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)
69 static bool need_page_idle(void)
70 {
71 return true;
72 }
73 static struct page_ext_operations page_idle_ops __initdata = {
74 .need = need_page_idle,
75 .need_shared_flags = true,
76 };
77 #endif
78
79 static 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
94 unsigned long page_ext_size;
95
96 static 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 */
104 bool early_page_ext __meminitdata = true;
105 #else
106 bool early_page_ext __meminitdata;
107 #endif
108 static int __init setup_early_page_ext(char *str)
109 {
110 early_page_ext = true;
111 return 0;
112 }
113 early_param("early_page_ext", setup_early_page_ext);
114
115 static 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
141 static 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
152 static 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
158 void __init page_ext_init_flatmem_late(void)
159 {
160 invoke_init_callbacks();
161 }
162
163 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
164 {
165 pgdat->node_page_ext = NULL;
166 }
167
168 static 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
189 static 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
221 void __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
237 fail:
238 pr_crit("allocation of page_ext failed.\n");
239 panic("Out of memory");
240 }
241
242 #else /* CONFIG_SPARSEMEM */
243 static 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
248 static 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(page_ext, pfn);
264 }
265
266 static 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(addr, size, 1, 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
283 static 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(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(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
319 static 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(-1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
326
327 if (is_vmalloc_addr(addr)) {
328 vfree(addr);
329 } else {
330 page = virt_to_page(addr);
331 BUG_ON(PageReserved(page));
332 kmemleak_free(addr);
333 free_pages_exact(addr, table_size);
334 }
335 }
336
337 static 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(base))
352 base = (void *)base - PAGE_EXT_INVALID;
353 WRITE_ONCE(ms->page_ext, NULL);
354
355 base = get_entry(base, pfn);
356 free_page_ext(base);
357 }
358
359 static 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
371 static int __meminit online_page_ext(unsigned long start_pfn,
372 unsigned long nr_pages,
373 int nid)
374 {
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 if (nid == NUMA_NO_NODE) {
382 /*
383 * In this case, "nid" already exists and contains valid memory.
384 * "start_pfn" passed to us is a pfn which is an arg for
385 * online__pages(), and start_pfn should exist.
386 */
387 nid = pfn_to_nid(start_pfn);
388 VM_BUG_ON(!node_online(nid));
389 }
390
391 for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
392 fail = init_section_page_ext(pfn, nid);
393 if (!fail)
394 return 0;
395
396 /* rollback */
397 end = pfn - PAGES_PER_SECTION;
398 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
399 __free_page_ext(pfn);
400
401 return -ENOMEM;
402 }
403
404 static void __meminit offline_page_ext(unsigned long start_pfn,
405 unsigned long nr_pages)
406 {
407 unsigned long start, end, pfn;
408
409 start = SECTION_ALIGN_DOWN(start_pfn);
410 end = SECTION_ALIGN_UP(start_pfn + nr_pages);
411
412 /*
413 * Freeing of page_ext is done in 3 steps to avoid
414 * use-after-free of it:
415 * 1) Traverse all the sections and mark their page_ext
416 * as invalid.
417 * 2) Wait for all the existing users of page_ext who
418 * started before invalidation to finish.
419 * 3) Free the page_ext.
420 */
421 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
422 __invalidate_page_ext(pfn);
423
424 synchronize_rcu();
425
426 for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
427 __free_page_ext(pfn);
428 }
429
430 static int __meminit page_ext_callback(struct notifier_block *self,
431 unsigned long action, void *arg)
432 {
433 struct memory_notify *mn = arg;
434 int ret = 0;
435
436 switch (action) {
437 case MEM_GOING_ONLINE:
438 ret = online_page_ext(mn->start_pfn,
439 mn->nr_pages, mn->status_change_nid);
440 break;
441 case MEM_OFFLINE:
442 offline_page_ext(mn->start_pfn,
443 mn->nr_pages);
444 break;
445 case MEM_CANCEL_ONLINE:
446 offline_page_ext(mn->start_pfn,
447 mn->nr_pages);
448 break;
449 case MEM_GOING_OFFLINE:
450 break;
451 case MEM_ONLINE:
452 case MEM_CANCEL_OFFLINE:
453 break;
454 }
455
456 return notifier_from_errno(ret);
457 }
458
459 void __init page_ext_init(void)
460 {
461 unsigned long pfn;
462 int nid;
463
464 if (!invoke_need_callbacks())
465 return;
466
467 for_each_node_state(nid, N_MEMORY) {
468 unsigned long start_pfn, end_pfn;
469
470 start_pfn = node_start_pfn(nid);
471 end_pfn = node_end_pfn(nid);
472 /*
473 * start_pfn and end_pfn may not be aligned to SECTION and the
474 * page->flags of out of node pages are not initialized. So we
475 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
476 */
477 for (pfn = start_pfn; pfn < end_pfn;
478 pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
479
480 if (!pfn_valid(pfn))
481 continue;
482 /*
483 * Nodes's pfns can be overlapping.
484 * We know some arch can have a nodes layout such as
485 * -------------pfn-------------->
486 * N0 | N1 | N2 | N0 | N1 | N2|....
487 */
488 if (pfn_to_nid(pfn) != nid)
489 continue;
490 if (init_section_page_ext(pfn, nid))
491 goto oom;
492 cond_resched();
493 }
494 }
495 hotplug_memory_notifier(page_ext_callback, DEFAULT_CALLBACK_PRI);
496 pr_info("allocated %ld bytes of page_ext\n", total_usage);
497 invoke_init_callbacks();
498 return;
499
500 oom:
501 panic("Out of memory");
502 }
503
504 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
505 {
506 }
507
508 #endif
509
510 /**
511 * page_ext_get() - Get the extended information for a page.
512 * @page: The page we're interested in.
513 *
514 * Ensures that the page_ext will remain valid until page_ext_put()
515 * is called.
516 *
517 * Return: NULL if no page_ext exists for this page.
518 * Context: Any context. Caller may not sleep until they have called
519 * page_ext_put().
520 */
521 struct page_ext *page_ext_get(const struct page *page)
522 {
523 struct page_ext *page_ext;
524
525 rcu_read_lock();
526 page_ext = lookup_page_ext(page);
527 if (!page_ext) {
528 rcu_read_unlock();
529 return NULL;
530 }
531
532 return page_ext;
533 }
534
535 /**
536 * page_ext_put() - Working with page extended information is done.
537 * @page_ext: Page extended information received from page_ext_get().
538 *
539 * The page extended information of the page may not be valid after this
540 * function is called.
541 *
542 * Return: None.
543 * Context: Any context with corresponding page_ext_get() is called.
544 */
545 void page_ext_put(struct page_ext *page_ext)
546 {
547 if (unlikely(!page_ext))
548 return;
549
550 rcu_read_unlock();
551 }
552
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