xref: /openbmc/linux/mm/page_ext.c (revision 6f52b16c5b29b89d92c0e7236f4655dc8491ad70)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mm.h>
3 #include <linux/mmzone.h>
4 #include <linux/bootmem.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 
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
37  * boot and extra memory would be unneccessary. In this case, to avoid
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  *
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  *
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[] = {
62 	&debug_guardpage_ops,
63 #ifdef CONFIG_PAGE_OWNER
64 	&page_owner_ops,
65 #endif
66 #if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
67 	&page_idle_ops,
68 #endif
69 };
70 
71 static unsigned long total_usage;
72 static unsigned long extra_mem;
73 
74 static bool __init invoke_need_callbacks(void)
75 {
76 	int i;
77 	int entries = ARRAY_SIZE(page_ext_ops);
78 	bool need = false;
79 
80 	for (i = 0; i < entries; i++) {
81 		if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
82 			page_ext_ops[i]->offset = sizeof(struct page_ext) +
83 						extra_mem;
84 			extra_mem += page_ext_ops[i]->size;
85 			need = true;
86 		}
87 	}
88 
89 	return need;
90 }
91 
92 static void __init invoke_init_callbacks(void)
93 {
94 	int i;
95 	int entries = ARRAY_SIZE(page_ext_ops);
96 
97 	for (i = 0; i < entries; i++) {
98 		if (page_ext_ops[i]->init)
99 			page_ext_ops[i]->init();
100 	}
101 }
102 
103 static unsigned long get_entry_size(void)
104 {
105 	return sizeof(struct page_ext) + extra_mem;
106 }
107 
108 static inline struct page_ext *get_entry(void *base, unsigned long index)
109 {
110 	return base + get_entry_size() * index;
111 }
112 
113 #if !defined(CONFIG_SPARSEMEM)
114 
115 
116 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
117 {
118 	pgdat->node_page_ext = NULL;
119 }
120 
121 struct page_ext *lookup_page_ext(struct page *page)
122 {
123 	unsigned long pfn = page_to_pfn(page);
124 	unsigned long index;
125 	struct page_ext *base;
126 
127 	base = NODE_DATA(page_to_nid(page))->node_page_ext;
128 #if defined(CONFIG_DEBUG_VM)
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;
137 #endif
138 	index = pfn - round_down(node_start_pfn(page_to_nid(page)),
139 					MAX_ORDER_NR_PAGES);
140 	return get_entry(base, index);
141 }
142 
143 static int __init alloc_node_page_ext(int nid)
144 {
145 	struct page_ext *base;
146 	unsigned long table_size;
147 	unsigned long nr_pages;
148 
149 	nr_pages = NODE_DATA(nid)->node_spanned_pages;
150 	if (!nr_pages)
151 		return 0;
152 
153 	/*
154 	 * Need extra space if node range is not aligned with
155 	 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
156 	 * checks buddy's status, range could be out of exact node range.
157 	 */
158 	if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
159 		!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
160 		nr_pages += MAX_ORDER_NR_PAGES;
161 
162 	table_size = get_entry_size() * nr_pages;
163 
164 	base = memblock_virt_alloc_try_nid_nopanic(
165 			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
166 			BOOTMEM_ALLOC_ACCESSIBLE, nid);
167 	if (!base)
168 		return -ENOMEM;
169 	NODE_DATA(nid)->node_page_ext = base;
170 	total_usage += table_size;
171 	return 0;
172 }
173 
174 void __init page_ext_init_flatmem(void)
175 {
176 
177 	int nid, fail;
178 
179 	if (!invoke_need_callbacks())
180 		return;
181 
182 	for_each_online_node(nid)  {
183 		fail = alloc_node_page_ext(nid);
184 		if (fail)
185 			goto fail;
186 	}
187 	pr_info("allocated %ld bytes of page_ext\n", total_usage);
188 	invoke_init_callbacks();
189 	return;
190 
191 fail:
192 	pr_crit("allocation of page_ext failed.\n");
193 	panic("Out of memory");
194 }
195 
196 #else /* CONFIG_FLAT_NODE_MEM_MAP */
197 
198 struct page_ext *lookup_page_ext(struct page *page)
199 {
200 	unsigned long pfn = page_to_pfn(page);
201 	struct mem_section *section = __pfn_to_section(pfn);
202 #if defined(CONFIG_DEBUG_VM)
203 	/*
204 	 * The sanity checks the page allocator does upon freeing a
205 	 * page can reach here before the page_ext arrays are
206 	 * allocated when feeding a range of pages to the allocator
207 	 * for the first time during bootup or memory hotplug.
208 	 */
209 	if (!section->page_ext)
210 		return NULL;
211 #endif
212 	return get_entry(section->page_ext, pfn);
213 }
214 
215 static void *__meminit alloc_page_ext(size_t size, int nid)
216 {
217 	gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
218 	void *addr = NULL;
219 
220 	addr = alloc_pages_exact_nid(nid, size, flags);
221 	if (addr) {
222 		kmemleak_alloc(addr, size, 1, flags);
223 		return addr;
224 	}
225 
226 	addr = vzalloc_node(size, nid);
227 
228 	return addr;
229 }
230 
231 static int __meminit init_section_page_ext(unsigned long pfn, int nid)
232 {
233 	struct mem_section *section;
234 	struct page_ext *base;
235 	unsigned long table_size;
236 
237 	section = __pfn_to_section(pfn);
238 
239 	if (section->page_ext)
240 		return 0;
241 
242 	table_size = get_entry_size() * PAGES_PER_SECTION;
243 	base = alloc_page_ext(table_size, nid);
244 
245 	/*
246 	 * The value stored in section->page_ext is (base - pfn)
247 	 * and it does not point to the memory block allocated above,
248 	 * causing kmemleak false positives.
249 	 */
250 	kmemleak_not_leak(base);
251 
252 	if (!base) {
253 		pr_err("page ext allocation failure\n");
254 		return -ENOMEM;
255 	}
256 
257 	/*
258 	 * The passed "pfn" may not be aligned to SECTION.  For the calculation
259 	 * we need to apply a mask.
260 	 */
261 	pfn &= PAGE_SECTION_MASK;
262 	section->page_ext = (void *)base - get_entry_size() * pfn;
263 	total_usage += table_size;
264 	return 0;
265 }
266 #ifdef CONFIG_MEMORY_HOTPLUG
267 static void free_page_ext(void *addr)
268 {
269 	if (is_vmalloc_addr(addr)) {
270 		vfree(addr);
271 	} else {
272 		struct page *page = virt_to_page(addr);
273 		size_t table_size;
274 
275 		table_size = get_entry_size() * PAGES_PER_SECTION;
276 
277 		BUG_ON(PageReserved(page));
278 		free_pages_exact(addr, table_size);
279 	}
280 }
281 
282 static void __free_page_ext(unsigned long pfn)
283 {
284 	struct mem_section *ms;
285 	struct page_ext *base;
286 
287 	ms = __pfn_to_section(pfn);
288 	if (!ms || !ms->page_ext)
289 		return;
290 	base = get_entry(ms->page_ext, pfn);
291 	free_page_ext(base);
292 	ms->page_ext = NULL;
293 }
294 
295 static int __meminit online_page_ext(unsigned long start_pfn,
296 				unsigned long nr_pages,
297 				int nid)
298 {
299 	unsigned long start, end, pfn;
300 	int fail = 0;
301 
302 	start = SECTION_ALIGN_DOWN(start_pfn);
303 	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
304 
305 	if (nid == -1) {
306 		/*
307 		 * In this case, "nid" already exists and contains valid memory.
308 		 * "start_pfn" passed to us is a pfn which is an arg for
309 		 * online__pages(), and start_pfn should exist.
310 		 */
311 		nid = pfn_to_nid(start_pfn);
312 		VM_BUG_ON(!node_state(nid, N_ONLINE));
313 	}
314 
315 	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
316 		if (!pfn_present(pfn))
317 			continue;
318 		fail = init_section_page_ext(pfn, nid);
319 	}
320 	if (!fail)
321 		return 0;
322 
323 	/* rollback */
324 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
325 		__free_page_ext(pfn);
326 
327 	return -ENOMEM;
328 }
329 
330 static int __meminit offline_page_ext(unsigned long start_pfn,
331 				unsigned long nr_pages, int nid)
332 {
333 	unsigned long start, end, pfn;
334 
335 	start = SECTION_ALIGN_DOWN(start_pfn);
336 	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
337 
338 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
339 		__free_page_ext(pfn);
340 	return 0;
341 
342 }
343 
344 static int __meminit page_ext_callback(struct notifier_block *self,
345 			       unsigned long action, void *arg)
346 {
347 	struct memory_notify *mn = arg;
348 	int ret = 0;
349 
350 	switch (action) {
351 	case MEM_GOING_ONLINE:
352 		ret = online_page_ext(mn->start_pfn,
353 				   mn->nr_pages, mn->status_change_nid);
354 		break;
355 	case MEM_OFFLINE:
356 		offline_page_ext(mn->start_pfn,
357 				mn->nr_pages, mn->status_change_nid);
358 		break;
359 	case MEM_CANCEL_ONLINE:
360 		offline_page_ext(mn->start_pfn,
361 				mn->nr_pages, mn->status_change_nid);
362 		break;
363 	case MEM_GOING_OFFLINE:
364 		break;
365 	case MEM_ONLINE:
366 	case MEM_CANCEL_OFFLINE:
367 		break;
368 	}
369 
370 	return notifier_from_errno(ret);
371 }
372 
373 #endif
374 
375 void __init page_ext_init(void)
376 {
377 	unsigned long pfn;
378 	int nid;
379 
380 	if (!invoke_need_callbacks())
381 		return;
382 
383 	for_each_node_state(nid, N_MEMORY) {
384 		unsigned long start_pfn, end_pfn;
385 
386 		start_pfn = node_start_pfn(nid);
387 		end_pfn = node_end_pfn(nid);
388 		/*
389 		 * start_pfn and end_pfn may not be aligned to SECTION and the
390 		 * page->flags of out of node pages are not initialized.  So we
391 		 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
392 		 */
393 		for (pfn = start_pfn; pfn < end_pfn;
394 			pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
395 
396 			if (!pfn_valid(pfn))
397 				continue;
398 			/*
399 			 * Nodes's pfns can be overlapping.
400 			 * We know some arch can have a nodes layout such as
401 			 * -------------pfn-------------->
402 			 * N0 | N1 | N2 | N0 | N1 | N2|....
403 			 *
404 			 * Take into account DEFERRED_STRUCT_PAGE_INIT.
405 			 */
406 			if (early_pfn_to_nid(pfn) != nid)
407 				continue;
408 			if (init_section_page_ext(pfn, nid))
409 				goto oom;
410 			cond_resched();
411 		}
412 	}
413 	hotplug_memory_notifier(page_ext_callback, 0);
414 	pr_info("allocated %ld bytes of page_ext\n", total_usage);
415 	invoke_init_callbacks();
416 	return;
417 
418 oom:
419 	panic("Out of memory");
420 }
421 
422 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
423 {
424 }
425 
426 #endif
427