// SPDX-License-Identifier: GPL-2.0
/*
 * Virtual Memory Map support
 *
 * (C) 2007 sgi. Christoph Lameter.
 *
 * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
 * virt_to_page, page_address() to be implemented as a base offset
 * calculation without memory access.
 *
 * However, virtual mappings need a page table and TLBs. Many Linux
 * architectures already map their physical space using 1-1 mappings
 * via TLBs. For those arches the virtual memory map is essentially
 * for free if we use the same page size as the 1-1 mappings. In that
 * case the overhead consists of a few additional pages that are
 * allocated to create a view of memory for vmemmap.
 *
 * The architecture is expected to provide a vmemmap_populate() function
 * to instantiate the mapping.
 */
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/memblock.h>
#include <linux/memremap.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/sched.h>
#include <linux/pgalloc.h>

#include <asm/dma.h>
#include <asm/tlbflush.h>

#include "hugetlb_vmemmap.h"

/*
 * Flags for vmemmap_populate_range and friends.
 */
/* Get a ref on the head page struct page, for ZONE_DEVICE compound pages */
#define VMEMMAP_POPULATE_PAGEREF        0x0001

#include "internal.h"

/*
 * Allocate a block of memory to be used to back the virtual memory map
 * or to back the page tables that are used to create the mapping.
 * Uses the main allocators if they are available, else bootmem.
 */

static void * __ref __earlyonly_bootmem_alloc(int node,
                                unsigned long size,
                                unsigned long align,
                                unsigned long goal)
{
        return memmap_alloc(size, align, goal, node, false);
}

void * __meminit vmemmap_alloc_block(unsigned long size, int node)
{
        /* If the main allocator is up use that, fallback to bootmem. */
        if (slab_is_available()) {
                gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
                int order = get_order(size);
                static bool warned __meminitdata;
                struct page *page;

                page = alloc_pages_node(node, gfp_mask, order);
                if (page)
                        return page_address(page);

                if (!warned) {
                        warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
                                   "vmemmap alloc failure: order:%u", order);
                        warned = true;
                }
                return NULL;
        } else
                return __earlyonly_bootmem_alloc(node, size, size,
                                __pa(MAX_DMA_ADDRESS));
}

static void * __meminit altmap_alloc_block_buf(unsigned long size,
                                               struct vmem_altmap *altmap);

/* need to make sure size is all the same during early stage */
void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
                                         struct vmem_altmap *altmap)
{
        if (altmap)
                return altmap_alloc_block_buf(size, altmap);

        return vmemmap_alloc_block(size, node);
}

static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
{
        return altmap->base_pfn + altmap->reserve + altmap->alloc
                + altmap->align;
}

static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
{
        unsigned long allocated = altmap->alloc + altmap->align;

        if (altmap->free > allocated)
                return altmap->free - allocated;
        return 0;
}

static void * __meminit altmap_alloc_block_buf(unsigned long size,
                                               struct vmem_altmap *altmap)
{
        unsigned long pfn, nr_pfns, nr_align;

        if (size & ~PAGE_MASK) {
                pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n",
                                __func__, size);
                return NULL;
        }

        pfn = vmem_altmap_next_pfn(altmap);
        nr_pfns = size >> PAGE_SHIFT;
        nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
        nr_align = ALIGN(pfn, nr_align) - pfn;
        if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
                return NULL;

        altmap->alloc += nr_pfns;
        altmap->align += nr_align;
        pfn += nr_align;

        pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n",
                        __func__, pfn, altmap->alloc, altmap->align, nr_pfns);
        return __va(__pfn_to_phys(pfn));
}

void __meminit vmemmap_verify(pte_t *pte, int node,
                                unsigned long start, unsigned long end)
{
        unsigned long pfn = pte_pfn(ptep_get(pte));
        int actual_node = early_pfn_to_nid(pfn);

        if (node_distance(actual_node, node) > LOCAL_DISTANCE)
                pr_warn_once("[%lx-%lx] potential offnode page_structs\n",
                        start, end - 1);
}

static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
                                       struct vmem_altmap *altmap,
                                       unsigned long ptpfn, unsigned long flags)
{
        pte_t *pte = pte_offset_kernel(pmd, addr);
        if (pte_none(ptep_get(pte))) {
                pte_t entry;
                void *p;

                if (ptpfn == (unsigned long)-1) {
                        p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);
                        if (!p)
                                return NULL;
                        ptpfn = PHYS_PFN(__pa(p));
                } else {
                        /*
                         * When a PTE/PMD entry is freed from the init_mm
                         * there's a free_pages() call to this page allocated
                         * above. Thus this get_page() is paired with the
                         * put_page_testzero() on the freeing path.
                         * This can only called by certain ZONE_DEVICE path,
                         * and through vmemmap_populate_compound_pages() when
                         * slab is available.
                         */
                        if (flags & VMEMMAP_POPULATE_PAGEREF)
                                get_page(pfn_to_page(ptpfn));
                }
                entry = pfn_pte(ptpfn, PAGE_KERNEL);
                set_pte_at(&init_mm, addr, pte, entry);
        }
        return pte;
}

static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
{
        void *p = vmemmap_alloc_block(size, node);

        if (!p)
                return NULL;
        memset(p, 0, size);

        return p;
}

static pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
{
        pmd_t *pmd = pmd_offset(pud, addr);
        if (pmd_none(*pmd)) {
                void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
                if (!p)
                        return NULL;
                kernel_pte_init(p);
                pmd_populate_kernel(&init_mm, pmd, p);
        }
        return pmd;
}

static pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
{
        pud_t *pud = pud_offset(p4d, addr);
        if (pud_none(*pud)) {
                void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
                if (!p)
                        return NULL;
                pmd_init(p);
                pud_populate(&init_mm, pud, p);
        }
        return pud;
}

static p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
{
        p4d_t *p4d = p4d_offset(pgd, addr);
        if (p4d_none(*p4d)) {
                void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
                if (!p)
                        return NULL;
                pud_init(p);
                p4d_populate_kernel(addr, p4d, p);
        }
        return p4d;
}

static pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
{
        pgd_t *pgd = pgd_offset_k(addr);
        if (pgd_none(*pgd)) {
                void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
                if (!p)
                        return NULL;
                pgd_populate_kernel(addr, pgd, p);
        }
        return pgd;
}

static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,
                                              struct vmem_altmap *altmap,
                                              unsigned long ptpfn,
                                              unsigned long flags)
{
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        pgd = vmemmap_pgd_populate(addr, node);
        if (!pgd)
                return NULL;
        p4d = vmemmap_p4d_populate(pgd, addr, node);
        if (!p4d)
                return NULL;
        pud = vmemmap_pud_populate(p4d, addr, node);
        if (!pud)
                return NULL;
        pmd = vmemmap_pmd_populate(pud, addr, node);
        if (!pmd)
                return NULL;
        pte = vmemmap_pte_populate(pmd, addr, node, altmap, ptpfn, flags);
        if (!pte)
                return NULL;
        vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);

        return pte;
}

static int __meminit vmemmap_populate_range(unsigned long start,
                                            unsigned long end, int node,
                                            struct vmem_altmap *altmap,
                                            unsigned long ptpfn,
                                            unsigned long flags)
{
        unsigned long addr = start;
        pte_t *pte;

        for (; addr < end; addr += PAGE_SIZE) {
                pte = vmemmap_populate_address(addr, node, altmap,
                                               ptpfn, flags);
                if (!pte)
                        return -ENOMEM;
        }

        return 0;
}

int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
                                         int node, struct vmem_altmap *altmap)
{
        return vmemmap_populate_range(start, end, node, altmap, -1, 0);
}

/*
 * Write protect the mirrored tail page structs for HVO. This will be
 * called from the hugetlb code when gathering and initializing the
 * memblock allocated gigantic pages. The write protect can't be
 * done earlier, since it can't be guaranteed that the reserved
 * page structures will not be written to during initialization,
 * even if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
 *
 * The PTEs are known to exist, and nothing else should be touching
 * these pages. The caller is responsible for any TLB flushing.
 */
void vmemmap_wrprotect_hvo(unsigned long addr, unsigned long end,
                                    int node, unsigned long headsize)
{
        unsigned long maddr;
        pte_t *pte;

        for (maddr = addr + headsize; maddr < end; maddr += PAGE_SIZE) {
                pte = virt_to_kpte(maddr);
                ptep_set_wrprotect(&init_mm, maddr, pte);
        }
}

#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *zone)
{
        struct page *p, *tail;
        unsigned int idx;
        int node = zone_to_nid(zone);

        if (WARN_ON_ONCE(order < VMEMMAP_TAIL_MIN_ORDER))
                return NULL;
        if (WARN_ON_ONCE(order > MAX_FOLIO_ORDER))
                return NULL;

        idx = order - VMEMMAP_TAIL_MIN_ORDER;
        tail = zone->vmemmap_tails[idx];
        if (tail)
                return tail;

        /*
         * Only allocate the page, but do not initialize it.
         *
         * Any initialization done here will be overwritten by memmap_init().
         *
         * hugetlb_vmemmap_init() will take care of initialization after
         * memmap_init().
         */

        p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
        if (!p)
                return NULL;

        tail = virt_to_page(p);
        zone->vmemmap_tails[idx] = tail;

        return tail;
}

int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end,
                                       unsigned int order, struct zone *zone,
                                       unsigned long headsize)
{
        unsigned long maddr;
        struct page *tail;
        pte_t *pte;
        int node = zone_to_nid(zone);

        tail = vmemmap_get_tail(order, zone);
        if (!tail)
                return -ENOMEM;

        for (maddr = addr; maddr < addr + headsize; maddr += PAGE_SIZE) {
                pte = vmemmap_populate_address(maddr, node, NULL, -1, 0);
                if (!pte)
                        return -ENOMEM;
        }

        /*
         * Reuse the last page struct page mapped above for the rest.
         */
        return vmemmap_populate_range(maddr, end, node, NULL,
                                      page_to_pfn(tail), 0);
}
#endif

void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
                                      unsigned long addr, unsigned long next)
{
        WARN_ON_ONCE(!pmd_set_huge(pmd, virt_to_phys(p), PAGE_KERNEL));
}

int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
                                       unsigned long addr, unsigned long next)
{
        if (!pmd_leaf(pmdp_get(pmd)))
                return 0;
        vmemmap_verify((pte_t *)pmd, node, addr, next);

        return 1;
}

int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
                                         int node, struct vmem_altmap *altmap)
{
        unsigned long addr;
        unsigned long next;
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;

        for (addr = start; addr < end; addr = next) {
                next = pmd_addr_end(addr, end);

                pgd = vmemmap_pgd_populate(addr, node);
                if (!pgd)
                        return -ENOMEM;

                p4d = vmemmap_p4d_populate(pgd, addr, node);
                if (!p4d)
                        return -ENOMEM;

                pud = vmemmap_pud_populate(p4d, addr, node);
                if (!pud)
                        return -ENOMEM;

                pmd = pmd_offset(pud, addr);
                if (pmd_none(pmdp_get(pmd))) {
                        void *p;

                        p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
                        if (p) {
                                vmemmap_set_pmd(pmd, p, node, addr, next);
                                continue;
                        } else if (altmap) {
                                /*
                                 * No fallback: In any case we care about, the
                                 * altmap should be reasonably sized and aligned
                                 * such that vmemmap_alloc_block_buf() will always
                                 * succeed. For consistency with the PTE case,
                                 * return an error here as failure could indicate
                                 * a configuration issue with the size of the altmap.
                                 */
                                return -ENOMEM;
                        }
                } else if (vmemmap_check_pmd(pmd, node, addr, next))
                        continue;
                if (vmemmap_populate_basepages(addr, next, node, altmap))
                        return -ENOMEM;
        }
        return 0;
}

#ifndef vmemmap_populate_compound_pages
/*
 * For compound pages bigger than section size (e.g. x86 1G compound
 * pages with 2M subsection size) fill the rest of sections as tail
 * pages.
 *
 * Note that memremap_pages() resets @nr_range value and will increment
 * it after each range successful onlining. Thus the value or @nr_range
 * at section memmap populate corresponds to the in-progress range
 * being onlined here.
 */
static bool __meminit reuse_compound_section(unsigned long start_pfn,
                                             struct dev_pagemap *pgmap)
{
        unsigned long nr_pages = pgmap_vmemmap_nr(pgmap);
        unsigned long offset = start_pfn -
                PHYS_PFN(pgmap->ranges[pgmap->nr_range].start);

        return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION;
}

static pte_t * __meminit compound_section_tail_page(unsigned long addr)
{
        pte_t *pte;

        addr -= PAGE_SIZE;

        /*
         * Assuming sections are populated sequentially, the previous section's
         * page data can be reused.
         */
        pte = pte_offset_kernel(pmd_off_k(addr), addr);
        if (!pte)
                return NULL;

        return pte;
}

static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
                                                     unsigned long start,
                                                     unsigned long end, int node,
                                                     struct dev_pagemap *pgmap)
{
        unsigned long size, addr;
        pte_t *pte;
        int rc;

        if (reuse_compound_section(start_pfn, pgmap)) {
                pte = compound_section_tail_page(start);
                if (!pte)
                        return -ENOMEM;

                /*
                 * Reuse the page that was populated in the prior iteration
                 * with just tail struct pages.
                 */
                return vmemmap_populate_range(start, end, node, NULL,
                                              pte_pfn(ptep_get(pte)),
                                              VMEMMAP_POPULATE_PAGEREF);
        }

        size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page));
        for (addr = start; addr < end; addr += size) {
                unsigned long next, last = addr + size;

                /* Populate the head page vmemmap page */
                pte = vmemmap_populate_address(addr, node, NULL, -1, 0);
                if (!pte)
                        return -ENOMEM;

                /* Populate the tail pages vmemmap page */
                next = addr + PAGE_SIZE;
                pte = vmemmap_populate_address(next, node, NULL, -1, 0);
                if (!pte)
                        return -ENOMEM;

                /*
                 * Reuse the previous page for the rest of tail pages
                 * See layout diagram in Documentation/mm/vmemmap_dedup.rst
                 */
                next += PAGE_SIZE;
                rc = vmemmap_populate_range(next, last, node, NULL,
                                            pte_pfn(ptep_get(pte)),
                                            VMEMMAP_POPULATE_PAGEREF);
                if (rc)
                        return -ENOMEM;
        }

        return 0;
}

#endif

struct page * __meminit __populate_section_memmap(unsigned long pfn,
                unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
                struct dev_pagemap *pgmap)
{
        unsigned long start = (unsigned long) pfn_to_page(pfn);
        unsigned long end = start + nr_pages * sizeof(struct page);
        int r;

        if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) ||
                !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
                return NULL;

        if (vmemmap_can_optimize(altmap, pgmap))
                r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
        else
                r = vmemmap_populate(start, end, nid, altmap);

        if (r < 0)
                return NULL;

        flush_cache_vmap(start, end);

        return pfn_to_page(pfn);
}

#ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
/*
 * This is called just before initializing sections for a NUMA node.
 * Any special initialization that needs to be done before the
 * generic initialization can be done from here. Sections that
 * are initialized in hooks called from here will be skipped by
 * the generic initialization.
 */
void __init sparse_vmemmap_init_nid_early(int nid)
{
        hugetlb_vmemmap_init_early(nid);
}

/*
 * This is called just before the initialization of page structures
 * through memmap_init. Zones are now initialized, so any work that
 * needs to be done that needs zone information can be done from
 * here.
 */
void __init sparse_vmemmap_init_nid_late(int nid)
{
        hugetlb_vmemmap_init_late(nid);
}
#endif

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 sparse_init_subsection_map(unsigned long pfn, unsigned long nr_pages)
{
        int end_sec_nr = pfn_to_section_nr(pfn + nr_pages - 1);
        unsigned long nr, start_sec_nr = pfn_to_section_nr(pfn);

        for (nr = start_sec_nr; nr <= end_sec_nr; 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;
        }
}

#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 = __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 = __nr_to_section(section_nr);

                ms->section_mem_map &= ~SECTION_IS_ONLINE;
        }
}

static int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages,
                struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
{
        const unsigned int order = pgmap ? pgmap->vmemmap_shift : 0;
        const unsigned long pages_per_compound = 1UL << order;

        VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION));
        VM_WARN_ON_ONCE(nr_pages > PAGES_PER_SECTION);

        if (!vmemmap_can_optimize(altmap, pgmap))
                return DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE);

        if (order < PFN_SECTION_SHIFT) {
                VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound));
                return VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound;
        }

        VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION));

        if (IS_ALIGNED(pfn, pages_per_compound))
                return VMEMMAP_RESERVE_NR;

        return 0;
}

static struct page * __meminit populate_section_memmap(unsigned long pfn,
                unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
                struct dev_pagemap *pgmap)
{
        struct page *page = __populate_section_memmap(pfn, nr_pages, nid, altmap,
                                                      pgmap);

        memmap_pages_add(section_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap));

        return page;
}

static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
                struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
{
        unsigned long start = (unsigned long) pfn_to_page(pfn);
        unsigned long end = start + nr_pages * sizeof(struct page);

        memmap_pages_add(-section_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap));
        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);
        unsigned long pfn = page_to_pfn(memmap);

        memmap_boot_pages_add(-section_nr_vmemmap_pages(pfn, PAGES_PER_SECTION,
                                                        NULL, NULL));
        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;
}

/*
 * To deactivate a memory region, there are 3 cases to handle:
 *
 * 1. deactivation of a partial hot-added section:
 *      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.
 */
static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
                struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
{
        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) {
                /*
                 * 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 = pfn_to_page(SECTION_ALIGN_DOWN(pfn));
        }

        /*
         * 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, pgmap);
        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;

        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, pgmap);
                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);
        __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(unsigned long pfn, unsigned long nr_pages,
                struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
{
        struct mem_section *ms = __pfn_to_section(pfn);

        if (WARN_ON_ONCE(!valid_section(ms)))
                return;

        section_deactivate(pfn, nr_pages, altmap, pgmap);
}
#endif /* CONFIG_MEMORY_HOTPLUG */