linux/mm/percpu-vm.c
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   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
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