Root/mm/percpu-vm.c

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
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_and_bitmap - get temp pages array and bitmap
24 * @chunk: chunk of interest
25 * @bitmapp: output parameter for bitmap
26 * @may_alloc: may allocate the array
27 *
28 * Returns pointer to array of pointers to struct page and bitmap,
29 * both of which can be indexed with pcpu_page_idx(). The returned
30 * array is cleared to zero and *@bitmapp is copied from
31 * @chunk->populated. Note that there is only one array and bitmap
32 * and access exclusion is the caller's responsibility.
33 *
34 * CONTEXT:
35 * pcpu_alloc_mutex and does GFP_KERNEL allocation if @may_alloc.
36 * Otherwise, don't care.
37 *
38 * RETURNS:
39 * Pointer to temp pages array on success, NULL on failure.
40 */
41static struct page **pcpu_get_pages_and_bitmap(struct pcpu_chunk *chunk,
42                           unsigned long **bitmapp,
43                           bool may_alloc)
44{
45    static struct page **pages;
46    static unsigned long *bitmap;
47    size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
48    size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
49                 sizeof(unsigned long);
50
51    if (!pages || !bitmap) {
52        if (may_alloc && !pages)
53            pages = pcpu_mem_alloc(pages_size);
54        if (may_alloc && !bitmap)
55            bitmap = pcpu_mem_alloc(bitmap_size);
56        if (!pages || !bitmap)
57            return NULL;
58    }
59
60    memset(pages, 0, pages_size);
61    bitmap_copy(bitmap, chunk->populated, pcpu_unit_pages);
62
63    *bitmapp = bitmap;
64    return pages;
65}
66
67/**
68 * pcpu_free_pages - free pages which were allocated for @chunk
69 * @chunk: chunk pages were allocated for
70 * @pages: array of pages to be freed, indexed by pcpu_page_idx()
71 * @populated: populated bitmap
72 * @page_start: page index of the first page to be freed
73 * @page_end: page index of the last page to be freed + 1
74 *
75 * Free pages [@page_start and @page_end) in @pages for all units.
76 * The pages were allocated for @chunk.
77 */
78static void pcpu_free_pages(struct pcpu_chunk *chunk,
79                struct page **pages, unsigned long *populated,
80                int page_start, int page_end)
81{
82    unsigned int cpu;
83    int i;
84
85    for_each_possible_cpu(cpu) {
86        for (i = page_start; i < page_end; i++) {
87            struct page *page = pages[pcpu_page_idx(cpu, i)];
88
89            if (page)
90                __free_page(page);
91        }
92    }
93}
94
95/**
96 * pcpu_alloc_pages - allocates pages for @chunk
97 * @chunk: target chunk
98 * @pages: array to put the allocated pages into, indexed by pcpu_page_idx()
99 * @populated: populated bitmap
100 * @page_start: page index of the first page to be allocated
101 * @page_end: page index of the last page to be allocated + 1
102 *
103 * Allocate pages [@page_start,@page_end) into @pages for all units.
104 * The allocation is for @chunk. Percpu core doesn't care about the
105 * content of @pages and will pass it verbatim to pcpu_map_pages().
106 */
107static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
108                struct page **pages, unsigned long *populated,
109                int page_start, int page_end)
110{
111    const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
112    unsigned int cpu;
113    int i;
114
115    for_each_possible_cpu(cpu) {
116        for (i = page_start; i < page_end; i++) {
117            struct page **pagep = &pages[pcpu_page_idx(cpu, i)];
118
119            *pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
120            if (!*pagep) {
121                pcpu_free_pages(chunk, pages, populated,
122                        page_start, page_end);
123                return -ENOMEM;
124            }
125        }
126    }
127    return 0;
128}
129
130/**
131 * pcpu_pre_unmap_flush - flush cache prior to unmapping
132 * @chunk: chunk the regions to be flushed belongs to
133 * @page_start: page index of the first page to be flushed
134 * @page_end: page index of the last page to be flushed + 1
135 *
136 * Pages in [@page_start,@page_end) of @chunk are about to be
137 * unmapped. Flush cache. As each flushing trial can be very
138 * expensive, issue flush on the whole region at once rather than
139 * doing it for each cpu. This could be an overkill but is more
140 * scalable.
141 */
142static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
143                 int page_start, int page_end)
144{
145    flush_cache_vunmap(
146        pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
147        pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
148}
149
150static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
151{
152    unmap_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT);
153}
154
155/**
156 * pcpu_unmap_pages - unmap pages out of a pcpu_chunk
157 * @chunk: chunk of interest
158 * @pages: pages array which can be used to pass information to free
159 * @populated: populated bitmap
160 * @page_start: page index of the first page to unmap
161 * @page_end: page index of the last page to unmap + 1
162 *
163 * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
164 * Corresponding elements in @pages were cleared by the caller and can
165 * be used to carry information to pcpu_free_pages() which will be
166 * called after all unmaps are finished. The caller should call
167 * proper pre/post flush functions.
168 */
169static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
170                 struct page **pages, unsigned long *populated,
171                 int page_start, int page_end)
172{
173    unsigned int cpu;
174    int i;
175
176    for_each_possible_cpu(cpu) {
177        for (i = page_start; i < page_end; i++) {
178            struct page *page;
179
180            page = pcpu_chunk_page(chunk, cpu, i);
181            WARN_ON(!page);
182            pages[pcpu_page_idx(cpu, i)] = page;
183        }
184        __pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
185                   page_end - page_start);
186    }
187
188    for (i = page_start; i < page_end; i++)
189        __clear_bit(i, populated);
190}
191
192/**
193 * pcpu_post_unmap_tlb_flush - flush TLB after unmapping
194 * @chunk: pcpu_chunk the regions to be flushed belong to
195 * @page_start: page index of the first page to be flushed
196 * @page_end: page index of the last page to be flushed + 1
197 *
198 * Pages [@page_start,@page_end) of @chunk have been unmapped. Flush
199 * TLB for the regions. This can be skipped if the area is to be
200 * returned to vmalloc as vmalloc will handle TLB flushing lazily.
201 *
202 * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
203 * for the whole region.
204 */
205static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
206                      int page_start, int page_end)
207{
208    flush_tlb_kernel_range(
209        pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
210        pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
211}
212
213static int __pcpu_map_pages(unsigned long addr, struct page **pages,
214                int nr_pages)
215{
216    return map_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT,
217                    PAGE_KERNEL, pages);
218}
219
220/**
221 * pcpu_map_pages - map pages into a pcpu_chunk
222 * @chunk: chunk of interest
223 * @pages: pages array containing pages to be mapped
224 * @populated: populated bitmap
225 * @page_start: page index of the first page to map
226 * @page_end: page index of the last page to map + 1
227 *
228 * For each cpu, map pages [@page_start,@page_end) into @chunk. The
229 * caller is responsible for calling pcpu_post_map_flush() after all
230 * mappings are complete.
231 *
232 * This function is responsible for setting corresponding bits in
233 * @chunk->populated bitmap and whatever is necessary for reverse
234 * lookup (addr -> chunk).
235 */
236static int pcpu_map_pages(struct pcpu_chunk *chunk,
237              struct page **pages, unsigned long *populated,
238              int page_start, int page_end)
239{
240    unsigned int cpu, tcpu;
241    int i, err;
242
243    for_each_possible_cpu(cpu) {
244        err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
245                       &pages[pcpu_page_idx(cpu, page_start)],
246                       page_end - page_start);
247        if (err < 0)
248            goto err;
249    }
250
251    /* mapping successful, link chunk and mark populated */
252    for (i = page_start; i < page_end; i++) {
253        for_each_possible_cpu(cpu)
254            pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
255                        chunk);
256        __set_bit(i, populated);
257    }
258
259    return 0;
260
261err:
262    for_each_possible_cpu(tcpu) {
263        if (tcpu == cpu)
264            break;
265        __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
266                   page_end - page_start);
267    }
268    return err;
269}
270
271/**
272 * pcpu_post_map_flush - flush cache after mapping
273 * @chunk: pcpu_chunk the regions to be flushed belong to
274 * @page_start: page index of the first page to be flushed
275 * @page_end: page index of the last page to be flushed + 1
276 *
277 * Pages [@page_start,@page_end) of @chunk have been mapped. Flush
278 * cache.
279 *
280 * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
281 * for the whole region.
282 */
283static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
284                int page_start, int page_end)
285{
286    flush_cache_vmap(
287        pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
288        pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
289}
290
291/**
292 * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
293 * @chunk: chunk of interest
294 * @off: offset to the area to populate
295 * @size: size of the area to populate in bytes
296 *
297 * For each cpu, populate and map pages [@page_start,@page_end) into
298 * @chunk. The area is cleared on return.
299 *
300 * CONTEXT:
301 * pcpu_alloc_mutex, does GFP_KERNEL allocation.
302 */
303static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
304{
305    int page_start = PFN_DOWN(off);
306    int page_end = PFN_UP(off + size);
307    int free_end = page_start, unmap_end = page_start;
308    struct page **pages;
309    unsigned long *populated;
310    unsigned int cpu;
311    int rs, re, rc;
312
313    /* quick path, check whether all pages are already there */
314    rs = page_start;
315    pcpu_next_pop(chunk, &rs, &re, page_end);
316    if (rs == page_start && re == page_end)
317        goto clear;
318
319    /* need to allocate and map pages, this chunk can't be immutable */
320    WARN_ON(chunk->immutable);
321
322    pages = pcpu_get_pages_and_bitmap(chunk, &populated, true);
323    if (!pages)
324        return -ENOMEM;
325
326    /* alloc and map */
327    pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
328        rc = pcpu_alloc_pages(chunk, pages, populated, rs, re);
329        if (rc)
330            goto err_free;
331        free_end = re;
332    }
333
334    pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
335        rc = pcpu_map_pages(chunk, pages, populated, rs, re);
336        if (rc)
337            goto err_unmap;
338        unmap_end = re;
339    }
340    pcpu_post_map_flush(chunk, page_start, page_end);
341
342    /* commit new bitmap */
343    bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
344clear:
345    for_each_possible_cpu(cpu)
346        memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
347    return 0;
348
349err_unmap:
350    pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
351    pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
352        pcpu_unmap_pages(chunk, pages, populated, rs, re);
353    pcpu_post_unmap_tlb_flush(chunk, page_start, unmap_end);
354err_free:
355    pcpu_for_each_unpop_region(chunk, rs, re, page_start, free_end)
356        pcpu_free_pages(chunk, pages, populated, rs, re);
357    return rc;
358}
359
360/**
361 * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
362 * @chunk: chunk to depopulate
363 * @off: offset to the area to depopulate
364 * @size: size of the area to depopulate in bytes
365 * @flush: whether to flush cache and tlb or not
366 *
367 * For each cpu, depopulate and unmap pages [@page_start,@page_end)
368 * from @chunk. If @flush is true, vcache is flushed before unmapping
369 * and tlb after.
370 *
371 * CONTEXT:
372 * pcpu_alloc_mutex.
373 */
374static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
375{
376    int page_start = PFN_DOWN(off);
377    int page_end = PFN_UP(off + size);
378    struct page **pages;
379    unsigned long *populated;
380    int rs, re;
381
382    /* quick path, check whether it's empty already */
383    rs = page_start;
384    pcpu_next_unpop(chunk, &rs, &re, page_end);
385    if (rs == page_start && re == page_end)
386        return;
387
388    /* immutable chunks can't be depopulated */
389    WARN_ON(chunk->immutable);
390
391    /*
392     * If control reaches here, there must have been at least one
393     * successful population attempt so the temp pages array must
394     * be available now.
395     */
396    pages = pcpu_get_pages_and_bitmap(chunk, &populated, false);
397    BUG_ON(!pages);
398
399    /* unmap and free */
400    pcpu_pre_unmap_flush(chunk, page_start, page_end);
401
402    pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
403        pcpu_unmap_pages(chunk, pages, populated, rs, re);
404
405    /* no need to flush tlb, vmalloc will handle it lazily */
406
407    pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
408        pcpu_free_pages(chunk, pages, populated, rs, re);
409
410    /* commit new bitmap */
411    bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
412}
413
414static struct pcpu_chunk *pcpu_create_chunk(void)
415{
416    struct pcpu_chunk *chunk;
417    struct vm_struct **vms;
418
419    chunk = pcpu_alloc_chunk();
420    if (!chunk)
421        return NULL;
422
423    vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,
424                pcpu_nr_groups, pcpu_atom_size, GFP_KERNEL);
425    if (!vms) {
426        pcpu_free_chunk(chunk);
427        return NULL;
428    }
429
430    chunk->data = vms;
431    chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
432    return chunk;
433}
434
435static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
436{
437    if (chunk && chunk->data)
438        pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
439    pcpu_free_chunk(chunk);
440}
441
442static struct page *pcpu_addr_to_page(void *addr)
443{
444    return vmalloc_to_page(addr);
445}
446
447static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
448{
449    /* no extra restriction */
450    return 0;
451}
452

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