[linux.git] / mm / page_ext.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>

/*
 * 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.
 */

static struct page_ext_operations *page_ext_ops[] = {
#ifdef CONFIG_PAGE_OWNER
	&page_owner_ops,
#endif
#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
	&page_idle_ops,
#endif
};

unsigned long page_ext_size = sizeof(struct page_ext);

static unsigned long total_usage;

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 && 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();
	}
}

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

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

#ifndef CONFIG_SPARSEMEM


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

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

	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;
	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_FLAT_NODE_MEM_MAP */

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);
	/*
	 * 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 (!section->page_ext)
		return NULL;
	return get_entry(section->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);
		return addr;
	}

	addr = vzalloc_node(size, nid);

	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;
}
#ifdef CONFIG_MEMORY_HOTPLUG
static void free_page_ext(void *addr)
{
	if (is_vmalloc_addr(addr)) {
		vfree(addr);
	} else {
		struct page *page = virt_to_page(addr);
		size_t table_size;

		table_size = page_ext_size * PAGES_PER_SECTION;

		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 = get_entry(ms->page_ext, pfn);
	free_page_ext(base);
	ms->page_ext = NULL;
}

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

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

	if (nid == NUMA_NO_NODE) {
		/*
		 * In this case, "nid" already exists and contains valid memory.
		 * "start_pfn" passed to us is a pfn which is an arg for
		 * online__pages(), and start_pfn should exist.
		 */
		nid = pfn_to_nid(start_pfn);
		VM_BUG_ON(!node_state(nid, N_ONLINE));
	}

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

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

	return -ENOMEM;
}

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

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

	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
		__free_page_ext(pfn);
	return 0;

}

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, mn->status_change_nid);
		break;
	case MEM_OFFLINE:
		offline_page_ext(mn->start_pfn,
				mn->nr_pages, mn->status_change_nid);
		break;
	case MEM_CANCEL_ONLINE:
		offline_page_ext(mn->start_pfn,
				mn->nr_pages, mn->status_change_nid);
		break;
	case MEM_GOING_OFFLINE:
		break;
	case MEM_ONLINE:
	case MEM_CANCEL_OFFLINE:
		break;
	}

	return notifier_from_errno(ret);
}

#endif

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, 0);
	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
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
eefa864b JK	2	#include <linux/mm.h>
eefa864b JK	3	#include <linux/mmzone.h>
57c8a661	4	#include <linux/memblock.h>
eefa864b JK	5	#include <linux/page_ext.h>
	6	#include <linux/memory.h>
	7	#include <linux/vmalloc.h>
	8	#include <linux/kmemleak.h>
48c96a36	9	#include <linux/page_owner.h>
33c3fc71	10	#include <linux/page_idle.h>
eefa864b JK	11
	12	/*
	13	* struct page extension
	14	*
	15	* This is the feature to manage memory for extended data per page.
	16	*
	17	* Until now, we must modify struct page itself to store extra data per page.
	18	* This requires rebuilding the kernel and it is really time consuming process.
	19	* And, sometimes, rebuild is impossible due to third party module dependency.
	20	* At last, enlarging struct page could cause un-wanted system behaviour change.
	21	*
	22	* This feature is intended to overcome above mentioned problems. This feature
	23	* allocates memory for extended data per page in certain place rather than
	24	* the struct page itself. This memory can be accessed by the accessor
	25	* functions provided by this code. During the boot process, it checks whether
	26	* allocation of huge chunk of memory is needed or not. If not, it avoids
	27	* allocating memory at all. With this advantage, we can include this feature
	28	* into the kernel in default and can avoid rebuild and solve related problems.
	29	*
	30	* To help these things to work well, there are two callbacks for clients. One
	31	* is the need callback which is mandatory if user wants to avoid useless
	32	* memory allocation at boot-time. The other is optional, init callback, which
	33	* is used to do proper initialization after memory is allocated.
	34	*
	35	* The need callback is used to decide whether extended memory allocation is
	36	* needed or not. Sometimes users want to deactivate some features in this
8958b249	37	* boot and extra memory would be unnecessary. In this case, to avoid
eefa864b JK	38	* allocating huge chunk of memory, each clients represent their need of
	39	* extra memory through the need callback. If one of the need callbacks
	40	* returns true, it means that someone needs extra memory so that
	41	* page extension core should allocates memory for page extension. If
	42	* none of need callbacks return true, memory isn't needed at all in this boot
	43	* and page extension core can skip to allocate memory. As result,
	44	* none of memory is wasted.
	45	*
980ac167 JK	46	* When need callback returns true, page_ext checks if there is a request for
	47	* extra memory through size in struct page_ext_operations. If it is non-zero,
	48	* extra space is allocated for each page_ext entry and offset is returned to
	49	* user through offset in struct page_ext_operations.
	50	*
eefa864b JK	51	* The init callback is used to do proper initialization after page extension
	52	* is completely initialized. In sparse memory system, extra memory is
	53	* allocated some time later than memmap is allocated. In other words, lifetime
	54	* of memory for page extension isn't same with memmap for struct page.
	55	* Therefore, clients can't store extra data until page extension is
	56	* initialized, even if pages are allocated and used freely. This could
	57	* cause inadequate state of extra data per page, so, to prevent it, client
	58	* can utilize this callback to initialize the state of it correctly.
	59	*/
	60
	61	static struct page_ext_operations *page_ext_ops[] = {
48c96a36 JK	62	#ifdef CONFIG_PAGE_OWNER
	63	&page_owner_ops,
	64	#endif
33c3fc71 VD	65	#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
	66	&page_idle_ops,
	67	#endif
eefa864b JK	68	};
eefa864b JK	69
5556cfe8 VB	70	unsigned long page_ext_size = sizeof(struct page_ext);
5556cfe8 VB	71
eefa864b JK	72	static unsigned long total_usage;
	73
	74	static bool __init invoke_need_callbacks(void)
	75	{
	76	int i;
	77	int entries = ARRAY_SIZE(page_ext_ops);
980ac167	78	bool need = false;
eefa864b JK	79
eefa864b JK	80	for (i = 0; i < entries; i++) {
980ac167	81	if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
5556cfe8 VB	82	page_ext_ops[i]->offset = page_ext_size;
5556cfe8 VB	83	page_ext_size += page_ext_ops[i]->size;
980ac167 JK	84	need = true;
980ac167 JK	85	}
eefa864b JK	86	}
eefa864b JK	87
980ac167	88	return need;
eefa864b JK	89	}
	90
	91	static void __init invoke_init_callbacks(void)
	92	{
	93	int i;
	94	int entries = ARRAY_SIZE(page_ext_ops);
	95
	96	for (i = 0; i < entries; i++) {
	97	if (page_ext_ops[i]->init)
	98	page_ext_ops[i]->init();
	99	}
	100	}
	101
7fb7ab6d ZH	102	#ifndef CONFIG_SPARSEMEM
	103	void __init page_ext_init_flatmem_late(void)
	104	{
	105	invoke_init_callbacks();
	106	}
	107	#endif
	108
980ac167 JK	109	static inline struct page_ext get_entry(void base, unsigned long index)
980ac167 JK	110	{
5556cfe8	111	return base + page_ext_size * index;
980ac167 JK	112	}
980ac167 JK	113
7fb7ab6d	114	#ifndef CONFIG_SPARSEMEM
eefa864b JK	115
	116
	117	void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
	118	{
	119	pgdat->node_page_ext = NULL;
	120	}
	121
10ed6341	122	struct page_ext lookup_page_ext(const struct page page)
eefa864b JK	123	{
eefa864b JK	124	unsigned long pfn = page_to_pfn(page);
0b06bb3f	125	unsigned long index;
eefa864b JK	126	struct page_ext *base;
	127
	128	base = NODE_DATA(page_to_nid(page))->node_page_ext;
eefa864b JK	129	/*
	130	* The sanity checks the page allocator does upon freeing a
	131	* page can reach here before the page_ext arrays are
	132	* allocated when feeding a range of pages to the allocator
	133	* for the first time during bootup or memory hotplug.
	134	*/
	135	if (unlikely(!base))
	136	return NULL;
0b06bb3f	137	index = pfn - round_down(node_start_pfn(page_to_nid(page)),
eefa864b	138	MAX_ORDER_NR_PAGES);
980ac167	139	return get_entry(base, index);
eefa864b JK	140	}
	141
	142	static int __init alloc_node_page_ext(int nid)
	143	{
	144	struct page_ext *base;
	145	unsigned long table_size;
	146	unsigned long nr_pages;
	147
	148	nr_pages = NODE_DATA(nid)->node_spanned_pages;
	149	if (!nr_pages)
	150	return 0;
	151
	152	/*
	153	* Need extra space if node range is not aligned with
	154	* MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
	155	* checks buddy's status, range could be out of exact node range.
	156	*/
	157	if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) \|\|
	158	!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
	159	nr_pages += MAX_ORDER_NR_PAGES;
	160
5556cfe8	161	table_size = page_ext_size * nr_pages;
eefa864b	162
26fb3dae	163	base = memblock_alloc_try_nid(
eefa864b	164	table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
97ad1087	165	MEMBLOCK_ALLOC_ACCESSIBLE, nid);
eefa864b JK	166	if (!base)
	167	return -ENOMEM;
	168	NODE_DATA(nid)->node_page_ext = base;
	169	total_usage += table_size;
	170	return 0;
	171	}
	172
	173	void __init page_ext_init_flatmem(void)
	174	{
	175
	176	int nid, fail;
	177
	178	if (!invoke_need_callbacks())
	179	return;
	180
	181	for_each_online_node(nid) {
	182	fail = alloc_node_page_ext(nid);
	183	if (fail)
	184	goto fail;
	185	}
	186	pr_info("allocated %ld bytes of page_ext\n", total_usage);
eefa864b JK	187	return;
	188
	189	fail:
	190	pr_crit("allocation of page_ext failed.\n");
	191	panic("Out of memory");
	192	}
	193
	194	#else /* CONFIG_FLAT_NODE_MEM_MAP */
	195
10ed6341	196	struct page_ext lookup_page_ext(const struct page page)
eefa864b JK	197	{
	198	unsigned long pfn = page_to_pfn(page);
	199	struct mem_section *section = __pfn_to_section(pfn);
eefa864b JK	200	/*
	201	* The sanity checks the page allocator does upon freeing a
	202	* page can reach here before the page_ext arrays are
	203	* allocated when feeding a range of pages to the allocator
	204	* for the first time during bootup or memory hotplug.
	205	*/
	206	if (!section->page_ext)
	207	return NULL;
980ac167	208	return get_entry(section->page_ext, pfn);
eefa864b JK	209	}
	210
	211	static void *__meminit alloc_page_ext(size_t size, int nid)
	212	{
	213	gfp_t flags = GFP_KERNEL \| __GFP_ZERO \| __GFP_NOWARN;
	214	void *addr = NULL;
	215
	216	addr = alloc_pages_exact_nid(nid, size, flags);
	217	if (addr) {
	218	kmemleak_alloc(addr, size, 1, flags);
	219	return addr;
	220	}
	221
b95046b0	222	addr = vzalloc_node(size, nid);
eefa864b JK	223
	224	return addr;
	225	}
	226
	227	static int __meminit init_section_page_ext(unsigned long pfn, int nid)
	228	{
	229	struct mem_section *section;
	230	struct page_ext *base;
	231	unsigned long table_size;
	232
	233	section = __pfn_to_section(pfn);
	234
	235	if (section->page_ext)
	236	return 0;
	237
5556cfe8	238	table_size = page_ext_size * PAGES_PER_SECTION;
eefa864b JK	239	base = alloc_page_ext(table_size, nid);
	240
	241	/*
	242	* The value stored in section->page_ext is (base - pfn)
	243	* and it does not point to the memory block allocated above,
	244	* causing kmemleak false positives.
	245	*/
	246	kmemleak_not_leak(base);
	247
	248	if (!base) {
	249	pr_err("page ext allocation failure\n");
	250	return -ENOMEM;
	251	}
	252
	253	/*
	254	* The passed "pfn" may not be aligned to SECTION. For the calculation
	255	* we need to apply a mask.
	256	*/
	257	pfn &= PAGE_SECTION_MASK;
5556cfe8	258	section->page_ext = (void )base - page_ext_size pfn;
eefa864b JK	259	total_usage += table_size;
	260	return 0;
	261	}
	262	#ifdef CONFIG_MEMORY_HOTPLUG
	263	static void free_page_ext(void *addr)
	264	{
	265	if (is_vmalloc_addr(addr)) {
	266	vfree(addr);
	267	} else {
	268	struct page *page = virt_to_page(addr);
	269	size_t table_size;
	270
5556cfe8	271	table_size = page_ext_size * PAGES_PER_SECTION;
eefa864b JK	272
eefa864b JK	273	BUG_ON(PageReserved(page));
0c815854	274	kmemleak_free(addr);
eefa864b JK	275	free_pages_exact(addr, table_size);
	276	}
	277	}
	278
	279	static void __free_page_ext(unsigned long pfn)
	280	{
	281	struct mem_section *ms;
	282	struct page_ext *base;
	283
	284	ms = __pfn_to_section(pfn);
	285	if (!ms \|\| !ms->page_ext)
	286	return;
980ac167	287	base = get_entry(ms->page_ext, pfn);
eefa864b JK	288	free_page_ext(base);
	289	ms->page_ext = NULL;
	290	}
	291
	292	static int __meminit online_page_ext(unsigned long start_pfn,
	293	unsigned long nr_pages,
	294	int nid)
	295	{
	296	unsigned long start, end, pfn;
	297	int fail = 0;
	298
	299	start = SECTION_ALIGN_DOWN(start_pfn);
	300	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
	301
98fa15f3	302	if (nid == NUMA_NO_NODE) {
eefa864b JK	303	/*
	304	* In this case, "nid" already exists and contains valid memory.
	305	* "start_pfn" passed to us is a pfn which is an arg for
	306	* online__pages(), and start_pfn should exist.
	307	*/
	308	nid = pfn_to_nid(start_pfn);
	309	VM_BUG_ON(!node_state(nid, N_ONLINE));
	310	}
	311
dccacf8d	312	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
eefa864b	313	fail = init_section_page_ext(pfn, nid);
eefa864b JK	314	if (!fail)
	315	return 0;
	316
	317	/* rollback */
	318	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
	319	__free_page_ext(pfn);
	320
	321	return -ENOMEM;
	322	}
	323
	324	static int __meminit offline_page_ext(unsigned long start_pfn,
	325	unsigned long nr_pages, int nid)
	326	{
	327	unsigned long start, end, pfn;
	328
	329	start = SECTION_ALIGN_DOWN(start_pfn);
	330	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
	331
	332	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
	333	__free_page_ext(pfn);
	334	return 0;
	335
	336	}
	337
	338	static int __meminit page_ext_callback(struct notifier_block *self,
	339	unsigned long action, void *arg)
	340	{
	341	struct memory_notify *mn = arg;
	342	int ret = 0;
	343
	344	switch (action) {
	345	case MEM_GOING_ONLINE:
	346	ret = online_page_ext(mn->start_pfn,
	347	mn->nr_pages, mn->status_change_nid);
	348	break;
	349	case MEM_OFFLINE:
	350	offline_page_ext(mn->start_pfn,
	351	mn->nr_pages, mn->status_change_nid);
	352	break;
	353	case MEM_CANCEL_ONLINE:
	354	offline_page_ext(mn->start_pfn,
	355	mn->nr_pages, mn->status_change_nid);
	356	break;
	357	case MEM_GOING_OFFLINE:
	358	break;
	359	case MEM_ONLINE:
	360	case MEM_CANCEL_OFFLINE:
	361	break;
	362	}
	363
	364	return notifier_from_errno(ret);
	365	}
	366
	367	#endif
	368
	369	void __init page_ext_init(void)
	370	{
	371	unsigned long pfn;
	372	int nid;
	373
	374	if (!invoke_need_callbacks())
	375	return;
	376
	377	for_each_node_state(nid, N_MEMORY) {
378	unsigned long start_pfn, end_pfn;
379
380	start_pfn = node_start_pfn(nid);
381	end_pfn = node_end_pfn(nid);
382	/*
383	* start_pfn and end_pfn may not be aligned to SECTION and the
384	* page->flags of out of node pages are not initialized. So we
385	* scan [start_pfn, the biggest section's pfn < end_pfn) here.
386	*/
387	for (pfn = start_pfn; pfn < end_pfn;
388	pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
389
390	if (!pfn_valid(pfn))
391	continue;
392	/*
393	* Nodes's pfns can be overlapping.
394	* We know some arch can have a nodes layout such as
395	* -------------pfn-------------->
396	* N0 \| N1 \| N2 \| N0 \| N1 \| N2\|....
397	*/
2f1ee091	398	if (pfn_to_nid(pfn) != nid)
eefa864b JK	399	continue;
	400	if (init_section_page_ext(pfn, nid))
	401	goto oom;
0fc542b7	402	cond_resched();
eefa864b JK	403	}
	404	}
	405	hotplug_memory_notifier(page_ext_callback, 0);
	406	pr_info("allocated %ld bytes of page_ext\n", total_usage);
	407	invoke_init_callbacks();
	408	return;
	409
	410	oom:
	411	panic("Out of memory");
	412	}
	413
	414	void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
	415	{
	416	}
	417
	418	#endif