mm/hugetlb.c

   1 /*
   2  * Generic hugetlb support.
   3  * (C) William Irwin, April 2004
   4  */
   5 #include <linux/gfp.h>
   6 #include <linux/list.h>
   7 #include <linux/init.h>
   8 #include <linux/module.h>
   9 #include <linux/mm.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/highmem.h>
  12 #include <linux/nodemask.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/mempolicy.h>
  15 #include <linux/cpuset.h>
  16 #include <linux/mutex.h>
  17
  18 #include <asm/page.h>
  19 #include <asm/pgtable.h>
  20
  21 #include <linux/hugetlb.h>
  22 #include "internal.h"
  23
  24 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  25 static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
  26 unsigned long max_huge_pages;
  27 static struct list_head hugepage_freelists[MAX_NUMNODES];
  28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  30 /*
  31  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  32  */
  33 static DEFINE_SPINLOCK(hugetlb_lock);
  34
  35 static void clear_huge_page(struct page *page, unsigned long addr)
  36 {
  37         int i;
  38
  39         might_sleep();
  40         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  41                 cond_resched();
  42                 clear_user_highpage(page + i, addr);
  43         }
  44 }
  45
  46 static void copy_huge_page(struct page *dst, struct page *src,
  47                            unsigned long addr)
  48 {
  49         int i;
  50
  51         might_sleep();
  52         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  53                 cond_resched();
  54                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
  55         }
  56 }
  57
  58 static void enqueue_huge_page(struct page *page)
  59 {
  60         int nid = page_to_nid(page);
  61         list_add(&page->lru, &hugepage_freelists[nid]);
  62         free_huge_pages++;
  63         free_huge_pages_node[nid]++;
  64 }
  65
  66 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  67                                 unsigned long address)
  68 {
  69         int nid = numa_node_id();
  70         struct page *page = NULL;
  71         struct zonelist *zonelist = huge_zonelist(vma, address);
  72         struct zone **z;
  73
  74         for (z = zonelist->zones; *z; z++) {
  75                 nid = zone_to_nid(*z);
  76                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
  77                     !list_empty(&hugepage_freelists[nid]))
  78                         break;
  79         }
  80
  81         if (*z) {
  82                 page = list_entry(hugepage_freelists[nid].next,
  83                                   struct page, lru);
  84                 list_del(&page->lru);
  85                 free_huge_pages--;
  86                 free_huge_pages_node[nid]--;
  87         }
  88         return page;
  89 }
  90
  91 static void free_huge_page(struct page *page)
  92 {
  93         BUG_ON(page_count(page));
  94
  95         INIT_LIST_HEAD(&page->lru);
  96
  97         spin_lock(&hugetlb_lock);
  98         enqueue_huge_page(page);
  99         spin_unlock(&hugetlb_lock);
 100 }
 101
 102 static int alloc_fresh_huge_page(void)
 103 {
 104         static int nid = 0;
 105         struct page *page;
 106         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
 107                                         HUGETLB_PAGE_ORDER);
 108         nid = next_node(nid, node_online_map);
 109         if (nid == MAX_NUMNODES)
 110                 nid = first_node(node_online_map);
 111         if (page) {
 112                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
 113                 spin_lock(&hugetlb_lock);
 114                 nr_huge_pages++;
 115                 nr_huge_pages_node[page_to_nid(page)]++;
 116                 spin_unlock(&hugetlb_lock);
 117                 put_page(page); /* free it into the hugepage allocator */
 118                 return 1;
 119         }
 120         return 0;
 121 }
 122
 123 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 124                                     unsigned long addr)
 125 {
 126         struct page *page;
 127
 128         spin_lock(&hugetlb_lock);
 129         if (vma->vm_flags & VM_MAYSHARE)
 130                 resv_huge_pages--;
 131         else if (free_huge_pages <= resv_huge_pages)
 132                 goto fail;
 133
 134         page = dequeue_huge_page(vma, addr);
 135         if (!page)
 136                 goto fail;
 137
 138         spin_unlock(&hugetlb_lock);
 139         set_page_refcounted(page);
 140         return page;
 141
 142 fail:
 143         spin_unlock(&hugetlb_lock);
 144         return NULL;
 145 }
 146
 147 static int __init hugetlb_init(void)
 148 {
 149         unsigned long i;
 150
 151         if (HPAGE_SHIFT == 0)
 152                 return 0;
 153
 154         for (i = 0; i < MAX_NUMNODES; ++i)
 155                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 156
 157         for (i = 0; i < max_huge_pages; ++i) {
 158                 if (!alloc_fresh_huge_page())
 159                         break;
 160         }
 161         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 162         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 163         return 0;
 164 }
 165 module_init(hugetlb_init);
 166
 167 static int __init hugetlb_setup(char *s)
 168 {
 169         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 170                 max_huge_pages = 0;
 171         return 1;
 172 }
 173 __setup("hugepages=", hugetlb_setup);
 174
 175 #ifdef CONFIG_SYSCTL
 176 static void update_and_free_page(struct page *page)
 177 {
 178         int i;
 179         nr_huge_pages--;
 180         nr_huge_pages_node[page_to_nid(page)]--;
 181         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 182                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 183                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 184                                 1 << PG_private | 1<< PG_writeback);
 185         }
 186         page[1].lru.next = NULL;
 187         set_page_refcounted(page);
 188         __free_pages(page, HUGETLB_PAGE_ORDER);
 189 }
 190
 191 #ifdef CONFIG_HIGHMEM
 192 static void try_to_free_low(unsigned long count)
 193 {
 194         int i;
 195
 196         for (i = 0; i < MAX_NUMNODES; ++i) {
 197                 struct page *page, *next;
 198                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 199                         if (PageHighMem(page))
 200                                 continue;
 201                         list_del(&page->lru);
 202                         update_and_free_page(page);
 203                         free_huge_pages--;
 204                         free_huge_pages_node[page_to_nid(page)]--;
 205                         if (count >= nr_huge_pages)
 206                                 return;
 207                 }
 208         }
 209 }
 210 #else
 211 static inline void try_to_free_low(unsigned long count)
 212 {
 213 }
 214 #endif
 215
 216 static unsigned long set_max_huge_pages(unsigned long count)
 217 {
 218         while (count > nr_huge_pages) {
 219                 if (!alloc_fresh_huge_page())
 220                         return nr_huge_pages;
 221         }
 222         if (count >= nr_huge_pages)
 223                 return nr_huge_pages;
 224
 225         spin_lock(&hugetlb_lock);
 226         count = max(count, resv_huge_pages);
 227         try_to_free_low(count);
 228         while (count < nr_huge_pages) {
 229                 struct page *page = dequeue_huge_page(NULL, 0);
 230                 if (!page)
 231                         break;
 232                 update_and_free_page(page);
 233         }
 234         spin_unlock(&hugetlb_lock);
 235         return nr_huge_pages;
 236 }
 237
 238 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 239                            struct file *file, void __user *buffer,
 240                            size_t *length, loff_t *ppos)
 241 {
 242         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 243         max_huge_pages = set_max_huge_pages(max_huge_pages);
 244         return 0;
 245 }
 246 #endif /* CONFIG_SYSCTL */
 247
 248 int hugetlb_report_meminfo(char *buf)
 249 {
 250         return sprintf(buf,
 251                         "HugePages_Total: %5lu\n"
 252                         "HugePages_Free:  %5lu\n"
 253                         "HugePages_Rsvd:  %5lu\n"
 254                         "Hugepagesize:    %5lu kB\n",
 255                         nr_huge_pages,
 256                         free_huge_pages,
 257                         resv_huge_pages,
 258                         HPAGE_SIZE/1024);
 259 }
 260
 261 int hugetlb_report_node_meminfo(int nid, char *buf)
 262 {
 263         return sprintf(buf,
 264                 "Node %d HugePages_Total: %5u\n"
 265                 "Node %d HugePages_Free:  %5u\n",
 266                 nid, nr_huge_pages_node[nid],
 267                 nid, free_huge_pages_node[nid]);
 268 }
 269
 270 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 271 unsigned long hugetlb_total_pages(void)
 272 {
 273         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 274 }
 275
 276 /*
 277  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 278  * handle_mm_fault() to try to instantiate regular-sized pages in the
 279  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 280  * this far.
 281  */
 282 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 283                                 unsigned long address, int *unused)
 284 {
 285         BUG();
 286         return NULL;
 287 }
 288
 289 struct vm_operations_struct hugetlb_vm_ops = {
 290         .nopage = hugetlb_nopage,
 291 };
 292
 293 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 294                                 int writable)
 295 {
 296         pte_t entry;
 297
 298         if (writable) {
 299                 entry =
 300                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 301         } else {
 302                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 303         }
 304         entry = pte_mkyoung(entry);
 305         entry = pte_mkhuge(entry);
 306
 307         return entry;
 308 }
 309
 310 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 311                                    unsigned long address, pte_t *ptep)
 312 {
 313         pte_t entry;
 314
 315         entry = pte_mkwrite(pte_mkdirty(*ptep));
 316         ptep_set_access_flags(vma, address, ptep, entry, 1);
 317         update_mmu_cache(vma, address, entry);
 318         lazy_mmu_prot_update(entry);
 319 }
 320
 321
 322 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 323                             struct vm_area_struct *vma)
 324 {
 325         pte_t *src_pte, *dst_pte, entry;
 326         struct page *ptepage;
 327         unsigned long addr;
 328         int cow;
 329
 330         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 331
 332         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 333                 src_pte = huge_pte_offset(src, addr);
 334                 if (!src_pte)
 335                         continue;
 336                 dst_pte = huge_pte_alloc(dst, addr);
 337                 if (!dst_pte)
 338                         goto nomem;
 339                 spin_lock(&dst->page_table_lock);
 340                 spin_lock(&src->page_table_lock);
 341                 if (!pte_none(*src_pte)) {
 342                         if (cow)
 343                                 ptep_set_wrprotect(src, addr, src_pte);
 344                         entry = *src_pte;
 345                         ptepage = pte_page(entry);
 346                         get_page(ptepage);
 347                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 348                         set_huge_pte_at(dst, addr, dst_pte, entry);
 349                 }
 350                 spin_unlock(&src->page_table_lock);
 351                 spin_unlock(&dst->page_table_lock);
 352         }
 353         return 0;
 354
 355 nomem:
 356         return -ENOMEM;
 357 }
 358
 359 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 360                           unsigned long end)
 361 {
 362         struct mm_struct *mm = vma->vm_mm;
 363         unsigned long address;
 364         pte_t *ptep;
 365         pte_t pte;
 366         struct page *page;
 367
 368         WARN_ON(!is_vm_hugetlb_page(vma));
 369         BUG_ON(start & ~HPAGE_MASK);
 370         BUG_ON(end & ~HPAGE_MASK);
 371
 372         spin_lock(&mm->page_table_lock);
 373
 374         /* Update high watermark before we lower rss */
 375         update_hiwater_rss(mm);
 376
 377         for (address = start; address < end; address += HPAGE_SIZE) {
 378                 ptep = huge_pte_offset(mm, address);
 379                 if (!ptep)
 380                         continue;
 381
 382                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 383                 if (pte_none(pte))
 384                         continue;
 385
 386                 page = pte_page(pte);
 387                 put_page(page);
 388                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 389         }
 390
 391         spin_unlock(&mm->page_table_lock);
 392         flush_tlb_range(vma, start, end);
 393 }
 394
 395 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 396                         unsigned long address, pte_t *ptep, pte_t pte)
 397 {
 398         struct page *old_page, *new_page;
 399         int avoidcopy;
 400
 401         old_page = pte_page(pte);
 402
 403         /* If no-one else is actually using this page, avoid the copy
 404          * and just make the page writable */
 405         avoidcopy = (page_count(old_page) == 1);
 406         if (avoidcopy) {
 407                 set_huge_ptep_writable(vma, address, ptep);
 408                 return VM_FAULT_MINOR;
 409         }
 410
 411         page_cache_get(old_page);
 412         new_page = alloc_huge_page(vma, address);
 413
 414         if (!new_page) {
 415                 page_cache_release(old_page);
 416                 return VM_FAULT_OOM;
 417         }
 418
 419         spin_unlock(&mm->page_table_lock);
 420         copy_huge_page(new_page, old_page, address);
 421         spin_lock(&mm->page_table_lock);
 422
 423         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 424         if (likely(pte_same(*ptep, pte))) {
 425                 /* Break COW */
 426                 set_huge_pte_at(mm, address, ptep,
 427                                 make_huge_pte(vma, new_page, 1));
 428                 /* Make the old page be freed below */
 429                 new_page = old_page;
 430         }
 431         page_cache_release(new_page);
 432         page_cache_release(old_page);
 433         return VM_FAULT_MINOR;
 434 }
 435
 436 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 437                         unsigned long address, pte_t *ptep, int write_access)
 438 {
 439         int ret = VM_FAULT_SIGBUS;
 440         unsigned long idx;
 441         unsigned long size;
 442         struct page *page;
 443         struct address_space *mapping;
 444         pte_t new_pte;
 445
 446         mapping = vma->vm_file->f_mapping;
 447         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 448                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 449
 450         /*
 451          * Use page lock to guard against racing truncation
 452          * before we get page_table_lock.
 453          */
 454 retry:
 455         page = find_lock_page(mapping, idx);
 456         if (!page) {
 457                 if (hugetlb_get_quota(mapping))
 458                         goto out;
 459                 page = alloc_huge_page(vma, address);
 460                 if (!page) {
 461                         hugetlb_put_quota(mapping);
 462                         ret = VM_FAULT_OOM;
 463                         goto out;
 464                 }
 465                 clear_huge_page(page, address);
 466
 467                 if (vma->vm_flags & VM_SHARED) {
 468                         int err;
 469
 470                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 471                         if (err) {
 472                                 put_page(page);
 473                                 hugetlb_put_quota(mapping);
 474                                 if (err == -EEXIST)
 475                                         goto retry;
 476                                 goto out;
 477                         }
 478                 } else
 479                         lock_page(page);
 480         }
 481
 482         spin_lock(&mm->page_table_lock);
 483         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 484         if (idx >= size)
 485                 goto backout;
 486
 487         ret = VM_FAULT_MINOR;
 488         if (!pte_none(*ptep))
 489                 goto backout;
 490
 491         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 492         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 493                                 && (vma->vm_flags & VM_SHARED)));
 494         set_huge_pte_at(mm, address, ptep, new_pte);
 495
 496         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 497                 /* Optimization, do the COW without a second fault */
 498                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 499         }
 500
 501         spin_unlock(&mm->page_table_lock);
 502         unlock_page(page);
 503 out:
 504         return ret;
 505
 506 backout:
 507         spin_unlock(&mm->page_table_lock);
 508         hugetlb_put_quota(mapping);
 509         unlock_page(page);
 510         put_page(page);
 511         goto out;
 512 }
 513
 514 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 515                         unsigned long address, int write_access)
 516 {
 517         pte_t *ptep;
 518         pte_t entry;
 519         int ret;
 520         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 521
 522         ptep = huge_pte_alloc(mm, address);
 523         if (!ptep)
 524                 return VM_FAULT_OOM;
 525
 526         /*
 527          * Serialize hugepage allocation and instantiation, so that we don't
 528          * get spurious allocation failures if two CPUs race to instantiate
 529          * the same page in the page cache.
 530          */
 531         mutex_lock(&hugetlb_instantiation_mutex);
 532         entry = *ptep;
 533         if (pte_none(entry)) {
 534                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 535                 mutex_unlock(&hugetlb_instantiation_mutex);
 536                 return ret;
 537         }
 538
 539         ret = VM_FAULT_MINOR;
 540
 541         spin_lock(&mm->page_table_lock);
 542         /* Check for a racing update before calling hugetlb_cow */
 543         if (likely(pte_same(entry, *ptep)))
 544                 if (write_access && !pte_write(entry))
 545                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 546         spin_unlock(&mm->page_table_lock);
 547         mutex_unlock(&hugetlb_instantiation_mutex);
 548
 549         return ret;
 550 }
 551
 552 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 553                         struct page **pages, struct vm_area_struct **vmas,
 554                         unsigned long *position, int *length, int i)
 555 {
 556         unsigned long pfn_offset;
 557         unsigned long vaddr = *position;
 558         int remainder = *length;
 559
 560         spin_lock(&mm->page_table_lock);
 561         while (vaddr < vma->vm_end && remainder) {
 562                 pte_t *pte;
 563                 struct page *page;
 564
 565                 /*
 566                  * Some archs (sparc64, sh*) have multiple pte_ts to
 567                  * each hugepage.  We have to make * sure we get the
 568                  * first, for the page indexing below to work.
 569                  */
 570                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 571
 572                 if (!pte || pte_none(*pte)) {
 573                         int ret;
 574
 575                         spin_unlock(&mm->page_table_lock);
 576                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 577                         spin_lock(&mm->page_table_lock);
 578                         if (ret == VM_FAULT_MINOR)
 579                                 continue;
 580
 581                         remainder = 0;
 582                         if (!i)
 583                                 i = -EFAULT;
 584                         break;
 585                 }
 586
 587                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 588                 page = pte_page(*pte);
 589 same_page:
 590                 if (pages) {
 591                         get_page(page);
 592                         pages[i] = page + pfn_offset;
 593                 }
 594
 595                 if (vmas)
 596                         vmas[i] = vma;
 597
 598                 vaddr += PAGE_SIZE;
 599                 ++pfn_offset;
 600                 --remainder;
 601                 ++i;
 602                 if (vaddr < vma->vm_end && remainder &&
 603                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 604                         /*
 605                          * We use pfn_offset to avoid touching the pageframes
 606                          * of this compound page.
 607                          */
 608                         goto same_page;
 609                 }
 610         }
 611         spin_unlock(&mm->page_table_lock);
 612         *length = remainder;
 613         *position = vaddr;
 614
 615         return i;
 616 }
 617
 618 void hugetlb_change_protection(struct vm_area_struct *vma,
 619                 unsigned long address, unsigned long end, pgprot_t newprot)
 620 {
 621         struct mm_struct *mm = vma->vm_mm;
 622         unsigned long start = address;
 623         pte_t *ptep;
 624         pte_t pte;
 625
 626         BUG_ON(address >= end);
 627         flush_cache_range(vma, address, end);
 628
 629         spin_lock(&mm->page_table_lock);
 630         for (; address < end; address += HPAGE_SIZE) {
 631                 ptep = huge_pte_offset(mm, address);
 632                 if (!ptep)
 633                         continue;
 634                 if (!pte_none(*ptep)) {
 635                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 636                         pte = pte_mkhuge(pte_modify(pte, newprot));
 637                         set_huge_pte_at(mm, address, ptep, pte);
 638                         lazy_mmu_prot_update(pte);
 639                 }
 640         }
 641         spin_unlock(&mm->page_table_lock);
 642
 643         flush_tlb_range(vma, start, end);
 644 }
 645
 646 struct file_region {
 647         struct list_head link;
 648         long from;
 649         long to;
 650 };
 651
 652 static long region_add(struct list_head *head, long f, long t)
 653 {
 654         struct file_region *rg, *nrg, *trg;
 655
 656         /* Locate the region we are either in or before. */
 657         list_for_each_entry(rg, head, link)
 658                 if (f <= rg->to)
 659                         break;
 660
 661         /* Round our left edge to the current segment if it encloses us. */
 662         if (f > rg->from)
 663                 f = rg->from;
 664
 665         /* Check for and consume any regions we now overlap with. */
 666         nrg = rg;
 667         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 668                 if (&rg->link == head)
 669                         break;
 670                 if (rg->from > t)
 671                         break;
 672
 673                 /* If this area reaches higher then extend our area to
 674                  * include it completely.  If this is not the first area
 675                  * which we intend to reuse, free it. */
 676                 if (rg->to > t)
 677                         t = rg->to;
 678                 if (rg != nrg) {
 679                         list_del(&rg->link);
 680                         kfree(rg);
 681                 }
 682         }
 683         nrg->from = f;
 684         nrg->to = t;
 685         return 0;
 686 }
 687
 688 static long region_chg(struct list_head *head, long f, long t)
 689 {
 690         struct file_region *rg, *nrg;
 691         long chg = 0;
 692
 693         /* Locate the region we are before or in. */
 694         list_for_each_entry(rg, head, link)
 695                 if (f <= rg->to)
 696                         break;
 697
 698         /* If we are below the current region then a new region is required.
 699          * Subtle, allocate a new region at the position but make it zero
 700          * size such that we can guarentee to record the reservation. */
 701         if (&rg->link == head || t < rg->from) {
 702                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 703                 if (nrg == 0)
 704                         return -ENOMEM;
 705                 nrg->from = f;
 706                 nrg->to   = f;
 707                 INIT_LIST_HEAD(&nrg->link);
 708                 list_add(&nrg->link, rg->link.prev);
 709
 710                 return t - f;
 711         }
 712
 713         /* Round our left edge to the current segment if it encloses us. */
 714         if (f > rg->from)
 715                 f = rg->from;
 716         chg = t - f;
 717
 718         /* Check for and consume any regions we now overlap with. */
 719         list_for_each_entry(rg, rg->link.prev, link) {
 720                 if (&rg->link == head)
 721                         break;
 722                 if (rg->from > t)
 723                         return chg;
 724
 725                 /* We overlap with this area, if it extends futher than
 726                  * us then we must extend ourselves.  Account for its
 727                  * existing reservation. */
 728                 if (rg->to > t) {
 729                         chg += rg->to - t;
 730                         t = rg->to;
 731                 }
 732                 chg -= rg->to - rg->from;
 733         }
 734         return chg;
 735 }
 736
 737 static long region_truncate(struct list_head *head, long end)
 738 {
 739         struct file_region *rg, *trg;
 740         long chg = 0;
 741
 742         /* Locate the region we are either in or before. */
 743         list_for_each_entry(rg, head, link)
 744                 if (end <= rg->to)
 745                         break;
 746         if (&rg->link == head)
 747                 return 0;
 748
 749         /* If we are in the middle of a region then adjust it. */
 750         if (end > rg->from) {
 751                 chg = rg->to - end;
 752                 rg->to = end;
 753                 rg = list_entry(rg->link.next, typeof(*rg), link);
 754         }
 755
 756         /* Drop any remaining regions. */
 757         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 758                 if (&rg->link == head)
 759                         break;
 760                 chg += rg->to - rg->from;
 761                 list_del(&rg->link);
 762                 kfree(rg);
 763         }
 764         return chg;
 765 }
 766
 767 static int hugetlb_acct_memory(long delta)
 768 {
 769         int ret = -ENOMEM;
 770
 771         spin_lock(&hugetlb_lock);
 772         if ((delta + resv_huge_pages) <= free_huge_pages) {
 773                 resv_huge_pages += delta;
 774                 ret = 0;
 775         }
 776         spin_unlock(&hugetlb_lock);
 777         return ret;
 778 }
 779
 780 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 781 {
 782         long ret, chg;
 783
 784         chg = region_chg(&inode->i_mapping->private_list, from, to);
 785         if (chg < 0)
 786                 return chg;
 787         ret = hugetlb_acct_memory(chg);
 788         if (ret < 0)
 789                 return ret;
 790         region_add(&inode->i_mapping->private_list, from, to);
 791         return 0;
 792 }
 793
 794 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 795 {
 796         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 797         hugetlb_acct_memory(freed - chg);
 798 }