  		}

  	}
  	return ptr;
  }

  void __weak __meminit vmemmap_populate_print_last(void)

  {
  }

  /*
   * Initialize sparse on a specific node. The node spans [pnum_begin, pnum_end)
   * And number of present sections in this node is map_count.
   */
  static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
  				   unsigned long pnum_end,
  				   unsigned long map_count)
  {

  	struct mem_section_usage *usage;
  	unsigned long pnum;

  	struct page *map;

  	usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid),
  			mem_section_usage_size() * map_count);
  	if (!usage) {

  		pr_err("%s: node[%d] usemap allocation failed", __func__, nid);
  		goto failed;
  	}
  	sparse_buffer_init(map_count * section_map_size(), nid);
  	for_each_present_section_nr(pnum_begin, pnum) {

  		unsigned long pfn = section_nr_to_pfn(pnum);

  		if (pnum >= pnum_end)
  			break;

  		map = __populate_section_memmap(pfn, PAGES_PER_SECTION,
  				nid, NULL);

  		if (!map) {
  			pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.",
  			       __func__, nid);
  			pnum_begin = pnum;
  			goto failed;
  		}

  		check_usemap_section_nr(nid, 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();
  	return;
  failed:
  	/* We failed to allocate, mark all the following pnums as not present */
  	for_each_present_section_nr(pnum_begin, pnum) {
  		struct mem_section *ms;
  
  		if (pnum >= pnum_end)
  			break;
  		ms = __nr_to_section(pnum);
  		ms->section_mem_map = 0;
  	}
  }
  
  /*
   * Allocate the accumulated non-linear sections, allocate a mem_map
   * for each and record the physical to section mapping.
   */

  void __init sparse_init(void)

  {

  	unsigned long pnum_end, pnum_begin, map_count = 1;
  	int nid_begin;
  
  	memblocks_present();
  
  	pnum_begin = first_present_section_nr();
  	nid_begin = sparse_early_nid(__nr_to_section(pnum_begin));

  
  	/* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
  	set_pageblock_order();
  
  	for_each_present_section_nr(pnum_begin + 1, pnum_end) {
  		int nid = sparse_early_nid(__nr_to_section(pnum_end));
  
  		if (nid == nid_begin) {
  			map_count++;
  			continue;
  		}
  		/* Init node with sections in range [pnum_begin, pnum_end) */
  		sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
  		nid_begin = nid;
  		pnum_begin = pnum_end;
  		map_count = 1;
  	}
  	/* cover the last node */
  	sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
  	vmemmap_populate_print_last();
  }

  #ifdef CONFIG_MEMORY_HOTPLUG

  
  /* Mark all memory sections within the pfn range as online */
  void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {

  		unsigned long section_nr = pfn_to_section_nr(pfn);

  		struct mem_section *ms;
  
  		/* onlining code should never touch invalid ranges */
  		if (WARN_ON(!valid_section_nr(section_nr)))
  			continue;
  
  		ms = __nr_to_section(section_nr);
  		ms->section_mem_map |= SECTION_IS_ONLINE;
  	}
  }
  
  #ifdef CONFIG_MEMORY_HOTREMOVE

  /* Mark all memory sections within the pfn range as offline */

  void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {

  		unsigned long section_nr = pfn_to_section_nr(pfn);

  		struct mem_section *ms;
  
  		/*
  		 * TODO this needs some double checking. Offlining code makes
  		 * sure to check pfn_valid but those checks might be just bogus
  		 */
  		if (WARN_ON(!valid_section_nr(section_nr)))
  			continue;
  
  		ms = __nr_to_section(section_nr);
  		ms->section_mem_map &= ~SECTION_IS_ONLINE;
  	}
  }
  #endif

  #ifdef CONFIG_SPARSEMEM_VMEMMAP

  static struct page * __meminit populate_section_memmap(unsigned long pfn,

  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)

  {

  	return __populate_section_memmap(pfn, nr_pages, nid, altmap);

  }

  
  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,

  		struct vmem_altmap *altmap)

  {

  	unsigned long start = (unsigned long) pfn_to_page(pfn);
  	unsigned long end = start + nr_pages * sizeof(struct page);

  	vmemmap_free(start, end, altmap);

  }

  static void free_map_bootmem(struct page *memmap)

  {

  	unsigned long start = (unsigned long)memmap;

  	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);

  	vmemmap_free(start, end, NULL);

  }

  
  static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
  {
  	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
  	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
  	struct mem_section *ms = __pfn_to_section(pfn);
  	unsigned long *subsection_map = ms->usage
  		? &ms->usage->subsection_map[0] : NULL;
  
  	subsection_mask_set(map, pfn, nr_pages);
  	if (subsection_map)
  		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
  
  	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
  				"section already deactivated (%#lx + %ld)
  ",
  				pfn, nr_pages))
  		return -EINVAL;
  
  	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
  	return 0;
  }
  
  static bool is_subsection_map_empty(struct mem_section *ms)
  {
  	return bitmap_empty(&ms->usage->subsection_map[0],
  			    SUBSECTIONS_PER_SECTION);
  }
  
  static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
  {
  	struct mem_section *ms = __pfn_to_section(pfn);
  	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
  	unsigned long *subsection_map;
  	int rc = 0;
  
  	subsection_mask_set(map, pfn, nr_pages);
  
  	subsection_map = &ms->usage->subsection_map[0];
  
  	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
  		rc = -EINVAL;
  	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
  		rc = -EEXIST;
  	else
  		bitmap_or(subsection_map, map, subsection_map,
  				SUBSECTIONS_PER_SECTION);
  
  	return rc;
  }

  #else

  struct page * __meminit populate_section_memmap(unsigned long pfn,

  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)

  {

  	return kvmalloc_node(array_size(sizeof(struct page),
  					PAGES_PER_SECTION), GFP_KERNEL, nid);

  }

  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,

  		struct vmem_altmap *altmap)

  {

  	kvfree(pfn_to_page(pfn));

  }

  static void free_map_bootmem(struct page *memmap)

  {
  	unsigned long maps_section_nr, removing_section_nr, i;

  	unsigned long magic, nr_pages;

  	struct page *page = virt_to_page(memmap);

  	nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
  		>> PAGE_SHIFT;

  	for (i = 0; i < nr_pages; i++, page++) {

  		magic = (unsigned long) page->freelist;

  
  		BUG_ON(magic == NODE_INFO);
  
  		maps_section_nr = pfn_to_section_nr(page_to_pfn(page));

  		removing_section_nr = page_private(page);

  
  		/*
  		 * When this function is called, the removing section is
  		 * logical offlined state. This means all pages are isolated
  		 * from page allocator. If removing section's memmap is placed
  		 * on the same section, it must not be freed.
  		 * If it is freed, page allocator may allocate it which will
  		 * be removed physically soon.
  		 */
  		if (maps_section_nr != removing_section_nr)
  			put_page_bootmem(page);
  	}
  }

  static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)

  {

  	return 0;
  }
  
  static bool is_subsection_map_empty(struct mem_section *ms)
  {

  	return true;

  }

  static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)

  {

  	return 0;

  }

  #endif /* CONFIG_SPARSEMEM_VMEMMAP */

  /*
   * To deactivate a memory region, there are 3 cases to handle across
   * two configurations (SPARSEMEM_VMEMMAP={y,n}):
   *
   * 1. deactivation of a partial hot-added section (only possible in
   *    the SPARSEMEM_VMEMMAP=y case).
   *      a) section was present at memory init.
   *      b) section was hot-added post memory init.
   * 2. deactivation of a complete hot-added section.
   * 3. deactivation of a complete section from memory init.
   *
   * For 1, when subsection_map does not empty we will not be freeing the
   * usage map, but still need to free the vmemmap range.
   *
   * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
   */

  static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
  		struct vmem_altmap *altmap)
  {
  	struct mem_section *ms = __pfn_to_section(pfn);
  	bool section_is_early = early_section(ms);
  	struct page *memmap = NULL;
  	bool empty;
  
  	if (clear_subsection_map(pfn, nr_pages))
  		return;

  	empty = is_subsection_map_empty(ms);

  	if (empty) {

  		unsigned long section_nr = pfn_to_section_nr(pfn);

  		/*
  		 * When removing an early section, the usage map is kept (as the
  		 * usage maps of other sections fall into the same page). It
  		 * will be re-used when re-adding the section - which is then no
  		 * longer an early section. If the usage map is PageReserved, it
  		 * was allocated during boot.
  		 */
  		if (!PageReserved(virt_to_page(ms->usage))) {

  			kfree(ms->usage);
  			ms->usage = NULL;
  		}
  		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);

  		/*
  		 * Mark the section invalid so that valid_section()
  		 * return false. This prevents code from dereferencing
  		 * ms->usage array.
  		 */
  		ms->section_mem_map &= ~SECTION_HAS_MEM_MAP;

  	}

  	/*
  	 * The memmap of early sections is always fully populated. See
  	 * section_activate() and pfn_valid() .
  	 */
  	if (!section_is_early)

  		depopulate_section_memmap(pfn, nr_pages, altmap);

  	else if (memmap)
  		free_map_bootmem(memmap);

  
  	if (empty)
  		ms->section_mem_map = (unsigned long)NULL;

  }

  static struct page * __meminit section_activate(int nid, unsigned long pfn,
  		unsigned long nr_pages, struct vmem_altmap *altmap)
  {
  	struct mem_section *ms = __pfn_to_section(pfn);
  	struct mem_section_usage *usage = NULL;
  	struct page *memmap;
  	int rc = 0;
  
  	if (!ms->usage) {
  		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
  		if (!usage)
  			return ERR_PTR(-ENOMEM);
  		ms->usage = usage;
  	}
  
  	rc = fill_subsection_map(pfn, nr_pages);

  	if (rc) {
  		if (usage)
  			ms->usage = NULL;
  		kfree(usage);
  		return ERR_PTR(rc);
  	}
  
  	/*
  	 * The early init code does not consider partially populated
  	 * initial sections, it simply assumes that memory will never be
  	 * referenced.  If we hot-add memory into such a section then we
  	 * do not need to populate the memmap and can simply reuse what
  	 * is already there.
  	 */
  	if (nr_pages < PAGES_PER_SECTION && early_section(ms))
  		return pfn_to_page(pfn);
  
  	memmap = populate_section_memmap(pfn, nr_pages, nid, altmap);
  	if (!memmap) {
  		section_deactivate(pfn, nr_pages, altmap);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	return memmap;
  }

  /**

   * sparse_add_section - add a memory section, or populate an existing one

   * @nid: The node to add section on
   * @start_pfn: start pfn of the memory range

   * @nr_pages: number of pfns to add in the section

   * @altmap: device page map
   *
   * This is only intended for hotplug.
   *

   * Note that only VMEMMAP supports sub-section aligned hotplug,
   * the proper alignment and size are gated by check_pfn_span().
   *
   *

   * Return:
   * * 0		- On success.
   * * -EEXIST	- Section has been present.
   * * -ENOMEM	- Out of memory.

   */

  int __meminit sparse_add_section(int nid, unsigned long start_pfn,
  		unsigned long nr_pages, struct vmem_altmap *altmap)

  {

  	unsigned long section_nr = pfn_to_section_nr(start_pfn);

  	struct mem_section *ms;
  	struct page *memmap;

  	int ret;

  	ret = sparse_index_init(section_nr, nid);

  	if (ret < 0)

  		return ret;

  	memmap = section_activate(nid, start_pfn, nr_pages, altmap);
  	if (IS_ERR(memmap))
  		return PTR_ERR(memmap);

  	/*
  	 * Poison uninitialized struct pages in order to catch invalid flags
  	 * combinations.
  	 */

  	page_init_poison(memmap, sizeof(struct page) * nr_pages);

  	ms = __nr_to_section(section_nr);

  	set_section_nid(section_nr, nid);

  	section_mark_present(ms);

  	/* Align memmap to section boundary in the subsection case */
  	if (section_nr_to_pfn(section_nr) != start_pfn)

  		memmap = pfn_to_page(section_nr_to_pfn(section_nr));

  	sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
  
  	return 0;

  }

  #ifdef CONFIG_MEMORY_FAILURE
  static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
  {
  	int i;

  	/*
  	 * A further optimization is to have per section refcounted
  	 * num_poisoned_pages.  But that would need more space per memmap, so
  	 * for now just do a quick global check to speed up this routine in the
  	 * absence of bad pages.
  	 */
  	if (atomic_long_read(&num_poisoned_pages) == 0)
  		return;

  	for (i = 0; i < nr_pages; i++) {

  		if (PageHWPoison(&memmap[i])) {

  			num_poisoned_pages_dec();

  			ClearPageHWPoison(&memmap[i]);
  		}
  	}
  }
  #else
  static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
  {
  }
  #endif

  void sparse_remove_section(struct mem_section *ms, unsigned long pfn,

  		unsigned long nr_pages, unsigned long map_offset,
  		struct vmem_altmap *altmap)

  {

  	clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset,
  			nr_pages - map_offset);
  	section_deactivate(pfn, nr_pages, altmap);

  }

  #endif /* CONFIG_MEMORY_HOTPLUG */