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
13static 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 */
32static 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 */
54static 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 */
82static 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
102err:
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 */
127static 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
135static 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 */
153static 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 */
185static 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
193static 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 */
214static 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;
232err:
233	for_each_possible_cpu(tcpu) {
234		if (tcpu == cpu)
235			break;
236		__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
237				   page_end - page_start);
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 */
255static 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 */
276static 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 */
312static 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
333static 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
358static 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
371static struct page *pcpu_addr_to_page(void *addr)
372{
373	return vmalloc_to_page(addr);
374}
375
376static 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 */
394static 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