sparse.c

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/*
 * sparse memory mappings.
 */
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/mmzone.h>
#include <linux/bootmem.h>
#include <linux/highmem.h>
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include "internal.h"
#include <asm/dma.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>

/*
 * Permanent SPARSEMEM data:
 *
 * 1) mem_section   - memory sections, mem_map's for valid memory
 */
#ifdef CONFIG_SPARSEMEM_EXTREME
struct mem_section *mem_section[NR_SECTION_ROOTS]
    ____cacheline_internodealigned_in_smp;
#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 struct mem_section noinline __init_refok *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()) {
        if (node_state(nid, N_HIGH_MEMORY))
            section = kzalloc_node(array_size, GFP_KERNEL, nid);
        else
            section = kzalloc(array_size, GFP_KERNEL);
    } else {
        section = alloc_bootmem_node(NODE_DATA(nid), array_size);
    }

    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;
    int ret = 0;

    if (mem_section[root])
        return -EEXIST;

    section = sparse_index_alloc(nid);
    if (!section)
        return -ENOMEM;

    mem_section[root] = section;

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

/*
 * Although written for the SPARSEMEM_EXTREME case, this happens
 * to also work for the flat array case because
 * NR_SECTION_ROOTS==NR_MEM_SECTIONS.
 */
int __section_nr(struct mem_section* ms)
{
    unsigned long root_nr;
    struct mem_section* root;

    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_nr == NR_SECTION_ROOTS);

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

/*
 * 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\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;
    }
}

/* Record a memory area against a node. */
void __init memory_present(int nid, unsigned long start, unsigned long end)
{
    unsigned long pfn;

    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_MARKED_PRESENT;
    }
}

/*
 * Only used by the i386 NUMA architecures, but relatively
 * generic code.
 */
unsigned long __init node_memmap_size_bytes(int nid, unsigned long start_pfn,
                             unsigned long end_pfn)
{
    unsigned long pfn;
    unsigned long nr_pages = 0;

    mminit_validate_memmodel_limits(&start_pfn, &end_pfn);
    for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
        if (nid != early_pfn_to_nid(pfn))
            continue;

        if (pfn_present(pfn))
            nr_pages += PAGES_PER_SECTION;
    }

    return nr_pages * sizeof(struct page);
}

/*
 * 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)
{
    return (unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
}

/*
 * 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);
}

static int __meminit sparse_init_one_section(struct mem_section *ms,
        unsigned long pnum, struct page *mem_map,
        unsigned long *pageblock_bitmap)
{
    if (!present_section(ms))
        return -EINVAL;

    ms->section_mem_map &= ~SECTION_MAP_MASK;
    ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) |
                            SECTION_HAS_MEM_MAP;
    ms->pageblock_flags = pageblock_bitmap;

    return 1;
}

unsigned long usemap_size(void)
{
    unsigned long size_bytes;
    size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
    size_bytes = roundup(size_bytes, sizeof(unsigned long));
    return size_bytes;
}

#ifdef CONFIG_MEMORY_HOTPLUG
static unsigned long *__kmalloc_section_usemap(void)
{
    return kmalloc(usemap_size(), GFP_KERNEL);
}
#endif /* CONFIG_MEMORY_HOTPLUG */

#ifdef CONFIG_MEMORY_HOTREMOVE
static unsigned long * __init
sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
                     unsigned long size)
{
    unsigned long goal, limit;
    unsigned long *p;
    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 retmain 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:
    p = ___alloc_bootmem_node_nopanic(NODE_DATA(nid), size,
                      SMP_CACHE_BYTES, goal, limit);
    if (!p && limit) {
        limit = 0;
        goto again;
    }
    return p;
}

static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
{
    unsigned long usemap_snr, pgdat_snr;
    static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
    static unsigned long old_pgdat_snr = NR_MEM_SECTIONS;
    struct pglist_data *pgdat = NODE_DATA(nid);
    int usemap_nid;

    usemap_snr = pfn_to_section_nr(__pa(usemap) >> 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) {
        printk(KERN_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.
     */
    printk(KERN_INFO "Section %ld and %ld (node %d)", usemap_snr,
           pgdat_snr, nid);
    printk(KERN_CONT
           " have a circular dependency on usemap and pgdat allocations\n");
}
#else
static unsigned long * __init
sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
                     unsigned long size)
{
    return alloc_bootmem_node_nopanic(pgdat, size);
}

static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
{
}
#endif /* CONFIG_MEMORY_HOTREMOVE */

static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map,
                 unsigned long pnum_begin,
                 unsigned long pnum_end,
                 unsigned long usemap_count, int nodeid)
{
    void *usemap;
    unsigned long pnum;
    int size = usemap_size();

    usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid),
                              size * usemap_count);
    if (!usemap) {
        printk(KERN_WARNING "%s: allocation failed\n", __func__);
        return;
    }

    for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
        if (!present_section_nr(pnum))
            continue;
        usemap_map[pnum] = usemap;
        usemap += size;
        check_usemap_section_nr(nodeid, usemap_map[pnum]);
    }
}

#ifndef CONFIG_SPARSEMEM_VMEMMAP
struct page __init *sparse_mem_map_populate(unsigned long pnum, int nid)
{
    struct page *map;
    unsigned long size;

    map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
    if (map)
        return map;

    size = PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
    map = __alloc_bootmem_node_high(NODE_DATA(nid), size,
                     PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
    return map;
}
void __init sparse_mem_maps_populate_node(struct page **map_map,
                      unsigned long pnum_begin,
                      unsigned long pnum_end,
                      unsigned long map_count, int nodeid)
{
    void *map;
    unsigned long pnum;
    unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;

    map = alloc_remap(nodeid, size * map_count);
    if (map) {
        for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
            if (!present_section_nr(pnum))
                continue;
            map_map[pnum] = map;
            map += size;
        }
        return;
    }

    size = PAGE_ALIGN(size);
    map = __alloc_bootmem_node_high(NODE_DATA(nodeid), size * map_count,
                     PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
    if (map) {
        for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
            if (!present_section_nr(pnum))
                continue;
            map_map[pnum] = map;
            map += size;
        }
        return;
    }

    /* fallback */
    for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
        struct mem_section *ms;

        if (!present_section_nr(pnum))
            continue;
        map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
        if (map_map[pnum])
            continue;
        ms = __nr_to_section(pnum);
        printk(KERN_ERR "%s: sparsemem memory map backing failed "
            "some memory will not be available.\n", __func__);
        ms->section_mem_map = 0;
    }
}
#endif /* !CONFIG_SPARSEMEM_VMEMMAP */

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
static void __init sparse_early_mem_maps_alloc_node(struct page **map_map,
                 unsigned long pnum_begin,
                 unsigned long pnum_end,
                 unsigned long map_count, int nodeid)
{
    sparse_mem_maps_populate_node(map_map, pnum_begin, pnum_end,
                     map_count, nodeid);
}
#else
static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
{
    struct page *map;
    struct mem_section *ms = __nr_to_section(pnum);
    int nid = sparse_early_nid(ms);

    map = sparse_mem_map_populate(pnum, nid);
    if (map)
        return map;

    printk(KERN_ERR "%s: sparsemem memory map backing failed "
            "some memory will not be available.\n", __func__);
    ms->section_mem_map = 0;
    return NULL;
}
#endif

void __attribute__((weak)) __meminit vmemmap_populate_print_last(void)
{
}

/*
 * 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;
    struct page *map;
    unsigned long *usemap;
    unsigned long **usemap_map;
    int size;
    int nodeid_begin = 0;
    unsigned long pnum_begin = 0;
    unsigned long usemap_count;
#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
    unsigned long map_count;
    int size2;
    struct page **map_map;
#endif

    /* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
    set_pageblock_order();

    /*
     * map is using big page (aka 2M in x86 64 bit)
     * usemap is less one page (aka 24 bytes)
     * so alloc 2M (with 2M align) and 24 bytes in turn will
     * make next 2M slip to one more 2M later.
     * then in big system, the memory will have a lot of holes...
     * here try to allocate 2M pages continuously.
     *
     * powerpc need to call sparse_init_one_section right after each
     * sparse_early_mem_map_alloc, so allocate usemap_map at first.
     */
    size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
    usemap_map = alloc_bootmem(size);
    if (!usemap_map)
        panic("can not allocate usemap_map\n");

    for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
        struct mem_section *ms;

        if (!present_section_nr(pnum))
            continue;
        ms = __nr_to_section(pnum);
        nodeid_begin = sparse_early_nid(ms);
        pnum_begin = pnum;
        break;
    }
    usemap_count = 1;
    for (pnum = pnum_begin + 1; pnum < NR_MEM_SECTIONS; pnum++) {
        struct mem_section *ms;
        int nodeid;

        if (!present_section_nr(pnum))
            continue;
        ms = __nr_to_section(pnum);
        nodeid = sparse_early_nid(ms);
        if (nodeid == nodeid_begin) {
            usemap_count++;
            continue;
        }
        /* ok, we need to take cake of from pnum_begin to pnum - 1*/
        sparse_early_usemaps_alloc_node(usemap_map, pnum_begin, pnum,
                         usemap_count, nodeid_begin);
        /* new start, update count etc*/
        nodeid_begin = nodeid;
        pnum_begin = pnum;
        usemap_count = 1;
    }
    /* ok, last chunk */
    sparse_early_usemaps_alloc_node(usemap_map, pnum_begin, NR_MEM_SECTIONS,
                     usemap_count, nodeid_begin);

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
    size2 = sizeof(struct page *) * NR_MEM_SECTIONS;
    map_map = alloc_bootmem(size2);
    if (!map_map)
        panic("can not allocate map_map\n");

    for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
        struct mem_section *ms;

        if (!present_section_nr(pnum))
            continue;
        ms = __nr_to_section(pnum);
        nodeid_begin = sparse_early_nid(ms);
        pnum_begin = pnum;
        break;
    }
    map_count = 1;
    for (pnum = pnum_begin + 1; pnum < NR_MEM_SECTIONS; pnum++) {
        struct mem_section *ms;
        int nodeid;

        if (!present_section_nr(pnum))
            continue;
        ms = __nr_to_section(pnum);
        nodeid = sparse_early_nid(ms);
        if (nodeid == nodeid_begin) {
            map_count++;
            continue;
        }
        /* ok, we need to take cake of from pnum_begin to pnum - 1*/
        sparse_early_mem_maps_alloc_node(map_map, pnum_begin, pnum,
                         map_count, nodeid_begin);
        /* new start, update count etc*/
        nodeid_begin = nodeid;
        pnum_begin = pnum;
        map_count = 1;
    }
    /* ok, last chunk */
    sparse_early_mem_maps_alloc_node(map_map, pnum_begin, NR_MEM_SECTIONS,
                     map_count, nodeid_begin);
#endif

    for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
        if (!present_section_nr(pnum))
            continue;

        usemap = usemap_map[pnum];
        if (!usemap)
            continue;

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
        map = map_map[pnum];
#else
        map = sparse_early_mem_map_alloc(pnum);
#endif
        if (!map)
            continue;

        sparse_init_one_section(__nr_to_section(pnum), pnum, map,
                                usemap);
    }

    vmemmap_populate_print_last();

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
    free_bootmem(__pa(map_map), size2);
#endif
    free_bootmem(__pa(usemap_map), size);
}

#ifdef CONFIG_MEMORY_HOTPLUG
#ifdef CONFIG_SPARSEMEM_VMEMMAP
static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
                         unsigned long nr_pages)
{
    /* This will make the necessary allocations eventually. */
    return sparse_mem_map_populate(pnum, nid);
}
static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
{
    return; /* XXX: Not implemented yet */
}
static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
{
}
#else
static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
{
    struct page *page, *ret;
    unsigned long memmap_size = sizeof(struct page) * nr_pages;

    page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
    if (page)
        goto got_map_page;

    ret = vmalloc(memmap_size);
    if (ret)
        goto got_map_ptr;

    return NULL;
got_map_page:
    ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
got_map_ptr:
    memset(ret, 0, memmap_size);

    return ret;
}

static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
                          unsigned long nr_pages)
{
    return __kmalloc_section_memmap(nr_pages);
}

static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
{
    if (is_vmalloc_addr(memmap))
        vfree(memmap);
    else
        free_pages((unsigned long)memmap,
               get_order(sizeof(struct page) * nr_pages));
}

static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
{
    unsigned long maps_section_nr, removing_section_nr, i;
    unsigned long magic;
    struct page *page = virt_to_page(memmap);

    for (i = 0; i < nr_pages; i++, page++) {
        magic = (unsigned long) page->lru.next;

        BUG_ON(magic == NODE_INFO);

        maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
        removing_section_nr = page->private;

        /*
         * 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);
    }
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

static void free_section_usemap(struct page *memmap, unsigned long *usemap)
{
    struct page *usemap_page;
    unsigned long nr_pages;

    if (!usemap)
        return;

    usemap_page = virt_to_page(usemap);
    /*
     * Check to see if allocation came from hot-plug-add
     */
    if (PageSlab(usemap_page)) {
        kfree(usemap);
        if (memmap)
            __kfree_section_memmap(memmap, PAGES_PER_SECTION);
        return;
    }

    /*
     * The usemap came from bootmem. This is packed with other usemaps
     * on the section which has pgdat at boot time. Just keep it as is now.
     */

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

        free_map_bootmem(memmap, nr_pages);
    }
}

/*
 * returns the number of sections whose mem_maps were properly
 * set.  If this is <=0, then that means that the passed-in
 * map was not consumed and must be freed.
 */
int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
               int nr_pages)
{
    unsigned long section_nr = pfn_to_section_nr(start_pfn);
    struct pglist_data *pgdat = zone->zone_pgdat;
    struct mem_section *ms;
    struct page *memmap;
    unsigned long *usemap;
    unsigned long flags;
    int ret;

    /*
     * no locking for this, because it does its own
     * plus, it does a kmalloc
     */
    ret = sparse_index_init(section_nr, pgdat->node_id);
    if (ret < 0 && ret != -EEXIST)
        return ret;
    memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, nr_pages);
    if (!memmap)
        return -ENOMEM;
    usemap = __kmalloc_section_usemap();
    if (!usemap) {
        __kfree_section_memmap(memmap, nr_pages);
        return -ENOMEM;
    }

    pgdat_resize_lock(pgdat, &flags);

    ms = __pfn_to_section(start_pfn);
    if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
        ret = -EEXIST;
        goto out;
    }

    ms->section_mem_map |= SECTION_MARKED_PRESENT;

    ret = sparse_init_one_section(ms, section_nr, memmap, usemap);

out:
    pgdat_resize_unlock(pgdat, &flags);
    if (ret <= 0) {
        kfree(usemap);
        __kfree_section_memmap(memmap, nr_pages);
    }
    return ret;
}

void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)
{
    struct page *memmap = NULL;
    unsigned long *usemap = NULL;

    if (ms->section_mem_map) {
        usemap = ms->pageblock_flags;
        memmap = sparse_decode_mem_map(ms->section_mem_map,
                        __section_nr(ms));
        ms->section_mem_map = 0;
        ms->pageblock_flags = NULL;
    }

    free_section_usemap(memmap, usemap);
}
#endif