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_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  */
  78 static 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  */
 107 static 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  */
 142 static 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
 150 static 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  */
 169 static 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  */
 205 static 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
 213 static 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  */
 236 static 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
 261 err:
 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  */
 283 static 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  */
 303 static 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);
 344 clear:
 345         for_each_possible_cpu(cpu)
 346                 memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
 347         return 0;
 348
 349 err_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);
 354 err_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  */
 374 static 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
 414 static 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
 435 static 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
 442 static struct page *pcpu_addr_to_page(void *addr)
 443 {
 444         return vmalloc_to_page(addr);
 445 }
 446
 447 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
 448 {
 449         /* no extra restriction */
 450         return 0;
 451 }