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#include <linux/pgalloc_tag.h>
14
15/*
16 * struct page extension
17 *
18 * This is the feature to manage memory for extended data per page.
19 *
20 * Until now, we must modify struct page itself to store extra data per page.
21 * This requires rebuilding the kernel and it is really time consuming process.
22 * And, sometimes, rebuild is impossible due to third party module dependency.
23 * At last, enlarging struct page could cause un-wanted system behaviour change.
24 *
25 * This feature is intended to overcome above mentioned problems. This feature
26 * allocates memory for extended data per page in certain place rather than
27 * the struct page itself. This memory can be accessed by the accessor
28 * functions provided by this code. During the boot process, it checks whether
29 * allocation of huge chunk of memory is needed or not. If not, it avoids
30 * allocating memory at all. With this advantage, we can include this feature
31 * into the kernel in default and can avoid rebuild and solve related problems.
32 *
33 * To help these things to work well, there are two callbacks for clients. One
34 * is the need callback which is mandatory if user wants to avoid useless
35 * memory allocation at boot-time. The other is optional, init callback, which
36 * is used to do proper initialization after memory is allocated.
37 *
38 * The need callback is used to decide whether extended memory allocation is
39 * needed or not. Sometimes users want to deactivate some features in this
40 * boot and extra memory would be unnecessary. In this case, to avoid
41 * allocating huge chunk of memory, each clients represent their need of
42 * extra memory through the need callback. If one of the need callbacks
43 * returns true, it means that someone needs extra memory so that
44 * page extension core should allocates memory for page extension. If
45 * none of need callbacks return true, memory isn't needed at all in this boot
46 * and page extension core can skip to allocate memory. As result,
47 * none of memory is wasted.
48 *
49 * When need callback returns true, page_ext checks if there is a request for
50 * extra memory through size in struct page_ext_operations. If it is non-zero,
51 * extra space is allocated for each page_ext entry and offset is returned to
52 * user through offset in struct page_ext_operations.
53 *
54 * The init callback is used to do proper initialization after page extension
55 * is completely initialized. In sparse memory system, extra memory is
56 * allocated some time later than memmap is allocated. In other words, lifetime
57 * of memory for page extension isn't same with memmap for struct page.
58 * Therefore, clients can't store extra data until page extension is
59 * initialized, even if pages are allocated and used freely. This could
60 * cause inadequate state of extra data per page, so, to prevent it, client
61 * can utilize this callback to initialize the state of it correctly.
62 */
63
64#ifdef CONFIG_SPARSEMEM
65#define PAGE_EXT_INVALID (0x1)
66#endif
67
68#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
69static bool need_page_idle(void)
70{
71 return true;
72}
73static struct page_ext_operations page_idle_ops __initdata = {
74 .need = need_page_idle,
75 .need_shared_flags = true,
76};
77#endif
78
79static struct page_ext_operations *page_ext_ops[] __initdata = {
80#ifdef CONFIG_PAGE_OWNER
81 &page_owner_ops,
82#endif
83#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
84 &page_idle_ops,
85#endif
86#ifdef CONFIG_MEM_ALLOC_PROFILING
87 &page_alloc_tagging_ops,
88#endif
89#ifdef CONFIG_PAGE_TABLE_CHECK
90 &page_table_check_ops,
91#endif
92};
93
94unsigned long page_ext_size;
95
96static unsigned long total_usage;
97
98#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
99/*
100 * To ensure correct allocation tagging for pages, page_ext should be available
101 * before the first page allocation. Otherwise early task stacks will be
102 * allocated before page_ext initialization and missing tags will be flagged.
103 */
104bool early_page_ext __meminitdata = true;
105#else
106bool early_page_ext __meminitdata;
107#endif
108static int __init setup_early_page_ext(char *str)
109{
110 early_page_ext = true;
111 return 0;
112}
113early_param("early_page_ext", setup_early_page_ext);
114
115static bool __init invoke_need_callbacks(void)
116{
117 int i;
118 int entries = ARRAY_SIZE(page_ext_ops);
119 bool need = false;
120
121 for (i = 0; i < entries; i++) {
122 if (page_ext_ops[i]->need()) {
123 if (page_ext_ops[i]->need_shared_flags) {
124 page_ext_size = sizeof(struct page_ext);
125 break;
126 }
127 }
128 }
129
130 for (i = 0; i < entries; i++) {
131 if (page_ext_ops[i]->need()) {
132 page_ext_ops[i]->offset = page_ext_size;
133 page_ext_size += page_ext_ops[i]->size;
134 need = true;
135 }
136 }
137
138 return need;
139}
140
141static void __init invoke_init_callbacks(void)
142{
143 int i;
144 int entries = ARRAY_SIZE(page_ext_ops);
145
146 for (i = 0; i < entries; i++) {
147 if (page_ext_ops[i]->init)
148 page_ext_ops[i]->init();
149 }
150}
151
152static inline struct page_ext *get_entry(void *base, unsigned long index)
153{
154 return base + page_ext_size * index;
155}
156
157#ifndef CONFIG_SPARSEMEM
158void __init page_ext_init_flatmem_late(void)
159{
160 invoke_init_callbacks();
161}
162
163void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
164{
165 pgdat->node_page_ext = NULL;
166}
167
168static struct page_ext *lookup_page_ext(const struct page *page)
169{
170 unsigned long pfn = page_to_pfn(page);
171 unsigned long index;
172 struct page_ext *base;
173
174 WARN_ON_ONCE(!rcu_read_lock_held());
175 base = NODE_DATA(page_to_nid(page))->node_page_ext;
176 /*
177 * The sanity checks the page allocator does upon freeing a
178 * page can reach here before the page_ext arrays are
179 * allocated when feeding a range of pages to the allocator
180 * for the first time during bootup or memory hotplug.
181 */
182 if (unlikely(!base))
183 return NULL;
184 index = pfn - round_down(node_start_pfn(page_to_nid(page)),
185 MAX_ORDER_NR_PAGES);
186 return get_entry(base, index);
187}
188
189static int __init alloc_node_page_ext(int nid)
190{
191 struct page_ext *base;
192 unsigned long table_size;
193 unsigned long nr_pages;
194
195 nr_pages = NODE_DATA(nid)->node_spanned_pages;
196 if (!nr_pages)
197 return 0;
198
199 /*
200 * Need extra space if node range is not aligned with
201 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
202 * checks buddy's status, range could be out of exact node range.
203 */
204 if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
205 !IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
206 nr_pages += MAX_ORDER_NR_PAGES;
207
208 table_size = page_ext_size * nr_pages;
209
210 base = memblock_alloc_try_nid(
211 table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
212 MEMBLOCK_ALLOC_ACCESSIBLE, nid);
213 if (!base)
214 return -ENOMEM;
215 NODE_DATA(nid)->node_page_ext = base;
216 total_usage += table_size;
217 memmap_boot_pages_add(DIV_ROUND_UP(table_size, PAGE_SIZE));
218 return 0;
219}
220
221void __init page_ext_init_flatmem(void)
222{
223
224 int nid, fail;
225
226 if (!invoke_need_callbacks())
227 return;
228
229 for_each_online_node(nid) {
230 fail = alloc_node_page_ext(nid);
231 if (fail)
232 goto fail;
233 }
234 pr_info("allocated %ld bytes of page_ext\n", total_usage);
235 return;
236
237fail:
238 pr_crit("allocation of page_ext failed.\n");
239 panic("Out of memory");
240}
241
242#else /* CONFIG_SPARSEMEM */
243static bool page_ext_invalid(struct page_ext *page_ext)
244{
245 return !page_ext || (((unsigned long)page_ext & PAGE_EXT_INVALID) == PAGE_EXT_INVALID);
246}
247
248static struct page_ext *lookup_page_ext(const struct page *page)
249{
250 unsigned long pfn = page_to_pfn(page);
251 struct mem_section *section = __pfn_to_section(pfn);
252 struct page_ext *page_ext = READ_ONCE(section->page_ext);
253
254 WARN_ON_ONCE(!rcu_read_lock_held());
255 /*
256 * The sanity checks the page allocator does upon freeing a
257 * page can reach here before the page_ext arrays are
258 * allocated when feeding a range of pages to the allocator
259 * for the first time during bootup or memory hotplug.
260 */
261 if (page_ext_invalid(page_ext))
262 return NULL;
263 return get_entry(base: page_ext, index: pfn);
264}
265
266static void *__meminit alloc_page_ext(size_t size, int nid)
267{
268 gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
269 void *addr = NULL;
270
271 addr = alloc_pages_exact_nid(nid, size, flags);
272 if (addr)
273 kmemleak_alloc(ptr: addr, size, min_count: 1, gfp: flags);
274 else
275 addr = vzalloc_node(size, nid);
276
277 if (addr)
278 memmap_pages_add(DIV_ROUND_UP(size, PAGE_SIZE));
279
280 return addr;
281}
282
283static int __meminit init_section_page_ext(unsigned long pfn, int nid)
284{
285 struct mem_section *section;
286 struct page_ext *base;
287 unsigned long table_size;
288
289 section = __pfn_to_section(pfn);
290
291 if (section->page_ext)
292 return 0;
293
294 table_size = page_ext_size * PAGES_PER_SECTION;
295 base = alloc_page_ext(size: table_size, nid);
296
297 /*
298 * The value stored in section->page_ext is (base - pfn)
299 * and it does not point to the memory block allocated above,
300 * causing kmemleak false positives.
301 */
302 kmemleak_not_leak(ptr: base);
303
304 if (!base) {
305 pr_err("page ext allocation failure\n");
306 return -ENOMEM;
307 }
308
309 /*
310 * The passed "pfn" may not be aligned to SECTION. For the calculation
311 * we need to apply a mask.
312 */
313 pfn &= PAGE_SECTION_MASK;
314 section->page_ext = (void *)base - page_ext_size * pfn;
315 total_usage += table_size;
316 return 0;
317}
318
319static void free_page_ext(void *addr)
320{
321 size_t table_size;
322 struct page *page;
323
324 table_size = page_ext_size * PAGES_PER_SECTION;
325 memmap_pages_add(delta: -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
326
327 if (is_vmalloc_addr(x: addr)) {
328 vfree(addr);
329 } else {
330 page = virt_to_page(addr);
331 BUG_ON(PageReserved(page));
332 kmemleak_free(ptr: addr);
333 free_pages_exact(virt: addr, size: table_size);
334 }
335}
336
337static void __free_page_ext(unsigned long pfn)
338{
339 struct mem_section *ms;
340 struct page_ext *base;
341
342 ms = __pfn_to_section(pfn);
343 if (!ms || !ms->page_ext)
344 return;
345
346 base = READ_ONCE(ms->page_ext);
347 /*
348 * page_ext here can be valid while doing the roll back
349 * operation in online_page_ext().
350 */
351 if (page_ext_invalid(page_ext: base))
352 base = (void *)base - PAGE_EXT_INVALID;
353 WRITE_ONCE(ms->page_ext, NULL);
354
355 base = get_entry(base, index: pfn);
356 free_page_ext(addr: base);
357}
358
359static void __invalidate_page_ext(unsigned long pfn)
360{
361 struct mem_section *ms;
362 void *val;
363
364 ms = __pfn_to_section(pfn);
365 if (!ms || !ms->page_ext)
366 return;
367 val = (void *)ms->page_ext + PAGE_EXT_INVALID;
368 WRITE_ONCE(ms->page_ext, val);
369}
370
371static int __meminit online_page_ext(unsigned long start_pfn,
372 unsigned long nr_pages)
373{
374 int nid = pfn_to_nid(start_pfn);
375 unsigned long start, end, pfn;
376 int fail = 0;
377
378 start = SECTION_ALIGN_DOWN(start_pfn);
379 end = SECTION_ALIGN_UP(start_pfn + nr_pages);
380
381 for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
382 fail = init_section_page_ext(pfn, nid);
383 if (!fail)
384 return 0;
385
386 /* rollback */
387 end = pfn - PAGES_PER_SECTION;
388 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
389 __free_page_ext(pfn);
390
391 return -ENOMEM;
392}
393
394static void __meminit offline_page_ext(unsigned long start_pfn,
395 unsigned long nr_pages)
396{
397 unsigned long start, end, pfn;
398
399 start = SECTION_ALIGN_DOWN(start_pfn);
400 end = SECTION_ALIGN_UP(start_pfn + nr_pages);
401
402 /*
403 * Freeing of page_ext is done in 3 steps to avoid
404 * use-after-free of it:
405 * 1) Traverse all the sections and mark their page_ext
406 * as invalid.
407 * 2) Wait for all the existing users of page_ext who
408 * started before invalidation to finish.
409 * 3) Free the page_ext.
410 */
411 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
412 __invalidate_page_ext(pfn);
413
414 synchronize_rcu();
415
416 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
417 __free_page_ext(pfn);
418}
419
420static int __meminit page_ext_callback(struct notifier_block *self,
421 unsigned long action, void *arg)
422{
423 struct memory_notify *mn = arg;
424 int ret = 0;
425
426 switch (action) {
427 case MEM_GOING_ONLINE:
428 ret = online_page_ext(start_pfn: mn->start_pfn, nr_pages: mn->nr_pages);
429 break;
430 case MEM_OFFLINE:
431 offline_page_ext(start_pfn: mn->start_pfn,
432 nr_pages: mn->nr_pages);
433 break;
434 case MEM_CANCEL_ONLINE:
435 offline_page_ext(start_pfn: mn->start_pfn,
436 nr_pages: mn->nr_pages);
437 break;
438 case MEM_GOING_OFFLINE:
439 break;
440 case MEM_ONLINE:
441 case MEM_CANCEL_OFFLINE:
442 break;
443 }
444
445 return notifier_from_errno(err: ret);
446}
447
448void __init page_ext_init(void)
449{
450 unsigned long pfn;
451 int nid;
452
453 if (!invoke_need_callbacks())
454 return;
455
456 for_each_node_state(nid, N_MEMORY) {
457 unsigned long start_pfn, end_pfn;
458
459 start_pfn = node_start_pfn(nid);
460 end_pfn = node_end_pfn(nid);
461 /*
462 * start_pfn and end_pfn may not be aligned to SECTION and the
463 * page->flags of out of node pages are not initialized. So we
464 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
465 */
466 for (pfn = start_pfn; pfn < end_pfn;
467 pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
468
469 if (!pfn_valid(pfn))
470 continue;
471 /*
472 * Nodes's pfns can be overlapping.
473 * We know some arch can have a nodes layout such as
474 * -------------pfn-------------->
475 * N0 | N1 | N2 | N0 | N1 | N2|....
476 */
477 if (pfn_to_nid(pfn) != nid)
478 continue;
479 if (init_section_page_ext(pfn, nid))
480 goto oom;
481 cond_resched();
482 }
483 }
484 hotplug_memory_notifier(page_ext_callback, DEFAULT_CALLBACK_PRI);
485 pr_info("allocated %ld bytes of page_ext\n", total_usage);
486 invoke_init_callbacks();
487 return;
488
489oom:
490 panic(fmt: "Out of memory");
491}
492
493void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
494{
495}
496
497#endif
498
499/**
500 * page_ext_lookup() - Lookup a page extension for a PFN.
501 * @pfn: PFN of the page we're interested in.
502 *
503 * Must be called with RCU read lock taken and @pfn must be valid.
504 *
505 * Return: NULL if no page_ext exists for this page.
506 */
507struct page_ext *page_ext_lookup(unsigned long pfn)
508{
509 return lookup_page_ext(pfn_to_page(pfn));
510}
511
512/**
513 * page_ext_get() - Get the extended information for a page.
514 * @page: The page we're interested in.
515 *
516 * Ensures that the page_ext will remain valid until page_ext_put()
517 * is called.
518 *
519 * Return: NULL if no page_ext exists for this page.
520 * Context: Any context. Caller may not sleep until they have called
521 * page_ext_put().
522 */
523struct page_ext *page_ext_get(const struct page *page)
524{
525 struct page_ext *page_ext;
526
527 rcu_read_lock();
528 page_ext = lookup_page_ext(page);
529 if (!page_ext) {
530 rcu_read_unlock();
531 return NULL;
532 }
533
534 return page_ext;
535}
536
537/**
538 * page_ext_put() - Working with page extended information is done.
539 * @page_ext: Page extended information received from page_ext_get().
540 *
541 * The page extended information of the page may not be valid after this
542 * function is called.
543 *
544 * Return: None.
545 * Context: Any context with corresponding page_ext_get() is called.
546 */
547void page_ext_put(struct page_ext *page_ext)
548{
549 if (unlikely(!page_ext))
550 return;
551
552 rcu_read_unlock();
553}
554

source code of linux/mm/page_ext.c