xref: /openbmc/linux/mm/page_ext.c (revision 021ed9f5)
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 
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 #ifdef CONFIG_PAGE_OWNER
63 	&page_owner_ops,
64 #endif
65 #if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
66 	&page_idle_ops,
67 #endif
68 };
69 
70 unsigned long page_ext_size = sizeof(struct page_ext);
71 
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);
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 = page_ext_size;
83 			page_ext_size += page_ext_ops[i]->size;
84 			need = true;
85 		}
86 	}
87 
88 	return need;
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 
102 static inline struct page_ext *get_entry(void *base, unsigned long index)
103 {
104 	return base + page_ext_size * index;
105 }
106 
107 #if !defined(CONFIG_SPARSEMEM)
108 
109 
110 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
111 {
112 	pgdat->node_page_ext = NULL;
113 }
114 
115 struct page_ext *lookup_page_ext(const struct page *page)
116 {
117 	unsigned long pfn = page_to_pfn(page);
118 	unsigned long index;
119 	struct page_ext *base;
120 
121 	base = NODE_DATA(page_to_nid(page))->node_page_ext;
122 	/*
123 	 * The sanity checks the page allocator does upon freeing a
124 	 * page can reach here before the page_ext arrays are
125 	 * allocated when feeding a range of pages to the allocator
126 	 * for the first time during bootup or memory hotplug.
127 	 */
128 	if (unlikely(!base))
129 		return NULL;
130 	index = pfn - round_down(node_start_pfn(page_to_nid(page)),
131 					MAX_ORDER_NR_PAGES);
132 	return get_entry(base, index);
133 }
134 
135 static int __init alloc_node_page_ext(int nid)
136 {
137 	struct page_ext *base;
138 	unsigned long table_size;
139 	unsigned long nr_pages;
140 
141 	nr_pages = NODE_DATA(nid)->node_spanned_pages;
142 	if (!nr_pages)
143 		return 0;
144 
145 	/*
146 	 * Need extra space if node range is not aligned with
147 	 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
148 	 * checks buddy's status, range could be out of exact node range.
149 	 */
150 	if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
151 		!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
152 		nr_pages += MAX_ORDER_NR_PAGES;
153 
154 	table_size = page_ext_size * nr_pages;
155 
156 	base = memblock_alloc_try_nid(
157 			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
158 			MEMBLOCK_ALLOC_ACCESSIBLE, nid);
159 	if (!base)
160 		return -ENOMEM;
161 	NODE_DATA(nid)->node_page_ext = base;
162 	total_usage += table_size;
163 	return 0;
164 }
165 
166 void __init page_ext_init_flatmem(void)
167 {
168 
169 	int nid, fail;
170 
171 	if (!invoke_need_callbacks())
172 		return;
173 
174 	for_each_online_node(nid)  {
175 		fail = alloc_node_page_ext(nid);
176 		if (fail)
177 			goto fail;
178 	}
179 	pr_info("allocated %ld bytes of page_ext\n", total_usage);
180 	invoke_init_callbacks();
181 	return;
182 
183 fail:
184 	pr_crit("allocation of page_ext failed.\n");
185 	panic("Out of memory");
186 }
187 
188 #else /* CONFIG_FLAT_NODE_MEM_MAP */
189 
190 struct page_ext *lookup_page_ext(const struct page *page)
191 {
192 	unsigned long pfn = page_to_pfn(page);
193 	struct mem_section *section = __pfn_to_section(pfn);
194 	/*
195 	 * The sanity checks the page allocator does upon freeing a
196 	 * page can reach here before the page_ext arrays are
197 	 * allocated when feeding a range of pages to the allocator
198 	 * for the first time during bootup or memory hotplug.
199 	 */
200 	if (!section->page_ext)
201 		return NULL;
202 	return get_entry(section->page_ext, pfn);
203 }
204 
205 static void *__meminit alloc_page_ext(size_t size, int nid)
206 {
207 	gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
208 	void *addr = NULL;
209 
210 	addr = alloc_pages_exact_nid(nid, size, flags);
211 	if (addr) {
212 		kmemleak_alloc(addr, size, 1, flags);
213 		return addr;
214 	}
215 
216 	addr = vzalloc_node(size, nid);
217 
218 	return addr;
219 }
220 
221 static int __meminit init_section_page_ext(unsigned long pfn, int nid)
222 {
223 	struct mem_section *section;
224 	struct page_ext *base;
225 	unsigned long table_size;
226 
227 	section = __pfn_to_section(pfn);
228 
229 	if (section->page_ext)
230 		return 0;
231 
232 	table_size = page_ext_size * PAGES_PER_SECTION;
233 	base = alloc_page_ext(table_size, nid);
234 
235 	/*
236 	 * The value stored in section->page_ext is (base - pfn)
237 	 * and it does not point to the memory block allocated above,
238 	 * causing kmemleak false positives.
239 	 */
240 	kmemleak_not_leak(base);
241 
242 	if (!base) {
243 		pr_err("page ext allocation failure\n");
244 		return -ENOMEM;
245 	}
246 
247 	/*
248 	 * The passed "pfn" may not be aligned to SECTION.  For the calculation
249 	 * we need to apply a mask.
250 	 */
251 	pfn &= PAGE_SECTION_MASK;
252 	section->page_ext = (void *)base - page_ext_size * pfn;
253 	total_usage += table_size;
254 	return 0;
255 }
256 #ifdef CONFIG_MEMORY_HOTPLUG
257 static void free_page_ext(void *addr)
258 {
259 	if (is_vmalloc_addr(addr)) {
260 		vfree(addr);
261 	} else {
262 		struct page *page = virt_to_page(addr);
263 		size_t table_size;
264 
265 		table_size = page_ext_size * PAGES_PER_SECTION;
266 
267 		BUG_ON(PageReserved(page));
268 		kmemleak_free(addr);
269 		free_pages_exact(addr, table_size);
270 	}
271 }
272 
273 static void __free_page_ext(unsigned long pfn)
274 {
275 	struct mem_section *ms;
276 	struct page_ext *base;
277 
278 	ms = __pfn_to_section(pfn);
279 	if (!ms || !ms->page_ext)
280 		return;
281 	base = get_entry(ms->page_ext, pfn);
282 	free_page_ext(base);
283 	ms->page_ext = NULL;
284 }
285 
286 static int __meminit online_page_ext(unsigned long start_pfn,
287 				unsigned long nr_pages,
288 				int nid)
289 {
290 	unsigned long start, end, pfn;
291 	int fail = 0;
292 
293 	start = SECTION_ALIGN_DOWN(start_pfn);
294 	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
295 
296 	if (nid == NUMA_NO_NODE) {
297 		/*
298 		 * In this case, "nid" already exists and contains valid memory.
299 		 * "start_pfn" passed to us is a pfn which is an arg for
300 		 * online__pages(), and start_pfn should exist.
301 		 */
302 		nid = pfn_to_nid(start_pfn);
303 		VM_BUG_ON(!node_state(nid, N_ONLINE));
304 	}
305 
306 	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
307 		if (!pfn_present(pfn))
308 			continue;
309 		fail = init_section_page_ext(pfn, nid);
310 	}
311 	if (!fail)
312 		return 0;
313 
314 	/* rollback */
315 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
316 		__free_page_ext(pfn);
317 
318 	return -ENOMEM;
319 }
320 
321 static int __meminit offline_page_ext(unsigned long start_pfn,
322 				unsigned long nr_pages, int nid)
323 {
324 	unsigned long start, end, pfn;
325 
326 	start = SECTION_ALIGN_DOWN(start_pfn);
327 	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
328 
329 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
330 		__free_page_ext(pfn);
331 	return 0;
332 
333 }
334 
335 static int __meminit page_ext_callback(struct notifier_block *self,
336 			       unsigned long action, void *arg)
337 {
338 	struct memory_notify *mn = arg;
339 	int ret = 0;
340 
341 	switch (action) {
342 	case MEM_GOING_ONLINE:
343 		ret = online_page_ext(mn->start_pfn,
344 				   mn->nr_pages, mn->status_change_nid);
345 		break;
346 	case MEM_OFFLINE:
347 		offline_page_ext(mn->start_pfn,
348 				mn->nr_pages, mn->status_change_nid);
349 		break;
350 	case MEM_CANCEL_ONLINE:
351 		offline_page_ext(mn->start_pfn,
352 				mn->nr_pages, mn->status_change_nid);
353 		break;
354 	case MEM_GOING_OFFLINE:
355 		break;
356 	case MEM_ONLINE:
357 	case MEM_CANCEL_OFFLINE:
358 		break;
359 	}
360 
361 	return notifier_from_errno(ret);
362 }
363 
364 #endif
365 
366 void __init page_ext_init(void)
367 {
368 	unsigned long pfn;
369 	int nid;
370 
371 	if (!invoke_need_callbacks())
372 		return;
373 
374 	for_each_node_state(nid, N_MEMORY) {
375 		unsigned long start_pfn, end_pfn;
376 
377 		start_pfn = node_start_pfn(nid);
378 		end_pfn = node_end_pfn(nid);
379 		/*
380 		 * start_pfn and end_pfn may not be aligned to SECTION and the
381 		 * page->flags of out of node pages are not initialized.  So we
382 		 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
383 		 */
384 		for (pfn = start_pfn; pfn < end_pfn;
385 			pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
386 
387 			if (!pfn_valid(pfn))
388 				continue;
389 			/*
390 			 * Nodes's pfns can be overlapping.
391 			 * We know some arch can have a nodes layout such as
392 			 * -------------pfn-------------->
393 			 * N0 | N1 | N2 | N0 | N1 | N2|....
394 			 */
395 			if (pfn_to_nid(pfn) != nid)
396 				continue;
397 			if (init_section_page_ext(pfn, nid))
398 				goto oom;
399 			cond_resched();
400 		}
401 	}
402 	hotplug_memory_notifier(page_ext_callback, 0);
403 	pr_info("allocated %ld bytes of page_ext\n", total_usage);
404 	invoke_init_callbacks();
405 	return;
406 
407 oom:
408 	panic("Out of memory");
409 }
410 
411 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
412 {
413 }
414 
415 #endif
416