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

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