fix hugepages leak due to pagetable page sharing
[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 static unsigned long surplus_huge_pages;
27 unsigned long max_huge_pages;
28 static struct list_head hugepage_freelists[MAX_NUMNODES];
29 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
30 static unsigned int free_huge_pages_node[MAX_NUMNODES];
31 static unsigned int surplus_huge_pages_node[MAX_NUMNODES];
32 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
33 unsigned long hugepages_treat_as_movable;
34 unsigned long nr_overcommit_huge_pages;
35 static int hugetlb_next_nid;
36
37 /*
38  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
39  */
40 static DEFINE_SPINLOCK(hugetlb_lock);
41
42 static void clear_huge_page(struct page *page, unsigned long addr)
43 {
44         int i;
45
46         might_sleep();
47         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
48                 cond_resched();
49                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
50         }
51 }
52
53 static void copy_huge_page(struct page *dst, struct page *src,
54                            unsigned long addr, struct vm_area_struct *vma)
55 {
56         int i;
57
58         might_sleep();
59         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
60                 cond_resched();
61                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
62         }
63 }
64
65 static void enqueue_huge_page(struct page *page)
66 {
67         int nid = page_to_nid(page);
68         list_add(&page->lru, &hugepage_freelists[nid]);
69         free_huge_pages++;
70         free_huge_pages_node[nid]++;
71 }
72
73 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
74                                 unsigned long address)
75 {
76         int nid;
77         struct page *page = NULL;
78         struct mempolicy *mpol;
79         struct zonelist *zonelist = huge_zonelist(vma, address,
80                                         htlb_alloc_mask, &mpol);
81         struct zone **z;
82
83         for (z = zonelist->zones; *z; z++) {
84                 nid = zone_to_nid(*z);
85                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
86                     !list_empty(&hugepage_freelists[nid])) {
87                         page = list_entry(hugepage_freelists[nid].next,
88                                           struct page, lru);
89                         list_del(&page->lru);
90                         free_huge_pages--;
91                         free_huge_pages_node[nid]--;
92                         if (vma && vma->vm_flags & VM_MAYSHARE)
93                                 resv_huge_pages--;
94                         break;
95                 }
96         }
97         mpol_free(mpol);        /* unref if mpol !NULL */
98         return page;
99 }
100
101 static void update_and_free_page(struct page *page)
102 {
103         int i;
104         nr_huge_pages--;
105         nr_huge_pages_node[page_to_nid(page)]--;
106         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
107                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
108                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
109                                 1 << PG_private | 1<< PG_writeback);
110         }
111         set_compound_page_dtor(page, NULL);
112         set_page_refcounted(page);
113         __free_pages(page, HUGETLB_PAGE_ORDER);
114 }
115
116 static void free_huge_page(struct page *page)
117 {
118         int nid = page_to_nid(page);
119         struct address_space *mapping;
120
121         mapping = (struct address_space *) page_private(page);
122         BUG_ON(page_count(page));
123         INIT_LIST_HEAD(&page->lru);
124
125         spin_lock(&hugetlb_lock);
126         if (surplus_huge_pages_node[nid]) {
127                 update_and_free_page(page);
128                 surplus_huge_pages--;
129                 surplus_huge_pages_node[nid]--;
130         } else {
131                 enqueue_huge_page(page);
132         }
133         spin_unlock(&hugetlb_lock);
134         if (mapping)
135                 hugetlb_put_quota(mapping, 1);
136         set_page_private(page, 0);
137 }
138
139 /*
140  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
141  * balanced by operating on them in a round-robin fashion.
142  * Returns 1 if an adjustment was made.
143  */
144 static int adjust_pool_surplus(int delta)
145 {
146         static int prev_nid;
147         int nid = prev_nid;
148         int ret = 0;
149
150         VM_BUG_ON(delta != -1 && delta != 1);
151         do {
152                 nid = next_node(nid, node_online_map);
153                 if (nid == MAX_NUMNODES)
154                         nid = first_node(node_online_map);
155
156                 /* To shrink on this node, there must be a surplus page */
157                 if (delta < 0 && !surplus_huge_pages_node[nid])
158                         continue;
159                 /* Surplus cannot exceed the total number of pages */
160                 if (delta > 0 && surplus_huge_pages_node[nid] >=
161                                                 nr_huge_pages_node[nid])
162                         continue;
163
164                 surplus_huge_pages += delta;
165                 surplus_huge_pages_node[nid] += delta;
166                 ret = 1;
167                 break;
168         } while (nid != prev_nid);
169
170         prev_nid = nid;
171         return ret;
172 }
173
174 static struct page *alloc_fresh_huge_page_node(int nid)
175 {
176         struct page *page;
177
178         page = alloc_pages_node(nid,
179                 htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|__GFP_NOWARN,
180                 HUGETLB_PAGE_ORDER);
181         if (page) {
182                 set_compound_page_dtor(page, free_huge_page);
183                 spin_lock(&hugetlb_lock);
184                 nr_huge_pages++;
185                 nr_huge_pages_node[nid]++;
186                 spin_unlock(&hugetlb_lock);
187                 put_page(page); /* free it into the hugepage allocator */
188         }
189
190         return page;
191 }
192
193 static int alloc_fresh_huge_page(void)
194 {
195         struct page *page;
196         int start_nid;
197         int next_nid;
198         int ret = 0;
199
200         start_nid = hugetlb_next_nid;
201
202         do {
203                 page = alloc_fresh_huge_page_node(hugetlb_next_nid);
204                 if (page)
205                         ret = 1;
206                 /*
207                  * Use a helper variable to find the next node and then
208                  * copy it back to hugetlb_next_nid afterwards:
209                  * otherwise there's a window in which a racer might
210                  * pass invalid nid MAX_NUMNODES to alloc_pages_node.
211                  * But we don't need to use a spin_lock here: it really
212                  * doesn't matter if occasionally a racer chooses the
213                  * same nid as we do.  Move nid forward in the mask even
214                  * if we just successfully allocated a hugepage so that
215                  * the next caller gets hugepages on the next node.
216                  */
217                 next_nid = next_node(hugetlb_next_nid, node_online_map);
218                 if (next_nid == MAX_NUMNODES)
219                         next_nid = first_node(node_online_map);
220                 hugetlb_next_nid = next_nid;
221         } while (!page && hugetlb_next_nid != start_nid);
222
223         return ret;
224 }
225
226 static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
227                                                 unsigned long address)
228 {
229         struct page *page;
230         unsigned int nid;
231
232         /*
233          * Assume we will successfully allocate the surplus page to
234          * prevent racing processes from causing the surplus to exceed
235          * overcommit
236          *
237          * This however introduces a different race, where a process B
238          * tries to grow the static hugepage pool while alloc_pages() is
239          * called by process A. B will only examine the per-node
240          * counters in determining if surplus huge pages can be
241          * converted to normal huge pages in adjust_pool_surplus(). A
242          * won't be able to increment the per-node counter, until the
243          * lock is dropped by B, but B doesn't drop hugetlb_lock until
244          * no more huge pages can be converted from surplus to normal
245          * state (and doesn't try to convert again). Thus, we have a
246          * case where a surplus huge page exists, the pool is grown, and
247          * the surplus huge page still exists after, even though it
248          * should just have been converted to a normal huge page. This
249          * does not leak memory, though, as the hugepage will be freed
250          * once it is out of use. It also does not allow the counters to
251          * go out of whack in adjust_pool_surplus() as we don't modify
252          * the node values until we've gotten the hugepage and only the
253          * per-node value is checked there.
254          */
255         spin_lock(&hugetlb_lock);
256         if (surplus_huge_pages >= nr_overcommit_huge_pages) {
257                 spin_unlock(&hugetlb_lock);
258                 return NULL;
259         } else {
260                 nr_huge_pages++;
261                 surplus_huge_pages++;
262         }
263         spin_unlock(&hugetlb_lock);
264
265         page = alloc_pages(htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
266                                         HUGETLB_PAGE_ORDER);
267
268         spin_lock(&hugetlb_lock);
269         if (page) {
270                 nid = page_to_nid(page);
271                 set_compound_page_dtor(page, free_huge_page);
272                 /*
273                  * We incremented the global counters already
274                  */
275                 nr_huge_pages_node[nid]++;
276                 surplus_huge_pages_node[nid]++;
277         } else {
278                 nr_huge_pages--;
279                 surplus_huge_pages--;
280         }
281         spin_unlock(&hugetlb_lock);
282
283         return page;
284 }
285
286 /*
287  * Increase the hugetlb pool such that it can accomodate a reservation
288  * of size 'delta'.
289  */
290 static int gather_surplus_pages(int delta)
291 {
292         struct list_head surplus_list;
293         struct page *page, *tmp;
294         int ret, i;
295         int needed, allocated;
296
297         needed = (resv_huge_pages + delta) - free_huge_pages;
298         if (needed <= 0)
299                 return 0;
300
301         allocated = 0;
302         INIT_LIST_HEAD(&surplus_list);
303
304         ret = -ENOMEM;
305 retry:
306         spin_unlock(&hugetlb_lock);
307         for (i = 0; i < needed; i++) {
308                 page = alloc_buddy_huge_page(NULL, 0);
309                 if (!page) {
310                         /*
311                          * We were not able to allocate enough pages to
312                          * satisfy the entire reservation so we free what
313                          * we've allocated so far.
314                          */
315                         spin_lock(&hugetlb_lock);
316                         needed = 0;
317                         goto free;
318                 }
319
320                 list_add(&page->lru, &surplus_list);
321         }
322         allocated += needed;
323
324         /*
325          * After retaking hugetlb_lock, we need to recalculate 'needed'
326          * because either resv_huge_pages or free_huge_pages may have changed.
327          */
328         spin_lock(&hugetlb_lock);
329         needed = (resv_huge_pages + delta) - (free_huge_pages + allocated);
330         if (needed > 0)
331                 goto retry;
332
333         /*
334          * The surplus_list now contains _at_least_ the number of extra pages
335          * needed to accomodate the reservation.  Add the appropriate number
336          * of pages to the hugetlb pool and free the extras back to the buddy
337          * allocator.
338          */
339         needed += allocated;
340         ret = 0;
341 free:
342         list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
343                 list_del(&page->lru);
344                 if ((--needed) >= 0)
345                         enqueue_huge_page(page);
346                 else {
347                         /*
348                          * Decrement the refcount and free the page using its
349                          * destructor.  This must be done with hugetlb_lock
350                          * unlocked which is safe because free_huge_page takes
351                          * hugetlb_lock before deciding how to free the page.
352                          */
353                         spin_unlock(&hugetlb_lock);
354                         put_page(page);
355                         spin_lock(&hugetlb_lock);
356                 }
357         }
358
359         return ret;
360 }
361
362 /*
363  * When releasing a hugetlb pool reservation, any surplus pages that were
364  * allocated to satisfy the reservation must be explicitly freed if they were
365  * never used.
366  */
367 static void return_unused_surplus_pages(unsigned long unused_resv_pages)
368 {
369         static int nid = -1;
370         struct page *page;
371         unsigned long nr_pages;
372
373         nr_pages = min(unused_resv_pages, surplus_huge_pages);
374
375         while (nr_pages) {
376                 nid = next_node(nid, node_online_map);
377                 if (nid == MAX_NUMNODES)
378                         nid = first_node(node_online_map);
379
380                 if (!surplus_huge_pages_node[nid])
381                         continue;
382
383                 if (!list_empty(&hugepage_freelists[nid])) {
384                         page = list_entry(hugepage_freelists[nid].next,
385                                           struct page, lru);
386                         list_del(&page->lru);
387                         update_and_free_page(page);
388                         free_huge_pages--;
389                         free_huge_pages_node[nid]--;
390                         surplus_huge_pages--;
391                         surplus_huge_pages_node[nid]--;
392                         nr_pages--;
393                 }
394         }
395 }
396
397
398 static struct page *alloc_huge_page_shared(struct vm_area_struct *vma,
399                                                 unsigned long addr)
400 {
401         struct page *page;
402
403         spin_lock(&hugetlb_lock);
404         page = dequeue_huge_page(vma, addr);
405         spin_unlock(&hugetlb_lock);
406         return page ? page : ERR_PTR(-VM_FAULT_OOM);
407 }
408
409 static struct page *alloc_huge_page_private(struct vm_area_struct *vma,
410                                                 unsigned long addr)
411 {
412         struct page *page = NULL;
413
414         if (hugetlb_get_quota(vma->vm_file->f_mapping, 1))
415                 return ERR_PTR(-VM_FAULT_SIGBUS);
416
417         spin_lock(&hugetlb_lock);
418         if (free_huge_pages > resv_huge_pages)
419                 page = dequeue_huge_page(vma, addr);
420         spin_unlock(&hugetlb_lock);
421         if (!page) {
422                 page = alloc_buddy_huge_page(vma, addr);
423                 if (!page) {
424                         hugetlb_put_quota(vma->vm_file->f_mapping, 1);
425                         return ERR_PTR(-VM_FAULT_OOM);
426                 }
427         }
428         return page;
429 }
430
431 static struct page *alloc_huge_page(struct vm_area_struct *vma,
432                                     unsigned long addr)
433 {
434         struct page *page;
435         struct address_space *mapping = vma->vm_file->f_mapping;
436
437         if (vma->vm_flags & VM_MAYSHARE)
438                 page = alloc_huge_page_shared(vma, addr);
439         else
440                 page = alloc_huge_page_private(vma, addr);
441
442         if (!IS_ERR(page)) {
443                 set_page_refcounted(page);
444                 set_page_private(page, (unsigned long) mapping);
445         }
446         return page;
447 }
448
449 static int __init hugetlb_init(void)
450 {
451         unsigned long i;
452
453         if (HPAGE_SHIFT == 0)
454                 return 0;
455
456         for (i = 0; i < MAX_NUMNODES; ++i)
457                 INIT_LIST_HEAD(&hugepage_freelists[i]);
458
459         hugetlb_next_nid = first_node(node_online_map);
460
461         for (i = 0; i < max_huge_pages; ++i) {
462                 if (!alloc_fresh_huge_page())
463                         break;
464         }
465         max_huge_pages = free_huge_pages = nr_huge_pages = i;
466         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
467         return 0;
468 }
469 module_init(hugetlb_init);
470
471 static int __init hugetlb_setup(char *s)
472 {
473         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
474                 max_huge_pages = 0;
475         return 1;
476 }
477 __setup("hugepages=", hugetlb_setup);
478
479 static unsigned int cpuset_mems_nr(unsigned int *array)
480 {
481         int node;
482         unsigned int nr = 0;
483
484         for_each_node_mask(node, cpuset_current_mems_allowed)
485                 nr += array[node];
486
487         return nr;
488 }
489
490 #ifdef CONFIG_SYSCTL
491 #ifdef CONFIG_HIGHMEM
492 static void try_to_free_low(unsigned long count)
493 {
494         int i;
495
496         for (i = 0; i < MAX_NUMNODES; ++i) {
497                 struct page *page, *next;
498                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
499                         if (count >= nr_huge_pages)
500                                 return;
501                         if (PageHighMem(page))
502                                 continue;
503                         list_del(&page->lru);
504                         update_and_free_page(page);
505                         free_huge_pages--;
506                         free_huge_pages_node[page_to_nid(page)]--;
507                 }
508         }
509 }
510 #else
511 static inline void try_to_free_low(unsigned long count)
512 {
513 }
514 #endif
515
516 #define persistent_huge_pages (nr_huge_pages - surplus_huge_pages)
517 static unsigned long set_max_huge_pages(unsigned long count)
518 {
519         unsigned long min_count, ret;
520
521         /*
522          * Increase the pool size
523          * First take pages out of surplus state.  Then make up the
524          * remaining difference by allocating fresh huge pages.
525          *
526          * We might race with alloc_buddy_huge_page() here and be unable
527          * to convert a surplus huge page to a normal huge page. That is
528          * not critical, though, it just means the overall size of the
529          * pool might be one hugepage larger than it needs to be, but
530          * within all the constraints specified by the sysctls.
531          */
532         spin_lock(&hugetlb_lock);
533         while (surplus_huge_pages && count > persistent_huge_pages) {
534                 if (!adjust_pool_surplus(-1))
535                         break;
536         }
537
538         while (count > persistent_huge_pages) {
539                 int ret;
540                 /*
541                  * If this allocation races such that we no longer need the
542                  * page, free_huge_page will handle it by freeing the page
543                  * and reducing the surplus.
544                  */
545                 spin_unlock(&hugetlb_lock);
546                 ret = alloc_fresh_huge_page();
547                 spin_lock(&hugetlb_lock);
548                 if (!ret)
549                         goto out;
550
551         }
552
553         /*
554          * Decrease the pool size
555          * First return free pages to the buddy allocator (being careful
556          * to keep enough around to satisfy reservations).  Then place
557          * pages into surplus state as needed so the pool will shrink
558          * to the desired size as pages become free.
559          *
560          * By placing pages into the surplus state independent of the
561          * overcommit value, we are allowing the surplus pool size to
562          * exceed overcommit. There are few sane options here. Since
563          * alloc_buddy_huge_page() is checking the global counter,
564          * though, we'll note that we're not allowed to exceed surplus
565          * and won't grow the pool anywhere else. Not until one of the
566          * sysctls are changed, or the surplus pages go out of use.
567          */
568         min_count = resv_huge_pages + nr_huge_pages - free_huge_pages;
569         min_count = max(count, min_count);
570         try_to_free_low(min_count);
571         while (min_count < persistent_huge_pages) {
572                 struct page *page = dequeue_huge_page(NULL, 0);
573                 if (!page)
574                         break;
575                 update_and_free_page(page);
576         }
577         while (count < persistent_huge_pages) {
578                 if (!adjust_pool_surplus(1))
579                         break;
580         }
581 out:
582         ret = persistent_huge_pages;
583         spin_unlock(&hugetlb_lock);
584         return ret;
585 }
586
587 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
588                            struct file *file, void __user *buffer,
589                            size_t *length, loff_t *ppos)
590 {
591         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
592         max_huge_pages = set_max_huge_pages(max_huge_pages);
593         return 0;
594 }
595
596 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
597                         struct file *file, void __user *buffer,
598                         size_t *length, loff_t *ppos)
599 {
600         proc_dointvec(table, write, file, buffer, length, ppos);
601         if (hugepages_treat_as_movable)
602                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
603         else
604                 htlb_alloc_mask = GFP_HIGHUSER;
605         return 0;
606 }
607
608 #endif /* CONFIG_SYSCTL */
609
610 int hugetlb_report_meminfo(char *buf)
611 {
612         return sprintf(buf,
613                         "HugePages_Total: %5lu\n"
614                         "HugePages_Free:  %5lu\n"
615                         "HugePages_Rsvd:  %5lu\n"
616                         "HugePages_Surp:  %5lu\n"
617                         "Hugepagesize:    %5lu kB\n",
618                         nr_huge_pages,
619                         free_huge_pages,
620                         resv_huge_pages,
621                         surplus_huge_pages,
622                         HPAGE_SIZE/1024);
623 }
624
625 int hugetlb_report_node_meminfo(int nid, char *buf)
626 {
627         return sprintf(buf,
628                 "Node %d HugePages_Total: %5u\n"
629                 "Node %d HugePages_Free:  %5u\n",
630                 nid, nr_huge_pages_node[nid],
631                 nid, free_huge_pages_node[nid]);
632 }
633
634 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
635 unsigned long hugetlb_total_pages(void)
636 {
637         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
638 }
639
640 /*
641  * We cannot handle pagefaults against hugetlb pages at all.  They cause
642  * handle_mm_fault() to try to instantiate regular-sized pages in the
643  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
644  * this far.
645  */
646 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
647 {
648         BUG();
649         return 0;
650 }
651
652 struct vm_operations_struct hugetlb_vm_ops = {
653         .fault = hugetlb_vm_op_fault,
654 };
655
656 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
657                                 int writable)
658 {
659         pte_t entry;
660
661         if (writable) {
662                 entry =
663                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
664         } else {
665                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
666         }
667         entry = pte_mkyoung(entry);
668         entry = pte_mkhuge(entry);
669
670         return entry;
671 }
672
673 static void set_huge_ptep_writable(struct vm_area_struct *vma,
674                                    unsigned long address, pte_t *ptep)
675 {
676         pte_t entry;
677
678         entry = pte_mkwrite(pte_mkdirty(*ptep));
679         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
680                 update_mmu_cache(vma, address, entry);
681         }
682 }
683
684
685 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
686                             struct vm_area_struct *vma)
687 {
688         pte_t *src_pte, *dst_pte, entry;
689         struct page *ptepage;
690         unsigned long addr;
691         int cow;
692
693         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
694
695         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
696                 src_pte = huge_pte_offset(src, addr);
697                 if (!src_pte)
698                         continue;
699                 dst_pte = huge_pte_alloc(dst, addr);
700                 if (!dst_pte)
701                         goto nomem;
702
703                 /* If the pagetables are shared don't copy or take references */
704                 if (dst_pte == src_pte)
705                         continue;
706
707                 spin_lock(&dst->page_table_lock);
708                 spin_lock(&src->page_table_lock);
709                 if (!pte_none(*src_pte)) {
710                         if (cow)
711                                 ptep_set_wrprotect(src, addr, src_pte);
712                         entry = *src_pte;
713                         ptepage = pte_page(entry);
714                         get_page(ptepage);
715                         set_huge_pte_at(dst, addr, dst_pte, entry);
716                 }
717                 spin_unlock(&src->page_table_lock);
718                 spin_unlock(&dst->page_table_lock);
719         }
720         return 0;
721
722 nomem:
723         return -ENOMEM;
724 }
725
726 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
727                             unsigned long end)
728 {
729         struct mm_struct *mm = vma->vm_mm;
730         unsigned long address;
731         pte_t *ptep;
732         pte_t pte;
733         struct page *page;
734         struct page *tmp;
735         /*
736          * A page gathering list, protected by per file i_mmap_lock. The
737          * lock is used to avoid list corruption from multiple unmapping
738          * of the same page since we are using page->lru.
739          */
740         LIST_HEAD(page_list);
741
742         WARN_ON(!is_vm_hugetlb_page(vma));
743         BUG_ON(start & ~HPAGE_MASK);
744         BUG_ON(end & ~HPAGE_MASK);
745
746         spin_lock(&mm->page_table_lock);
747         for (address = start; address < end; address += HPAGE_SIZE) {
748                 ptep = huge_pte_offset(mm, address);
749                 if (!ptep)
750                         continue;
751
752                 if (huge_pmd_unshare(mm, &address, ptep))
753                         continue;
754
755                 pte = huge_ptep_get_and_clear(mm, address, ptep);
756                 if (pte_none(pte))
757                         continue;
758
759                 page = pte_page(pte);
760                 if (pte_dirty(pte))
761                         set_page_dirty(page);
762                 list_add(&page->lru, &page_list);
763         }
764         spin_unlock(&mm->page_table_lock);
765         flush_tlb_range(vma, start, end);
766         list_for_each_entry_safe(page, tmp, &page_list, lru) {
767                 list_del(&page->lru);
768                 put_page(page);
769         }
770 }
771
772 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
773                           unsigned long end)
774 {
775         /*
776          * It is undesirable to test vma->vm_file as it should be non-null
777          * for valid hugetlb area. However, vm_file will be NULL in the error
778          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
779          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
780          * to clean up. Since no pte has actually been setup, it is safe to
781          * do nothing in this case.
782          */
783         if (vma->vm_file) {
784                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
785                 __unmap_hugepage_range(vma, start, end);
786                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
787         }
788 }
789
790 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
791                         unsigned long address, pte_t *ptep, pte_t pte)
792 {
793         struct page *old_page, *new_page;
794         int avoidcopy;
795
796         old_page = pte_page(pte);
797
798         /* If no-one else is actually using this page, avoid the copy
799          * and just make the page writable */
800         avoidcopy = (page_count(old_page) == 1);
801         if (avoidcopy) {
802                 set_huge_ptep_writable(vma, address, ptep);
803                 return 0;
804         }
805
806         page_cache_get(old_page);
807         new_page = alloc_huge_page(vma, address);
808
809         if (IS_ERR(new_page)) {
810                 page_cache_release(old_page);
811                 return -PTR_ERR(new_page);
812         }
813
814         spin_unlock(&mm->page_table_lock);
815         copy_huge_page(new_page, old_page, address, vma);
816         spin_lock(&mm->page_table_lock);
817
818         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
819         if (likely(pte_same(*ptep, pte))) {
820                 /* Break COW */
821                 set_huge_pte_at(mm, address, ptep,
822                                 make_huge_pte(vma, new_page, 1));
823                 /* Make the old page be freed below */
824                 new_page = old_page;
825         }
826         page_cache_release(new_page);
827         page_cache_release(old_page);
828         return 0;
829 }
830
831 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
832                         unsigned long address, pte_t *ptep, int write_access)
833 {
834         int ret = VM_FAULT_SIGBUS;
835         unsigned long idx;
836         unsigned long size;
837         struct page *page;
838         struct address_space *mapping;
839         pte_t new_pte;
840
841         mapping = vma->vm_file->f_mapping;
842         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
843                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
844
845         /*
846          * Use page lock to guard against racing truncation
847          * before we get page_table_lock.
848          */
849 retry:
850         page = find_lock_page(mapping, idx);
851         if (!page) {
852                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
853                 if (idx >= size)
854                         goto out;
855                 page = alloc_huge_page(vma, address);
856                 if (IS_ERR(page)) {
857                         ret = -PTR_ERR(page);
858                         goto out;
859                 }
860                 clear_huge_page(page, address);
861
862                 if (vma->vm_flags & VM_SHARED) {
863                         int err;
864                         struct inode *inode = mapping->host;
865
866                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
867                         if (err) {
868                                 put_page(page);
869                                 if (err == -EEXIST)
870                                         goto retry;
871                                 goto out;
872                         }
873
874                         spin_lock(&inode->i_lock);
875                         inode->i_blocks += BLOCKS_PER_HUGEPAGE;
876                         spin_unlock(&inode->i_lock);
877                 } else
878                         lock_page(page);
879         }
880
881         spin_lock(&mm->page_table_lock);
882         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
883         if (idx >= size)
884                 goto backout;
885
886         ret = 0;
887         if (!pte_none(*ptep))
888                 goto backout;
889
890         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
891                                 && (vma->vm_flags & VM_SHARED)));
892         set_huge_pte_at(mm, address, ptep, new_pte);
893
894         if (write_access && !(vma->vm_flags & VM_SHARED)) {
895                 /* Optimization, do the COW without a second fault */
896                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
897         }
898
899         spin_unlock(&mm->page_table_lock);
900         unlock_page(page);
901 out:
902         return ret;
903
904 backout:
905         spin_unlock(&mm->page_table_lock);
906         unlock_page(page);
907         put_page(page);
908         goto out;
909 }
910
911 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
912                         unsigned long address, int write_access)
913 {
914         pte_t *ptep;
915         pte_t entry;
916         int ret;
917         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
918
919         ptep = huge_pte_alloc(mm, address);
920         if (!ptep)
921                 return VM_FAULT_OOM;
922
923         /*
924          * Serialize hugepage allocation and instantiation, so that we don't
925          * get spurious allocation failures if two CPUs race to instantiate
926          * the same page in the page cache.
927          */
928         mutex_lock(&hugetlb_instantiation_mutex);
929         entry = *ptep;
930         if (pte_none(entry)) {
931                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
932                 mutex_unlock(&hugetlb_instantiation_mutex);
933                 return ret;
934         }
935
936         ret = 0;
937
938         spin_lock(&mm->page_table_lock);
939         /* Check for a racing update before calling hugetlb_cow */
940         if (likely(pte_same(entry, *ptep)))
941                 if (write_access && !pte_write(entry))
942                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
943         spin_unlock(&mm->page_table_lock);
944         mutex_unlock(&hugetlb_instantiation_mutex);
945
946         return ret;
947 }
948
949 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
950                         struct page **pages, struct vm_area_struct **vmas,
951                         unsigned long *position, int *length, int i,
952                         int write)
953 {
954         unsigned long pfn_offset;
955         unsigned long vaddr = *position;
956         int remainder = *length;
957
958         spin_lock(&mm->page_table_lock);
959         while (vaddr < vma->vm_end && remainder) {
960                 pte_t *pte;
961                 struct page *page;
962
963                 /*
964                  * Some archs (sparc64, sh*) have multiple pte_ts to
965                  * each hugepage.  We have to make * sure we get the
966                  * first, for the page indexing below to work.
967                  */
968                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
969
970                 if (!pte || pte_none(*pte) || (write && !pte_write(*pte))) {
971                         int ret;
972
973                         spin_unlock(&mm->page_table_lock);
974                         ret = hugetlb_fault(mm, vma, vaddr, write);
975                         spin_lock(&mm->page_table_lock);
976                         if (!(ret & VM_FAULT_ERROR))
977                                 continue;
978
979                         remainder = 0;
980                         if (!i)
981                                 i = -EFAULT;
982                         break;
983                 }
984
985                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
986                 page = pte_page(*pte);
987 same_page:
988                 if (pages) {
989                         get_page(page);
990                         pages[i] = page + pfn_offset;
991                 }
992
993                 if (vmas)
994                         vmas[i] = vma;
995
996                 vaddr += PAGE_SIZE;
997                 ++pfn_offset;
998                 --remainder;
999                 ++i;
1000                 if (vaddr < vma->vm_end && remainder &&
1001                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
1002                         /*
1003                          * We use pfn_offset to avoid touching the pageframes
1004                          * of this compound page.
1005                          */
1006                         goto same_page;
1007                 }
1008         }
1009         spin_unlock(&mm->page_table_lock);
1010         *length = remainder;
1011         *position = vaddr;
1012
1013         return i;
1014 }
1015
1016 void hugetlb_change_protection(struct vm_area_struct *vma,
1017                 unsigned long address, unsigned long end, pgprot_t newprot)
1018 {
1019         struct mm_struct *mm = vma->vm_mm;
1020         unsigned long start = address;
1021         pte_t *ptep;
1022         pte_t pte;
1023
1024         BUG_ON(address >= end);
1025         flush_cache_range(vma, address, end);
1026
1027         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
1028         spin_lock(&mm->page_table_lock);
1029         for (; address < end; address += HPAGE_SIZE) {
1030                 ptep = huge_pte_offset(mm, address);
1031                 if (!ptep)
1032                         continue;
1033                 if (huge_pmd_unshare(mm, &address, ptep))
1034                         continue;
1035                 if (!pte_none(*ptep)) {
1036                         pte = huge_ptep_get_and_clear(mm, address, ptep);
1037                         pte = pte_mkhuge(pte_modify(pte, newprot));
1038                         set_huge_pte_at(mm, address, ptep, pte);
1039                 }
1040         }
1041         spin_unlock(&mm->page_table_lock);
1042         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
1043
1044         flush_tlb_range(vma, start, end);
1045 }
1046
1047 struct file_region {
1048         struct list_head link;
1049         long from;
1050         long to;
1051 };
1052
1053 static long region_add(struct list_head *head, long f, long t)
1054 {
1055         struct file_region *rg, *nrg, *trg;
1056
1057         /* Locate the region we are either in or before. */
1058         list_for_each_entry(rg, head, link)
1059                 if (f <= rg->to)
1060                         break;
1061
1062         /* Round our left edge to the current segment if it encloses us. */
1063         if (f > rg->from)
1064                 f = rg->from;
1065
1066         /* Check for and consume any regions we now overlap with. */
1067         nrg = rg;
1068         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1069                 if (&rg->link == head)
1070                         break;
1071                 if (rg->from > t)
1072                         break;
1073
1074                 /* If this area reaches higher then extend our area to
1075                  * include it completely.  If this is not the first area
1076                  * which we intend to reuse, free it. */
1077                 if (rg->to > t)
1078                         t = rg->to;
1079                 if (rg != nrg) {
1080                         list_del(&rg->link);
1081                         kfree(rg);
1082                 }
1083         }
1084         nrg->from = f;
1085         nrg->to = t;
1086         return 0;
1087 }
1088
1089 static long region_chg(struct list_head *head, long f, long t)
1090 {
1091         struct file_region *rg, *nrg;
1092         long chg = 0;
1093
1094         /* Locate the region we are before or in. */
1095         list_for_each_entry(rg, head, link)
1096                 if (f <= rg->to)
1097                         break;
1098
1099         /* If we are below the current region then a new region is required.
1100          * Subtle, allocate a new region at the position but make it zero
1101          * size such that we can guarantee to record the reservation. */
1102         if (&rg->link == head || t < rg->from) {
1103                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
1104                 if (!nrg)
1105                         return -ENOMEM;
1106                 nrg->from = f;
1107                 nrg->to   = f;
1108                 INIT_LIST_HEAD(&nrg->link);
1109                 list_add(&nrg->link, rg->link.prev);
1110
1111                 return t - f;
1112         }
1113
1114         /* Round our left edge to the current segment if it encloses us. */
1115         if (f > rg->from)
1116                 f = rg->from;
1117         chg = t - f;
1118
1119         /* Check for and consume any regions we now overlap with. */
1120         list_for_each_entry(rg, rg->link.prev, link) {
1121                 if (&rg->link == head)
1122                         break;
1123                 if (rg->from > t)
1124                         return chg;
1125
1126                 /* We overlap with this area, if it extends futher than
1127                  * us then we must extend ourselves.  Account for its
1128                  * existing reservation. */
1129                 if (rg->to > t) {
1130                         chg += rg->to - t;
1131                         t = rg->to;
1132                 }
1133                 chg -= rg->to - rg->from;
1134         }
1135         return chg;
1136 }
1137
1138 static long region_truncate(struct list_head *head, long end)
1139 {
1140         struct file_region *rg, *trg;
1141         long chg = 0;
1142
1143         /* Locate the region we are either in or before. */
1144         list_for_each_entry(rg, head, link)
1145                 if (end <= rg->to)
1146                         break;
1147         if (&rg->link == head)
1148                 return 0;
1149
1150         /* If we are in the middle of a region then adjust it. */
1151         if (end > rg->from) {
1152                 chg = rg->to - end;
1153                 rg->to = end;
1154                 rg = list_entry(rg->link.next, typeof(*rg), link);
1155         }
1156
1157         /* Drop any remaining regions. */
1158         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1159                 if (&rg->link == head)
1160                         break;
1161                 chg += rg->to - rg->from;
1162                 list_del(&rg->link);
1163                 kfree(rg);
1164         }
1165         return chg;
1166 }
1167
1168 static int hugetlb_acct_memory(long delta)
1169 {
1170         int ret = -ENOMEM;
1171
1172         spin_lock(&hugetlb_lock);
1173         /*
1174          * When cpuset is configured, it breaks the strict hugetlb page
1175          * reservation as the accounting is done on a global variable. Such
1176          * reservation is completely rubbish in the presence of cpuset because
1177          * the reservation is not checked against page availability for the
1178          * current cpuset. Application can still potentially OOM'ed by kernel
1179          * with lack of free htlb page in cpuset that the task is in.
1180          * Attempt to enforce strict accounting with cpuset is almost
1181          * impossible (or too ugly) because cpuset is too fluid that
1182          * task or memory node can be dynamically moved between cpusets.
1183          *
1184          * The change of semantics for shared hugetlb mapping with cpuset is
1185          * undesirable. However, in order to preserve some of the semantics,
1186          * we fall back to check against current free page availability as
1187          * a best attempt and hopefully to minimize the impact of changing
1188          * semantics that cpuset has.
1189          */
1190         if (delta > 0) {
1191                 if (gather_surplus_pages(delta) < 0)
1192                         goto out;
1193
1194                 if (delta > cpuset_mems_nr(free_huge_pages_node))
1195                         goto out;
1196         }
1197
1198         ret = 0;
1199         resv_huge_pages += delta;
1200         if (delta < 0)
1201                 return_unused_surplus_pages((unsigned long) -delta);
1202
1203 out:
1204         spin_unlock(&hugetlb_lock);
1205         return ret;
1206 }
1207
1208 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
1209 {
1210         long ret, chg;
1211
1212         chg = region_chg(&inode->i_mapping->private_list, from, to);
1213         if (chg < 0)
1214                 return chg;
1215
1216         if (hugetlb_get_quota(inode->i_mapping, chg))
1217                 return -ENOSPC;
1218         ret = hugetlb_acct_memory(chg);
1219         if (ret < 0) {
1220                 hugetlb_put_quota(inode->i_mapping, chg);
1221                 return ret;
1222         }
1223         region_add(&inode->i_mapping->private_list, from, to);
1224         return 0;
1225 }
1226
1227 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
1228 {
1229         long chg = region_truncate(&inode->i_mapping->private_list, offset);
1230
1231         spin_lock(&inode->i_lock);
1232         inode->i_blocks -= BLOCKS_PER_HUGEPAGE * freed;
1233         spin_unlock(&inode->i_lock);
1234
1235         hugetlb_put_quota(inode->i_mapping, (chg - freed));
1236         hugetlb_acct_memory(-(chg - freed));
1237 }