Quelle page_ext.c Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/memblock.h>
#include <linux/page_ext.h>
#include <linux/memory.h>
#include <linux/vmalloc.h>
#include <linux/kmemleak.h>
#include <linux/page_owner.h>
#include <linux/page_idle.h>
#include <linux/page_table_check.h>
#include <linux/rcupdate.h>
#include <linux/pgalloc_tag.h>

/*
* struct page extension
*
* This is the feature to manage memory for extended data per page.
*
* Until now, we must modify struct page itself to store extra data per page.
* This requires rebuilding the kernel and it is really time consuming process.
* And, sometimes, rebuild is impossible due to third party module dependency.
* At last, enlarging struct page could cause un-wanted system behaviour change.
*
* This feature is intended to overcome above mentioned problems. This feature
* allocates memory for extended data per page in certain place rather than
* the struct page itself. This memory can be accessed by the accessor
* functions provided by this code. During the boot process, it checks whether
* allocation of huge chunk of memory is needed or not. If not, it avoids
* allocating memory at all. With this advantage, we can include this feature
* into the kernel in default and can avoid rebuild and solve related problems.
*
* To help these things to work well, there are two callbacks for clients. One
* is the need callback which is mandatory if user wants to avoid useless
* memory allocation at boot-time. The other is optional, init callback, which
* is used to do proper initialization after memory is allocated.
*
* The need callback is used to decide whether extended memory allocation is
* needed or not. Sometimes users want to deactivate some features in this
* boot and extra memory would be unnecessary. In this case, to avoid
* allocating huge chunk of memory, each clients represent their need of
* extra memory through the need callback. If one of the need callbacks
* returns true, it means that someone needs extra memory so that
* page extension core should allocates memory for page extension. If
* none of need callbacks return true, memory isn't needed at all in this boot
* and page extension core can skip to allocate memory. As result,
* none of memory is wasted.
*
* When need callback returns true, page_ext checks if there is a request for
* extra memory through size in struct page_ext_operations. If it is non-zero,
* extra space is allocated for each page_ext entry and offset is returned to
* user through offset in struct page_ext_operations.
*
* The init callback is used to do proper initialization after page extension
* is completely initialized. In sparse memory system, extra memory is
* allocated some time later than memmap is allocated. In other words, lifetime
* of memory for page extension isn't same with memmap for struct page.
* Therefore, clients can't store extra data until page extension is
* initialized, even if pages are allocated and used freely. This could
* cause inadequate state of extra data per page, so, to prevent it, client
* can utilize this callback to initialize the state of it correctly.
*/

#ifdef CONFIG_SPARSEMEM
#define PAGE_EXT_INVALID       (0x1)
#endif

#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
static bool need_page_idle(void)
{
return true;
}
static struct page_ext_operations page_idle_ops __initdata = {
.need = need_page_idle,
.need_shared_flags = true,
};
#endif

static struct page_ext_operations *page_ext_ops[] __initdata = {
#ifdef CONFIG_PAGE_OWNER
&page_owner_ops,
#endif
#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
&page_idle_ops,
#endif
#ifdef CONFIG_MEM_ALLOC_PROFILING
&page_alloc_tagging_ops,
#endif
#ifdef CONFIG_PAGE_TABLE_CHECK
&page_table_check_ops,
#endif
};

unsigned long page_ext_size;

static unsigned long total_usage;

#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
/*
* To ensure correct allocation tagging for pages, page_ext should be available
* before the first page allocation. Otherwise early task stacks will be
* allocated before page_ext initialization and missing tags will be flagged.
*/
bool early_page_ext __meminitdata = true;
#else
bool early_page_ext __meminitdata;
#endif
static int __init setup_early_page_ext(char *str)
{
early_page_ext = true;
return 0;
}
early_param("early_page_ext", setup_early_page_ext);

static bool __init invoke_need_callbacks(void)
{
int i;
int entries = ARRAY_SIZE(page_ext_ops);
bool need = false;

for (i = 0; i < entries; i++) {
  if (page_ext_ops[i]->need()) {
   if (page_ext_ops[i]->need_shared_flags) {
    page_ext_size = sizeof(struct page_ext);
    break;
   }
  }
}

for (i = 0; i < entries; i++) {
  if (page_ext_ops[i]->need()) {
   page_ext_ops[i]->offset = page_ext_size;
   page_ext_size += page_ext_ops[i]->size;
   need = true;
  }
}

return need;
}

static void __init invoke_init_callbacks(void)
{
int i;
int entries = ARRAY_SIZE(page_ext_ops);

for (i = 0; i < entries; i++) {
  if (page_ext_ops[i]->init)
   page_ext_ops[i]->init();
}
}

static inline struct page_ext *get_entry(void *base, unsigned long index)
{
return base + page_ext_size * index;
}

#ifndef CONFIG_SPARSEMEM
void __init page_ext_init_flatmem_late(void)
{
invoke_init_callbacks();
}

void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
{
pgdat->node_page_ext = NULL;
}

static struct page_ext *lookup_page_ext(const struct page *page)
{
unsigned long pfn = page_to_pfn(page);
unsigned long index;
struct page_ext *base;

WARN_ON_ONCE(!rcu_read_lock_held());
base = NODE_DATA(page_to_nid(page))->node_page_ext;
/*
* The sanity checks the page allocator does upon freeing a
* page can reach here before the page_ext arrays are
* allocated when feeding a range of pages to the allocator
* for the first time during bootup or memory hotplug.
*/
if (unlikely(!base))
  return NULL;
index = pfn - round_down(node_start_pfn(page_to_nid(page)),
     MAX_ORDER_NR_PAGES);
return get_entry(base, index);
}

static int __init alloc_node_page_ext(int nid)
{
struct page_ext *base;
unsigned long table_size;
unsigned long nr_pages;

nr_pages = NODE_DATA(nid)->node_spanned_pages;
if (!nr_pages)
  return 0;

/*
* Need extra space if node range is not aligned with
* MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
* checks buddy's status, range could be out of exact node range.
*/
if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
  !IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
  nr_pages += MAX_ORDER_NR_PAGES;

table_size = page_ext_size * nr_pages;

base = memblock_alloc_try_nid(
   table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
   MEMBLOCK_ALLOC_ACCESSIBLE, nid);
if (!base)
  return -ENOMEM;
NODE_DATA(nid)->node_page_ext = base;
total_usage += table_size;
memmap_boot_pages_add(DIV_ROUND_UP(table_size, PAGE_SIZE));
return 0;
}

void __init page_ext_init_flatmem(void)
{

int nid, fail;

if (!invoke_need_callbacks())
  return;

for_each_online_node(nid)  {
  fail = alloc_node_page_ext(nid);
  if (fail)
   goto fail;
}
pr_info("allocated %ld bytes of page_ext\n", total_usage);
return;

fail:
pr_crit("allocation of page_ext failed.\n");
panic("Out of memory");
}

#else /* CONFIG_SPARSEMEM */
static bool page_ext_invalid(struct page_ext *page_ext)
{
return !page_ext || (((unsigned long)page_ext & PAGE_EXT_INVALID) == PAGE_EXT_INVALID);
}

static struct page_ext *lookup_page_ext(const struct page *page)
{
unsigned long pfn = page_to_pfn(page);
struct mem_section *section = __pfn_to_section(pfn);
struct page_ext *page_ext = READ_ONCE(section->page_ext);

WARN_ON_ONCE(!rcu_read_lock_held());
/*
* The sanity checks the page allocator does upon freeing a
* page can reach here before the page_ext arrays are
* allocated when feeding a range of pages to the allocator
* for the first time during bootup or memory hotplug.
*/
if (page_ext_invalid(page_ext))
  return NULL;
return get_entry(page_ext, pfn);
}

static void *__meminit alloc_page_ext(size_t size, int nid)
{
gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
void *addr = NULL;

addr = alloc_pages_exact_nid(nid, size, flags);
if (addr)
  kmemleak_alloc(addr, size, 1, flags);
else
  addr = vzalloc_node(size, nid);

if (addr)
  memmap_pages_add(DIV_ROUND_UP(size, PAGE_SIZE));

return addr;
}

static int __meminit init_section_page_ext(unsigned long pfn, int nid)
{
struct mem_section *section;
struct page_ext *base;
unsigned long table_size;

section = __pfn_to_section(pfn);

if (section->page_ext)
  return 0;

table_size = page_ext_size * PAGES_PER_SECTION;
base = alloc_page_ext(table_size, nid);

/*
* The value stored in section->page_ext is (base - pfn)
* and it does not point to the memory block allocated above,
* causing kmemleak false positives.
*/
kmemleak_not_leak(base);

if (!base) {
  pr_err("page ext allocation failure\n");
  return -ENOMEM;
}

/*
* The passed "pfn" may not be aligned to SECTION.  For the calculation
* we need to apply a mask.
*/
pfn &= PAGE_SECTION_MASK;
section->page_ext = (void *)base - page_ext_size * pfn;
total_usage += table_size;
return 0;
}

static void free_page_ext(void *addr)
{
size_t table_size;
struct page *page;

table_size = page_ext_size * PAGES_PER_SECTION;
memmap_pages_add(-1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));

if (is_vmalloc_addr(addr)) {
  vfree(addr);
} else {
  page = virt_to_page(addr);
  BUG_ON(PageReserved(page));
  kmemleak_free(addr);
  free_pages_exact(addr, table_size);
}
}

static void __free_page_ext(unsigned long pfn)
{
struct mem_section *ms;
struct page_ext *base;

ms = __pfn_to_section(pfn);
if (!ms || !ms->page_ext)
  return;

base = READ_ONCE(ms->page_ext);
/*
* page_ext here can be valid while doing the roll back
* operation in online_page_ext().
*/
if (page_ext_invalid(base))
  base = (void *)base - PAGE_EXT_INVALID;
WRITE_ONCE(ms->page_ext, NULL);

base = get_entry(base, pfn);
free_page_ext(base);
}

static void __invalidate_page_ext(unsigned long pfn)
{
struct mem_section *ms;
void *val;

ms = __pfn_to_section(pfn);
if (!ms || !ms->page_ext)
  return;
val = (void *)ms->page_ext + PAGE_EXT_INVALID;
WRITE_ONCE(ms->page_ext, val);
}

static int __meminit online_page_ext(unsigned long start_pfn,
    unsigned long nr_pages)
{
int nid = pfn_to_nid(start_pfn);
unsigned long start, end, pfn;
int fail = 0;

start = SECTION_ALIGN_DOWN(start_pfn);
end = SECTION_ALIGN_UP(start_pfn + nr_pages);

for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
  fail = init_section_page_ext(pfn, nid);
if (!fail)
  return 0;

/* rollback */
end = pfn - PAGES_PER_SECTION;
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
  __free_page_ext(pfn);

return -ENOMEM;
}

static void __meminit offline_page_ext(unsigned long start_pfn,
    unsigned long nr_pages)
{
unsigned long start, end, pfn;

start = SECTION_ALIGN_DOWN(start_pfn);
end = SECTION_ALIGN_UP(start_pfn + nr_pages);

/*
* Freeing of page_ext is done in 3 steps to avoid
* use-after-free of it:
* 1) Traverse all the sections and mark their page_ext
*    as invalid.
* 2) Wait for all the existing users of page_ext who
*    started before invalidation to finish.
* 3) Free the page_ext.
*/
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
  __invalidate_page_ext(pfn);

synchronize_rcu();

for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
  __free_page_ext(pfn);
}

static int __meminit page_ext_callback(struct notifier_block *self,
          unsigned long action, void *arg)
{
struct memory_notify *mn = arg;
int ret = 0;

switch (action) {
case MEM_GOING_ONLINE:
  ret = online_page_ext(mn->start_pfn, mn->nr_pages);
  break;
case MEM_OFFLINE:
  offline_page_ext(mn->start_pfn,
    mn->nr_pages);
  break;
case MEM_CANCEL_ONLINE:
  offline_page_ext(mn->start_pfn,
    mn->nr_pages);
  break;
case MEM_GOING_OFFLINE:
  break;
case MEM_ONLINE:
case MEM_CANCEL_OFFLINE:
  break;
}

return notifier_from_errno(ret);
}

void __init page_ext_init(void)
{
unsigned long pfn;
int nid;

if (!invoke_need_callbacks())
  return;

for_each_node_state(nid, N_MEMORY) {
  unsigned long start_pfn, end_pfn;

  start_pfn = node_start_pfn(nid);
  end_pfn = node_end_pfn(nid);
  /*
* start_pfn and end_pfn may not be aligned to SECTION and the
* page->flags of out of node pages are not initialized.  So we
* scan [start_pfn, the biggest section's pfn < end_pfn) here.
*/
  for (pfn = start_pfn; pfn < end_pfn;
   pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {

   if (!pfn_valid(pfn))
    continue;
   /*
* Nodes's pfns can be overlapping.
* We know some arch can have a nodes layout such as
* -------------pfn-------------->
* N0 | N1 | N2 | N0 | N1 | N2|....
*/
   if (pfn_to_nid(pfn) != nid)
    continue;
   if (init_section_page_ext(pfn, nid))
    goto oom;
   cond_resched();
  }
}
hotplug_memory_notifier(page_ext_callback, DEFAULT_CALLBACK_PRI);
pr_info("allocated %ld bytes of page_ext\n", total_usage);
invoke_init_callbacks();
return;

oom:
panic("Out of memory");
}

void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
{
}

#endif

/**
* page_ext_lookup() - Lookup a page extension for a PFN.
* @pfn: PFN of the page we're interested in.
*
* Must be called with RCU read lock taken and @pfn must be valid.
*
* Return: NULL if no page_ext exists for this page.
*/
struct page_ext *page_ext_lookup(unsigned long pfn)
{
return lookup_page_ext(pfn_to_page(pfn));
}

/**
* page_ext_get() - Get the extended information for a page.
* @page: The page we're interested in.
*
* Ensures that the page_ext will remain valid until page_ext_put()
* is called.
*
* Return: NULL if no page_ext exists for this page.
* Context: Any context.  Caller may not sleep until they have called
* page_ext_put().
*/
struct page_ext *page_ext_get(const struct page *page)
{
struct page_ext *page_ext;

rcu_read_lock();
page_ext = lookup_page_ext(page);
if (!page_ext) {
  rcu_read_unlock();
  return NULL;
}

return page_ext;
}

/**
* page_ext_put() - Working with page extended information is done.
* @page_ext: Page extended information received from page_ext_get().
*
* The page extended information of the page may not be valid after this
* function is called.
*
* Return: None.
* Context: Any context with corresponding page_ext_get() is called.
*/
void page_ext_put(struct page_ext *page_ext)
{
if (unlikely(!page_ext))
  return;

rcu_read_unlock();
}

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