[PATCH] hugetlb: fix linked list corruption in unmap_hugepage_range()
[linux-2.6.git] / 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         struct page *tmp;
368         LIST_HEAD(page_list);
369
370         WARN_ON(!is_vm_hugetlb_page(vma));
371         BUG_ON(start & ~HPAGE_MASK);
372         BUG_ON(end & ~HPAGE_MASK);
373
374         spin_lock(&mm->page_table_lock);
375
376         /* Update high watermark before we lower rss */
377         update_hiwater_rss(mm);
378
379         for (address = start; address < end; address += HPAGE_SIZE) {
380                 ptep = huge_pte_offset(mm, address);
381                 if (!ptep)
382                         continue;
383
384                 pte = huge_ptep_get_and_clear(mm, address, ptep);
385                 if (pte_none(pte))
386                         continue;
387
388                 page = pte_page(pte);
389                 list_add(&page->lru, &page_list);
390                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
391         }
392
393         spin_unlock(&mm->page_table_lock);
394         flush_tlb_range(vma, start, end);
395         list_for_each_entry_safe(page, tmp, &page_list, lru) {
396                 list_del(&page->lru);
397                 put_page(page);
398         }
399 }
400
401 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
402                           unsigned long end)
403 {
404         /*
405          * It is undesirable to test vma->vm_file as it should be non-null
406          * for valid hugetlb area. However, vm_file will be NULL in the error
407          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
408          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
409          * to clean up. Since no pte has actually been setup, it is safe to
410          * do nothing in this case.
411          */
412         if (vma->vm_file) {
413                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
414                 __unmap_hugepage_range(vma, start, end);
415                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
416         }
417 }
418
419 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
420                         unsigned long address, pte_t *ptep, pte_t pte)
421 {
422         struct page *old_page, *new_page;
423         int avoidcopy;
424
425         old_page = pte_page(pte);
426
427         /* If no-one else is actually using this page, avoid the copy
428          * and just make the page writable */
429         avoidcopy = (page_count(old_page) == 1);
430         if (avoidcopy) {
431                 set_huge_ptep_writable(vma, address, ptep);
432                 return VM_FAULT_MINOR;
433         }
434
435         page_cache_get(old_page);
436         new_page = alloc_huge_page(vma, address);
437
438         if (!new_page) {
439                 page_cache_release(old_page);
440                 return VM_FAULT_OOM;
441         }
442
443         spin_unlock(&mm->page_table_lock);
444         copy_huge_page(new_page, old_page, address);
445         spin_lock(&mm->page_table_lock);
446
447         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
448         if (likely(pte_same(*ptep, pte))) {
449                 /* Break COW */
450                 set_huge_pte_at(mm, address, ptep,
451                                 make_huge_pte(vma, new_page, 1));
452                 /* Make the old page be freed below */
453                 new_page = old_page;
454         }
455         page_cache_release(new_page);
456         page_cache_release(old_page);
457         return VM_FAULT_MINOR;
458 }
459
460 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
461                         unsigned long address, pte_t *ptep, int write_access)
462 {
463         int ret = VM_FAULT_SIGBUS;
464         unsigned long idx;
465         unsigned long size;
466         struct page *page;
467         struct address_space *mapping;
468         pte_t new_pte;
469
470         mapping = vma->vm_file->f_mapping;
471         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
472                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
473
474         /*
475          * Use page lock to guard against racing truncation
476          * before we get page_table_lock.
477          */
478 retry:
479         page = find_lock_page(mapping, idx);
480         if (!page) {
481                 if (hugetlb_get_quota(mapping))
482                         goto out;
483                 page = alloc_huge_page(vma, address);
484                 if (!page) {
485                         hugetlb_put_quota(mapping);
486                         ret = VM_FAULT_OOM;
487                         goto out;
488                 }
489                 clear_huge_page(page, address);
490
491                 if (vma->vm_flags & VM_SHARED) {
492                         int err;
493
494                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
495                         if (err) {
496                                 put_page(page);
497                                 hugetlb_put_quota(mapping);
498                                 if (err == -EEXIST)
499                                         goto retry;
500                                 goto out;
501                         }
502                 } else
503                         lock_page(page);
504         }
505
506         spin_lock(&mm->page_table_lock);
507         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
508         if (idx >= size)
509                 goto backout;
510
511         ret = VM_FAULT_MINOR;
512         if (!pte_none(*ptep))
513                 goto backout;
514
515         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
516         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
517                                 && (vma->vm_flags & VM_SHARED)));
518         set_huge_pte_at(mm, address, ptep, new_pte);
519
520         if (write_access && !(vma->vm_flags & VM_SHARED)) {
521                 /* Optimization, do the COW without a second fault */
522                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
523         }
524
525         spin_unlock(&mm->page_table_lock);
526         unlock_page(page);
527 out:
528         return ret;
529
530 backout:
531         spin_unlock(&mm->page_table_lock);
532         hugetlb_put_quota(mapping);
533         unlock_page(page);
534         put_page(page);
535         goto out;
536 }
537
538 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
539                         unsigned long address, int write_access)
540 {
541         pte_t *ptep;
542         pte_t entry;
543         int ret;
544         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
545
546         ptep = huge_pte_alloc(mm, address);
547         if (!ptep)
548                 return VM_FAULT_OOM;
549
550         /*
551          * Serialize hugepage allocation and instantiation, so that we don't
552          * get spurious allocation failures if two CPUs race to instantiate
553          * the same page in the page cache.
554          */
555         mutex_lock(&hugetlb_instantiation_mutex);
556         entry = *ptep;
557         if (pte_none(entry)) {
558                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
559                 mutex_unlock(&hugetlb_instantiation_mutex);
560                 return ret;
561         }
562
563         ret = VM_FAULT_MINOR;
564
565         spin_lock(&mm->page_table_lock);
566         /* Check for a racing update before calling hugetlb_cow */
567         if (likely(pte_same(entry, *ptep)))
568                 if (write_access && !pte_write(entry))
569                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
570         spin_unlock(&mm->page_table_lock);
571         mutex_unlock(&hugetlb_instantiation_mutex);
572
573         return ret;
574 }
575
576 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
577                         struct page **pages, struct vm_area_struct **vmas,
578                         unsigned long *position, int *length, int i)
579 {
580         unsigned long pfn_offset;
581         unsigned long vaddr = *position;
582         int remainder = *length;
583
584         spin_lock(&mm->page_table_lock);
585         while (vaddr < vma->vm_end && remainder) {
586                 pte_t *pte;
587                 struct page *page;
588
589                 /*
590                  * Some archs (sparc64, sh*) have multiple pte_ts to
591                  * each hugepage.  We have to make * sure we get the
592                  * first, for the page indexing below to work.
593                  */
594                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
595
596                 if (!pte || pte_none(*pte)) {
597                         int ret;
598
599                         spin_unlock(&mm->page_table_lock);
600                         ret = hugetlb_fault(mm, vma, vaddr, 0);
601                         spin_lock(&mm->page_table_lock);
602                         if (ret == VM_FAULT_MINOR)
603                                 continue;
604
605                         remainder = 0;
606                         if (!i)
607                                 i = -EFAULT;
608                         break;
609                 }
610
611                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
612                 page = pte_page(*pte);
613 same_page:
614                 if (pages) {
615                         get_page(page);
616                         pages[i] = page + pfn_offset;
617                 }
618
619                 if (vmas)
620                         vmas[i] = vma;
621
622                 vaddr += PAGE_SIZE;
623                 ++pfn_offset;
624                 --remainder;
625                 ++i;
626                 if (vaddr < vma->vm_end && remainder &&
627                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
628                         /*
629                          * We use pfn_offset to avoid touching the pageframes
630                          * of this compound page.
631                          */
632                         goto same_page;
633                 }
634         }
635         spin_unlock(&mm->page_table_lock);
636         *length = remainder;
637         *position = vaddr;
638
639         return i;
640 }
641
642 void hugetlb_change_protection(struct vm_area_struct *vma,
643                 unsigned long address, unsigned long end, pgprot_t newprot)
644 {
645         struct mm_struct *mm = vma->vm_mm;
646         unsigned long start = address;
647         pte_t *ptep;
648         pte_t pte;
649
650         BUG_ON(address >= end);
651         flush_cache_range(vma, address, end);
652
653         spin_lock(&mm->page_table_lock);
654         for (; address < end; address += HPAGE_SIZE) {
655                 ptep = huge_pte_offset(mm, address);
656                 if (!ptep)
657                         continue;
658                 if (!pte_none(*ptep)) {
659                         pte = huge_ptep_get_and_clear(mm, address, ptep);
660                         pte = pte_mkhuge(pte_modify(pte, newprot));
661                         set_huge_pte_at(mm, address, ptep, pte);
662                         lazy_mmu_prot_update(pte);
663                 }
664         }
665         spin_unlock(&mm->page_table_lock);
666
667         flush_tlb_range(vma, start, end);
668 }
669
670 struct file_region {
671         struct list_head link;
672         long from;
673         long to;
674 };
675
676 static long region_add(struct list_head *head, long f, long t)
677 {
678         struct file_region *rg, *nrg, *trg;
679
680         /* Locate the region we are either in or before. */
681         list_for_each_entry(rg, head, link)
682                 if (f <= rg->to)
683                         break;
684
685         /* Round our left edge to the current segment if it encloses us. */
686         if (f > rg->from)
687                 f = rg->from;
688
689         /* Check for and consume any regions we now overlap with. */
690         nrg = rg;
691         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
692                 if (&rg->link == head)
693                         break;
694                 if (rg->from > t)
695                         break;
696
697                 /* If this area reaches higher then extend our area to
698                  * include it completely.  If this is not the first area
699                  * which we intend to reuse, free it. */
700                 if (rg->to > t)
701                         t = rg->to;
702                 if (rg != nrg) {
703                         list_del(&rg->link);
704                         kfree(rg);
705                 }
706         }
707         nrg->from = f;
708         nrg->to = t;
709         return 0;
710 }
711
712 static long region_chg(struct list_head *head, long f, long t)
713 {
714         struct file_region *rg, *nrg;
715         long chg = 0;
716
717         /* Locate the region we are before or in. */
718         list_for_each_entry(rg, head, link)
719                 if (f <= rg->to)
720                         break;
721
722         /* If we are below the current region then a new region is required.
723          * Subtle, allocate a new region at the position but make it zero
724          * size such that we can guarentee to record the reservation. */
725         if (&rg->link == head || t < rg->from) {
726                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
727                 if (nrg == 0)
728                         return -ENOMEM;
729                 nrg->from = f;
730                 nrg->to   = f;
731                 INIT_LIST_HEAD(&nrg->link);
732                 list_add(&nrg->link, rg->link.prev);
733
734                 return t - f;
735         }
736
737         /* Round our left edge to the current segment if it encloses us. */
738         if (f > rg->from)
739                 f = rg->from;
740         chg = t - f;
741
742         /* Check for and consume any regions we now overlap with. */
743         list_for_each_entry(rg, rg->link.prev, link) {
744                 if (&rg->link == head)
745                         break;
746                 if (rg->from > t)
747                         return chg;
748
749                 /* We overlap with this area, if it extends futher than
750                  * us then we must extend ourselves.  Account for its
751                  * existing reservation. */
752                 if (rg->to > t) {
753                         chg += rg->to - t;
754                         t = rg->to;
755                 }
756                 chg -= rg->to - rg->from;
757         }
758         return chg;
759 }
760
761 static long region_truncate(struct list_head *head, long end)
762 {
763         struct file_region *rg, *trg;
764         long chg = 0;
765
766         /* Locate the region we are either in or before. */
767         list_for_each_entry(rg, head, link)
768                 if (end <= rg->to)
769                         break;
770         if (&rg->link == head)
771                 return 0;
772
773         /* If we are in the middle of a region then adjust it. */
774         if (end > rg->from) {
775                 chg = rg->to - end;
776                 rg->to = end;
777                 rg = list_entry(rg->link.next, typeof(*rg), link);
778         }
779
780         /* Drop any remaining regions. */
781         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
782                 if (&rg->link == head)
783                         break;
784                 chg += rg->to - rg->from;
785                 list_del(&rg->link);
786                 kfree(rg);
787         }
788         return chg;
789 }
790
791 static int hugetlb_acct_memory(long delta)
792 {
793         int ret = -ENOMEM;
794
795         spin_lock(&hugetlb_lock);
796         if ((delta + resv_huge_pages) <= free_huge_pages) {
797                 resv_huge_pages += delta;
798                 ret = 0;
799         }
800         spin_unlock(&hugetlb_lock);
801         return ret;
802 }
803
804 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
805 {
806         long ret, chg;
807
808         chg = region_chg(&inode->i_mapping->private_list, from, to);
809         if (chg < 0)
810                 return chg;
811         ret = hugetlb_acct_memory(chg);
812         if (ret < 0)
813                 return ret;
814         region_add(&inode->i_mapping->private_list, from, to);
815         return 0;
816 }
817
818 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
819 {
820         long chg = region_truncate(&inode->i_mapping->private_list, offset);
821         hugetlb_acct_memory(freed - chg);
822 }