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