mm/bootmem.c

   1 /*
   2  *  bootmem - A boot-time physical memory allocator and configurator
   3  *
   4  *  Copyright (C) 1999 Ingo Molnar
   5  *                1999 Kanoj Sarcar, SGI
   6  *                2008 Johannes Weiner
   7  *
   8  * Access to this subsystem has to be serialized externally (which is true
   9  * for the boot process anyway).
  10  */
  11 #include <linux/init.h>
  12 #include <linux/pfn.h>
  13 #include <linux/bootmem.h>
  14 #include <linux/module.h>
  15
  16 #include <asm/bug.h>
  17 #include <asm/io.h>
  18 #include <asm/processor.h>
  19
  20 #include "internal.h"
  21
  22 unsigned long max_low_pfn;
  23 unsigned long min_low_pfn;
  24 unsigned long max_pfn;
  25
  26 #ifdef CONFIG_CRASH_DUMP
  27 /*
  28  * If we have booted due to a crash, max_pfn will be a very low value. We need
  29  * to know the amount of memory that the previous kernel used.
  30  */
  31 unsigned long saved_max_pfn;
  32 #endif
  33
  34 bootmem_data_t bootmem_node_data[MAX_NUMNODES] __initdata;
  35
  36 static struct list_head bdata_list __initdata = LIST_HEAD_INIT(bdata_list);
  37
  38 static int bootmem_debug;
  39
  40 static int __init bootmem_debug_setup(char *buf)
  41 {
  42         bootmem_debug = 1;
  43         return 0;
  44 }
  45 early_param("bootmem_debug", bootmem_debug_setup);
  46
  47 #define bdebug(fmt, args...) ({                         \
  48         if (unlikely(bootmem_debug))                    \
  49                 printk(KERN_INFO                        \
  50                         "bootmem::%s " fmt,             \
  51                         __func__, ## args);             \
  52 })
  53
  54 static unsigned long __init bootmap_bytes(unsigned long pages)
  55 {
  56         unsigned long bytes = (pages + 7) / 8;
  57
  58         return ALIGN(bytes, sizeof(long));
  59 }
  60
  61 /**
  62  * bootmem_bootmap_pages - calculate bitmap size in pages
  63  * @pages: number of pages the bitmap has to represent
  64  */
  65 unsigned long __init bootmem_bootmap_pages(unsigned long pages)
  66 {
  67         unsigned long bytes = bootmap_bytes(pages);
  68
  69         return PAGE_ALIGN(bytes) >> PAGE_SHIFT;
  70 }
  71
  72 /*
  73  * link bdata in order
  74  */
  75 static void __init link_bootmem(bootmem_data_t *bdata)
  76 {
  77         struct list_head *iter;
  78
  79         list_for_each(iter, &bdata_list) {
  80                 bootmem_data_t *ent;
  81
  82                 ent = list_entry(iter, bootmem_data_t, list);
  83                 if (bdata->node_min_pfn < ent->node_min_pfn)
  84                         break;
  85         }
  86         list_add_tail(&bdata->list, iter);
  87 }
  88
  89 /*
  90  * Called once to set up the allocator itself.
  91  */
  92 static unsigned long __init init_bootmem_core(bootmem_data_t *bdata,
  93         unsigned long mapstart, unsigned long start, unsigned long end)
  94 {
  95         unsigned long mapsize;
  96
  97         mminit_validate_memmodel_limits(&start, &end);
  98         bdata->node_bootmem_map = phys_to_virt(PFN_PHYS(mapstart));
  99         bdata->node_min_pfn = start;
 100         bdata->node_low_pfn = end;
 101         link_bootmem(bdata);
 102
 103         /*
 104          * Initially all pages are reserved - setup_arch() has to
 105          * register free RAM areas explicitly.
 106          */
 107         mapsize = bootmap_bytes(end - start);
 108         memset(bdata->node_bootmem_map, 0xff, mapsize);
 109
 110         bdebug("nid=%td start=%lx map=%lx end=%lx mapsize=%lx\n",
 111                 bdata - bootmem_node_data, start, mapstart, end, mapsize);
 112
 113         return mapsize;
 114 }
 115
 116 /**
 117  * init_bootmem_node - register a node as boot memory
 118  * @pgdat: node to register
 119  * @freepfn: pfn where the bitmap for this node is to be placed
 120  * @startpfn: first pfn on the node
 121  * @endpfn: first pfn after the node
 122  *
 123  * Returns the number of bytes needed to hold the bitmap for this node.
 124  */
 125 unsigned long __init init_bootmem_node(pg_data_t *pgdat, unsigned long freepfn,
 126                                 unsigned long startpfn, unsigned long endpfn)
 127 {
 128         return init_bootmem_core(pgdat->bdata, freepfn, startpfn, endpfn);
 129 }
 130
 131 /**
 132  * init_bootmem - register boot memory
 133  * @start: pfn where the bitmap is to be placed
 134  * @pages: number of available physical pages
 135  *
 136  * Returns the number of bytes needed to hold the bitmap.
 137  */
 138 unsigned long __init init_bootmem(unsigned long start, unsigned long pages)
 139 {
 140         max_low_pfn = pages;
 141         min_low_pfn = start;
 142         return init_bootmem_core(NODE_DATA(0)->bdata, start, 0, pages);
 143 }
 144
 145 static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 146 {
 147         int aligned;
 148         struct page *page;
 149         unsigned long start, end, pages, count = 0;
 150
 151         if (!bdata->node_bootmem_map)
 152                 return 0;
 153
 154         start = bdata->node_min_pfn;
 155         end = bdata->node_low_pfn;
 156
 157         /*
 158          * If the start is aligned to the machines wordsize, we might
 159          * be able to free pages in bulks of that order.
 160          */
 161         aligned = !(start & (BITS_PER_LONG - 1));
 162
 163         bdebug("nid=%td start=%lx end=%lx aligned=%d\n",
 164                 bdata - bootmem_node_data, start, end, aligned);
 165
 166         while (start < end) {
 167                 unsigned long *map, idx, vec;
 168
 169                 map = bdata->node_bootmem_map;
 170                 idx = start - bdata->node_min_pfn;
 171                 vec = ~map[idx / BITS_PER_LONG];
 172
 173                 if (aligned && vec == ~0UL && start + BITS_PER_LONG < end) {
 174                         int order = ilog2(BITS_PER_LONG);
 175
 176                         __free_pages_bootmem(pfn_to_page(start), order);
 177                         count += BITS_PER_LONG;
 178                 } else {
 179                         unsigned long off = 0;
 180
 181                         while (vec && off < BITS_PER_LONG) {
 182                                 if (vec & 1) {
 183                                         page = pfn_to_page(start + off);
 184                                         __free_pages_bootmem(page, 0);
 185                                         count++;
 186                                 }
 187                                 vec >>= 1;
 188                                 off++;
 189                         }
 190                 }
 191                 start += BITS_PER_LONG;
 192         }
 193
 194         page = virt_to_page(bdata->node_bootmem_map);
 195         pages = bdata->node_low_pfn - bdata->node_min_pfn;
 196         pages = bootmem_bootmap_pages(pages);
 197         count += pages;
 198         while (pages--)
 199                 __free_pages_bootmem(page++, 0);
 200
 201         bdebug("nid=%td released=%lx\n", bdata - bootmem_node_data, count);
 202
 203         return count;
 204 }
 205
 206 /**
 207  * free_all_bootmem_node - release a node's free pages to the buddy allocator
 208  * @pgdat: node to be released
 209  *
 210  * Returns the number of pages actually released.
 211  */
 212 unsigned long __init free_all_bootmem_node(pg_data_t *pgdat)
 213 {
 214         register_page_bootmem_info_node(pgdat);
 215         return free_all_bootmem_core(pgdat->bdata);
 216 }
 217
 218 /**
 219  * free_all_bootmem - release free pages to the buddy allocator
 220  *
 221  * Returns the number of pages actually released.
 222  */
 223 unsigned long __init free_all_bootmem(void)
 224 {
 225         return free_all_bootmem_core(NODE_DATA(0)->bdata);
 226 }
 227
 228 static void __init __free(bootmem_data_t *bdata,
 229                         unsigned long sidx, unsigned long eidx)
 230 {
 231         unsigned long idx;
 232
 233         bdebug("nid=%td start=%lx end=%lx\n", bdata - bootmem_node_data,
 234                 sidx + bdata->node_min_pfn,
 235                 eidx + bdata->node_min_pfn);
 236
 237         if (bdata->hint_idx > sidx)
 238                 bdata->hint_idx = sidx;
 239
 240         for (idx = sidx; idx < eidx; idx++)
 241                 if (!test_and_clear_bit(idx, bdata->node_bootmem_map))
 242                         BUG();
 243 }
 244
 245 static int __init __reserve(bootmem_data_t *bdata, unsigned long sidx,
 246                         unsigned long eidx, int flags)
 247 {
 248         unsigned long idx;
 249         int exclusive = flags & BOOTMEM_EXCLUSIVE;
 250
 251         bdebug("nid=%td start=%lx end=%lx flags=%x\n",
 252                 bdata - bootmem_node_data,
 253                 sidx + bdata->node_min_pfn,
 254                 eidx + bdata->node_min_pfn,
 255                 flags);
 256
 257         for (idx = sidx; idx < eidx; idx++)
 258                 if (test_and_set_bit(idx, bdata->node_bootmem_map)) {
 259                         if (exclusive) {
 260                                 __free(bdata, sidx, idx);
 261                                 return -EBUSY;
 262                         }
 263                         bdebug("silent double reserve of PFN %lx\n",
 264                                 idx + bdata->node_min_pfn);
 265                 }
 266         return 0;
 267 }
 268
 269 static int __init mark_bootmem_node(bootmem_data_t *bdata,
 270                                 unsigned long start, unsigned long end,
 271                                 int reserve, int flags)
 272 {
 273         unsigned long sidx, eidx;
 274
 275         bdebug("nid=%td start=%lx end=%lx reserve=%d flags=%x\n",
 276                 bdata - bootmem_node_data, start, end, reserve, flags);
 277
 278         BUG_ON(start < bdata->node_min_pfn);
 279         BUG_ON(end > bdata->node_low_pfn);
 280
 281         sidx = start - bdata->node_min_pfn;
 282         eidx = end - bdata->node_min_pfn;
 283
 284         if (reserve)
 285                 return __reserve(bdata, sidx, eidx, flags);
 286         else
 287                 __free(bdata, sidx, eidx);
 288         return 0;
 289 }
 290
 291 static int __init mark_bootmem(unsigned long start, unsigned long end,
 292                                 int reserve, int flags)
 293 {
 294         unsigned long pos;
 295         bootmem_data_t *bdata;
 296
 297         pos = start;
 298         list_for_each_entry(bdata, &bdata_list, list) {
 299                 int err;
 300                 unsigned long max;
 301
 302                 if (pos < bdata->node_min_pfn ||
 303                     pos >= bdata->node_low_pfn) {
 304                         BUG_ON(pos != start);
 305                         continue;
 306                 }
 307
 308                 max = min(bdata->node_low_pfn, end);
 309
 310                 err = mark_bootmem_node(bdata, pos, max, reserve, flags);
 311                 if (reserve && err) {
 312                         mark_bootmem(start, pos, 0, 0);
 313                         return err;
 314                 }
 315
 316                 if (max == end)
 317                         return 0;
 318                 pos = bdata->node_low_pfn;
 319         }
 320         BUG();
 321 }
 322
 323 /**
 324  * free_bootmem_node - mark a page range as usable
 325  * @pgdat: node the range resides on
 326  * @physaddr: starting address of the range
 327  * @size: size of the range in bytes
 328  *
 329  * Partial pages will be considered reserved and left as they are.
 330  *
 331  * The range must reside completely on the specified node.
 332  */
 333 void __init free_bootmem_node(pg_data_t *pgdat, unsigned long physaddr,
 334                               unsigned long size)
 335 {
 336         unsigned long start, end;
 337
 338         start = PFN_UP(physaddr);
 339         end = PFN_DOWN(physaddr + size);
 340
 341         mark_bootmem_node(pgdat->bdata, start, end, 0, 0);
 342 }
 343
 344 /**
 345  * free_bootmem - mark a page range as usable
 346  * @addr: starting address of the range
 347  * @size: size of the range in bytes
 348  *
 349  * Partial pages will be considered reserved and left as they are.
 350  *
 351  * The range must be contiguous but may span node boundaries.
 352  */
 353 void __init free_bootmem(unsigned long addr, unsigned long size)
 354 {
 355         unsigned long start, end;
 356
 357         start = PFN_UP(addr);
 358         end = PFN_DOWN(addr + size);
 359
 360         mark_bootmem(start, end, 0, 0);
 361 }
 362
 363 /**
 364  * reserve_bootmem_node - mark a page range as reserved
 365  * @pgdat: node the range resides on
 366  * @physaddr: starting address of the range
 367  * @size: size of the range in bytes
 368  * @flags: reservation flags (see linux/bootmem.h)
 369  *
 370  * Partial pages will be reserved.
 371  *
 372  * The range must reside completely on the specified node.
 373  */
 374 int __init reserve_bootmem_node(pg_data_t *pgdat, unsigned long physaddr,
 375                                  unsigned long size, int flags)
 376 {
 377         unsigned long start, end;
 378
 379         start = PFN_DOWN(physaddr);
 380         end = PFN_UP(physaddr + size);
 381
 382         return mark_bootmem_node(pgdat->bdata, start, end, 1, flags);
 383 }
 384
 385 #ifndef CONFIG_HAVE_ARCH_BOOTMEM_NODE
 386 /**
 387  * reserve_bootmem - mark a page range as usable
 388  * @addr: starting address of the range
 389  * @size: size of the range in bytes
 390  * @flags: reservation flags (see linux/bootmem.h)
 391  *
 392  * Partial pages will be reserved.
 393  *
 394  * The range must be contiguous but may span node boundaries.
 395  */
 396 int __init reserve_bootmem(unsigned long addr, unsigned long size,
 397                             int flags)
 398 {
 399         unsigned long start, end;
 400
 401         start = PFN_DOWN(addr);
 402         end = PFN_UP(addr + size);
 403
 404         return mark_bootmem(start, end, 1, flags);
 405 }
 406 #endif /* !CONFIG_HAVE_ARCH_BOOTMEM_NODE */
 407
 408 static unsigned long align_idx(struct bootmem_data *bdata, unsigned long idx,
 409                         unsigned long step)
 410 {
 411         unsigned long base = bdata->node_min_pfn;
 412
 413         /*
 414          * Align the index with respect to the node start so that the
 415          * combination of both satisfies the requested alignment.
 416          */
 417
 418         return ALIGN(base + idx, step) - base;
 419 }
 420
 421 static unsigned long align_off(struct bootmem_data *bdata, unsigned long off,
 422                         unsigned long align)
 423 {
 424         unsigned long base = PFN_PHYS(bdata->node_min_pfn);
 425
 426         /* Same as align_idx for byte offsets */
 427
 428         return ALIGN(base + off, align) - base;
 429 }
 430
 431 static void * __init alloc_bootmem_core(struct bootmem_data *bdata,
 432                                 unsigned long size, unsigned long align,
 433                                 unsigned long goal, unsigned long limit)
 434 {
 435         unsigned long fallback = 0;
 436         unsigned long min, max, start, sidx, midx, step;
 437
 438         bdebug("nid=%td size=%lx [%lu pages] align=%lx goal=%lx limit=%lx\n",
 439                 bdata - bootmem_node_data, size, PAGE_ALIGN(size) >> PAGE_SHIFT,
 440                 align, goal, limit);
 441
 442         BUG_ON(!size);
 443         BUG_ON(align & (align - 1));
 444         BUG_ON(limit && goal + size > limit);
 445
 446         if (!bdata->node_bootmem_map)
 447                 return NULL;
 448
 449         min = bdata->node_min_pfn;
 450         max = bdata->node_low_pfn;
 451
 452         goal >>= PAGE_SHIFT;
 453         limit >>= PAGE_SHIFT;
 454
 455         if (limit && max > limit)
 456                 max = limit;
 457         if (max <= min)
 458                 return NULL;
 459
 460         step = max(align >> PAGE_SHIFT, 1UL);
 461
 462         if (goal && min < goal && goal < max)
 463                 start = ALIGN(goal, step);
 464         else
 465                 start = ALIGN(min, step);
 466
 467         sidx = start - bdata->node_min_pfn;
 468         midx = max - bdata->node_min_pfn;
 469
 470         if (bdata->hint_idx > sidx) {
 471                 /*
 472                  * Handle the valid case of sidx being zero and still
 473                  * catch the fallback below.
 474                  */
 475                 fallback = sidx + 1;
 476                 sidx = align_idx(bdata, bdata->hint_idx, step);
 477         }
 478
 479         while (1) {
 480                 int merge;
 481                 void *region;
 482                 unsigned long eidx, i, start_off, end_off;
 483 find_block:
 484                 sidx = find_next_zero_bit(bdata->node_bootmem_map, midx, sidx);
 485                 sidx = align_idx(bdata, sidx, step);
 486                 eidx = sidx + PFN_UP(size);
 487
 488                 if (sidx >= midx || eidx > midx)
 489                         break;
 490
 491                 for (i = sidx; i < eidx; i++)
 492                         if (test_bit(i, bdata->node_bootmem_map)) {
 493                                 sidx = align_idx(bdata, i, step);
 494                                 if (sidx == i)
 495                                         sidx += step;
 496                                 goto find_block;
 497                         }
 498
 499                 if (bdata->last_end_off & (PAGE_SIZE - 1) &&
 500                                 PFN_DOWN(bdata->last_end_off) + 1 == sidx)
 501                         start_off = align_off(bdata, bdata->last_end_off, align);
 502                 else
 503                         start_off = PFN_PHYS(sidx);
 504
 505                 merge = PFN_DOWN(start_off) < sidx;
 506                 end_off = start_off + size;
 507
 508                 bdata->last_end_off = end_off;
 509                 bdata->hint_idx = PFN_UP(end_off);
 510
 511                 /*
 512                  * Reserve the area now:
 513                  */
 514                 if (__reserve(bdata, PFN_DOWN(start_off) + merge,
 515                                 PFN_UP(end_off), BOOTMEM_EXCLUSIVE))
 516                         BUG();
 517
 518                 region = phys_to_virt(PFN_PHYS(bdata->node_min_pfn) +
 519                                 start_off);
 520                 memset(region, 0, size);
 521                 return region;
 522         }
 523
 524         if (fallback) {
 525                 sidx = align_idx(bdata, fallback - 1, step);
 526                 fallback = 0;
 527                 goto find_block;
 528         }
 529
 530         return NULL;
 531 }
 532
 533 static void * __init ___alloc_bootmem_nopanic(unsigned long size,
 534                                         unsigned long align,
 535                                         unsigned long goal,
 536                                         unsigned long limit)
 537 {
 538         bootmem_data_t *bdata;
 539
 540 restart:
 541         list_for_each_entry(bdata, &bdata_list, list) {
 542                 void *region;
 543
 544                 if (goal && bdata->node_low_pfn <= PFN_DOWN(goal))
 545                         continue;
 546                 if (limit && bdata->node_min_pfn >= PFN_DOWN(limit))
 547                         break;
 548
 549                 region = alloc_bootmem_core(bdata, size, align, goal, limit);
 550                 if (region)
 551                         return region;
 552         }
 553
 554         if (goal) {
 555                 goal = 0;
 556                 goto restart;
 557         }
 558
 559         return NULL;
 560 }
 561
 562 /**
 563  * __alloc_bootmem_nopanic - allocate boot memory without panicking
 564  * @size: size of the request in bytes
 565  * @align: alignment of the region
 566  * @goal: preferred starting address of the region
 567  *
 568  * The goal is dropped if it can not be satisfied and the allocation will
 569  * fall back to memory below @goal.
 570  *
 571  * Allocation may happen on any node in the system.
 572  *
 573  * Returns NULL on failure.
 574  */
 575 void * __init __alloc_bootmem_nopanic(unsigned long size, unsigned long align,
 576                                         unsigned long goal)
 577 {
 578         return ___alloc_bootmem_nopanic(size, align, goal, 0);
 579 }
 580
 581 static void * __init ___alloc_bootmem(unsigned long size, unsigned long align,
 582                                         unsigned long goal, unsigned long limit)
 583 {
 584         void *mem = ___alloc_bootmem_nopanic(size, align, goal, limit);
 585
 586         if (mem)
 587                 return mem;
 588         /*
 589          * Whoops, we cannot satisfy the allocation request.
 590          */
 591         printk(KERN_ALERT "bootmem alloc of %lu bytes failed!\n", size);
 592         panic("Out of memory");
 593         return NULL;
 594 }
 595
 596 /**
 597  * __alloc_bootmem - allocate boot memory
 598  * @size: size of the request in bytes
 599  * @align: alignment of the region
 600  * @goal: preferred starting address of the region
 601  *
 602  * The goal is dropped if it can not be satisfied and the allocation will
 603  * fall back to memory below @goal.
 604  *
 605  * Allocation may happen on any node in the system.
 606  *
 607  * The function panics if the request can not be satisfied.
 608  */
 609 void * __init __alloc_bootmem(unsigned long size, unsigned long align,
 610                               unsigned long goal)
 611 {
 612         return ___alloc_bootmem(size, align, goal, 0);
 613 }
 614
 615 static void * __init ___alloc_bootmem_node(bootmem_data_t *bdata,
 616                                 unsigned long size, unsigned long align,
 617                                 unsigned long goal, unsigned long limit)
 618 {
 619         void *ptr;
 620
 621         ptr = alloc_bootmem_core(bdata, size, align, goal, limit);
 622         if (ptr)
 623                 return ptr;
 624
 625         return ___alloc_bootmem(size, align, goal, limit);
 626 }
 627
 628 /**
 629  * __alloc_bootmem_node - allocate boot memory from a specific node
 630  * @pgdat: node to allocate from
 631  * @size: size of the request in bytes
 632  * @align: alignment of the region
 633  * @goal: preferred starting address of the region
 634  *
 635  * The goal is dropped if it can not be satisfied and the allocation will
 636  * fall back to memory below @goal.
 637  *
 638  * Allocation may fall back to any node in the system if the specified node
 639  * can not hold the requested memory.
 640  *
 641  * The function panics if the request can not be satisfied.
 642  */
 643 void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
 644                                    unsigned long align, unsigned long goal)
 645 {
 646         return ___alloc_bootmem_node(pgdat->bdata, size, align, goal, 0);
 647 }
 648
 649 #ifdef CONFIG_SPARSEMEM
 650 /**
 651  * alloc_bootmem_section - allocate boot memory from a specific section
 652  * @size: size of the request in bytes
 653  * @section_nr: sparse map section to allocate from
 654  *
 655  * Return NULL on failure.
 656  */
 657 void * __init alloc_bootmem_section(unsigned long size,
 658                                     unsigned long section_nr)
 659 {
 660         bootmem_data_t *bdata;
 661         unsigned long pfn, goal, limit;
 662
 663         pfn = section_nr_to_pfn(section_nr);
 664         goal = pfn << PAGE_SHIFT;
 665         limit = section_nr_to_pfn(section_nr + 1) << PAGE_SHIFT;
 666         bdata = &bootmem_node_data[early_pfn_to_nid(pfn)];
 667
 668         return alloc_bootmem_core(bdata, size, SMP_CACHE_BYTES, goal, limit);
 669 }
 670 #endif
 671
 672 void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
 673                                    unsigned long align, unsigned long goal)
 674 {
 675         void *ptr;
 676
 677         ptr = alloc_bootmem_core(pgdat->bdata, size, align, goal, 0);
 678         if (ptr)
 679                 return ptr;
 680
 681         return __alloc_bootmem_nopanic(size, align, goal);
 682 }
 683
 684 #ifndef ARCH_LOW_ADDRESS_LIMIT
 685 #define ARCH_LOW_ADDRESS_LIMIT  0xffffffffUL
 686 #endif
 687
 688 /**
 689  * __alloc_bootmem_low - allocate low boot memory
 690  * @size: size of the request in bytes
 691  * @align: alignment of the region
 692  * @goal: preferred starting address of the region
 693  *
 694  * The goal is dropped if it can not be satisfied and the allocation will
 695  * fall back to memory below @goal.
 696  *
 697  * Allocation may happen on any node in the system.
 698  *
 699  * The function panics if the request can not be satisfied.
 700  */
 701 void * __init __alloc_bootmem_low(unsigned long size, unsigned long align,
 702                                   unsigned long goal)
 703 {
 704         return ___alloc_bootmem(size, align, goal, ARCH_LOW_ADDRESS_LIMIT);
 705 }
 706
 707 /**
 708  * __alloc_bootmem_low_node - allocate low boot memory from a specific node
 709  * @pgdat: node to allocate from
 710  * @size: size of the request in bytes
 711  * @align: alignment of the region
 712  * @goal: preferred starting address of the region
 713  *
 714  * The goal is dropped if it can not be satisfied and the allocation will
 715  * fall back to memory below @goal.
 716  *
 717  * Allocation may fall back to any node in the system if the specified node
 718  * can not hold the requested memory.
 719  *
 720  * The function panics if the request can not be satisfied.
 721  */
 722 void * __init __alloc_bootmem_low_node(pg_data_t *pgdat, unsigned long size,
 723                                        unsigned long align, unsigned long goal)
 724 {
 725         return ___alloc_bootmem_node(pgdat->bdata, size, align,
 726                                 goal, ARCH_LOW_ADDRESS_LIMIT);
 727 }