dequeue_huge_page() warning fix
[linux-2.6] / 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 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
31 unsigned long hugepages_treat_as_movable;
32
33 /*
34  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
35  */
36 static DEFINE_SPINLOCK(hugetlb_lock);
37
38 static void clear_huge_page(struct page *page, unsigned long addr)
39 {
40         int i;
41
42         might_sleep();
43         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
44                 cond_resched();
45                 clear_user_highpage(page + i, addr);
46         }
47 }
48
49 static void copy_huge_page(struct page *dst, struct page *src,
50                            unsigned long addr, struct vm_area_struct *vma)
51 {
52         int i;
53
54         might_sleep();
55         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
56                 cond_resched();
57                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
58         }
59 }
60
61 static void enqueue_huge_page(struct page *page)
62 {
63         int nid = page_to_nid(page);
64         list_add(&page->lru, &hugepage_freelists[nid]);
65         free_huge_pages++;
66         free_huge_pages_node[nid]++;
67 }
68
69 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
70                                 unsigned long address)
71 {
72         int nid;
73         struct page *page = NULL;
74         struct zonelist *zonelist = huge_zonelist(vma, address,
75                                                 htlb_alloc_mask);
76         struct zone **z;
77
78         for (z = zonelist->zones; *z; z++) {
79                 nid = zone_to_nid(*z);
80                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
81                     !list_empty(&hugepage_freelists[nid])) {
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         }
89         return page;
90 }
91
92 static void free_huge_page(struct page *page)
93 {
94         BUG_ON(page_count(page));
95
96         INIT_LIST_HEAD(&page->lru);
97
98         spin_lock(&hugetlb_lock);
99         enqueue_huge_page(page);
100         spin_unlock(&hugetlb_lock);
101 }
102
103 static int alloc_fresh_huge_page(void)
104 {
105         static int prev_nid;
106         struct page *page;
107         static DEFINE_SPINLOCK(nid_lock);
108         int nid;
109
110         spin_lock(&nid_lock);
111         nid = next_node(prev_nid, node_online_map);
112         if (nid == MAX_NUMNODES)
113                 nid = first_node(node_online_map);
114         prev_nid = nid;
115         spin_unlock(&nid_lock);
116
117         page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
118                                         HUGETLB_PAGE_ORDER);
119         if (page) {
120                 set_compound_page_dtor(page, free_huge_page);
121                 spin_lock(&hugetlb_lock);
122                 nr_huge_pages++;
123                 nr_huge_pages_node[page_to_nid(page)]++;
124                 spin_unlock(&hugetlb_lock);
125                 put_page(page); /* free it into the hugepage allocator */
126                 return 1;
127         }
128         return 0;
129 }
130
131 static struct page *alloc_huge_page(struct vm_area_struct *vma,
132                                     unsigned long addr)
133 {
134         struct page *page;
135
136         spin_lock(&hugetlb_lock);
137         if (vma->vm_flags & VM_MAYSHARE)
138                 resv_huge_pages--;
139         else if (free_huge_pages <= resv_huge_pages)
140                 goto fail;
141
142         page = dequeue_huge_page(vma, addr);
143         if (!page)
144                 goto fail;
145
146         spin_unlock(&hugetlb_lock);
147         set_page_refcounted(page);
148         return page;
149
150 fail:
151         if (vma->vm_flags & VM_MAYSHARE)
152                 resv_huge_pages++;
153         spin_unlock(&hugetlb_lock);
154         return NULL;
155 }
156
157 static int __init hugetlb_init(void)
158 {
159         unsigned long i;
160
161         if (HPAGE_SHIFT == 0)
162                 return 0;
163
164         for (i = 0; i < MAX_NUMNODES; ++i)
165                 INIT_LIST_HEAD(&hugepage_freelists[i]);
166
167         for (i = 0; i < max_huge_pages; ++i) {
168                 if (!alloc_fresh_huge_page())
169                         break;
170         }
171         max_huge_pages = free_huge_pages = nr_huge_pages = i;
172         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
173         return 0;
174 }
175 module_init(hugetlb_init);
176
177 static int __init hugetlb_setup(char *s)
178 {
179         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
180                 max_huge_pages = 0;
181         return 1;
182 }
183 __setup("hugepages=", hugetlb_setup);
184
185 static unsigned int cpuset_mems_nr(unsigned int *array)
186 {
187         int node;
188         unsigned int nr = 0;
189
190         for_each_node_mask(node, cpuset_current_mems_allowed)
191                 nr += array[node];
192
193         return nr;
194 }
195
196 #ifdef CONFIG_SYSCTL
197 static void update_and_free_page(struct page *page)
198 {
199         int i;
200         nr_huge_pages--;
201         nr_huge_pages_node[page_to_nid(page)]--;
202         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
203                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
204                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
205                                 1 << PG_private | 1<< PG_writeback);
206         }
207         page[1].lru.next = NULL;
208         set_page_refcounted(page);
209         __free_pages(page, HUGETLB_PAGE_ORDER);
210 }
211
212 #ifdef CONFIG_HIGHMEM
213 static void try_to_free_low(unsigned long count)
214 {
215         int i;
216
217         for (i = 0; i < MAX_NUMNODES; ++i) {
218                 struct page *page, *next;
219                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
220                         if (PageHighMem(page))
221                                 continue;
222                         list_del(&page->lru);
223                         update_and_free_page(page);
224                         free_huge_pages--;
225                         free_huge_pages_node[page_to_nid(page)]--;
226                         if (count >= nr_huge_pages)
227                                 return;
228                 }
229         }
230 }
231 #else
232 static inline void try_to_free_low(unsigned long count)
233 {
234 }
235 #endif
236
237 static unsigned long set_max_huge_pages(unsigned long count)
238 {
239         while (count > nr_huge_pages) {
240                 if (!alloc_fresh_huge_page())
241                         return nr_huge_pages;
242         }
243         if (count >= nr_huge_pages)
244                 return nr_huge_pages;
245
246         spin_lock(&hugetlb_lock);
247         count = max(count, resv_huge_pages);
248         try_to_free_low(count);
249         while (count < nr_huge_pages) {
250                 struct page *page = dequeue_huge_page(NULL, 0);
251                 if (!page)
252                         break;
253                 update_and_free_page(page);
254         }
255         spin_unlock(&hugetlb_lock);
256         return nr_huge_pages;
257 }
258
259 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
260                            struct file *file, void __user *buffer,
261                            size_t *length, loff_t *ppos)
262 {
263         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
264         max_huge_pages = set_max_huge_pages(max_huge_pages);
265         return 0;
266 }
267
268 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
269                         struct file *file, void __user *buffer,
270                         size_t *length, loff_t *ppos)
271 {
272         proc_dointvec(table, write, file, buffer, length, ppos);
273         if (hugepages_treat_as_movable)
274                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
275         else
276                 htlb_alloc_mask = GFP_HIGHUSER;
277         return 0;
278 }
279
280 #endif /* CONFIG_SYSCTL */
281
282 int hugetlb_report_meminfo(char *buf)
283 {
284         return sprintf(buf,
285                         "HugePages_Total: %5lu\n"
286                         "HugePages_Free:  %5lu\n"
287                         "HugePages_Rsvd:  %5lu\n"
288                         "Hugepagesize:    %5lu kB\n",
289                         nr_huge_pages,
290                         free_huge_pages,
291                         resv_huge_pages,
292                         HPAGE_SIZE/1024);
293 }
294
295 int hugetlb_report_node_meminfo(int nid, char *buf)
296 {
297         return sprintf(buf,
298                 "Node %d HugePages_Total: %5u\n"
299                 "Node %d HugePages_Free:  %5u\n",
300                 nid, nr_huge_pages_node[nid],
301                 nid, free_huge_pages_node[nid]);
302 }
303
304 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
305 unsigned long hugetlb_total_pages(void)
306 {
307         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
308 }
309
310 /*
311  * We cannot handle pagefaults against hugetlb pages at all.  They cause
312  * handle_mm_fault() to try to instantiate regular-sized pages in the
313  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
314  * this far.
315  */
316 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
317 {
318         BUG();
319         return 0;
320 }
321
322 struct vm_operations_struct hugetlb_vm_ops = {
323         .fault = hugetlb_vm_op_fault,
324 };
325
326 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
327                                 int writable)
328 {
329         pte_t entry;
330
331         if (writable) {
332                 entry =
333                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
334         } else {
335                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
336         }
337         entry = pte_mkyoung(entry);
338         entry = pte_mkhuge(entry);
339
340         return entry;
341 }
342
343 static void set_huge_ptep_writable(struct vm_area_struct *vma,
344                                    unsigned long address, pte_t *ptep)
345 {
346         pte_t entry;
347
348         entry = pte_mkwrite(pte_mkdirty(*ptep));
349         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
350                 update_mmu_cache(vma, address, entry);
351                 lazy_mmu_prot_update(entry);
352         }
353 }
354
355
356 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
357                             struct vm_area_struct *vma)
358 {
359         pte_t *src_pte, *dst_pte, entry;
360         struct page *ptepage;
361         unsigned long addr;
362         int cow;
363
364         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
365
366         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
367                 src_pte = huge_pte_offset(src, addr);
368                 if (!src_pte)
369                         continue;
370                 dst_pte = huge_pte_alloc(dst, addr);
371                 if (!dst_pte)
372                         goto nomem;
373                 spin_lock(&dst->page_table_lock);
374                 spin_lock(&src->page_table_lock);
375                 if (!pte_none(*src_pte)) {
376                         if (cow)
377                                 ptep_set_wrprotect(src, addr, src_pte);
378                         entry = *src_pte;
379                         ptepage = pte_page(entry);
380                         get_page(ptepage);
381                         set_huge_pte_at(dst, addr, dst_pte, entry);
382                 }
383                 spin_unlock(&src->page_table_lock);
384                 spin_unlock(&dst->page_table_lock);
385         }
386         return 0;
387
388 nomem:
389         return -ENOMEM;
390 }
391
392 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
393                             unsigned long end)
394 {
395         struct mm_struct *mm = vma->vm_mm;
396         unsigned long address;
397         pte_t *ptep;
398         pte_t pte;
399         struct page *page;
400         struct page *tmp;
401         /*
402          * A page gathering list, protected by per file i_mmap_lock. The
403          * lock is used to avoid list corruption from multiple unmapping
404          * of the same page since we are using page->lru.
405          */
406         LIST_HEAD(page_list);
407
408         WARN_ON(!is_vm_hugetlb_page(vma));
409         BUG_ON(start & ~HPAGE_MASK);
410         BUG_ON(end & ~HPAGE_MASK);
411
412         spin_lock(&mm->page_table_lock);
413         for (address = start; address < end; address += HPAGE_SIZE) {
414                 ptep = huge_pte_offset(mm, address);
415                 if (!ptep)
416                         continue;
417
418                 if (huge_pmd_unshare(mm, &address, ptep))
419                         continue;
420
421                 pte = huge_ptep_get_and_clear(mm, address, ptep);
422                 if (pte_none(pte))
423                         continue;
424
425                 page = pte_page(pte);
426                 if (pte_dirty(pte))
427                         set_page_dirty(page);
428                 list_add(&page->lru, &page_list);
429         }
430         spin_unlock(&mm->page_table_lock);
431         flush_tlb_range(vma, start, end);
432         list_for_each_entry_safe(page, tmp, &page_list, lru) {
433                 list_del(&page->lru);
434                 put_page(page);
435         }
436 }
437
438 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
439                           unsigned long end)
440 {
441         /*
442          * It is undesirable to test vma->vm_file as it should be non-null
443          * for valid hugetlb area. However, vm_file will be NULL in the error
444          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
445          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
446          * to clean up. Since no pte has actually been setup, it is safe to
447          * do nothing in this case.
448          */
449         if (vma->vm_file) {
450                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
451                 __unmap_hugepage_range(vma, start, end);
452                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
453         }
454 }
455
456 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
457                         unsigned long address, pte_t *ptep, pte_t pte)
458 {
459         struct page *old_page, *new_page;
460         int avoidcopy;
461
462         old_page = pte_page(pte);
463
464         /* If no-one else is actually using this page, avoid the copy
465          * and just make the page writable */
466         avoidcopy = (page_count(old_page) == 1);
467         if (avoidcopy) {
468                 set_huge_ptep_writable(vma, address, ptep);
469                 return 0;
470         }
471
472         page_cache_get(old_page);
473         new_page = alloc_huge_page(vma, address);
474
475         if (!new_page) {
476                 page_cache_release(old_page);
477                 return VM_FAULT_OOM;
478         }
479
480         spin_unlock(&mm->page_table_lock);
481         copy_huge_page(new_page, old_page, address, vma);
482         spin_lock(&mm->page_table_lock);
483
484         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
485         if (likely(pte_same(*ptep, pte))) {
486                 /* Break COW */
487                 set_huge_pte_at(mm, address, ptep,
488                                 make_huge_pte(vma, new_page, 1));
489                 /* Make the old page be freed below */
490                 new_page = old_page;
491         }
492         page_cache_release(new_page);
493         page_cache_release(old_page);
494         return 0;
495 }
496
497 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
498                         unsigned long address, pte_t *ptep, int write_access)
499 {
500         int ret = VM_FAULT_SIGBUS;
501         unsigned long idx;
502         unsigned long size;
503         struct page *page;
504         struct address_space *mapping;
505         pte_t new_pte;
506
507         mapping = vma->vm_file->f_mapping;
508         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
509                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
510
511         /*
512          * Use page lock to guard against racing truncation
513          * before we get page_table_lock.
514          */
515 retry:
516         page = find_lock_page(mapping, idx);
517         if (!page) {
518                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
519                 if (idx >= size)
520                         goto out;
521                 if (hugetlb_get_quota(mapping))
522                         goto out;
523                 page = alloc_huge_page(vma, address);
524                 if (!page) {
525                         hugetlb_put_quota(mapping);
526                         ret = VM_FAULT_OOM;
527                         goto out;
528                 }
529                 clear_huge_page(page, address);
530
531                 if (vma->vm_flags & VM_SHARED) {
532                         int err;
533
534                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
535                         if (err) {
536                                 put_page(page);
537                                 hugetlb_put_quota(mapping);
538                                 if (err == -EEXIST)
539                                         goto retry;
540                                 goto out;
541                         }
542                 } else
543                         lock_page(page);
544         }
545
546         spin_lock(&mm->page_table_lock);
547         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
548         if (idx >= size)
549                 goto backout;
550
551         ret = 0;
552         if (!pte_none(*ptep))
553                 goto backout;
554
555         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
556                                 && (vma->vm_flags & VM_SHARED)));
557         set_huge_pte_at(mm, address, ptep, new_pte);
558
559         if (write_access && !(vma->vm_flags & VM_SHARED)) {
560                 /* Optimization, do the COW without a second fault */
561                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
562         }
563
564         spin_unlock(&mm->page_table_lock);
565         unlock_page(page);
566 out:
567         return ret;
568
569 backout:
570         spin_unlock(&mm->page_table_lock);
571         hugetlb_put_quota(mapping);
572         unlock_page(page);
573         put_page(page);
574         goto out;
575 }
576
577 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
578                         unsigned long address, int write_access)
579 {
580         pte_t *ptep;
581         pte_t entry;
582         int ret;
583         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
584
585         ptep = huge_pte_alloc(mm, address);
586         if (!ptep)
587                 return VM_FAULT_OOM;
588
589         /*
590          * Serialize hugepage allocation and instantiation, so that we don't
591          * get spurious allocation failures if two CPUs race to instantiate
592          * the same page in the page cache.
593          */
594         mutex_lock(&hugetlb_instantiation_mutex);
595         entry = *ptep;
596         if (pte_none(entry)) {
597                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
598                 mutex_unlock(&hugetlb_instantiation_mutex);
599                 return ret;
600         }
601
602         ret = 0;
603
604         spin_lock(&mm->page_table_lock);
605         /* Check for a racing update before calling hugetlb_cow */
606         if (likely(pte_same(entry, *ptep)))
607                 if (write_access && !pte_write(entry))
608                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
609         spin_unlock(&mm->page_table_lock);
610         mutex_unlock(&hugetlb_instantiation_mutex);
611
612         return ret;
613 }
614
615 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
616                         struct page **pages, struct vm_area_struct **vmas,
617                         unsigned long *position, int *length, int i)
618 {
619         unsigned long pfn_offset;
620         unsigned long vaddr = *position;
621         int remainder = *length;
622
623         spin_lock(&mm->page_table_lock);
624         while (vaddr < vma->vm_end && remainder) {
625                 pte_t *pte;
626                 struct page *page;
627
628                 /*
629                  * Some archs (sparc64, sh*) have multiple pte_ts to
630                  * each hugepage.  We have to make * sure we get the
631                  * first, for the page indexing below to work.
632                  */
633                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
634
635                 if (!pte || pte_none(*pte)) {
636                         int ret;
637
638                         spin_unlock(&mm->page_table_lock);
639                         ret = hugetlb_fault(mm, vma, vaddr, 0);
640                         spin_lock(&mm->page_table_lock);
641                         if (!(ret & VM_FAULT_MAJOR))
642                                 continue;
643
644                         remainder = 0;
645                         if (!i)
646                                 i = -EFAULT;
647                         break;
648                 }
649
650                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
651                 page = pte_page(*pte);
652 same_page:
653                 if (pages) {
654                         get_page(page);
655                         pages[i] = page + pfn_offset;
656                 }
657
658                 if (vmas)
659                         vmas[i] = vma;
660
661                 vaddr += PAGE_SIZE;
662                 ++pfn_offset;
663                 --remainder;
664                 ++i;
665                 if (vaddr < vma->vm_end && remainder &&
666                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
667                         /*
668                          * We use pfn_offset to avoid touching the pageframes
669                          * of this compound page.
670                          */
671                         goto same_page;
672                 }
673         }
674         spin_unlock(&mm->page_table_lock);
675         *length = remainder;
676         *position = vaddr;
677
678         return i;
679 }
680
681 void hugetlb_change_protection(struct vm_area_struct *vma,
682                 unsigned long address, unsigned long end, pgprot_t newprot)
683 {
684         struct mm_struct *mm = vma->vm_mm;
685         unsigned long start = address;
686         pte_t *ptep;
687         pte_t pte;
688
689         BUG_ON(address >= end);
690         flush_cache_range(vma, address, end);
691
692         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
693         spin_lock(&mm->page_table_lock);
694         for (; address < end; address += HPAGE_SIZE) {
695                 ptep = huge_pte_offset(mm, address);
696                 if (!ptep)
697                         continue;
698                 if (huge_pmd_unshare(mm, &address, ptep))
699                         continue;
700                 if (!pte_none(*ptep)) {
701                         pte = huge_ptep_get_and_clear(mm, address, ptep);
702                         pte = pte_mkhuge(pte_modify(pte, newprot));
703                         set_huge_pte_at(mm, address, ptep, pte);
704                         lazy_mmu_prot_update(pte);
705                 }
706         }
707         spin_unlock(&mm->page_table_lock);
708         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
709
710         flush_tlb_range(vma, start, end);
711 }
712
713 struct file_region {
714         struct list_head link;
715         long from;
716         long to;
717 };
718
719 static long region_add(struct list_head *head, long f, long t)
720 {
721         struct file_region *rg, *nrg, *trg;
722
723         /* Locate the region we are either in or before. */
724         list_for_each_entry(rg, head, link)
725                 if (f <= rg->to)
726                         break;
727
728         /* Round our left edge to the current segment if it encloses us. */
729         if (f > rg->from)
730                 f = rg->from;
731
732         /* Check for and consume any regions we now overlap with. */
733         nrg = rg;
734         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
735                 if (&rg->link == head)
736                         break;
737                 if (rg->from > t)
738                         break;
739
740                 /* If this area reaches higher then extend our area to
741                  * include it completely.  If this is not the first area
742                  * which we intend to reuse, free it. */
743                 if (rg->to > t)
744                         t = rg->to;
745                 if (rg != nrg) {
746                         list_del(&rg->link);
747                         kfree(rg);
748                 }
749         }
750         nrg->from = f;
751         nrg->to = t;
752         return 0;
753 }
754
755 static long region_chg(struct list_head *head, long f, long t)
756 {
757         struct file_region *rg, *nrg;
758         long chg = 0;
759
760         /* Locate the region we are before or in. */
761         list_for_each_entry(rg, head, link)
762                 if (f <= rg->to)
763                         break;
764
765         /* If we are below the current region then a new region is required.
766          * Subtle, allocate a new region at the position but make it zero
767          * size such that we can guarentee to record the reservation. */
768         if (&rg->link == head || t < rg->from) {
769                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
770                 if (nrg == 0)
771                         return -ENOMEM;
772                 nrg->from = f;
773                 nrg->to   = f;
774                 INIT_LIST_HEAD(&nrg->link);
775                 list_add(&nrg->link, rg->link.prev);
776
777                 return t - f;
778         }
779
780         /* Round our left edge to the current segment if it encloses us. */
781         if (f > rg->from)
782                 f = rg->from;
783         chg = t - f;
784
785         /* Check for and consume any regions we now overlap with. */
786         list_for_each_entry(rg, rg->link.prev, link) {
787                 if (&rg->link == head)
788                         break;
789                 if (rg->from > t)
790                         return chg;
791
792                 /* We overlap with this area, if it extends futher than
793                  * us then we must extend ourselves.  Account for its
794                  * existing reservation. */
795                 if (rg->to > t) {
796                         chg += rg->to - t;
797                         t = rg->to;
798                 }
799                 chg -= rg->to - rg->from;
800         }
801         return chg;
802 }
803
804 static long region_truncate(struct list_head *head, long end)
805 {
806         struct file_region *rg, *trg;
807         long chg = 0;
808
809         /* Locate the region we are either in or before. */
810         list_for_each_entry(rg, head, link)
811                 if (end <= rg->to)
812                         break;
813         if (&rg->link == head)
814                 return 0;
815
816         /* If we are in the middle of a region then adjust it. */
817         if (end > rg->from) {
818                 chg = rg->to - end;
819                 rg->to = end;
820                 rg = list_entry(rg->link.next, typeof(*rg), link);
821         }
822
823         /* Drop any remaining regions. */
824         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
825                 if (&rg->link == head)
826                         break;
827                 chg += rg->to - rg->from;
828                 list_del(&rg->link);
829                 kfree(rg);
830         }
831         return chg;
832 }
833
834 static int hugetlb_acct_memory(long delta)
835 {
836         int ret = -ENOMEM;
837
838         spin_lock(&hugetlb_lock);
839         if ((delta + resv_huge_pages) <= free_huge_pages) {
840                 resv_huge_pages += delta;
841                 ret = 0;
842         }
843         spin_unlock(&hugetlb_lock);
844         return ret;
845 }
846
847 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
848 {
849         long ret, chg;
850
851         chg = region_chg(&inode->i_mapping->private_list, from, to);
852         if (chg < 0)
853                 return chg;
854         /*
855          * When cpuset is configured, it breaks the strict hugetlb page
856          * reservation as the accounting is done on a global variable. Such
857          * reservation is completely rubbish in the presence of cpuset because
858          * the reservation is not checked against page availability for the
859          * current cpuset. Application can still potentially OOM'ed by kernel
860          * with lack of free htlb page in cpuset that the task is in.
861          * Attempt to enforce strict accounting with cpuset is almost
862          * impossible (or too ugly) because cpuset is too fluid that
863          * task or memory node can be dynamically moved between cpusets.
864          *
865          * The change of semantics for shared hugetlb mapping with cpuset is
866          * undesirable. However, in order to preserve some of the semantics,
867          * we fall back to check against current free page availability as
868          * a best attempt and hopefully to minimize the impact of changing
869          * semantics that cpuset has.
870          */
871         if (chg > cpuset_mems_nr(free_huge_pages_node))
872                 return -ENOMEM;
873
874         ret = hugetlb_acct_memory(chg);
875         if (ret < 0)
876                 return ret;
877         region_add(&inode->i_mapping->private_list, from, to);
878         return 0;
879 }
880
881 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
882 {
883         long chg = region_truncate(&inode->i_mapping->private_list, offset);
884         hugetlb_acct_memory(freed - chg);
885 }