1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * mm/percpu-vm.c - vmalloc area based chunk allocation
4 *
5 * Copyright (C) 2010 SUSE Linux Products GmbH
6 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
7 *
8 * Chunks are mapped into vmalloc areas and populated page by page.
9 * This is the default chunk allocator.
10 */
11 #include "internal.h"
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, GFP_KERNEL);
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 * @gfp: allocation flags passed to the underlying allocator
77 *
78 * Allocate pages [@page_start,@page_end) into @pages for all units.
79 * The allocation is for @chunk. Percpu core doesn't care about the
80 * content of @pages and will pass it verbatim to pcpu_map_pages().
81 */
82 static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
83 struct page **pages, int page_start, int page_end,
84 gfp_t gfp)
85 {
86 unsigned int cpu, tcpu;
87 int i;
88
89 gfp |= __GFP_HIGHMEM;
90
91 for_each_possible_cpu(cpu) {
92 for (i = page_start; i < page_end; i++) {
93 struct page **pagep = &pages[pcpu_page_idx(cpu, i)];
94
95 *pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
96 if (!*pagep)
97 goto err;
98 }
99 }
100 return 0;
101
102 err:
103 while (--i >= page_start)
104 __free_page(pages[pcpu_page_idx(cpu, i)]);
105
106 for_each_possible_cpu(tcpu) {
107 if (tcpu == cpu)
108 break;
109 for (i = page_start; i < page_end; i++)
110 __free_page(pages[pcpu_page_idx(tcpu, i)]);
111 }
112 return -ENOMEM;
113 }
114
115 /**
116 * pcpu_pre_unmap_flush - flush cache prior to unmapping
117 * @chunk: chunk the regions to be flushed belongs to
118 * @page_start: page index of the first page to be flushed
119 * @page_end: page index of the last page to be flushed + 1
120 *
121 * Pages in [@page_start,@page_end) of @chunk are about to be
122 * unmapped. Flush cache. As each flushing trial can be very
123 * expensive, issue flush on the whole region at once rather than
124 * doing it for each cpu. This could be an overkill but is more
125 * scalable.
126 */
127 static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
128 int page_start, int page_end)
129 {
130 flush_cache_vunmap(
131 pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
132 pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
133 }
134
135 static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
136 {
137 vunmap_range_noflush(addr, addr + (nr_pages << PAGE_SHIFT));
138 }
139
140 /**
141 * pcpu_unmap_pages - unmap pages out of a pcpu_chunk
142 * @chunk: chunk of interest
143 * @pages: pages array which can be used to pass information to free
144 * @page_start: page index of the first page to unmap
145 * @page_end: page index of the last page to unmap + 1
146 *
147 * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
148 * Corresponding elements in @pages were cleared by the caller and can
149 * be used to carry information to pcpu_free_pages() which will be
150 * called after all unmaps are finished. The caller should call
151 * proper pre/post flush functions.
152 */
153 static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
154 struct page **pages, int page_start, int page_end)
155 {
156 unsigned int cpu;
157 int i;
158
159 for_each_possible_cpu(cpu) {
160 for (i = page_start; i < page_end; i++) {
161 struct page *page;
162
163 page = pcpu_chunk_page(chunk, cpu, i);
164 WARN_ON(!page);
165 pages[pcpu_page_idx(cpu, i)] = page;
166 }
167 __pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
168 page_end - page_start);
169 }
170 }
171
172 /**
173 * pcpu_post_unmap_tlb_flush - flush TLB after unmapping
174 * @chunk: pcpu_chunk the regions to be flushed belong to
175 * @page_start: page index of the first page to be flushed
176 * @page_end: page index of the last page to be flushed + 1
177 *
178 * Pages [@page_start,@page_end) of @chunk have been unmapped. Flush
179 * TLB for the regions. This can be skipped if the area is to be
180 * returned to vmalloc as vmalloc will handle TLB flushing lazily.
181 *
182 * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
183 * for the whole region.
184 */
185 static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
186 int page_start, int page_end)
187 {
188 flush_tlb_kernel_range(
189 pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
190 pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
191 }
192
193 static int __pcpu_map_pages(unsigned long addr, struct page **pages,
194 int nr_pages)
195 {
196 return vmap_pages_range_noflush(addr, addr + (nr_pages << PAGE_SHIFT),
197 PAGE_KERNEL, pages, PAGE_SHIFT);
198 }
199
200 /**
201 * pcpu_map_pages - map pages into a pcpu_chunk
202 * @chunk: chunk of interest
203 * @pages: pages array containing pages to be mapped
204 * @page_start: page index of the first page to map
205 * @page_end: page index of the last page to map + 1
206 *
207 * For each cpu, map pages [@page_start,@page_end) into @chunk. The
208 * caller is responsible for calling pcpu_post_map_flush() after all
209 * mappings are complete.
210 *
211 * This function is responsible for setting up whatever is necessary for
212 * reverse lookup (addr -> chunk).
213 */
214 static int pcpu_map_pages(struct pcpu_chunk *chunk,
215 struct page **pages, int page_start, int page_end)
216 {
217 unsigned int cpu, tcpu;
218 int i, err;
219
220 for_each_possible_cpu(cpu) {
221 err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
222 &pages[pcpu_page_idx(cpu, page_start)],
223 page_end - page_start);
224 if (err < 0)
225 goto err;
226
227 for (i = page_start; i < page_end; i++)
228 pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
229 chunk);
230 }
231 return 0;
232 err:
233 for_each_possible_cpu(tcpu) {
234 __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
235 page_end - page_start);
236 if (tcpu == cpu)
237 break;
238 }
239 pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);
240 return err;
241 }
242
243 /**
244 * pcpu_post_map_flush - flush cache after mapping
245 * @chunk: pcpu_chunk the regions to be flushed belong to
246 * @page_start: page index of the first page to be flushed
247 * @page_end: page index of the last page to be flushed + 1
248 *
249 * Pages [@page_start,@page_end) of @chunk have been mapped. Flush
250 * cache.
251 *
252 * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
253 * for the whole region.
254 */
255 static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
256 int page_start, int page_end)
257 {
258 flush_cache_vmap(
259 pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
260 pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
261 }
262
263 /**
264 * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
265 * @chunk: chunk of interest
266 * @page_start: the start page
267 * @page_end: the end page
268 * @gfp: allocation flags passed to the underlying memory allocator
269 *
270 * For each cpu, populate and map pages [@page_start,@page_end) into
271 * @chunk.
272 *
273 * CONTEXT:
274 * pcpu_alloc_mutex, does GFP_KERNEL allocation.
275 */
276 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
277 int page_start, int page_end, gfp_t gfp)
278 {
279 struct page **pages;
280
281 pages = pcpu_get_pages();
282 if (!pages)
283 return -ENOMEM;
284
285 if (pcpu_alloc_pages(chunk, pages, page_start, page_end, gfp))
286 return -ENOMEM;
287
288 if (pcpu_map_pages(chunk, pages, page_start, page_end)) {
289 pcpu_free_pages(chunk, pages, page_start, page_end);
290 return -ENOMEM;
291 }
292 pcpu_post_map_flush(chunk, page_start, page_end);
293
294 return 0;
295 }
296
297 /**
298 * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
299 * @chunk: chunk to depopulate
300 * @page_start: the start page
301 * @page_end: the end page
302 *
303 * For each cpu, depopulate and unmap pages [@page_start,@page_end)
304 * from @chunk.
305 *
306 * Caller is required to call pcpu_post_unmap_tlb_flush() if not returning the
307 * region back to vmalloc() which will lazily flush the tlb.
308 *
309 * CONTEXT:
310 * pcpu_alloc_mutex.
311 */
312 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
313 int page_start, int page_end)
314 {
315 struct page **pages;
316
317 /*
318 * If control reaches here, there must have been at least one
319 * successful population attempt so the temp pages array must
320 * be available now.
321 */
322 pages = pcpu_get_pages();
323 BUG_ON(!pages);
324
325 /* unmap and free */
326 pcpu_pre_unmap_flush(chunk, page_start, page_end);
327
328 pcpu_unmap_pages(chunk, pages, page_start, page_end);
329
330 pcpu_free_pages(chunk, pages, page_start, page_end);
331 }
332
333 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
334 {
335 struct pcpu_chunk *chunk;
336 struct vm_struct **vms;
337
338 chunk = pcpu_alloc_chunk(gfp);
339 if (!chunk)
340 return NULL;
341
342 vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,
343 pcpu_nr_groups, pcpu_atom_size);
344 if (!vms) {
345 pcpu_free_chunk(chunk);
346 return NULL;
347 }
348
349 chunk->data = vms;
350 chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
351
352 pcpu_stats_chunk_alloc();
353 trace_percpu_create_chunk(chunk->base_addr);
354
355 return chunk;
356 }
357
358 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
359 {
360 if (!chunk)
361 return;
362
363 pcpu_stats_chunk_dealloc();
364 trace_percpu_destroy_chunk(chunk->base_addr);
365
366 if (chunk->data)
367 pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
368 pcpu_free_chunk(chunk);
369 }
370
371 static struct page *pcpu_addr_to_page(void *addr)
372 {
373 return vmalloc_to_page(addr);
374 }
375
376 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
377 {
378 /* no extra restriction */
379 return 0;
380 }
381
382 /**
383 * pcpu_should_reclaim_chunk - determine if a chunk should go into reclaim
384 * @chunk: chunk of interest
385 *
386 * This is the entry point for percpu reclaim. If a chunk qualifies, it is then
387 * isolated and managed in separate lists at the back of pcpu_slot: sidelined
388 * and to_depopulate respectively. The to_depopulate list holds chunks slated
389 * for depopulation. They no longer contribute to pcpu_nr_empty_pop_pages once
390 * they are on this list. Once depopulated, they are moved onto the sidelined
391 * list which enables them to be pulled back in for allocation if no other chunk
392 * can suffice the allocation.
393 */
394 static bool pcpu_should_reclaim_chunk(struct pcpu_chunk *chunk)
395 {
396 /* do not reclaim either the first chunk or reserved chunk */
397 if (chunk == pcpu_first_chunk || chunk == pcpu_reserved_chunk)
398 return false;
399
400 /*
401 * If it is isolated, it may be on the sidelined list so move it back to
402 * the to_depopulate list. If we hit at least 1/4 pages empty pages AND
403 * there is no system-wide shortage of empty pages aside from this
404 * chunk, move it to the to_depopulate list.
405 */
406 return ((chunk->isolated && chunk->nr_empty_pop_pages) ||
407 (pcpu_nr_empty_pop_pages >
408 (PCPU_EMPTY_POP_PAGES_HIGH + chunk->nr_empty_pop_pages) &&
409 chunk->nr_empty_pop_pages >= chunk->nr_pages / 4));
410 }
411
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