Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 934 insertions, 0 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
new file mode 100644
index 000000000..05d1e7b6c
--- /dev/null
+++ b/mm/sparse.c
@@ -0,0 +1,934 @@
+// 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 <linux/bootmem_info.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\n",
+			      __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
+
+/*
+ * 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 ((unsigned long)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 */
+static 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\n",
+			*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\n",
+			*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)
+{
+	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)\n", __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\n",
+			      __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, section);
+		}
+	}
+}
+
+/*
+ * 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 > 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();
+}
+
+static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat)
+{
+#ifndef CONFIG_NUMA
+	VM_BUG_ON(pgdat != &contig_page_data);
+	return __pa_symbol(&contig_page_data);
+#else
+	return __pa(pgdat);
+#endif
+}
+
+#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 = pgdat_to_phys(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(pgdat_to_phys(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\n",
+			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\n",
+		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,
+		struct dev_pagemap *pgmap)
+{
+	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 = memmap_alloc(size, size, addr, nid, false);
+	if (!map)
+		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n",
+		      __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(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 = memmap_alloc(size, section_map_size(), addr, nid, true);
+	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, NULL);
+		if (!map) {
+			pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.",
+			       __func__, nid);
+			pnum_begin = pnum;
+			sparse_buffer_fini();
+			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;
+	}
+}
+
+/* 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;
+	}
+}
+
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static struct page * __meminit populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
+		struct dev_pagemap *pgmap)
+{
+	return __populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
+}
+
+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)\n",
+				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,
+		struct dev_pagemap *pgmap)
+{
+	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 = page->index;
+
+		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);
+
+		/*
+		 * 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;
+
+		/*
+		 * 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_rcu(ms->usage, rcu);
+			WRITE_ONCE(ms->usage, NULL);
+		}
+		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
+	}
+
+	/*
+	 * 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 dev_pagemap *pgmap)
+{
+	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, pgmap);
+	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: alternate pfns to allocate the memmap backing store
+ * @pgmap: alternate compound page geometry for devmap mappings
+ *
+ * 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,
+		struct dev_pagemap *pgmap)
+{
+	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, pgmap);
+	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, section_nr);
+
+	/* 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;
+}
+
+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 */