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
  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_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  */
  41 static 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  */
  77 static 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  */
 106 static 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  */
 141 static 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
 149 static 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  */
 168 static 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  */
 203 static 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
 211 static 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  */
 234 static 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
 259 err:
 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  */
 281 static 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  */
 301 static 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);
 342 clear:
 343         for_each_possible_cpu(cpu)
 344                 memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
 345         return 0;
 346
 347 err_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);
 352 err_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  */
 371 static 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
 411 static 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
 432 static 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
 439 static struct page *pcpu_addr_to_page(void *addr)
 440 {
 441         return vmalloc_to_page(addr);
 442 }
 443
 444 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
 445 {
 446         /* no extra restriction */
 447         return 0;
 448 }