1// SPDX-License-Identifier: GPL-2.0
2#include <linux/mm.h>
3#include <linux/mmzone.h>
4#include <linux/memblock.h>
5#include <linux/page_ext.h>
6#include <linux/memory.h>
7#include <linux/vmalloc.h>
8#include <linux/kmemleak.h>
9#include <linux/page_owner.h>
10#include <linux/page_idle.h>
11#include <linux/page_table_check.h>
12#include <linux/rcupdate.h>
13
14/*
15 * struct page extension
16 *
17 * This is the feature to manage memory for extended data per page.
18 *
19 * Until now, we must modify struct page itself to store extra data per page.
20 * This requires rebuilding the kernel and it is really time consuming process.
21 * And, sometimes, rebuild is impossible due to third party module dependency.
22 * At last, enlarging struct page could cause un-wanted system behaviour change.
23 *
24 * This feature is intended to overcome above mentioned problems. This feature
25 * allocates memory for extended data per page in certain place rather than
26 * the struct page itself. This memory can be accessed by the accessor
27 * functions provided by this code. During the boot process, it checks whether
28 * allocation of huge chunk of memory is needed or not. If not, it avoids
29 * allocating memory at all. With this advantage, we can include this feature
30 * into the kernel in default and can avoid rebuild and solve related problems.
31 *
32 * To help these things to work well, there are two callbacks for clients. One
33 * is the need callback which is mandatory if user wants to avoid useless
34 * memory allocation at boot-time. The other is optional, init callback, which
35 * is used to do proper initialization after memory is allocated.
36 *
37 * The need callback is used to decide whether extended memory allocation is
38 * needed or not. Sometimes users want to deactivate some features in this
39 * boot and extra memory would be unnecessary. In this case, to avoid
40 * allocating huge chunk of memory, each clients represent their need of
41 * extra memory through the need callback. If one of the need callbacks
42 * returns true, it means that someone needs extra memory so that
43 * page extension core should allocates memory for page extension. If
44 * none of need callbacks return true, memory isn't needed at all in this boot
45 * and page extension core can skip to allocate memory. As result,
46 * none of memory is wasted.
47 *
48 * When need callback returns true, page_ext checks if there is a request for
49 * extra memory through size in struct page_ext_operations. If it is non-zero,
50 * extra space is allocated for each page_ext entry and offset is returned to
51 * user through offset in struct page_ext_operations.
52 *
53 * The init callback is used to do proper initialization after page extension
54 * is completely initialized. In sparse memory system, extra memory is
55 * allocated some time later than memmap is allocated. In other words, lifetime
56 * of memory for page extension isn't same with memmap for struct page.
57 * Therefore, clients can't store extra data until page extension is
58 * initialized, even if pages are allocated and used freely. This could
59 * cause inadequate state of extra data per page, so, to prevent it, client
60 * can utilize this callback to initialize the state of it correctly.
61 */
62
63#ifdef CONFIG_SPARSEMEM
64#define PAGE_EXT_INVALID       (0x1)
65#endif
66
67#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
68static bool need_page_idle(void)
69{
70	return true;
71}
72static struct page_ext_operations page_idle_ops __initdata = {
73	.need = need_page_idle,
74	.need_shared_flags = true,
75};
76#endif
77
78static struct page_ext_operations *page_ext_ops[] __initdata = {
79#ifdef CONFIG_PAGE_OWNER
80	&page_owner_ops,
81#endif
82#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
83	&page_idle_ops,
84#endif
85#ifdef CONFIG_PAGE_TABLE_CHECK
86	&page_table_check_ops,
87#endif
88};
89
90unsigned long page_ext_size;
91
92static unsigned long total_usage;
93
94bool early_page_ext __meminitdata;
95static int __init setup_early_page_ext(char *str)
96{
97	early_page_ext = true;
98	return 0;
99}
100early_param("early_page_ext", setup_early_page_ext);
101
102static bool __init invoke_need_callbacks(void)
103{
104	int i;
105	int entries = ARRAY_SIZE(page_ext_ops);
106	bool need = false;
107
108	for (i = 0; i < entries; i++) {
109		if (page_ext_ops[i]->need()) {
110			if (page_ext_ops[i]->need_shared_flags) {
111				page_ext_size = sizeof(struct page_ext);
112				break;
113			}
114		}
115	}
116
117	for (i = 0; i < entries; i++) {
118		if (page_ext_ops[i]->need()) {
119			page_ext_ops[i]->offset = page_ext_size;
120			page_ext_size += page_ext_ops[i]->size;
121			need = true;
122		}
123	}
124
125	return need;
126}
127
128static void __init invoke_init_callbacks(void)
129{
130	int i;
131	int entries = ARRAY_SIZE(page_ext_ops);
132
133	for (i = 0; i < entries; i++) {
134		if (page_ext_ops[i]->init)
135			page_ext_ops[i]->init();
136	}
137}
138
139static inline struct page_ext *get_entry(void *base, unsigned long index)
140{
141	return base + page_ext_size * index;
142}
143
144#ifndef CONFIG_SPARSEMEM
145void __init page_ext_init_flatmem_late(void)
146{
147	invoke_init_callbacks();
148}
149
150void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
151{
152	pgdat->node_page_ext = NULL;
153}
154
155static struct page_ext *lookup_page_ext(const struct page *page)
156{
157	unsigned long pfn = page_to_pfn(page);
158	unsigned long index;
159	struct page_ext *base;
160
161	WARN_ON_ONCE(!rcu_read_lock_held());
162	base = NODE_DATA(page_to_nid(page))->node_page_ext;
163	/*
164	 * The sanity checks the page allocator does upon freeing a
165	 * page can reach here before the page_ext arrays are
166	 * allocated when feeding a range of pages to the allocator
167	 * for the first time during bootup or memory hotplug.
168	 */
169	if (unlikely(!base))
170		return NULL;
171	index = pfn - round_down(node_start_pfn(page_to_nid(page)),
172					MAX_ORDER_NR_PAGES);
173	return get_entry(base, index);
174}
175
176static int __init alloc_node_page_ext(int nid)
177{
178	struct page_ext *base;
179	unsigned long table_size;
180	unsigned long nr_pages;
181
182	nr_pages = NODE_DATA(nid)->node_spanned_pages;
183	if (!nr_pages)
184		return 0;
185
186	/*
187	 * Need extra space if node range is not aligned with
188	 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
189	 * checks buddy's status, range could be out of exact node range.
190	 */
191	if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
192		!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
193		nr_pages += MAX_ORDER_NR_PAGES;
194
195	table_size = page_ext_size * nr_pages;
196
197	base = memblock_alloc_try_nid(
198			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
199			MEMBLOCK_ALLOC_ACCESSIBLE, nid);
200	if (!base)
201		return -ENOMEM;
202	NODE_DATA(nid)->node_page_ext = base;
203	total_usage += table_size;
204	return 0;
205}
206
207void __init page_ext_init_flatmem(void)
208{
209
210	int nid, fail;
211
212	if (!invoke_need_callbacks())
213		return;
214
215	for_each_online_node(nid)  {
216		fail = alloc_node_page_ext(nid);
217		if (fail)
218			goto fail;
219	}
220	pr_info("allocated %ld bytes of page_ext\n", total_usage);
221	return;
222
223fail:
224	pr_crit("allocation of page_ext failed.\n");
225	panic("Out of memory");
226}
227
228#else /* CONFIG_SPARSEMEM */
229static bool page_ext_invalid(struct page_ext *page_ext)
230{
231	return !page_ext || (((unsigned long)page_ext & PAGE_EXT_INVALID) == PAGE_EXT_INVALID);
232}
233
234static struct page_ext *lookup_page_ext(const struct page *page)
235{
236	unsigned long pfn = page_to_pfn(page);
237	struct mem_section *section = __pfn_to_section(pfn);
238	struct page_ext *page_ext = READ_ONCE(section->page_ext);
239
240	WARN_ON_ONCE(!rcu_read_lock_held());
241	/*
242	 * The sanity checks the page allocator does upon freeing a
243	 * page can reach here before the page_ext arrays are
244	 * allocated when feeding a range of pages to the allocator
245	 * for the first time during bootup or memory hotplug.
246	 */
247	if (page_ext_invalid(page_ext))
248		return NULL;
249	return get_entry(page_ext, pfn);
250}
251
252static void *__meminit alloc_page_ext(size_t size, int nid)
253{
254	gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
255	void *addr = NULL;
256
257	addr = alloc_pages_exact_nid(nid, size, flags);
258	if (addr) {
259		kmemleak_alloc(addr, size, 1, flags);
260		return addr;
261	}
262
263	addr = vzalloc_node(size, nid);
264
265	return addr;
266}
267
268static int __meminit init_section_page_ext(unsigned long pfn, int nid)
269{
270	struct mem_section *section;
271	struct page_ext *base;
272	unsigned long table_size;
273
274	section = __pfn_to_section(pfn);
275
276	if (section->page_ext)
277		return 0;
278
279	table_size = page_ext_size * PAGES_PER_SECTION;
280	base = alloc_page_ext(table_size, nid);
281
282	/*
283	 * The value stored in section->page_ext is (base - pfn)
284	 * and it does not point to the memory block allocated above,
285	 * causing kmemleak false positives.
286	 */
287	kmemleak_not_leak(base);
288
289	if (!base) {
290		pr_err("page ext allocation failure\n");
291		return -ENOMEM;
292	}
293
294	/*
295	 * The passed "pfn" may not be aligned to SECTION.  For the calculation
296	 * we need to apply a mask.
297	 */
298	pfn &= PAGE_SECTION_MASK;
299	section->page_ext = (void *)base - page_ext_size * pfn;
300	total_usage += table_size;
301	return 0;
302}
303
304static void free_page_ext(void *addr)
305{
306	if (is_vmalloc_addr(addr)) {
307		vfree(addr);
308	} else {
309		struct page *page = virt_to_page(addr);
310		size_t table_size;
311
312		table_size = page_ext_size * PAGES_PER_SECTION;
313
314		BUG_ON(PageReserved(page));
315		kmemleak_free(addr);
316		free_pages_exact(addr, table_size);
317	}
318}
319
320static void __free_page_ext(unsigned long pfn)
321{
322	struct mem_section *ms;
323	struct page_ext *base;
324
325	ms = __pfn_to_section(pfn);
326	if (!ms || !ms->page_ext)
327		return;
328
329	base = READ_ONCE(ms->page_ext);
330	/*
331	 * page_ext here can be valid while doing the roll back
332	 * operation in online_page_ext().
333	 */
334	if (page_ext_invalid(base))
335		base = (void *)base - PAGE_EXT_INVALID;
336	WRITE_ONCE(ms->page_ext, NULL);
337
338	base = get_entry(base, pfn);
339	free_page_ext(base);
340}
341
342static void __invalidate_page_ext(unsigned long pfn)
343{
344	struct mem_section *ms;
345	void *val;
346
347	ms = __pfn_to_section(pfn);
348	if (!ms || !ms->page_ext)
349		return;
350	val = (void *)ms->page_ext + PAGE_EXT_INVALID;
351	WRITE_ONCE(ms->page_ext, val);
352}
353
354static int __meminit online_page_ext(unsigned long start_pfn,
355				unsigned long nr_pages,
356				int nid)
357{
358	unsigned long start, end, pfn;
359	int fail = 0;
360
361	start = SECTION_ALIGN_DOWN(start_pfn);
362	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
363
364	if (nid == NUMA_NO_NODE) {
365		/*
366		 * In this case, "nid" already exists and contains valid memory.
367		 * "start_pfn" passed to us is a pfn which is an arg for
368		 * online__pages(), and start_pfn should exist.
369		 */
370		nid = pfn_to_nid(start_pfn);
371		VM_BUG_ON(!node_online(nid));
372	}
373
374	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
375		fail = init_section_page_ext(pfn, nid);
376	if (!fail)
377		return 0;
378
379	/* rollback */
380	end = pfn - PAGES_PER_SECTION;
381	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
382		__free_page_ext(pfn);
383
384	return -ENOMEM;
385}
386
387static void __meminit offline_page_ext(unsigned long start_pfn,
388				unsigned long nr_pages)
389{
390	unsigned long start, end, pfn;
391
392	start = SECTION_ALIGN_DOWN(start_pfn);
393	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
394
395	/*
396	 * Freeing of page_ext is done in 3 steps to avoid
397	 * use-after-free of it:
398	 * 1) Traverse all the sections and mark their page_ext
399	 *    as invalid.
400	 * 2) Wait for all the existing users of page_ext who
401	 *    started before invalidation to finish.
402	 * 3) Free the page_ext.
403	 */
404	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
405		__invalidate_page_ext(pfn);
406
407	synchronize_rcu();
408
409	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
410		__free_page_ext(pfn);
411}
412
413static int __meminit page_ext_callback(struct notifier_block *self,
414			       unsigned long action, void *arg)
415{
416	struct memory_notify *mn = arg;
417	int ret = 0;
418
419	switch (action) {
420	case MEM_GOING_ONLINE:
421		ret = online_page_ext(mn->start_pfn,
422				   mn->nr_pages, mn->status_change_nid);
423		break;
424	case MEM_OFFLINE:
425		offline_page_ext(mn->start_pfn,
426				mn->nr_pages);
427		break;
428	case MEM_CANCEL_ONLINE:
429		offline_page_ext(mn->start_pfn,
430				mn->nr_pages);
431		break;
432	case MEM_GOING_OFFLINE:
433		break;
434	case MEM_ONLINE:
435	case MEM_CANCEL_OFFLINE:
436		break;
437	}
438
439	return notifier_from_errno(ret);
440}
441
442void __init page_ext_init(void)
443{
444	unsigned long pfn;
445	int nid;
446
447	if (!invoke_need_callbacks())
448		return;
449
450	for_each_node_state(nid, N_MEMORY) {
451		unsigned long start_pfn, end_pfn;
452
453		start_pfn = node_start_pfn(nid);
454		end_pfn = node_end_pfn(nid);
455		/*
456		 * start_pfn and end_pfn may not be aligned to SECTION and the
457		 * page->flags of out of node pages are not initialized.  So we
458		 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
459		 */
460		for (pfn = start_pfn; pfn < end_pfn;
461			pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
462
463			if (!pfn_valid(pfn))
464				continue;
465			/*
466			 * Nodes's pfns can be overlapping.
467			 * We know some arch can have a nodes layout such as
468			 * -------------pfn-------------->
469			 * N0 | N1 | N2 | N0 | N1 | N2|....
470			 */
471			if (pfn_to_nid(pfn) != nid)
472				continue;
473			if (init_section_page_ext(pfn, nid))
474				goto oom;
475			cond_resched();
476		}
477	}
478	hotplug_memory_notifier(page_ext_callback, DEFAULT_CALLBACK_PRI);
479	pr_info("allocated %ld bytes of page_ext\n", total_usage);
480	invoke_init_callbacks();
481	return;
482
483oom:
484	panic("Out of memory");
485}
486
487void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
488{
489}
490
491#endif
492
493/**
494 * page_ext_get() - Get the extended information for a page.
495 * @page: The page we're interested in.
496 *
497 * Ensures that the page_ext will remain valid until page_ext_put()
498 * is called.
499 *
500 * Return: NULL if no page_ext exists for this page.
501 * Context: Any context.  Caller may not sleep until they have called
502 * page_ext_put().
503 */
504struct page_ext *page_ext_get(struct page *page)
505{
506	struct page_ext *page_ext;
507
508	rcu_read_lock();
509	page_ext = lookup_page_ext(page);
510	if (!page_ext) {
511		rcu_read_unlock();
512		return NULL;
513	}
514
515	return page_ext;
516}
517
518/**
519 * page_ext_put() - Working with page extended information is done.
520 * @page_ext: Page extended information received from page_ext_get().
521 *
522 * The page extended information of the page may not be valid after this
523 * function is called.
524 *
525 * Return: None.
526 * Context: Any context with corresponding page_ext_get() is called.
527 */
528void page_ext_put(struct page_ext *page_ext)
529{
530	if (unlikely(!page_ext))
531		return;
532
533	rcu_read_unlock();
534}
535