Quelle sparse.c Sprache: C

// 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 <linux/vmstat.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 = (DIRECT_MAP_PHYSMEM_END + 1) >> 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;
}

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_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;
}
}
#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;

start &= PAGE_SECTION_MASK;
mminit_validate_memmodel_limits(&start, &end);
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
  unsigned long section_nr = pfn_to_section_nr(pfn);
  struct mem_section *ms;

  sparse_index_init(section_nr, nid);
  set_section_nid(section_nr, nid);

  ms = __nr_to_section(section_nr);
  if (!ms->section_mem_map) {
   ms->section_mem_map = sparse_encode_early_nid(nid) |
       SECTION_IS_ONLINE;
   __section_mark_present(ms, section_nr);
  }
}
}

/*
* 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;

#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_or_panic(size, align);
}
#endif

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();
}

#ifdef CONFIG_MEMORY_HOTREMOVE
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
}

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 = MEMBLOCK_ALLOC_ACCESSIBLE;
  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
unsigned long __init section_map_size(void)
{
return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
}

#else
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)
{
}

static void *sparse_usagebuf __meminitdata;
static void *sparse_usagebuf_end __meminitdata;

/*
* Helper function that is used for generic section initialization, and
* can also be used by any hooks added above.
*/
void __init sparse_init_early_section(int nid, struct page *map,
          unsigned long pnum, unsigned long flags)
{
BUG_ON(!sparse_usagebuf || sparse_usagebuf >= sparse_usagebuf_end);
check_usemap_section_nr(nid, sparse_usagebuf);
sparse_init_one_section(__nr_to_section(pnum), pnum, map,
   sparse_usagebuf, SECTION_IS_EARLY | flags);
sparse_usagebuf = (void *)sparse_usagebuf + mem_section_usage_size();
}

static int __init sparse_usage_init(int nid, unsigned long map_count)
{
unsigned long size;

size = mem_section_usage_size() * map_count;
sparse_usagebuf = sparse_early_usemaps_alloc_pgdat_section(
    NODE_DATA(nid), size);
if (!sparse_usagebuf) {
  sparse_usagebuf_end = NULL;
  return -ENOMEM;
}

sparse_usagebuf_end = sparse_usagebuf + size;
return 0;
}

static void __init sparse_usage_fini(void)
{
sparse_usagebuf = sparse_usagebuf_end = NULL;
}

/*
* 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)
{
unsigned long pnum;
struct page *map;
struct mem_section *ms;

if (sparse_usage_init(nid, map_count)) {
  pr_err("%s: node[%d] usemap allocation failed", __func__, nid);
  goto failed;
}

sparse_buffer_init(map_count * section_map_size(), nid);

sparse_vmemmap_init_nid_early(nid);

for_each_present_section_nr(pnum_begin, pnum) {
  unsigned long pfn = section_nr_to_pfn(pnum);

  if (pnum >= pnum_end)
   break;

  ms = __nr_to_section(pnum);
  if (!preinited_vmemmap_section(ms)) {
   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_usage_fini();
    sparse_buffer_fini();
    goto failed;
   }
   memmap_boot_pages_add(DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page),
          PAGE_SIZE));
   sparse_init_early_section(nid, map, pnum, 0);
  }
}
sparse_usage_fini();
sparse_buffer_fini();
return;
failed:
/*
* We failed to allocate, mark all the following pnums as not present,
* except the ones already initialized earlier.
*/
for_each_present_section_nr(pnum_begin, pnum) {
  if (pnum >= pnum_end)
   break;
  ms = __nr_to_section(pnum);
  if (!preinited_vmemmap_section(ms))
   ms->section_mem_map = 0;
  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;

/* see include/linux/mmzone.h 'struct mem_section' definition */
BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section)));
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
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 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 type, 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++) {
  type = bootmem_type(page);

  BUG_ON(type == NODE_INFO);

  maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
  removing_section_nr = bootmem_info(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) {
  memmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)));
  depopulate_section_memmap(pfn, nr_pages, altmap);
} else if (memmap) {
  memmap_boot_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page),
         PAGE_SIZE)));
  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);
  return ERR_PTR(-ENOMEM);
}
memmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));

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.
*/
if (!altmap || !altmap->inaccessible)
  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(unsigned long pfn, unsigned long nr_pages,
      struct vmem_altmap *altmap)
{
struct mem_section *ms = __pfn_to_section(pfn);

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

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

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