xref: /openbmc/linux/mm/percpu-vm.c (revision bb0eb050)
1 /*
2  * mm/percpu-vm.c - vmalloc area based chunk allocation
3  *
4  * Copyright (C) 2010		SUSE Linux Products GmbH
5  * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
6  *
7  * This file is released under the GPLv2.
8  *
9  * Chunks are mapped into vmalloc areas and populated page by page.
10  * This is the default chunk allocator.
11  */
12 
13 static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
14 				    unsigned int cpu, int page_idx)
15 {
16 	/* must not be used on pre-mapped chunk */
17 	WARN_ON(chunk->immutable);
18 
19 	return vmalloc_to_page((void *)pcpu_chunk_addr(chunk, cpu, page_idx));
20 }
21 
22 /**
23  * pcpu_get_pages - get temp pages array
24  *
25  * Returns pointer to array of pointers to struct page which can be indexed
26  * with pcpu_page_idx().  Note that there is only one array and accesses
27  * should be serialized by pcpu_alloc_mutex.
28  *
29  * RETURNS:
30  * Pointer to temp pages array on success.
31  */
32 static struct page **pcpu_get_pages(void)
33 {
34 	static struct page **pages;
35 	size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
36 
37 	lockdep_assert_held(&pcpu_alloc_mutex);
38 
39 	if (!pages)
40 		pages = pcpu_mem_zalloc(pages_size);
41 	return pages;
42 }
43 
44 /**
45  * pcpu_free_pages - free pages which were allocated for @chunk
46  * @chunk: chunk pages were allocated for
47  * @pages: array of pages to be freed, indexed by pcpu_page_idx()
48  * @page_start: page index of the first page to be freed
49  * @page_end: page index of the last page to be freed + 1
50  *
51  * Free pages [@page_start and @page_end) in @pages for all units.
52  * The pages were allocated for @chunk.
53  */
54 static void pcpu_free_pages(struct pcpu_chunk *chunk,
55 			    struct page **pages, int page_start, int page_end)
56 {
57 	unsigned int cpu;
58 	int i;
59 
60 	for_each_possible_cpu(cpu) {
61 		for (i = page_start; i < page_end; i++) {
62 			struct page *page = pages[pcpu_page_idx(cpu, i)];
63 
64 			if (page)
65 				__free_page(page);
66 		}
67 	}
68 }
69 
70 /**
71  * pcpu_alloc_pages - allocates pages for @chunk
72  * @chunk: target chunk
73  * @pages: array to put the allocated pages into, indexed by pcpu_page_idx()
74  * @page_start: page index of the first page to be allocated
75  * @page_end: page index of the last page to be allocated + 1
76  *
77  * Allocate pages [@page_start,@page_end) into @pages for all units.
78  * The allocation is for @chunk.  Percpu core doesn't care about the
79  * content of @pages and will pass it verbatim to pcpu_map_pages().
80  */
81 static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
82 			    struct page **pages, int page_start, int page_end)
83 {
84 	const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
85 	unsigned int cpu, tcpu;
86 	int i;
87 
88 	for_each_possible_cpu(cpu) {
89 		for (i = page_start; i < page_end; i++) {
90 			struct page **pagep = &pages[pcpu_page_idx(cpu, i)];
91 
92 			*pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
93 			if (!*pagep)
94 				goto err;
95 		}
96 	}
97 	return 0;
98 
99 err:
100 	while (--i >= page_start)
101 		__free_page(pages[pcpu_page_idx(cpu, i)]);
102 
103 	for_each_possible_cpu(tcpu) {
104 		if (tcpu == cpu)
105 			break;
106 		for (i = page_start; i < page_end; i++)
107 			__free_page(pages[pcpu_page_idx(tcpu, i)]);
108 	}
109 	return -ENOMEM;
110 }
111 
112 /**
113  * pcpu_pre_unmap_flush - flush cache prior to unmapping
114  * @chunk: chunk the regions to be flushed belongs to
115  * @page_start: page index of the first page to be flushed
116  * @page_end: page index of the last page to be flushed + 1
117  *
118  * Pages in [@page_start,@page_end) of @chunk are about to be
119  * unmapped.  Flush cache.  As each flushing trial can be very
120  * expensive, issue flush on the whole region at once rather than
121  * doing it for each cpu.  This could be an overkill but is more
122  * scalable.
123  */
124 static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
125 				 int page_start, int page_end)
126 {
127 	flush_cache_vunmap(
128 		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
129 		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
130 }
131 
132 static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
133 {
134 	unmap_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT);
135 }
136 
137 /**
138  * pcpu_unmap_pages - unmap pages out of a pcpu_chunk
139  * @chunk: chunk of interest
140  * @pages: pages array which can be used to pass information to free
141  * @page_start: page index of the first page to unmap
142  * @page_end: page index of the last page to unmap + 1
143  *
144  * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
145  * Corresponding elements in @pages were cleared by the caller and can
146  * be used to carry information to pcpu_free_pages() which will be
147  * called after all unmaps are finished.  The caller should call
148  * proper pre/post flush functions.
149  */
150 static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
151 			     struct page **pages, int page_start, int page_end)
152 {
153 	unsigned int cpu;
154 	int i;
155 
156 	for_each_possible_cpu(cpu) {
157 		for (i = page_start; i < page_end; i++) {
158 			struct page *page;
159 
160 			page = pcpu_chunk_page(chunk, cpu, i);
161 			WARN_ON(!page);
162 			pages[pcpu_page_idx(cpu, i)] = page;
163 		}
164 		__pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
165 				   page_end - page_start);
166 	}
167 }
168 
169 /**
170  * pcpu_post_unmap_tlb_flush - flush TLB after unmapping
171  * @chunk: pcpu_chunk the regions to be flushed belong to
172  * @page_start: page index of the first page to be flushed
173  * @page_end: page index of the last page to be flushed + 1
174  *
175  * Pages [@page_start,@page_end) of @chunk have been unmapped.  Flush
176  * TLB for the regions.  This can be skipped if the area is to be
177  * returned to vmalloc as vmalloc will handle TLB flushing lazily.
178  *
179  * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
180  * for the whole region.
181  */
182 static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
183 				      int page_start, int page_end)
184 {
185 	flush_tlb_kernel_range(
186 		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
187 		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
188 }
189 
190 static int __pcpu_map_pages(unsigned long addr, struct page **pages,
191 			    int nr_pages)
192 {
193 	return map_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT,
194 					PAGE_KERNEL, pages);
195 }
196 
197 /**
198  * pcpu_map_pages - map pages into a pcpu_chunk
199  * @chunk: chunk of interest
200  * @pages: pages array containing pages to be mapped
201  * @page_start: page index of the first page to map
202  * @page_end: page index of the last page to map + 1
203  *
204  * For each cpu, map pages [@page_start,@page_end) into @chunk.  The
205  * caller is responsible for calling pcpu_post_map_flush() after all
206  * mappings are complete.
207  *
208  * This function is responsible for setting up whatever is necessary for
209  * reverse lookup (addr -> chunk).
210  */
211 static int pcpu_map_pages(struct pcpu_chunk *chunk,
212 			  struct page **pages, int page_start, int page_end)
213 {
214 	unsigned int cpu, tcpu;
215 	int i, err;
216 
217 	for_each_possible_cpu(cpu) {
218 		err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
219 				       &pages[pcpu_page_idx(cpu, page_start)],
220 				       page_end - page_start);
221 		if (err < 0)
222 			goto err;
223 
224 		for (i = page_start; i < page_end; i++)
225 			pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
226 					    chunk);
227 	}
228 	return 0;
229 err:
230 	for_each_possible_cpu(tcpu) {
231 		if (tcpu == cpu)
232 			break;
233 		__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
234 				   page_end - page_start);
235 	}
236 	pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);
237 	return err;
238 }
239 
240 /**
241  * pcpu_post_map_flush - flush cache after mapping
242  * @chunk: pcpu_chunk the regions to be flushed belong to
243  * @page_start: page index of the first page to be flushed
244  * @page_end: page index of the last page to be flushed + 1
245  *
246  * Pages [@page_start,@page_end) of @chunk have been mapped.  Flush
247  * cache.
248  *
249  * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
250  * for the whole region.
251  */
252 static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
253 				int page_start, int page_end)
254 {
255 	flush_cache_vmap(
256 		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
257 		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
258 }
259 
260 /**
261  * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
262  * @chunk: chunk of interest
263  * @page_start: the start page
264  * @page_end: the end page
265  *
266  * For each cpu, populate and map pages [@page_start,@page_end) into
267  * @chunk.
268  *
269  * CONTEXT:
270  * pcpu_alloc_mutex, does GFP_KERNEL allocation.
271  */
272 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
273 			       int page_start, int page_end)
274 {
275 	struct page **pages;
276 
277 	pages = pcpu_get_pages();
278 	if (!pages)
279 		return -ENOMEM;
280 
281 	if (pcpu_alloc_pages(chunk, pages, page_start, page_end))
282 		return -ENOMEM;
283 
284 	if (pcpu_map_pages(chunk, pages, page_start, page_end)) {
285 		pcpu_free_pages(chunk, pages, page_start, page_end);
286 		return -ENOMEM;
287 	}
288 	pcpu_post_map_flush(chunk, page_start, page_end);
289 
290 	return 0;
291 }
292 
293 /**
294  * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
295  * @chunk: chunk to depopulate
296  * @page_start: the start page
297  * @page_end: the end page
298  *
299  * For each cpu, depopulate and unmap pages [@page_start,@page_end)
300  * from @chunk.
301  *
302  * CONTEXT:
303  * pcpu_alloc_mutex.
304  */
305 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
306 				  int page_start, int page_end)
307 {
308 	struct page **pages;
309 
310 	/*
311 	 * If control reaches here, there must have been at least one
312 	 * successful population attempt so the temp pages array must
313 	 * be available now.
314 	 */
315 	pages = pcpu_get_pages();
316 	BUG_ON(!pages);
317 
318 	/* unmap and free */
319 	pcpu_pre_unmap_flush(chunk, page_start, page_end);
320 
321 	pcpu_unmap_pages(chunk, pages, page_start, page_end);
322 
323 	/* no need to flush tlb, vmalloc will handle it lazily */
324 
325 	pcpu_free_pages(chunk, pages, page_start, page_end);
326 }
327 
328 static struct pcpu_chunk *pcpu_create_chunk(void)
329 {
330 	struct pcpu_chunk *chunk;
331 	struct vm_struct **vms;
332 
333 	chunk = pcpu_alloc_chunk();
334 	if (!chunk)
335 		return NULL;
336 
337 	vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,
338 				pcpu_nr_groups, pcpu_atom_size);
339 	if (!vms) {
340 		pcpu_free_chunk(chunk);
341 		return NULL;
342 	}
343 
344 	chunk->data = vms;
345 	chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
346 	return chunk;
347 }
348 
349 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
350 {
351 	if (chunk && chunk->data)
352 		pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
353 	pcpu_free_chunk(chunk);
354 }
355 
356 static struct page *pcpu_addr_to_page(void *addr)
357 {
358 	return vmalloc_to_page(addr);
359 }
360 
361 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
362 {
363 	/* no extra restriction */
364 	return 0;
365 }
366