27fad5d9bcf648b27564465b35c3cd72969257fa
[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, reserved_huge_pages;
26 unsigned long max_huge_pages;
27 static struct list_head hugepage_freelists[MAX_NUMNODES];
28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
30 /*
31  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
32  */
33 static DEFINE_SPINLOCK(hugetlb_lock);
34
35 static void clear_huge_page(struct page *page, unsigned long addr)
36 {
37         int i;
38
39         might_sleep();
40         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
41                 cond_resched();
42                 clear_user_highpage(page + i, addr);
43         }
44 }
45
46 static void copy_huge_page(struct page *dst, struct page *src,
47                            unsigned long addr)
48 {
49         int i;
50
51         might_sleep();
52         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
53                 cond_resched();
54                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
55         }
56 }
57
58 static void enqueue_huge_page(struct page *page)
59 {
60         int nid = page_to_nid(page);
61         list_add(&page->lru, &hugepage_freelists[nid]);
62         free_huge_pages++;
63         free_huge_pages_node[nid]++;
64 }
65
66 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
67                                 unsigned long address)
68 {
69         int nid = numa_node_id();
70         struct page *page = NULL;
71         struct zonelist *zonelist = huge_zonelist(vma, address);
72         struct zone **z;
73
74         for (z = zonelist->zones; *z; z++) {
75                 nid = (*z)->zone_pgdat->node_id;
76                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
77                     !list_empty(&hugepage_freelists[nid]))
78                         break;
79         }
80
81         if (*z) {
82                 page = list_entry(hugepage_freelists[nid].next,
83                                   struct page, lru);
84                 list_del(&page->lru);
85                 free_huge_pages--;
86                 free_huge_pages_node[nid]--;
87         }
88         return page;
89 }
90
91 static int alloc_fresh_huge_page(void)
92 {
93         static int nid = 0;
94         struct page *page;
95         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
96                                         HUGETLB_PAGE_ORDER);
97         nid = (nid + 1) % num_online_nodes();
98         if (page) {
99                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
100                 spin_lock(&hugetlb_lock);
101                 nr_huge_pages++;
102                 nr_huge_pages_node[page_to_nid(page)]++;
103                 spin_unlock(&hugetlb_lock);
104                 put_page(page); /* free it into the hugepage allocator */
105                 return 1;
106         }
107         return 0;
108 }
109
110 void free_huge_page(struct page *page)
111 {
112         BUG_ON(page_count(page));
113
114         INIT_LIST_HEAD(&page->lru);
115
116         spin_lock(&hugetlb_lock);
117         enqueue_huge_page(page);
118         spin_unlock(&hugetlb_lock);
119 }
120
121 struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
122 {
123         struct inode *inode = vma->vm_file->f_dentry->d_inode;
124         struct page *page;
125         int use_reserve = 0;
126         unsigned long idx;
127
128         spin_lock(&hugetlb_lock);
129
130         if (vma->vm_flags & VM_MAYSHARE) {
131
132                 /* idx = radix tree index, i.e. offset into file in
133                  * HPAGE_SIZE units */
134                 idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
135                         + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
136
137                 /* The hugetlbfs specific inode info stores the number
138                  * of "guaranteed available" (huge) pages.  That is,
139                  * the first 'prereserved_hpages' pages of the inode
140                  * are either already instantiated, or have been
141                  * pre-reserved (by hugetlb_reserve_for_inode()). Here
142                  * we're in the process of instantiating the page, so
143                  * we use this to determine whether to draw from the
144                  * pre-reserved pool or the truly free pool. */
145                 if (idx < HUGETLBFS_I(inode)->prereserved_hpages)
146                         use_reserve = 1;
147         }
148
149         if (!use_reserve) {
150                 if (free_huge_pages <= reserved_huge_pages)
151                         goto fail;
152         } else {
153                 BUG_ON(reserved_huge_pages == 0);
154                 reserved_huge_pages--;
155         }
156
157         page = dequeue_huge_page(vma, addr);
158         if (!page)
159                 goto fail;
160
161         spin_unlock(&hugetlb_lock);
162         set_page_refcounted(page);
163         return page;
164
165  fail:
166         WARN_ON(use_reserve); /* reserved allocations shouldn't fail */
167         spin_unlock(&hugetlb_lock);
168         return NULL;
169 }
170
171 /* hugetlb_extend_reservation()
172  *
173  * Ensure that at least 'atleast' hugepages are, and will remain,
174  * available to instantiate the first 'atleast' pages of the given
175  * inode.  If the inode doesn't already have this many pages reserved
176  * or instantiated, set aside some hugepages in the reserved pool to
177  * satisfy later faults (or fail now if there aren't enough, rather
178  * than getting the SIGBUS later).
179  */
180 int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
181                                unsigned long atleast)
182 {
183         struct inode *inode = &info->vfs_inode;
184         unsigned long change_in_reserve = 0;
185         int ret = 0;
186
187         spin_lock(&hugetlb_lock);
188         read_lock_irq(&inode->i_mapping->tree_lock);
189
190         if (info->prereserved_hpages >= atleast)
191                 goto out;
192
193         /* Because we always call this on shared mappings, none of the
194          * pages beyond info->prereserved_hpages can have been
195          * instantiated, so we need to reserve all of them now. */
196         change_in_reserve = atleast - info->prereserved_hpages;
197
198         if ((reserved_huge_pages + change_in_reserve) > free_huge_pages) {
199                 ret = -ENOMEM;
200                 goto out;
201         }
202
203         reserved_huge_pages += change_in_reserve;
204         info->prereserved_hpages = atleast;
205
206  out:
207         read_unlock_irq(&inode->i_mapping->tree_lock);
208         spin_unlock(&hugetlb_lock);
209
210         return ret;
211 }
212
213 /* hugetlb_truncate_reservation()
214  *
215  * This returns pages reserved for the given inode to the general free
216  * hugepage pool.  If the inode has any pages prereserved, but not
217  * instantiated, beyond offset (atmost << HPAGE_SIZE), then release
218  * them.
219  */
220 void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
221                                   unsigned long atmost)
222 {
223         struct inode *inode = &info->vfs_inode;
224         struct address_space *mapping = inode->i_mapping;
225         unsigned long idx;
226         unsigned long change_in_reserve = 0;
227         struct page *page;
228
229         spin_lock(&hugetlb_lock);
230         read_lock_irq(&inode->i_mapping->tree_lock);
231
232         if (info->prereserved_hpages <= atmost)
233                 goto out;
234
235         /* Count pages which were reserved, but not instantiated, and
236          * which we can now release. */
237         for (idx = atmost; idx < info->prereserved_hpages; idx++) {
238                 page = radix_tree_lookup(&mapping->page_tree, idx);
239                 if (!page)
240                         /* Pages which are already instantiated can't
241                          * be unreserved (and in fact have already
242                          * been removed from the reserved pool) */
243                         change_in_reserve++;
244         }
245
246         BUG_ON(reserved_huge_pages < change_in_reserve);
247         reserved_huge_pages -= change_in_reserve;
248         info->prereserved_hpages = atmost;
249
250  out:
251         read_unlock_irq(&inode->i_mapping->tree_lock);
252         spin_unlock(&hugetlb_lock);
253 }
254
255 static int __init hugetlb_init(void)
256 {
257         unsigned long i;
258
259         if (HPAGE_SHIFT == 0)
260                 return 0;
261
262         for (i = 0; i < MAX_NUMNODES; ++i)
263                 INIT_LIST_HEAD(&hugepage_freelists[i]);
264
265         for (i = 0; i < max_huge_pages; ++i) {
266                 if (!alloc_fresh_huge_page())
267                         break;
268         }
269         max_huge_pages = free_huge_pages = nr_huge_pages = i;
270         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
271         return 0;
272 }
273 module_init(hugetlb_init);
274
275 static int __init hugetlb_setup(char *s)
276 {
277         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
278                 max_huge_pages = 0;
279         return 1;
280 }
281 __setup("hugepages=", hugetlb_setup);
282
283 #ifdef CONFIG_SYSCTL
284 static void update_and_free_page(struct page *page)
285 {
286         int i;
287         nr_huge_pages--;
288         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
289         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
290                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
291                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
292                                 1 << PG_private | 1<< PG_writeback);
293         }
294         page[1].lru.next = NULL;
295         set_page_refcounted(page);
296         __free_pages(page, HUGETLB_PAGE_ORDER);
297 }
298
299 #ifdef CONFIG_HIGHMEM
300 static void try_to_free_low(unsigned long count)
301 {
302         int i, nid;
303         for (i = 0; i < MAX_NUMNODES; ++i) {
304                 struct page *page, *next;
305                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
306                         if (PageHighMem(page))
307                                 continue;
308                         list_del(&page->lru);
309                         update_and_free_page(page);
310                         nid = page_zone(page)->zone_pgdat->node_id;
311                         free_huge_pages--;
312                         free_huge_pages_node[nid]--;
313                         if (count >= nr_huge_pages)
314                                 return;
315                 }
316         }
317 }
318 #else
319 static inline void try_to_free_low(unsigned long count)
320 {
321 }
322 #endif
323
324 static unsigned long set_max_huge_pages(unsigned long count)
325 {
326         while (count > nr_huge_pages) {
327                 if (!alloc_fresh_huge_page())
328                         return nr_huge_pages;
329         }
330         if (count >= nr_huge_pages)
331                 return nr_huge_pages;
332
333         spin_lock(&hugetlb_lock);
334         try_to_free_low(count);
335         while (count < nr_huge_pages) {
336                 struct page *page = dequeue_huge_page(NULL, 0);
337                 if (!page)
338                         break;
339                 update_and_free_page(page);
340         }
341         spin_unlock(&hugetlb_lock);
342         return nr_huge_pages;
343 }
344
345 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
346                            struct file *file, void __user *buffer,
347                            size_t *length, loff_t *ppos)
348 {
349         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
350         max_huge_pages = set_max_huge_pages(max_huge_pages);
351         return 0;
352 }
353 #endif /* CONFIG_SYSCTL */
354
355 int hugetlb_report_meminfo(char *buf)
356 {
357         return sprintf(buf,
358                         "HugePages_Total: %5lu\n"
359                         "HugePages_Free:  %5lu\n"
360                         "HugePages_Rsvd:  %5lu\n"
361                         "Hugepagesize:    %5lu kB\n",
362                         nr_huge_pages,
363                         free_huge_pages,
364                         reserved_huge_pages,
365                         HPAGE_SIZE/1024);
366 }
367
368 int hugetlb_report_node_meminfo(int nid, char *buf)
369 {
370         return sprintf(buf,
371                 "Node %d HugePages_Total: %5u\n"
372                 "Node %d HugePages_Free:  %5u\n",
373                 nid, nr_huge_pages_node[nid],
374                 nid, free_huge_pages_node[nid]);
375 }
376
377 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
378 unsigned long hugetlb_total_pages(void)
379 {
380         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
381 }
382
383 /*
384  * We cannot handle pagefaults against hugetlb pages at all.  They cause
385  * handle_mm_fault() to try to instantiate regular-sized pages in the
386  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
387  * this far.
388  */
389 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
390                                 unsigned long address, int *unused)
391 {
392         BUG();
393         return NULL;
394 }
395
396 struct vm_operations_struct hugetlb_vm_ops = {
397         .nopage = hugetlb_nopage,
398 };
399
400 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
401                                 int writable)
402 {
403         pte_t entry;
404
405         if (writable) {
406                 entry =
407                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
408         } else {
409                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
410         }
411         entry = pte_mkyoung(entry);
412         entry = pte_mkhuge(entry);
413
414         return entry;
415 }
416
417 static void set_huge_ptep_writable(struct vm_area_struct *vma,
418                                    unsigned long address, pte_t *ptep)
419 {
420         pte_t entry;
421
422         entry = pte_mkwrite(pte_mkdirty(*ptep));
423         ptep_set_access_flags(vma, address, ptep, entry, 1);
424         update_mmu_cache(vma, address, entry);
425         lazy_mmu_prot_update(entry);
426 }
427
428
429 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
430                             struct vm_area_struct *vma)
431 {
432         pte_t *src_pte, *dst_pte, entry;
433         struct page *ptepage;
434         unsigned long addr;
435         int cow;
436
437         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
438
439         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
440                 src_pte = huge_pte_offset(src, addr);
441                 if (!src_pte)
442                         continue;
443                 dst_pte = huge_pte_alloc(dst, addr);
444                 if (!dst_pte)
445                         goto nomem;
446                 spin_lock(&dst->page_table_lock);
447                 spin_lock(&src->page_table_lock);
448                 if (!pte_none(*src_pte)) {
449                         if (cow)
450                                 ptep_set_wrprotect(src, addr, src_pte);
451                         entry = *src_pte;
452                         ptepage = pte_page(entry);
453                         get_page(ptepage);
454                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
455                         set_huge_pte_at(dst, addr, dst_pte, entry);
456                 }
457                 spin_unlock(&src->page_table_lock);
458                 spin_unlock(&dst->page_table_lock);
459         }
460         return 0;
461
462 nomem:
463         return -ENOMEM;
464 }
465
466 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
467                           unsigned long end)
468 {
469         struct mm_struct *mm = vma->vm_mm;
470         unsigned long address;
471         pte_t *ptep;
472         pte_t pte;
473         struct page *page;
474
475         WARN_ON(!is_vm_hugetlb_page(vma));
476         BUG_ON(start & ~HPAGE_MASK);
477         BUG_ON(end & ~HPAGE_MASK);
478
479         spin_lock(&mm->page_table_lock);
480
481         /* Update high watermark before we lower rss */
482         update_hiwater_rss(mm);
483
484         for (address = start; address < end; address += HPAGE_SIZE) {
485                 ptep = huge_pte_offset(mm, address);
486                 if (!ptep)
487                         continue;
488
489                 pte = huge_ptep_get_and_clear(mm, address, ptep);
490                 if (pte_none(pte))
491                         continue;
492
493                 page = pte_page(pte);
494                 put_page(page);
495                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
496         }
497
498         spin_unlock(&mm->page_table_lock);
499         flush_tlb_range(vma, start, end);
500 }
501
502 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
503                         unsigned long address, pte_t *ptep, pte_t pte)
504 {
505         struct page *old_page, *new_page;
506         int avoidcopy;
507
508         old_page = pte_page(pte);
509
510         /* If no-one else is actually using this page, avoid the copy
511          * and just make the page writable */
512         avoidcopy = (page_count(old_page) == 1);
513         if (avoidcopy) {
514                 set_huge_ptep_writable(vma, address, ptep);
515                 return VM_FAULT_MINOR;
516         }
517
518         page_cache_get(old_page);
519         new_page = alloc_huge_page(vma, address);
520
521         if (!new_page) {
522                 page_cache_release(old_page);
523                 return VM_FAULT_OOM;
524         }
525
526         spin_unlock(&mm->page_table_lock);
527         copy_huge_page(new_page, old_page, address);
528         spin_lock(&mm->page_table_lock);
529
530         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
531         if (likely(pte_same(*ptep, pte))) {
532                 /* Break COW */
533                 set_huge_pte_at(mm, address, ptep,
534                                 make_huge_pte(vma, new_page, 1));
535                 /* Make the old page be freed below */
536                 new_page = old_page;
537         }
538         page_cache_release(new_page);
539         page_cache_release(old_page);
540         return VM_FAULT_MINOR;
541 }
542
543 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
544                         unsigned long address, pte_t *ptep, int write_access)
545 {
546         int ret = VM_FAULT_SIGBUS;
547         unsigned long idx;
548         unsigned long size;
549         struct page *page;
550         struct address_space *mapping;
551         pte_t new_pte;
552
553         mapping = vma->vm_file->f_mapping;
554         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
555                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
556
557         /*
558          * Use page lock to guard against racing truncation
559          * before we get page_table_lock.
560          */
561 retry:
562         page = find_lock_page(mapping, idx);
563         if (!page) {
564                 if (hugetlb_get_quota(mapping))
565                         goto out;
566                 page = alloc_huge_page(vma, address);
567                 if (!page) {
568                         hugetlb_put_quota(mapping);
569                         ret = VM_FAULT_OOM;
570                         goto out;
571                 }
572                 clear_huge_page(page, address);
573
574                 if (vma->vm_flags & VM_SHARED) {
575                         int err;
576
577                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
578                         if (err) {
579                                 put_page(page);
580                                 hugetlb_put_quota(mapping);
581                                 if (err == -EEXIST)
582                                         goto retry;
583                                 goto out;
584                         }
585                 } else
586                         lock_page(page);
587         }
588
589         spin_lock(&mm->page_table_lock);
590         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
591         if (idx >= size)
592                 goto backout;
593
594         ret = VM_FAULT_MINOR;
595         if (!pte_none(*ptep))
596                 goto backout;
597
598         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
599         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
600                                 && (vma->vm_flags & VM_SHARED)));
601         set_huge_pte_at(mm, address, ptep, new_pte);
602
603         if (write_access && !(vma->vm_flags & VM_SHARED)) {
604                 /* Optimization, do the COW without a second fault */
605                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
606         }
607
608         spin_unlock(&mm->page_table_lock);
609         unlock_page(page);
610 out:
611         return ret;
612
613 backout:
614         spin_unlock(&mm->page_table_lock);
615         hugetlb_put_quota(mapping);
616         unlock_page(page);
617         put_page(page);
618         goto out;
619 }
620
621 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
622                         unsigned long address, int write_access)
623 {
624         pte_t *ptep;
625         pte_t entry;
626         int ret;
627         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
628
629         ptep = huge_pte_alloc(mm, address);
630         if (!ptep)
631                 return VM_FAULT_OOM;
632
633         /*
634          * Serialize hugepage allocation and instantiation, so that we don't
635          * get spurious allocation failures if two CPUs race to instantiate
636          * the same page in the page cache.
637          */
638         mutex_lock(&hugetlb_instantiation_mutex);
639         entry = *ptep;
640         if (pte_none(entry)) {
641                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
642                 mutex_unlock(&hugetlb_instantiation_mutex);
643                 return ret;
644         }
645
646         ret = VM_FAULT_MINOR;
647
648         spin_lock(&mm->page_table_lock);
649         /* Check for a racing update before calling hugetlb_cow */
650         if (likely(pte_same(entry, *ptep)))
651                 if (write_access && !pte_write(entry))
652                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
653         spin_unlock(&mm->page_table_lock);
654         mutex_unlock(&hugetlb_instantiation_mutex);
655
656         return ret;
657 }
658
659 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
660                         struct page **pages, struct vm_area_struct **vmas,
661                         unsigned long *position, int *length, int i)
662 {
663         unsigned long vpfn, vaddr = *position;
664         int remainder = *length;
665
666         vpfn = vaddr/PAGE_SIZE;
667         spin_lock(&mm->page_table_lock);
668         while (vaddr < vma->vm_end && remainder) {
669                 pte_t *pte;
670                 struct page *page;
671
672                 /*
673                  * Some archs (sparc64, sh*) have multiple pte_ts to
674                  * each hugepage.  We have to make * sure we get the
675                  * first, for the page indexing below to work.
676                  */
677                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
678
679                 if (!pte || pte_none(*pte)) {
680                         int ret;
681
682                         spin_unlock(&mm->page_table_lock);
683                         ret = hugetlb_fault(mm, vma, vaddr, 0);
684                         spin_lock(&mm->page_table_lock);
685                         if (ret == VM_FAULT_MINOR)
686                                 continue;
687
688                         remainder = 0;
689                         if (!i)
690                                 i = -EFAULT;
691                         break;
692                 }
693
694                 if (pages) {
695                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
696                         get_page(page);
697                         pages[i] = page;
698                 }
699
700                 if (vmas)
701                         vmas[i] = vma;
702
703                 vaddr += PAGE_SIZE;
704                 ++vpfn;
705                 --remainder;
706                 ++i;
707         }
708         spin_unlock(&mm->page_table_lock);
709         *length = remainder;
710         *position = vaddr;
711
712         return i;
713 }
714
715 void hugetlb_change_protection(struct vm_area_struct *vma,
716                 unsigned long address, unsigned long end, pgprot_t newprot)
717 {
718         struct mm_struct *mm = vma->vm_mm;
719         unsigned long start = address;
720         pte_t *ptep;
721         pte_t pte;
722
723         BUG_ON(address >= end);
724         flush_cache_range(vma, address, end);
725
726         spin_lock(&mm->page_table_lock);
727         for (; address < end; address += HPAGE_SIZE) {
728                 ptep = huge_pte_offset(mm, address);
729                 if (!ptep)
730                         continue;
731                 if (!pte_none(*ptep)) {
732                         pte = huge_ptep_get_and_clear(mm, address, ptep);
733                         pte = pte_mkhuge(pte_modify(pte, newprot));
734                         set_huge_pte_at(mm, address, ptep, pte);
735                         lazy_mmu_prot_update(pte);
736                 }
737         }
738         spin_unlock(&mm->page_table_lock);
739
740         flush_tlb_range(vma, start, end);
741 }
742