ARM: OMAP3: PM: remove access to PRM_VOLTCTRL register
[pandora-kernel.git] / mm / mmap.c
1 /*
2  * mm/mmap.c
3  *
4  * Written by obz.
5  *
6  * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
7  */
8
9 #include <linux/slab.h>
10 #include <linux/backing-dev.h>
11 #include <linux/mm.h>
12 #include <linux/shm.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swap.h>
16 #include <linux/syscalls.h>
17 #include <linux/capability.h>
18 #include <linux/init.h>
19 #include <linux/file.h>
20 #include <linux/fs.h>
21 #include <linux/personality.h>
22 #include <linux/security.h>
23 #include <linux/hugetlb.h>
24 #include <linux/profile.h>
25 #include <linux/export.h>
26 #include <linux/mount.h>
27 #include <linux/mempolicy.h>
28 #include <linux/rmap.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/perf_event.h>
31 #include <linux/audit.h>
32 #include <linux/khugepaged.h>
33
34 #include <asm/uaccess.h>
35 #include <asm/cacheflush.h>
36 #include <asm/tlb.h>
37 #include <asm/mmu_context.h>
38
39 #include "internal.h"
40
41 #ifndef arch_mmap_check
42 #define arch_mmap_check(addr, len, flags)       (0)
43 #endif
44
45 #ifndef arch_rebalance_pgtables
46 #define arch_rebalance_pgtables(addr, len)              (addr)
47 #endif
48
49 static void unmap_region(struct mm_struct *mm,
50                 struct vm_area_struct *vma, struct vm_area_struct *prev,
51                 unsigned long start, unsigned long end);
52
53 /*
54  * WARNING: the debugging will use recursive algorithms so never enable this
55  * unless you know what you are doing.
56  */
57 #undef DEBUG_MM_RB
58
59 /* description of effects of mapping type and prot in current implementation.
60  * this is due to the limited x86 page protection hardware.  The expected
61  * behavior is in parens:
62  *
63  * map_type     prot
64  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
65  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
66  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
67  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
68  *              
69  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
70  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
71  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
72  *
73  */
74 pgprot_t protection_map[16] = {
75         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
76         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
77 };
78
79 pgprot_t vm_get_page_prot(unsigned long vm_flags)
80 {
81         return __pgprot(pgprot_val(protection_map[vm_flags &
82                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
83                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
84 }
85 EXPORT_SYMBOL(vm_get_page_prot);
86
87 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;  /* heuristic overcommit */
88 int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
89 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
90 /*
91  * Make sure vm_committed_as in one cacheline and not cacheline shared with
92  * other variables. It can be updated by several CPUs frequently.
93  */
94 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
95
96 /*
97  * Check that a process has enough memory to allocate a new virtual
98  * mapping. 0 means there is enough memory for the allocation to
99  * succeed and -ENOMEM implies there is not.
100  *
101  * We currently support three overcommit policies, which are set via the
102  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
103  *
104  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
105  * Additional code 2002 Jul 20 by Robert Love.
106  *
107  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
108  *
109  * Note this is a helper function intended to be used by LSMs which
110  * wish to use this logic.
111  */
112 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
113 {
114         unsigned long free, allowed;
115
116         vm_acct_memory(pages);
117
118         /*
119          * Sometimes we want to use more memory than we have
120          */
121         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
122                 return 0;
123
124         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
125                 free = global_page_state(NR_FREE_PAGES);
126                 free += global_page_state(NR_FILE_PAGES);
127
128                 /*
129                  * shmem pages shouldn't be counted as free in this
130                  * case, they can't be purged, only swapped out, and
131                  * that won't affect the overall amount of available
132                  * memory in the system.
133                  */
134                 free -= global_page_state(NR_SHMEM);
135
136                 free += nr_swap_pages;
137
138                 /*
139                  * Any slabs which are created with the
140                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
141                  * which are reclaimable, under pressure.  The dentry
142                  * cache and most inode caches should fall into this
143                  */
144                 free += global_page_state(NR_SLAB_RECLAIMABLE);
145
146                 /*
147                  * Leave reserved pages. The pages are not for anonymous pages.
148                  */
149                 if (free <= totalreserve_pages)
150                         goto error;
151                 else
152                         free -= totalreserve_pages;
153
154                 /*
155                  * Leave the last 3% for root
156                  */
157                 if (!cap_sys_admin)
158                         free -= free / 32;
159
160                 if (free > pages)
161                         return 0;
162
163                 goto error;
164         }
165
166         allowed = (totalram_pages - hugetlb_total_pages())
167                 * sysctl_overcommit_ratio / 100;
168         /*
169          * Leave the last 3% for root
170          */
171         if (!cap_sys_admin)
172                 allowed -= allowed / 32;
173         allowed += total_swap_pages;
174
175         /* Don't let a single process grow too big:
176            leave 3% of the size of this process for other processes */
177         if (mm)
178                 allowed -= mm->total_vm / 32;
179
180         if (percpu_counter_read_positive(&vm_committed_as) < allowed)
181                 return 0;
182 error:
183         vm_unacct_memory(pages);
184
185         return -ENOMEM;
186 }
187
188 /*
189  * Requires inode->i_mapping->i_mmap_mutex
190  */
191 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
192                 struct file *file, struct address_space *mapping)
193 {
194         if (vma->vm_flags & VM_DENYWRITE)
195                 atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
196         if (vma->vm_flags & VM_SHARED)
197                 mapping->i_mmap_writable--;
198
199         flush_dcache_mmap_lock(mapping);
200         if (unlikely(vma->vm_flags & VM_NONLINEAR))
201                 list_del_init(&vma->shared.vm_set.list);
202         else
203                 vma_prio_tree_remove(vma, &mapping->i_mmap);
204         flush_dcache_mmap_unlock(mapping);
205 }
206
207 /*
208  * Unlink a file-based vm structure from its prio_tree, to hide
209  * vma from rmap and vmtruncate before freeing its page tables.
210  */
211 void unlink_file_vma(struct vm_area_struct *vma)
212 {
213         struct file *file = vma->vm_file;
214
215         if (file) {
216                 struct address_space *mapping = file->f_mapping;
217                 mutex_lock(&mapping->i_mmap_mutex);
218                 __remove_shared_vm_struct(vma, file, mapping);
219                 mutex_unlock(&mapping->i_mmap_mutex);
220         }
221 }
222
223 /*
224  * Close a vm structure and free it, returning the next.
225  */
226 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
227 {
228         struct vm_area_struct *next = vma->vm_next;
229
230         might_sleep();
231         if (vma->vm_ops && vma->vm_ops->close)
232                 vma->vm_ops->close(vma);
233         if (vma->vm_file) {
234                 fput(vma->vm_file);
235                 if (vma->vm_flags & VM_EXECUTABLE)
236                         removed_exe_file_vma(vma->vm_mm);
237         }
238         mpol_put(vma_policy(vma));
239         kmem_cache_free(vm_area_cachep, vma);
240         return next;
241 }
242
243 SYSCALL_DEFINE1(brk, unsigned long, brk)
244 {
245         unsigned long rlim, retval;
246         unsigned long newbrk, oldbrk;
247         struct mm_struct *mm = current->mm;
248         unsigned long min_brk;
249
250         down_write(&mm->mmap_sem);
251
252 #ifdef CONFIG_COMPAT_BRK
253         /*
254          * CONFIG_COMPAT_BRK can still be overridden by setting
255          * randomize_va_space to 2, which will still cause mm->start_brk
256          * to be arbitrarily shifted
257          */
258         if (current->brk_randomized)
259                 min_brk = mm->start_brk;
260         else
261                 min_brk = mm->end_data;
262 #else
263         min_brk = mm->start_brk;
264 #endif
265         if (brk < min_brk)
266                 goto out;
267
268         /*
269          * Check against rlimit here. If this check is done later after the test
270          * of oldbrk with newbrk then it can escape the test and let the data
271          * segment grow beyond its set limit the in case where the limit is
272          * not page aligned -Ram Gupta
273          */
274         rlim = rlimit(RLIMIT_DATA);
275         if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
276                         (mm->end_data - mm->start_data) > rlim)
277                 goto out;
278
279         newbrk = PAGE_ALIGN(brk);
280         oldbrk = PAGE_ALIGN(mm->brk);
281         if (oldbrk == newbrk)
282                 goto set_brk;
283
284         /* Always allow shrinking brk. */
285         if (brk <= mm->brk) {
286                 if (!do_munmap(mm, newbrk, oldbrk-newbrk))
287                         goto set_brk;
288                 goto out;
289         }
290
291         /* Check against existing mmap mappings. */
292         if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
293                 goto out;
294
295         /* Ok, looks good - let it rip. */
296         if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
297                 goto out;
298 set_brk:
299         mm->brk = brk;
300 out:
301         retval = mm->brk;
302         up_write(&mm->mmap_sem);
303         return retval;
304 }
305
306 #ifdef DEBUG_MM_RB
307 static int browse_rb(struct rb_root *root)
308 {
309         int i = 0, j;
310         struct rb_node *nd, *pn = NULL;
311         unsigned long prev = 0, pend = 0;
312
313         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
314                 struct vm_area_struct *vma;
315                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
316                 if (vma->vm_start < prev)
317                         printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
318                 if (vma->vm_start < pend)
319                         printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
320                 if (vma->vm_start > vma->vm_end)
321                         printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
322                 i++;
323                 pn = nd;
324                 prev = vma->vm_start;
325                 pend = vma->vm_end;
326         }
327         j = 0;
328         for (nd = pn; nd; nd = rb_prev(nd)) {
329                 j++;
330         }
331         if (i != j)
332                 printk("backwards %d, forwards %d\n", j, i), i = 0;
333         return i;
334 }
335
336 void validate_mm(struct mm_struct *mm)
337 {
338         int bug = 0;
339         int i = 0;
340         struct vm_area_struct *tmp = mm->mmap;
341         while (tmp) {
342                 tmp = tmp->vm_next;
343                 i++;
344         }
345         if (i != mm->map_count)
346                 printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
347         i = browse_rb(&mm->mm_rb);
348         if (i != mm->map_count)
349                 printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
350         BUG_ON(bug);
351 }
352 #else
353 #define validate_mm(mm) do { } while (0)
354 #endif
355
356 static struct vm_area_struct *
357 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
358                 struct vm_area_struct **pprev, struct rb_node ***rb_link,
359                 struct rb_node ** rb_parent)
360 {
361         struct vm_area_struct * vma;
362         struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
363
364         __rb_link = &mm->mm_rb.rb_node;
365         rb_prev = __rb_parent = NULL;
366         vma = NULL;
367
368         while (*__rb_link) {
369                 struct vm_area_struct *vma_tmp;
370
371                 __rb_parent = *__rb_link;
372                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
373
374                 if (vma_tmp->vm_end > addr) {
375                         vma = vma_tmp;
376                         if (vma_tmp->vm_start <= addr)
377                                 break;
378                         __rb_link = &__rb_parent->rb_left;
379                 } else {
380                         rb_prev = __rb_parent;
381                         __rb_link = &__rb_parent->rb_right;
382                 }
383         }
384
385         *pprev = NULL;
386         if (rb_prev)
387                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
388         *rb_link = __rb_link;
389         *rb_parent = __rb_parent;
390         return vma;
391 }
392
393 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
394                 struct rb_node **rb_link, struct rb_node *rb_parent)
395 {
396         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
397         rb_insert_color(&vma->vm_rb, &mm->mm_rb);
398 }
399
400 static void __vma_link_file(struct vm_area_struct *vma)
401 {
402         struct file *file;
403
404         file = vma->vm_file;
405         if (file) {
406                 struct address_space *mapping = file->f_mapping;
407
408                 if (vma->vm_flags & VM_DENYWRITE)
409                         atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
410                 if (vma->vm_flags & VM_SHARED)
411                         mapping->i_mmap_writable++;
412
413                 flush_dcache_mmap_lock(mapping);
414                 if (unlikely(vma->vm_flags & VM_NONLINEAR))
415                         vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
416                 else
417                         vma_prio_tree_insert(vma, &mapping->i_mmap);
418                 flush_dcache_mmap_unlock(mapping);
419         }
420 }
421
422 static void
423 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
424         struct vm_area_struct *prev, struct rb_node **rb_link,
425         struct rb_node *rb_parent)
426 {
427         __vma_link_list(mm, vma, prev, rb_parent);
428         __vma_link_rb(mm, vma, rb_link, rb_parent);
429 }
430
431 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
432                         struct vm_area_struct *prev, struct rb_node **rb_link,
433                         struct rb_node *rb_parent)
434 {
435         struct address_space *mapping = NULL;
436
437         if (vma->vm_file)
438                 mapping = vma->vm_file->f_mapping;
439
440         if (mapping)
441                 mutex_lock(&mapping->i_mmap_mutex);
442
443         __vma_link(mm, vma, prev, rb_link, rb_parent);
444         __vma_link_file(vma);
445
446         if (mapping)
447                 mutex_unlock(&mapping->i_mmap_mutex);
448
449         mm->map_count++;
450         validate_mm(mm);
451 }
452
453 /*
454  * Helper for vma_adjust in the split_vma insert case:
455  * insert vm structure into list and rbtree and anon_vma,
456  * but it has already been inserted into prio_tree earlier.
457  */
458 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
459 {
460         struct vm_area_struct *__vma, *prev;
461         struct rb_node **rb_link, *rb_parent;
462
463         __vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
464         BUG_ON(__vma && __vma->vm_start < vma->vm_end);
465         __vma_link(mm, vma, prev, rb_link, rb_parent);
466         mm->map_count++;
467 }
468
469 static inline void
470 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
471                 struct vm_area_struct *prev)
472 {
473         struct vm_area_struct *next = vma->vm_next;
474
475         prev->vm_next = next;
476         if (next)
477                 next->vm_prev = prev;
478         rb_erase(&vma->vm_rb, &mm->mm_rb);
479         if (mm->mmap_cache == vma)
480                 mm->mmap_cache = prev;
481 }
482
483 /*
484  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
485  * is already present in an i_mmap tree without adjusting the tree.
486  * The following helper function should be used when such adjustments
487  * are necessary.  The "insert" vma (if any) is to be inserted
488  * before we drop the necessary locks.
489  */
490 int vma_adjust(struct vm_area_struct *vma, unsigned long start,
491         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
492 {
493         struct mm_struct *mm = vma->vm_mm;
494         struct vm_area_struct *next = vma->vm_next;
495         struct vm_area_struct *importer = NULL;
496         struct address_space *mapping = NULL;
497         struct prio_tree_root *root = NULL;
498         struct anon_vma *anon_vma = NULL;
499         struct file *file = vma->vm_file;
500         long adjust_next = 0;
501         int remove_next = 0;
502
503         if (next && !insert) {
504                 struct vm_area_struct *exporter = NULL;
505
506                 if (end >= next->vm_end) {
507                         /*
508                          * vma expands, overlapping all the next, and
509                          * perhaps the one after too (mprotect case 6).
510                          */
511 again:                  remove_next = 1 + (end > next->vm_end);
512                         end = next->vm_end;
513                         exporter = next;
514                         importer = vma;
515                 } else if (end > next->vm_start) {
516                         /*
517                          * vma expands, overlapping part of the next:
518                          * mprotect case 5 shifting the boundary up.
519                          */
520                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
521                         exporter = next;
522                         importer = vma;
523                 } else if (end < vma->vm_end) {
524                         /*
525                          * vma shrinks, and !insert tells it's not
526                          * split_vma inserting another: so it must be
527                          * mprotect case 4 shifting the boundary down.
528                          */
529                         adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
530                         exporter = vma;
531                         importer = next;
532                 }
533
534                 /*
535                  * Easily overlooked: when mprotect shifts the boundary,
536                  * make sure the expanding vma has anon_vma set if the
537                  * shrinking vma had, to cover any anon pages imported.
538                  */
539                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
540                         if (anon_vma_clone(importer, exporter))
541                                 return -ENOMEM;
542                         importer->anon_vma = exporter->anon_vma;
543                 }
544         }
545
546         if (file) {
547                 mapping = file->f_mapping;
548                 if (!(vma->vm_flags & VM_NONLINEAR))
549                         root = &mapping->i_mmap;
550                 mutex_lock(&mapping->i_mmap_mutex);
551                 if (insert) {
552                         /*
553                          * Put into prio_tree now, so instantiated pages
554                          * are visible to arm/parisc __flush_dcache_page
555                          * throughout; but we cannot insert into address
556                          * space until vma start or end is updated.
557                          */
558                         __vma_link_file(insert);
559                 }
560         }
561
562         vma_adjust_trans_huge(vma, start, end, adjust_next);
563
564         /*
565          * When changing only vma->vm_end, we don't really need anon_vma
566          * lock. This is a fairly rare case by itself, but the anon_vma
567          * lock may be shared between many sibling processes.  Skipping
568          * the lock for brk adjustments makes a difference sometimes.
569          */
570         if (vma->anon_vma && (importer || start != vma->vm_start)) {
571                 anon_vma = vma->anon_vma;
572                 anon_vma_lock(anon_vma);
573         }
574
575         if (root) {
576                 flush_dcache_mmap_lock(mapping);
577                 vma_prio_tree_remove(vma, root);
578                 if (adjust_next)
579                         vma_prio_tree_remove(next, root);
580         }
581
582         vma->vm_start = start;
583         vma->vm_end = end;
584         vma->vm_pgoff = pgoff;
585         if (adjust_next) {
586                 next->vm_start += adjust_next << PAGE_SHIFT;
587                 next->vm_pgoff += adjust_next;
588         }
589
590         if (root) {
591                 if (adjust_next)
592                         vma_prio_tree_insert(next, root);
593                 vma_prio_tree_insert(vma, root);
594                 flush_dcache_mmap_unlock(mapping);
595         }
596
597         if (remove_next) {
598                 /*
599                  * vma_merge has merged next into vma, and needs
600                  * us to remove next before dropping the locks.
601                  */
602                 __vma_unlink(mm, next, vma);
603                 if (file)
604                         __remove_shared_vm_struct(next, file, mapping);
605         } else if (insert) {
606                 /*
607                  * split_vma has split insert from vma, and needs
608                  * us to insert it before dropping the locks
609                  * (it may either follow vma or precede it).
610                  */
611                 __insert_vm_struct(mm, insert);
612         }
613
614         if (anon_vma)
615                 anon_vma_unlock(anon_vma);
616         if (mapping)
617                 mutex_unlock(&mapping->i_mmap_mutex);
618
619         if (remove_next) {
620                 if (file) {
621                         fput(file);
622                         if (next->vm_flags & VM_EXECUTABLE)
623                                 removed_exe_file_vma(mm);
624                 }
625                 if (next->anon_vma)
626                         anon_vma_merge(vma, next);
627                 mm->map_count--;
628                 mpol_put(vma_policy(next));
629                 kmem_cache_free(vm_area_cachep, next);
630                 /*
631                  * In mprotect's case 6 (see comments on vma_merge),
632                  * we must remove another next too. It would clutter
633                  * up the code too much to do both in one go.
634                  */
635                 if (remove_next == 2) {
636                         next = vma->vm_next;
637                         goto again;
638                 }
639         }
640
641         validate_mm(mm);
642
643         return 0;
644 }
645
646 /*
647  * If the vma has a ->close operation then the driver probably needs to release
648  * per-vma resources, so we don't attempt to merge those.
649  */
650 static inline int is_mergeable_vma(struct vm_area_struct *vma,
651                         struct file *file, unsigned long vm_flags)
652 {
653         /* VM_CAN_NONLINEAR may get set later by f_op->mmap() */
654         if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR)
655                 return 0;
656         if (vma->vm_file != file)
657                 return 0;
658         if (vma->vm_ops && vma->vm_ops->close)
659                 return 0;
660         return 1;
661 }
662
663 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
664                                         struct anon_vma *anon_vma2,
665                                         struct vm_area_struct *vma)
666 {
667         /*
668          * The list_is_singular() test is to avoid merging VMA cloned from
669          * parents. This can improve scalability caused by anon_vma lock.
670          */
671         if ((!anon_vma1 || !anon_vma2) && (!vma ||
672                 list_is_singular(&vma->anon_vma_chain)))
673                 return 1;
674         return anon_vma1 == anon_vma2;
675 }
676
677 /*
678  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
679  * in front of (at a lower virtual address and file offset than) the vma.
680  *
681  * We cannot merge two vmas if they have differently assigned (non-NULL)
682  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
683  *
684  * We don't check here for the merged mmap wrapping around the end of pagecache
685  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
686  * wrap, nor mmaps which cover the final page at index -1UL.
687  */
688 static int
689 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
690         struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
691 {
692         if (is_mergeable_vma(vma, file, vm_flags) &&
693             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
694                 if (vma->vm_pgoff == vm_pgoff)
695                         return 1;
696         }
697         return 0;
698 }
699
700 /*
701  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
702  * beyond (at a higher virtual address and file offset than) the vma.
703  *
704  * We cannot merge two vmas if they have differently assigned (non-NULL)
705  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
706  */
707 static int
708 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
709         struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
710 {
711         if (is_mergeable_vma(vma, file, vm_flags) &&
712             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
713                 pgoff_t vm_pglen;
714                 vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
715                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
716                         return 1;
717         }
718         return 0;
719 }
720
721 /*
722  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
723  * whether that can be merged with its predecessor or its successor.
724  * Or both (it neatly fills a hole).
725  *
726  * In most cases - when called for mmap, brk or mremap - [addr,end) is
727  * certain not to be mapped by the time vma_merge is called; but when
728  * called for mprotect, it is certain to be already mapped (either at
729  * an offset within prev, or at the start of next), and the flags of
730  * this area are about to be changed to vm_flags - and the no-change
731  * case has already been eliminated.
732  *
733  * The following mprotect cases have to be considered, where AAAA is
734  * the area passed down from mprotect_fixup, never extending beyond one
735  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
736  *
737  *     AAAA             AAAA                AAAA          AAAA
738  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
739  *    cannot merge    might become    might become    might become
740  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
741  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
742  *    mremap move:                                    PPPPNNNNNNNN 8
743  *        AAAA
744  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
745  *    might become    case 1 below    case 2 below    case 3 below
746  *
747  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
748  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
749  */
750 struct vm_area_struct *vma_merge(struct mm_struct *mm,
751                         struct vm_area_struct *prev, unsigned long addr,
752                         unsigned long end, unsigned long vm_flags,
753                         struct anon_vma *anon_vma, struct file *file,
754                         pgoff_t pgoff, struct mempolicy *policy)
755 {
756         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
757         struct vm_area_struct *area, *next;
758         int err;
759
760         /*
761          * We later require that vma->vm_flags == vm_flags,
762          * so this tests vma->vm_flags & VM_SPECIAL, too.
763          */
764         if (vm_flags & VM_SPECIAL)
765                 return NULL;
766
767         if (prev)
768                 next = prev->vm_next;
769         else
770                 next = mm->mmap;
771         area = next;
772         if (next && next->vm_end == end)                /* cases 6, 7, 8 */
773                 next = next->vm_next;
774
775         /*
776          * Can it merge with the predecessor?
777          */
778         if (prev && prev->vm_end == addr &&
779                         mpol_equal(vma_policy(prev), policy) &&
780                         can_vma_merge_after(prev, vm_flags,
781                                                 anon_vma, file, pgoff)) {
782                 /*
783                  * OK, it can.  Can we now merge in the successor as well?
784                  */
785                 if (next && end == next->vm_start &&
786                                 mpol_equal(policy, vma_policy(next)) &&
787                                 can_vma_merge_before(next, vm_flags,
788                                         anon_vma, file, pgoff+pglen) &&
789                                 is_mergeable_anon_vma(prev->anon_vma,
790                                                       next->anon_vma, NULL)) {
791                                                         /* cases 1, 6 */
792                         err = vma_adjust(prev, prev->vm_start,
793                                 next->vm_end, prev->vm_pgoff, NULL);
794                 } else                                  /* cases 2, 5, 7 */
795                         err = vma_adjust(prev, prev->vm_start,
796                                 end, prev->vm_pgoff, NULL);
797                 if (err)
798                         return NULL;
799                 khugepaged_enter_vma_merge(prev);
800                 return prev;
801         }
802
803         /*
804          * Can this new request be merged in front of next?
805          */
806         if (next && end == next->vm_start &&
807                         mpol_equal(policy, vma_policy(next)) &&
808                         can_vma_merge_before(next, vm_flags,
809                                         anon_vma, file, pgoff+pglen)) {
810                 if (prev && addr < prev->vm_end)        /* case 4 */
811                         err = vma_adjust(prev, prev->vm_start,
812                                 addr, prev->vm_pgoff, NULL);
813                 else                                    /* cases 3, 8 */
814                         err = vma_adjust(area, addr, next->vm_end,
815                                 next->vm_pgoff - pglen, NULL);
816                 if (err)
817                         return NULL;
818                 khugepaged_enter_vma_merge(area);
819                 return area;
820         }
821
822         return NULL;
823 }
824
825 /*
826  * Rough compatbility check to quickly see if it's even worth looking
827  * at sharing an anon_vma.
828  *
829  * They need to have the same vm_file, and the flags can only differ
830  * in things that mprotect may change.
831  *
832  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
833  * we can merge the two vma's. For example, we refuse to merge a vma if
834  * there is a vm_ops->close() function, because that indicates that the
835  * driver is doing some kind of reference counting. But that doesn't
836  * really matter for the anon_vma sharing case.
837  */
838 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
839 {
840         return a->vm_end == b->vm_start &&
841                 mpol_equal(vma_policy(a), vma_policy(b)) &&
842                 a->vm_file == b->vm_file &&
843                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) &&
844                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
845 }
846
847 /*
848  * Do some basic sanity checking to see if we can re-use the anon_vma
849  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
850  * the same as 'old', the other will be the new one that is trying
851  * to share the anon_vma.
852  *
853  * NOTE! This runs with mm_sem held for reading, so it is possible that
854  * the anon_vma of 'old' is concurrently in the process of being set up
855  * by another page fault trying to merge _that_. But that's ok: if it
856  * is being set up, that automatically means that it will be a singleton
857  * acceptable for merging, so we can do all of this optimistically. But
858  * we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
859  *
860  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
861  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
862  * is to return an anon_vma that is "complex" due to having gone through
863  * a fork).
864  *
865  * We also make sure that the two vma's are compatible (adjacent,
866  * and with the same memory policies). That's all stable, even with just
867  * a read lock on the mm_sem.
868  */
869 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
870 {
871         if (anon_vma_compatible(a, b)) {
872                 struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
873
874                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
875                         return anon_vma;
876         }
877         return NULL;
878 }
879
880 /*
881  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
882  * neighbouring vmas for a suitable anon_vma, before it goes off
883  * to allocate a new anon_vma.  It checks because a repetitive
884  * sequence of mprotects and faults may otherwise lead to distinct
885  * anon_vmas being allocated, preventing vma merge in subsequent
886  * mprotect.
887  */
888 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
889 {
890         struct anon_vma *anon_vma;
891         struct vm_area_struct *near;
892
893         near = vma->vm_next;
894         if (!near)
895                 goto try_prev;
896
897         anon_vma = reusable_anon_vma(near, vma, near);
898         if (anon_vma)
899                 return anon_vma;
900 try_prev:
901         near = vma->vm_prev;
902         if (!near)
903                 goto none;
904
905         anon_vma = reusable_anon_vma(near, near, vma);
906         if (anon_vma)
907                 return anon_vma;
908 none:
909         /*
910          * There's no absolute need to look only at touching neighbours:
911          * we could search further afield for "compatible" anon_vmas.
912          * But it would probably just be a waste of time searching,
913          * or lead to too many vmas hanging off the same anon_vma.
914          * We're trying to allow mprotect remerging later on,
915          * not trying to minimize memory used for anon_vmas.
916          */
917         return NULL;
918 }
919
920 #ifdef CONFIG_PROC_FS
921 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
922                                                 struct file *file, long pages)
923 {
924         const unsigned long stack_flags
925                 = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
926
927         if (file) {
928                 mm->shared_vm += pages;
929                 if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
930                         mm->exec_vm += pages;
931         } else if (flags & stack_flags)
932                 mm->stack_vm += pages;
933         if (flags & (VM_RESERVED|VM_IO))
934                 mm->reserved_vm += pages;
935 }
936 #endif /* CONFIG_PROC_FS */
937
938 /*
939  * The caller must hold down_write(&current->mm->mmap_sem).
940  */
941
942 unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
943                         unsigned long len, unsigned long prot,
944                         unsigned long flags, unsigned long pgoff)
945 {
946         struct mm_struct * mm = current->mm;
947         struct inode *inode;
948         vm_flags_t vm_flags;
949         int error;
950         unsigned long reqprot = prot;
951
952         /*
953          * Does the application expect PROT_READ to imply PROT_EXEC?
954          *
955          * (the exception is when the underlying filesystem is noexec
956          *  mounted, in which case we dont add PROT_EXEC.)
957          */
958         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
959                 if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
960                         prot |= PROT_EXEC;
961
962         if (!len)
963                 return -EINVAL;
964
965         if (!(flags & MAP_FIXED))
966                 addr = round_hint_to_min(addr);
967
968         /* Careful about overflows.. */
969         len = PAGE_ALIGN(len);
970         if (!len)
971                 return -ENOMEM;
972
973         /* offset overflow? */
974         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
975                return -EOVERFLOW;
976
977         /* Too many mappings? */
978         if (mm->map_count > sysctl_max_map_count)
979                 return -ENOMEM;
980
981         /* Obtain the address to map to. we verify (or select) it and ensure
982          * that it represents a valid section of the address space.
983          */
984         addr = get_unmapped_area(file, addr, len, pgoff, flags);
985         if (addr & ~PAGE_MASK)
986                 return addr;
987
988         /* Do simple checking here so the lower-level routines won't have
989          * to. we assume access permissions have been handled by the open
990          * of the memory object, so we don't do any here.
991          */
992         vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
993                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
994
995         if (flags & MAP_LOCKED)
996                 if (!can_do_mlock())
997                         return -EPERM;
998
999         /* mlock MCL_FUTURE? */
1000         if (vm_flags & VM_LOCKED) {
1001                 unsigned long locked, lock_limit;
1002                 locked = len >> PAGE_SHIFT;
1003                 locked += mm->locked_vm;
1004                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1005                 lock_limit >>= PAGE_SHIFT;
1006                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1007                         return -EAGAIN;
1008         }
1009
1010         inode = file ? file->f_path.dentry->d_inode : NULL;
1011
1012         if (file) {
1013                 switch (flags & MAP_TYPE) {
1014                 case MAP_SHARED:
1015                         if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1016                                 return -EACCES;
1017
1018                         /*
1019                          * Make sure we don't allow writing to an append-only
1020                          * file..
1021                          */
1022                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1023                                 return -EACCES;
1024
1025                         /*
1026                          * Make sure there are no mandatory locks on the file.
1027                          */
1028                         if (locks_verify_locked(inode))
1029                                 return -EAGAIN;
1030
1031                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1032                         if (!(file->f_mode & FMODE_WRITE))
1033                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1034
1035                         /* fall through */
1036                 case MAP_PRIVATE:
1037                         if (!(file->f_mode & FMODE_READ))
1038                                 return -EACCES;
1039                         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1040                                 if (vm_flags & VM_EXEC)
1041                                         return -EPERM;
1042                                 vm_flags &= ~VM_MAYEXEC;
1043                         }
1044
1045                         if (!file->f_op || !file->f_op->mmap)
1046                                 return -ENODEV;
1047                         break;
1048
1049                 default:
1050                         return -EINVAL;
1051                 }
1052         } else {
1053                 switch (flags & MAP_TYPE) {
1054                 case MAP_SHARED:
1055                         /*
1056                          * Ignore pgoff.
1057                          */
1058                         pgoff = 0;
1059                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1060                         break;
1061                 case MAP_PRIVATE:
1062                         /*
1063                          * Set pgoff according to addr for anon_vma.
1064                          */
1065                         pgoff = addr >> PAGE_SHIFT;
1066                         break;
1067                 default:
1068                         return -EINVAL;
1069                 }
1070         }
1071
1072         error = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1073         if (error)
1074                 return error;
1075
1076         return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1077 }
1078 EXPORT_SYMBOL(do_mmap_pgoff);
1079
1080 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1081                 unsigned long, prot, unsigned long, flags,
1082                 unsigned long, fd, unsigned long, pgoff)
1083 {
1084         struct file *file = NULL;
1085         unsigned long retval = -EBADF;
1086
1087         if (!(flags & MAP_ANONYMOUS)) {
1088                 audit_mmap_fd(fd, flags);
1089                 if (unlikely(flags & MAP_HUGETLB))
1090                         return -EINVAL;
1091                 file = fget(fd);
1092                 if (!file)
1093                         goto out;
1094         } else if (flags & MAP_HUGETLB) {
1095                 struct user_struct *user = NULL;
1096                 /*
1097                  * VM_NORESERVE is used because the reservations will be
1098                  * taken when vm_ops->mmap() is called
1099                  * A dummy user value is used because we are not locking
1100                  * memory so no accounting is necessary
1101                  */
1102                 len = ALIGN(len, huge_page_size(&default_hstate));
1103                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
1104                                                 &user, HUGETLB_ANONHUGE_INODE);
1105                 if (IS_ERR(file))
1106                         return PTR_ERR(file);
1107         }
1108
1109         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1110
1111         down_write(&current->mm->mmap_sem);
1112         retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1113         up_write(&current->mm->mmap_sem);
1114
1115         if (file)
1116                 fput(file);
1117 out:
1118         return retval;
1119 }
1120
1121 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1122 struct mmap_arg_struct {
1123         unsigned long addr;
1124         unsigned long len;
1125         unsigned long prot;
1126         unsigned long flags;
1127         unsigned long fd;
1128         unsigned long offset;
1129 };
1130
1131 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1132 {
1133         struct mmap_arg_struct a;
1134
1135         if (copy_from_user(&a, arg, sizeof(a)))
1136                 return -EFAULT;
1137         if (a.offset & ~PAGE_MASK)
1138                 return -EINVAL;
1139
1140         return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1141                               a.offset >> PAGE_SHIFT);
1142 }
1143 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1144
1145 /*
1146  * Some shared mappigns will want the pages marked read-only
1147  * to track write events. If so, we'll downgrade vm_page_prot
1148  * to the private version (using protection_map[] without the
1149  * VM_SHARED bit).
1150  */
1151 int vma_wants_writenotify(struct vm_area_struct *vma)
1152 {
1153         vm_flags_t vm_flags = vma->vm_flags;
1154
1155         /* If it was private or non-writable, the write bit is already clear */
1156         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1157                 return 0;
1158
1159         /* The backer wishes to know when pages are first written to? */
1160         if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1161                 return 1;
1162
1163         /* The open routine did something to the protections already? */
1164         if (pgprot_val(vma->vm_page_prot) !=
1165             pgprot_val(vm_get_page_prot(vm_flags)))
1166                 return 0;
1167
1168         /* Specialty mapping? */
1169         if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1170                 return 0;
1171
1172         /* Can the mapping track the dirty pages? */
1173         return vma->vm_file && vma->vm_file->f_mapping &&
1174                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1175 }
1176
1177 /*
1178  * We account for memory if it's a private writeable mapping,
1179  * not hugepages and VM_NORESERVE wasn't set.
1180  */
1181 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1182 {
1183         /*
1184          * hugetlb has its own accounting separate from the core VM
1185          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1186          */
1187         if (file && is_file_hugepages(file))
1188                 return 0;
1189
1190         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1191 }
1192
1193 unsigned long mmap_region(struct file *file, unsigned long addr,
1194                           unsigned long len, unsigned long flags,
1195                           vm_flags_t vm_flags, unsigned long pgoff)
1196 {
1197         struct mm_struct *mm = current->mm;
1198         struct vm_area_struct *vma, *prev;
1199         int correct_wcount = 0;
1200         int error;
1201         struct rb_node **rb_link, *rb_parent;
1202         unsigned long charged = 0;
1203         struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
1204
1205         /* Clear old maps */
1206         error = -ENOMEM;
1207 munmap_back:
1208         vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1209         if (vma && vma->vm_start < addr + len) {
1210                 if (do_munmap(mm, addr, len))
1211                         return -ENOMEM;
1212                 goto munmap_back;
1213         }
1214
1215         /* Check against address space limit. */
1216         if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1217                 return -ENOMEM;
1218
1219         /*
1220          * Set 'VM_NORESERVE' if we should not account for the
1221          * memory use of this mapping.
1222          */
1223         if ((flags & MAP_NORESERVE)) {
1224                 /* We honor MAP_NORESERVE if allowed to overcommit */
1225                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1226                         vm_flags |= VM_NORESERVE;
1227
1228                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1229                 if (file && is_file_hugepages(file))
1230                         vm_flags |= VM_NORESERVE;
1231         }
1232
1233         /*
1234          * Private writable mapping: check memory availability
1235          */
1236         if (accountable_mapping(file, vm_flags)) {
1237                 charged = len >> PAGE_SHIFT;
1238                 if (security_vm_enough_memory(charged))
1239                         return -ENOMEM;
1240                 vm_flags |= VM_ACCOUNT;
1241         }
1242
1243         /*
1244          * Can we just expand an old mapping?
1245          */
1246         vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1247         if (vma)
1248                 goto out;
1249
1250         /*
1251          * Determine the object being mapped and call the appropriate
1252          * specific mapper. the address has already been validated, but
1253          * not unmapped, but the maps are removed from the list.
1254          */
1255         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1256         if (!vma) {
1257                 error = -ENOMEM;
1258                 goto unacct_error;
1259         }
1260
1261         vma->vm_mm = mm;
1262         vma->vm_start = addr;
1263         vma->vm_end = addr + len;
1264         vma->vm_flags = vm_flags;
1265         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1266         vma->vm_pgoff = pgoff;
1267         INIT_LIST_HEAD(&vma->anon_vma_chain);
1268
1269         if (file) {
1270                 error = -EINVAL;
1271                 if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1272                         goto free_vma;
1273                 if (vm_flags & VM_DENYWRITE) {
1274                         error = deny_write_access(file);
1275                         if (error)
1276                                 goto free_vma;
1277                         correct_wcount = 1;
1278                 }
1279                 vma->vm_file = file;
1280                 get_file(file);
1281                 error = file->f_op->mmap(file, vma);
1282                 if (error)
1283                         goto unmap_and_free_vma;
1284                 if (vm_flags & VM_EXECUTABLE)
1285                         added_exe_file_vma(mm);
1286
1287                 /* Can addr have changed??
1288                  *
1289                  * Answer: Yes, several device drivers can do it in their
1290                  *         f_op->mmap method. -DaveM
1291                  */
1292                 addr = vma->vm_start;
1293                 pgoff = vma->vm_pgoff;
1294                 vm_flags = vma->vm_flags;
1295         } else if (vm_flags & VM_SHARED) {
1296                 error = shmem_zero_setup(vma);
1297                 if (error)
1298                         goto free_vma;
1299         }
1300
1301         if (vma_wants_writenotify(vma)) {
1302                 pgprot_t pprot = vma->vm_page_prot;
1303
1304                 /* Can vma->vm_page_prot have changed??
1305                  *
1306                  * Answer: Yes, drivers may have changed it in their
1307                  *         f_op->mmap method.
1308                  *
1309                  * Ensures that vmas marked as uncached stay that way.
1310                  */
1311                 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1312                 if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
1313                         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
1314         }
1315
1316         vma_link(mm, vma, prev, rb_link, rb_parent);
1317         file = vma->vm_file;
1318
1319         /* Once vma denies write, undo our temporary denial count */
1320         if (correct_wcount)
1321                 atomic_inc(&inode->i_writecount);
1322 out:
1323         perf_event_mmap(vma);
1324
1325         mm->total_vm += len >> PAGE_SHIFT;
1326         vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1327         if (vm_flags & VM_LOCKED) {
1328                 if (!mlock_vma_pages_range(vma, addr, addr + len))
1329                         mm->locked_vm += (len >> PAGE_SHIFT);
1330         } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1331                 make_pages_present(addr, addr + len);
1332         return addr;
1333
1334 unmap_and_free_vma:
1335         if (correct_wcount)
1336                 atomic_inc(&inode->i_writecount);
1337         vma->vm_file = NULL;
1338         fput(file);
1339
1340         /* Undo any partial mapping done by a device driver. */
1341         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1342         charged = 0;
1343 free_vma:
1344         kmem_cache_free(vm_area_cachep, vma);
1345 unacct_error:
1346         if (charged)
1347                 vm_unacct_memory(charged);
1348         return error;
1349 }
1350
1351 /* Get an address range which is currently unmapped.
1352  * For shmat() with addr=0.
1353  *
1354  * Ugly calling convention alert:
1355  * Return value with the low bits set means error value,
1356  * ie
1357  *      if (ret & ~PAGE_MASK)
1358  *              error = ret;
1359  *
1360  * This function "knows" that -ENOMEM has the bits set.
1361  */
1362 #ifndef HAVE_ARCH_UNMAPPED_AREA
1363 unsigned long
1364 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1365                 unsigned long len, unsigned long pgoff, unsigned long flags)
1366 {
1367         struct mm_struct *mm = current->mm;
1368         struct vm_area_struct *vma;
1369         unsigned long start_addr;
1370
1371         if (len > TASK_SIZE - mmap_min_addr)
1372                 return -ENOMEM;
1373
1374         if (flags & MAP_FIXED)
1375                 return addr;
1376
1377         if (addr) {
1378                 addr = PAGE_ALIGN(addr);
1379                 vma = find_vma(mm, addr);
1380                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1381                     (!vma || addr + len <= vma->vm_start))
1382                         return addr;
1383         }
1384         if (len > mm->cached_hole_size) {
1385                 start_addr = addr = mm->free_area_cache;
1386         } else {
1387                 start_addr = addr = TASK_UNMAPPED_BASE;
1388                 mm->cached_hole_size = 0;
1389         }
1390
1391 full_search:
1392         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1393                 /* At this point:  (!vma || addr < vma->vm_end). */
1394                 if (TASK_SIZE - len < addr) {
1395                         /*
1396                          * Start a new search - just in case we missed
1397                          * some holes.
1398                          */
1399                         if (start_addr != TASK_UNMAPPED_BASE) {
1400                                 addr = TASK_UNMAPPED_BASE;
1401                                 start_addr = addr;
1402                                 mm->cached_hole_size = 0;
1403                                 goto full_search;
1404                         }
1405                         return -ENOMEM;
1406                 }
1407                 if (!vma || addr + len <= vma->vm_start) {
1408                         /*
1409                          * Remember the place where we stopped the search:
1410                          */
1411                         mm->free_area_cache = addr + len;
1412                         return addr;
1413                 }
1414                 if (addr + mm->cached_hole_size < vma->vm_start)
1415                         mm->cached_hole_size = vma->vm_start - addr;
1416                 addr = vma->vm_end;
1417         }
1418 }
1419 #endif  
1420
1421 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1422 {
1423         /*
1424          * Is this a new hole at the lowest possible address?
1425          */
1426         if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1427                 mm->free_area_cache = addr;
1428                 mm->cached_hole_size = ~0UL;
1429         }
1430 }
1431
1432 /*
1433  * This mmap-allocator allocates new areas top-down from below the
1434  * stack's low limit (the base):
1435  */
1436 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1437 unsigned long
1438 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1439                           const unsigned long len, const unsigned long pgoff,
1440                           const unsigned long flags)
1441 {
1442         struct vm_area_struct *vma;
1443         struct mm_struct *mm = current->mm;
1444         unsigned long addr = addr0;
1445         unsigned long low_limit = max(PAGE_SIZE, mmap_min_addr);
1446
1447         /* requested length too big for entire address space */
1448         if (len > TASK_SIZE - mmap_min_addr)
1449                 return -ENOMEM;
1450
1451         if (flags & MAP_FIXED)
1452                 return addr;
1453
1454         /* requesting a specific address */
1455         if (addr) {
1456                 addr = PAGE_ALIGN(addr);
1457                 vma = find_vma(mm, addr);
1458                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1459                                 (!vma || addr + len <= vma->vm_start))
1460                         return addr;
1461         }
1462
1463         /* check if free_area_cache is useful for us */
1464         if (len <= mm->cached_hole_size) {
1465                 mm->cached_hole_size = 0;
1466                 mm->free_area_cache = mm->mmap_base;
1467         }
1468
1469         /* either no address requested or can't fit in requested address hole */
1470         addr = mm->free_area_cache;
1471
1472         /* make sure it can fit in the remaining address space */
1473         if (addr >= low_limit + len) {
1474                 vma = find_vma(mm, addr-len);
1475                 if (!vma || addr <= vma->vm_start)
1476                         /* remember the address as a hint for next time */
1477                         return (mm->free_area_cache = addr-len);
1478         }
1479
1480         if (mm->mmap_base < low_limit + len)
1481                 goto bottomup;
1482
1483         addr = mm->mmap_base-len;
1484
1485         do {
1486                 /*
1487                  * Lookup failure means no vma is above this address,
1488                  * else if new region fits below vma->vm_start,
1489                  * return with success:
1490                  */
1491                 vma = find_vma(mm, addr);
1492                 if (!vma || addr+len <= vma->vm_start)
1493                         /* remember the address as a hint for next time */
1494                         return (mm->free_area_cache = addr);
1495
1496                 /* remember the largest hole we saw so far */
1497                 if (addr + mm->cached_hole_size < vma->vm_start)
1498                         mm->cached_hole_size = vma->vm_start - addr;
1499
1500                 /* try just below the current vma->vm_start */
1501                 addr = vma->vm_start-len;
1502         } while (vma->vm_start >= low_limit + len);
1503
1504 bottomup:
1505         /*
1506          * A failed mmap() very likely causes application failure,
1507          * so fall back to the bottom-up function here. This scenario
1508          * can happen with large stack limits and large mmap()
1509          * allocations.
1510          */
1511         mm->cached_hole_size = ~0UL;
1512         mm->free_area_cache = TASK_UNMAPPED_BASE;
1513         addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1514         /*
1515          * Restore the topdown base:
1516          */
1517         mm->free_area_cache = mm->mmap_base;
1518         mm->cached_hole_size = ~0UL;
1519
1520         return addr;
1521 }
1522 #endif
1523
1524 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1525 {
1526         /*
1527          * Is this a new hole at the highest possible address?
1528          */
1529         if (addr > mm->free_area_cache)
1530                 mm->free_area_cache = addr;
1531
1532         /* dont allow allocations above current base */
1533         if (mm->free_area_cache > mm->mmap_base)
1534                 mm->free_area_cache = mm->mmap_base;
1535 }
1536
1537 unsigned long
1538 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1539                 unsigned long pgoff, unsigned long flags)
1540 {
1541         unsigned long (*get_area)(struct file *, unsigned long,
1542                                   unsigned long, unsigned long, unsigned long);
1543
1544         unsigned long error = arch_mmap_check(addr, len, flags);
1545         if (error)
1546                 return error;
1547
1548         /* Careful about overflows.. */
1549         if (len > TASK_SIZE)
1550                 return -ENOMEM;
1551
1552         get_area = current->mm->get_unmapped_area;
1553         if (file && file->f_op && file->f_op->get_unmapped_area)
1554                 get_area = file->f_op->get_unmapped_area;
1555         addr = get_area(file, addr, len, pgoff, flags);
1556         if (IS_ERR_VALUE(addr))
1557                 return addr;
1558
1559         if (addr > TASK_SIZE - len)
1560                 return -ENOMEM;
1561         if (addr & ~PAGE_MASK)
1562                 return -EINVAL;
1563
1564         return arch_rebalance_pgtables(addr, len);
1565 }
1566
1567 EXPORT_SYMBOL(get_unmapped_area);
1568
1569 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1570 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1571 {
1572         struct vm_area_struct *vma = NULL;
1573
1574         if (mm) {
1575                 /* Check the cache first. */
1576                 /* (Cache hit rate is typically around 35%.) */
1577                 vma = ACCESS_ONCE(mm->mmap_cache);
1578                 if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1579                         struct rb_node * rb_node;
1580
1581                         rb_node = mm->mm_rb.rb_node;
1582                         vma = NULL;
1583
1584                         while (rb_node) {
1585                                 struct vm_area_struct * vma_tmp;
1586
1587                                 vma_tmp = rb_entry(rb_node,
1588                                                 struct vm_area_struct, vm_rb);
1589
1590                                 if (vma_tmp->vm_end > addr) {
1591                                         vma = vma_tmp;
1592                                         if (vma_tmp->vm_start <= addr)
1593                                                 break;
1594                                         rb_node = rb_node->rb_left;
1595                                 } else
1596                                         rb_node = rb_node->rb_right;
1597                         }
1598                         if (vma)
1599                                 mm->mmap_cache = vma;
1600                 }
1601         }
1602         return vma;
1603 }
1604
1605 EXPORT_SYMBOL(find_vma);
1606
1607 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1608 struct vm_area_struct *
1609 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1610                         struct vm_area_struct **pprev)
1611 {
1612         struct vm_area_struct *vma = NULL, *prev = NULL;
1613         struct rb_node *rb_node;
1614         if (!mm)
1615                 goto out;
1616
1617         /* Guard against addr being lower than the first VMA */
1618         vma = mm->mmap;
1619
1620         /* Go through the RB tree quickly. */
1621         rb_node = mm->mm_rb.rb_node;
1622
1623         while (rb_node) {
1624                 struct vm_area_struct *vma_tmp;
1625                 vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1626
1627                 if (addr < vma_tmp->vm_end) {
1628                         rb_node = rb_node->rb_left;
1629                 } else {
1630                         prev = vma_tmp;
1631                         if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1632                                 break;
1633                         rb_node = rb_node->rb_right;
1634                 }
1635         }
1636
1637 out:
1638         *pprev = prev;
1639         return prev ? prev->vm_next : vma;
1640 }
1641
1642 /*
1643  * Verify that the stack growth is acceptable and
1644  * update accounting. This is shared with both the
1645  * grow-up and grow-down cases.
1646  */
1647 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1648 {
1649         struct mm_struct *mm = vma->vm_mm;
1650         struct rlimit *rlim = current->signal->rlim;
1651         unsigned long new_start;
1652
1653         /* address space limit tests */
1654         if (!may_expand_vm(mm, grow))
1655                 return -ENOMEM;
1656
1657         /* Stack limit test */
1658         if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
1659                 return -ENOMEM;
1660
1661         /* mlock limit tests */
1662         if (vma->vm_flags & VM_LOCKED) {
1663                 unsigned long locked;
1664                 unsigned long limit;
1665                 locked = mm->locked_vm + grow;
1666                 limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
1667                 limit >>= PAGE_SHIFT;
1668                 if (locked > limit && !capable(CAP_IPC_LOCK))
1669                         return -ENOMEM;
1670         }
1671
1672         /* Check to ensure the stack will not grow into a hugetlb-only region */
1673         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1674                         vma->vm_end - size;
1675         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1676                 return -EFAULT;
1677
1678         /*
1679          * Overcommit..  This must be the final test, as it will
1680          * update security statistics.
1681          */
1682         if (security_vm_enough_memory_mm(mm, grow))
1683                 return -ENOMEM;
1684
1685         /* Ok, everything looks good - let it rip */
1686         mm->total_vm += grow;
1687         if (vma->vm_flags & VM_LOCKED)
1688                 mm->locked_vm += grow;
1689         vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1690         return 0;
1691 }
1692
1693 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1694 /*
1695  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1696  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1697  */
1698 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1699 {
1700         int error;
1701
1702         if (!(vma->vm_flags & VM_GROWSUP))
1703                 return -EFAULT;
1704
1705         /*
1706          * We must make sure the anon_vma is allocated
1707          * so that the anon_vma locking is not a noop.
1708          */
1709         if (unlikely(anon_vma_prepare(vma)))
1710                 return -ENOMEM;
1711         vma_lock_anon_vma(vma);
1712
1713         /*
1714          * vma->vm_start/vm_end cannot change under us because the caller
1715          * is required to hold the mmap_sem in read mode.  We need the
1716          * anon_vma lock to serialize against concurrent expand_stacks.
1717          * Also guard against wrapping around to address 0.
1718          */
1719         if (address < PAGE_ALIGN(address+4))
1720                 address = PAGE_ALIGN(address+4);
1721         else {
1722                 vma_unlock_anon_vma(vma);
1723                 return -ENOMEM;
1724         }
1725         error = 0;
1726
1727         /* Somebody else might have raced and expanded it already */
1728         if (address > vma->vm_end) {
1729                 unsigned long size, grow;
1730
1731                 size = address - vma->vm_start;
1732                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
1733
1734                 error = -ENOMEM;
1735                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
1736                         error = acct_stack_growth(vma, size, grow);
1737                         if (!error) {
1738                                 vma->vm_end = address;
1739                                 perf_event_mmap(vma);
1740                         }
1741                 }
1742         }
1743         vma_unlock_anon_vma(vma);
1744         khugepaged_enter_vma_merge(vma);
1745         return error;
1746 }
1747 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1748
1749 /*
1750  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1751  */
1752 int expand_downwards(struct vm_area_struct *vma,
1753                                    unsigned long address)
1754 {
1755         int error;
1756
1757         /*
1758          * We must make sure the anon_vma is allocated
1759          * so that the anon_vma locking is not a noop.
1760          */
1761         if (unlikely(anon_vma_prepare(vma)))
1762                 return -ENOMEM;
1763
1764         address &= PAGE_MASK;
1765         error = security_file_mmap(NULL, 0, 0, 0, address, 1);
1766         if (error)
1767                 return error;
1768
1769         vma_lock_anon_vma(vma);
1770
1771         /*
1772          * vma->vm_start/vm_end cannot change under us because the caller
1773          * is required to hold the mmap_sem in read mode.  We need the
1774          * anon_vma lock to serialize against concurrent expand_stacks.
1775          */
1776
1777         /* Somebody else might have raced and expanded it already */
1778         if (address < vma->vm_start) {
1779                 unsigned long size, grow;
1780
1781                 size = vma->vm_end - address;
1782                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
1783
1784                 error = -ENOMEM;
1785                 if (grow <= vma->vm_pgoff) {
1786                         error = acct_stack_growth(vma, size, grow);
1787                         if (!error) {
1788                                 vma->vm_start = address;
1789                                 vma->vm_pgoff -= grow;
1790                                 perf_event_mmap(vma);
1791                         }
1792                 }
1793         }
1794         vma_unlock_anon_vma(vma);
1795         khugepaged_enter_vma_merge(vma);
1796         return error;
1797 }
1798
1799 #ifdef CONFIG_STACK_GROWSUP
1800 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1801 {
1802         return expand_upwards(vma, address);
1803 }
1804
1805 struct vm_area_struct *
1806 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1807 {
1808         struct vm_area_struct *vma, *prev;
1809
1810         addr &= PAGE_MASK;
1811         vma = find_vma_prev(mm, addr, &prev);
1812         if (vma && (vma->vm_start <= addr))
1813                 return vma;
1814         if (!prev || expand_stack(prev, addr))
1815                 return NULL;
1816         if (prev->vm_flags & VM_LOCKED) {
1817                 mlock_vma_pages_range(prev, addr, prev->vm_end);
1818         }
1819         return prev;
1820 }
1821 #else
1822 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1823 {
1824         return expand_downwards(vma, address);
1825 }
1826
1827 struct vm_area_struct *
1828 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1829 {
1830         struct vm_area_struct * vma;
1831         unsigned long start;
1832
1833         addr &= PAGE_MASK;
1834         vma = find_vma(mm,addr);
1835         if (!vma)
1836                 return NULL;
1837         if (vma->vm_start <= addr)
1838                 return vma;
1839         if (!(vma->vm_flags & VM_GROWSDOWN))
1840                 return NULL;
1841         start = vma->vm_start;
1842         if (expand_stack(vma, addr))
1843                 return NULL;
1844         if (vma->vm_flags & VM_LOCKED) {
1845                 mlock_vma_pages_range(vma, addr, start);
1846         }
1847         return vma;
1848 }
1849 #endif
1850
1851 /*
1852  * Ok - we have the memory areas we should free on the vma list,
1853  * so release them, and do the vma updates.
1854  *
1855  * Called with the mm semaphore held.
1856  */
1857 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1858 {
1859         /* Update high watermark before we lower total_vm */
1860         update_hiwater_vm(mm);
1861         do {
1862                 long nrpages = vma_pages(vma);
1863
1864                 mm->total_vm -= nrpages;
1865                 vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1866                 vma = remove_vma(vma);
1867         } while (vma);
1868         validate_mm(mm);
1869 }
1870
1871 /*
1872  * Get rid of page table information in the indicated region.
1873  *
1874  * Called with the mm semaphore held.
1875  */
1876 static void unmap_region(struct mm_struct *mm,
1877                 struct vm_area_struct *vma, struct vm_area_struct *prev,
1878                 unsigned long start, unsigned long end)
1879 {
1880         struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1881         struct mmu_gather tlb;
1882         unsigned long nr_accounted = 0;
1883
1884         lru_add_drain();
1885         tlb_gather_mmu(&tlb, mm, 0);
1886         update_hiwater_rss(mm);
1887         unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1888         vm_unacct_memory(nr_accounted);
1889         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
1890                                  next ? next->vm_start : 0);
1891         tlb_finish_mmu(&tlb, start, end);
1892 }
1893
1894 /*
1895  * Create a list of vma's touched by the unmap, removing them from the mm's
1896  * vma list as we go..
1897  */
1898 static void
1899 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1900         struct vm_area_struct *prev, unsigned long end)
1901 {
1902         struct vm_area_struct **insertion_point;
1903         struct vm_area_struct *tail_vma = NULL;
1904         unsigned long addr;
1905
1906         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1907         vma->vm_prev = NULL;
1908         do {
1909                 rb_erase(&vma->vm_rb, &mm->mm_rb);
1910                 mm->map_count--;
1911                 tail_vma = vma;
1912                 vma = vma->vm_next;
1913         } while (vma && vma->vm_start < end);
1914         *insertion_point = vma;
1915         if (vma)
1916                 vma->vm_prev = prev;
1917         tail_vma->vm_next = NULL;
1918         if (mm->unmap_area == arch_unmap_area)
1919                 addr = prev ? prev->vm_end : mm->mmap_base;
1920         else
1921                 addr = vma ?  vma->vm_start : mm->mmap_base;
1922         mm->unmap_area(mm, addr);
1923         mm->mmap_cache = NULL;          /* Kill the cache. */
1924 }
1925
1926 /*
1927  * __split_vma() bypasses sysctl_max_map_count checking.  We use this on the
1928  * munmap path where it doesn't make sense to fail.
1929  */
1930 static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1931               unsigned long addr, int new_below)
1932 {
1933         struct mempolicy *pol;
1934         struct vm_area_struct *new;
1935         int err = -ENOMEM;
1936
1937         if (is_vm_hugetlb_page(vma) && (addr &
1938                                         ~(huge_page_mask(hstate_vma(vma)))))
1939                 return -EINVAL;
1940
1941         new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1942         if (!new)
1943                 goto out_err;
1944
1945         /* most fields are the same, copy all, and then fixup */
1946         *new = *vma;
1947
1948         INIT_LIST_HEAD(&new->anon_vma_chain);
1949
1950         if (new_below)
1951                 new->vm_end = addr;
1952         else {
1953                 new->vm_start = addr;
1954                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1955         }
1956
1957         pol = mpol_dup(vma_policy(vma));
1958         if (IS_ERR(pol)) {
1959                 err = PTR_ERR(pol);
1960                 goto out_free_vma;
1961         }
1962         vma_set_policy(new, pol);
1963
1964         if (anon_vma_clone(new, vma))
1965                 goto out_free_mpol;
1966
1967         if (new->vm_file) {
1968                 get_file(new->vm_file);
1969                 if (vma->vm_flags & VM_EXECUTABLE)
1970                         added_exe_file_vma(mm);
1971         }
1972
1973         if (new->vm_ops && new->vm_ops->open)
1974                 new->vm_ops->open(new);
1975
1976         if (new_below)
1977                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1978                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
1979         else
1980                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1981
1982         /* Success. */
1983         if (!err)
1984                 return 0;
1985
1986         /* Clean everything up if vma_adjust failed. */
1987         if (new->vm_ops && new->vm_ops->close)
1988                 new->vm_ops->close(new);
1989         if (new->vm_file) {
1990                 if (vma->vm_flags & VM_EXECUTABLE)
1991                         removed_exe_file_vma(mm);
1992                 fput(new->vm_file);
1993         }
1994         unlink_anon_vmas(new);
1995  out_free_mpol:
1996         mpol_put(pol);
1997  out_free_vma:
1998         kmem_cache_free(vm_area_cachep, new);
1999  out_err:
2000         return err;
2001 }
2002
2003 /*
2004  * Split a vma into two pieces at address 'addr', a new vma is allocated
2005  * either for the first part or the tail.
2006  */
2007 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2008               unsigned long addr, int new_below)
2009 {
2010         if (mm->map_count >= sysctl_max_map_count)
2011                 return -ENOMEM;
2012
2013         return __split_vma(mm, vma, addr, new_below);
2014 }
2015
2016 /* Munmap is split into 2 main parts -- this part which finds
2017  * what needs doing, and the areas themselves, which do the
2018  * work.  This now handles partial unmappings.
2019  * Jeremy Fitzhardinge <jeremy@goop.org>
2020  */
2021 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2022 {
2023         unsigned long end;
2024         struct vm_area_struct *vma, *prev, *last;
2025
2026         if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
2027                 return -EINVAL;
2028
2029         if ((len = PAGE_ALIGN(len)) == 0)
2030                 return -EINVAL;
2031
2032         /* Find the first overlapping VMA */
2033         vma = find_vma(mm, start);
2034         if (!vma)
2035                 return 0;
2036         prev = vma->vm_prev;
2037         /* we have  start < vma->vm_end  */
2038
2039         /* if it doesn't overlap, we have nothing.. */
2040         end = start + len;
2041         if (vma->vm_start >= end)
2042                 return 0;
2043
2044         /*
2045          * If we need to split any vma, do it now to save pain later.
2046          *
2047          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2048          * unmapped vm_area_struct will remain in use: so lower split_vma
2049          * places tmp vma above, and higher split_vma places tmp vma below.
2050          */
2051         if (start > vma->vm_start) {
2052                 int error;
2053
2054                 /*
2055                  * Make sure that map_count on return from munmap() will
2056                  * not exceed its limit; but let map_count go just above
2057                  * its limit temporarily, to help free resources as expected.
2058                  */
2059                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2060                         return -ENOMEM;
2061
2062                 error = __split_vma(mm, vma, start, 0);
2063                 if (error)
2064                         return error;
2065                 prev = vma;
2066         }
2067
2068         /* Does it split the last one? */
2069         last = find_vma(mm, end);
2070         if (last && end > last->vm_start) {
2071                 int error = __split_vma(mm, last, end, 1);
2072                 if (error)
2073                         return error;
2074         }
2075         vma = prev? prev->vm_next: mm->mmap;
2076
2077         /*
2078          * unlock any mlock()ed ranges before detaching vmas
2079          */
2080         if (mm->locked_vm) {
2081                 struct vm_area_struct *tmp = vma;
2082                 while (tmp && tmp->vm_start < end) {
2083                         if (tmp->vm_flags & VM_LOCKED) {
2084                                 mm->locked_vm -= vma_pages(tmp);
2085                                 munlock_vma_pages_all(tmp);
2086                         }
2087                         tmp = tmp->vm_next;
2088                 }
2089         }
2090
2091         /*
2092          * Remove the vma's, and unmap the actual pages
2093          */
2094         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2095         unmap_region(mm, vma, prev, start, end);
2096
2097         /* Fix up all other VM information */
2098         remove_vma_list(mm, vma);
2099
2100         return 0;
2101 }
2102
2103 EXPORT_SYMBOL(do_munmap);
2104
2105 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2106 {
2107         int ret;
2108         struct mm_struct *mm = current->mm;
2109
2110         profile_munmap(addr);
2111
2112         down_write(&mm->mmap_sem);
2113         ret = do_munmap(mm, addr, len);
2114         up_write(&mm->mmap_sem);
2115         return ret;
2116 }
2117
2118 static inline void verify_mm_writelocked(struct mm_struct *mm)
2119 {
2120 #ifdef CONFIG_DEBUG_VM
2121         if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2122                 WARN_ON(1);
2123                 up_read(&mm->mmap_sem);
2124         }
2125 #endif
2126 }
2127
2128 /*
2129  *  this is really a simplified "do_mmap".  it only handles
2130  *  anonymous maps.  eventually we may be able to do some
2131  *  brk-specific accounting here.
2132  */
2133 unsigned long do_brk(unsigned long addr, unsigned long len)
2134 {
2135         struct mm_struct * mm = current->mm;
2136         struct vm_area_struct * vma, * prev;
2137         unsigned long flags;
2138         struct rb_node ** rb_link, * rb_parent;
2139         pgoff_t pgoff = addr >> PAGE_SHIFT;
2140         int error;
2141
2142         len = PAGE_ALIGN(len);
2143         if (!len)
2144                 return addr;
2145
2146         error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
2147         if (error)
2148                 return error;
2149
2150         flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2151
2152         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2153         if (error & ~PAGE_MASK)
2154                 return error;
2155
2156         /*
2157          * mlock MCL_FUTURE?
2158          */
2159         if (mm->def_flags & VM_LOCKED) {
2160                 unsigned long locked, lock_limit;
2161                 locked = len >> PAGE_SHIFT;
2162                 locked += mm->locked_vm;
2163                 lock_limit = rlimit(RLIMIT_MEMLOCK);
2164                 lock_limit >>= PAGE_SHIFT;
2165                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2166                         return -EAGAIN;
2167         }
2168
2169         /*
2170          * mm->mmap_sem is required to protect against another thread
2171          * changing the mappings in case we sleep.
2172          */
2173         verify_mm_writelocked(mm);
2174
2175         /*
2176          * Clear old maps.  this also does some error checking for us
2177          */
2178  munmap_back:
2179         vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2180         if (vma && vma->vm_start < addr + len) {
2181                 if (do_munmap(mm, addr, len))
2182                         return -ENOMEM;
2183                 goto munmap_back;
2184         }
2185
2186         /* Check against address space limits *after* clearing old maps... */
2187         if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2188                 return -ENOMEM;
2189
2190         if (mm->map_count > sysctl_max_map_count)
2191                 return -ENOMEM;
2192
2193         if (security_vm_enough_memory(len >> PAGE_SHIFT))
2194                 return -ENOMEM;
2195
2196         /* Can we just expand an old private anonymous mapping? */
2197         vma = vma_merge(mm, prev, addr, addr + len, flags,
2198                                         NULL, NULL, pgoff, NULL);
2199         if (vma)
2200                 goto out;
2201
2202         /*
2203          * create a vma struct for an anonymous mapping
2204          */
2205         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2206         if (!vma) {
2207                 vm_unacct_memory(len >> PAGE_SHIFT);
2208                 return -ENOMEM;
2209         }
2210
2211         INIT_LIST_HEAD(&vma->anon_vma_chain);
2212         vma->vm_mm = mm;
2213         vma->vm_start = addr;
2214         vma->vm_end = addr + len;
2215         vma->vm_pgoff = pgoff;
2216         vma->vm_flags = flags;
2217         vma->vm_page_prot = vm_get_page_prot(flags);
2218         vma_link(mm, vma, prev, rb_link, rb_parent);
2219 out:
2220         perf_event_mmap(vma);
2221         mm->total_vm += len >> PAGE_SHIFT;
2222         if (flags & VM_LOCKED) {
2223                 if (!mlock_vma_pages_range(vma, addr, addr + len))
2224                         mm->locked_vm += (len >> PAGE_SHIFT);
2225         }
2226         return addr;
2227 }
2228
2229 EXPORT_SYMBOL(do_brk);
2230
2231 /* Release all mmaps. */
2232 void exit_mmap(struct mm_struct *mm)
2233 {
2234         struct mmu_gather tlb;
2235         struct vm_area_struct *vma;
2236         unsigned long nr_accounted = 0;
2237         unsigned long end;
2238
2239         /* mm's last user has gone, and its about to be pulled down */
2240         mmu_notifier_release(mm);
2241
2242         if (mm->locked_vm) {
2243                 vma = mm->mmap;
2244                 while (vma) {
2245                         if (vma->vm_flags & VM_LOCKED)
2246                                 munlock_vma_pages_all(vma);
2247                         vma = vma->vm_next;
2248                 }
2249         }
2250
2251         arch_exit_mmap(mm);
2252
2253         vma = mm->mmap;
2254         if (!vma)       /* Can happen if dup_mmap() received an OOM */
2255                 return;
2256
2257         lru_add_drain();
2258         flush_cache_mm(mm);
2259         tlb_gather_mmu(&tlb, mm, 1);
2260         /* update_hiwater_rss(mm) here? but nobody should be looking */
2261         /* Use -1 here to ensure all VMAs in the mm are unmapped */
2262         end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
2263         vm_unacct_memory(nr_accounted);
2264
2265         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
2266         tlb_finish_mmu(&tlb, 0, end);
2267
2268         /*
2269          * Walk the list again, actually closing and freeing it,
2270          * with preemption enabled, without holding any MM locks.
2271          */
2272         while (vma)
2273                 vma = remove_vma(vma);
2274
2275         BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2276 }
2277
2278 /* Insert vm structure into process list sorted by address
2279  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2280  * then i_mmap_mutex is taken here.
2281  */
2282 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2283 {
2284         struct vm_area_struct * __vma, * prev;
2285         struct rb_node ** rb_link, * rb_parent;
2286
2287         /*
2288          * The vm_pgoff of a purely anonymous vma should be irrelevant
2289          * until its first write fault, when page's anon_vma and index
2290          * are set.  But now set the vm_pgoff it will almost certainly
2291          * end up with (unless mremap moves it elsewhere before that
2292          * first wfault), so /proc/pid/maps tells a consistent story.
2293          *
2294          * By setting it to reflect the virtual start address of the
2295          * vma, merges and splits can happen in a seamless way, just
2296          * using the existing file pgoff checks and manipulations.
2297          * Similarly in do_mmap_pgoff and in do_brk.
2298          */
2299         if (!vma->vm_file) {
2300                 BUG_ON(vma->anon_vma);
2301                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2302         }
2303         __vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2304         if (__vma && __vma->vm_start < vma->vm_end)
2305                 return -ENOMEM;
2306         if ((vma->vm_flags & VM_ACCOUNT) &&
2307              security_vm_enough_memory_mm(mm, vma_pages(vma)))
2308                 return -ENOMEM;
2309         vma_link(mm, vma, prev, rb_link, rb_parent);
2310         return 0;
2311 }
2312
2313 /*
2314  * Copy the vma structure to a new location in the same mm,
2315  * prior to moving page table entries, to effect an mremap move.
2316  */
2317 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2318         unsigned long addr, unsigned long len, pgoff_t pgoff)
2319 {
2320         struct vm_area_struct *vma = *vmap;
2321         unsigned long vma_start = vma->vm_start;
2322         struct mm_struct *mm = vma->vm_mm;
2323         struct vm_area_struct *new_vma, *prev;
2324         struct rb_node **rb_link, *rb_parent;
2325         struct mempolicy *pol;
2326
2327         /*
2328          * If anonymous vma has not yet been faulted, update new pgoff
2329          * to match new location, to increase its chance of merging.
2330          */
2331         if (!vma->vm_file && !vma->anon_vma)
2332                 pgoff = addr >> PAGE_SHIFT;
2333
2334         find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2335         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2336                         vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2337         if (new_vma) {
2338                 /*
2339                  * Source vma may have been merged into new_vma
2340                  */
2341                 if (vma_start >= new_vma->vm_start &&
2342                     vma_start < new_vma->vm_end)
2343                         *vmap = new_vma;
2344         } else {
2345                 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2346                 if (new_vma) {
2347                         *new_vma = *vma;
2348                         pol = mpol_dup(vma_policy(vma));
2349                         if (IS_ERR(pol))
2350                                 goto out_free_vma;
2351                         INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2352                         if (anon_vma_clone(new_vma, vma))
2353                                 goto out_free_mempol;
2354                         vma_set_policy(new_vma, pol);
2355                         new_vma->vm_start = addr;
2356                         new_vma->vm_end = addr + len;
2357                         new_vma->vm_pgoff = pgoff;
2358                         if (new_vma->vm_file) {
2359                                 get_file(new_vma->vm_file);
2360                                 if (vma->vm_flags & VM_EXECUTABLE)
2361                                         added_exe_file_vma(mm);
2362                         }
2363                         if (new_vma->vm_ops && new_vma->vm_ops->open)
2364                                 new_vma->vm_ops->open(new_vma);
2365                         vma_link(mm, new_vma, prev, rb_link, rb_parent);
2366                 }
2367         }
2368         return new_vma;
2369
2370  out_free_mempol:
2371         mpol_put(pol);
2372  out_free_vma:
2373         kmem_cache_free(vm_area_cachep, new_vma);
2374         return NULL;
2375 }
2376
2377 /*
2378  * Return true if the calling process may expand its vm space by the passed
2379  * number of pages
2380  */
2381 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2382 {
2383         unsigned long cur = mm->total_vm;       /* pages */
2384         unsigned long lim;
2385
2386         lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
2387
2388         if (cur + npages > lim)
2389                 return 0;
2390         return 1;
2391 }
2392
2393
2394 static int special_mapping_fault(struct vm_area_struct *vma,
2395                                 struct vm_fault *vmf)
2396 {
2397         pgoff_t pgoff;
2398         struct page **pages;
2399
2400         /*
2401          * special mappings have no vm_file, and in that case, the mm
2402          * uses vm_pgoff internally. So we have to subtract it from here.
2403          * We are allowed to do this because we are the mm; do not copy
2404          * this code into drivers!
2405          */
2406         pgoff = vmf->pgoff - vma->vm_pgoff;
2407
2408         for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2409                 pgoff--;
2410
2411         if (*pages) {
2412                 struct page *page = *pages;
2413                 get_page(page);
2414                 vmf->page = page;
2415                 return 0;
2416         }
2417
2418         return VM_FAULT_SIGBUS;
2419 }
2420
2421 /*
2422  * Having a close hook prevents vma merging regardless of flags.
2423  */
2424 static void special_mapping_close(struct vm_area_struct *vma)
2425 {
2426 }
2427
2428 static const struct vm_operations_struct special_mapping_vmops = {
2429         .close = special_mapping_close,
2430         .fault = special_mapping_fault,
2431 };
2432
2433 /*
2434  * Called with mm->mmap_sem held for writing.
2435  * Insert a new vma covering the given region, with the given flags.
2436  * Its pages are supplied by the given array of struct page *.
2437  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2438  * The region past the last page supplied will always produce SIGBUS.
2439  * The array pointer and the pages it points to are assumed to stay alive
2440  * for as long as this mapping might exist.
2441  */
2442 int install_special_mapping(struct mm_struct *mm,
2443                             unsigned long addr, unsigned long len,
2444                             unsigned long vm_flags, struct page **pages)
2445 {
2446         int ret;
2447         struct vm_area_struct *vma;
2448
2449         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2450         if (unlikely(vma == NULL))
2451                 return -ENOMEM;
2452
2453         INIT_LIST_HEAD(&vma->anon_vma_chain);
2454         vma->vm_mm = mm;
2455         vma->vm_start = addr;
2456         vma->vm_end = addr + len;
2457
2458         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2459         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2460
2461         vma->vm_ops = &special_mapping_vmops;
2462         vma->vm_private_data = pages;
2463
2464         ret = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
2465         if (ret)
2466                 goto out;
2467
2468         ret = insert_vm_struct(mm, vma);
2469         if (ret)
2470                 goto out;
2471
2472         mm->total_vm += len >> PAGE_SHIFT;
2473
2474         perf_event_mmap(vma);
2475
2476         return 0;
2477
2478 out:
2479         kmem_cache_free(vm_area_cachep, vma);
2480         return ret;
2481 }
2482
2483 static DEFINE_MUTEX(mm_all_locks_mutex);
2484
2485 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2486 {
2487         if (!test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2488                 /*
2489                  * The LSB of head.next can't change from under us
2490                  * because we hold the mm_all_locks_mutex.
2491                  */
2492                 mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem);
2493                 /*
2494                  * We can safely modify head.next after taking the
2495                  * anon_vma->root->mutex. If some other vma in this mm shares
2496                  * the same anon_vma we won't take it again.
2497                  *
2498                  * No need of atomic instructions here, head.next
2499                  * can't change from under us thanks to the
2500                  * anon_vma->root->mutex.
2501                  */
2502                 if (__test_and_set_bit(0, (unsigned long *)
2503                                        &anon_vma->root->head.next))
2504                         BUG();
2505         }
2506 }
2507
2508 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2509 {
2510         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2511                 /*
2512                  * AS_MM_ALL_LOCKS can't change from under us because
2513                  * we hold the mm_all_locks_mutex.
2514                  *
2515                  * Operations on ->flags have to be atomic because
2516                  * even if AS_MM_ALL_LOCKS is stable thanks to the
2517                  * mm_all_locks_mutex, there may be other cpus
2518                  * changing other bitflags in parallel to us.
2519                  */
2520                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2521                         BUG();
2522                 mutex_lock_nest_lock(&mapping->i_mmap_mutex, &mm->mmap_sem);
2523         }
2524 }
2525
2526 /*
2527  * This operation locks against the VM for all pte/vma/mm related
2528  * operations that could ever happen on a certain mm. This includes
2529  * vmtruncate, try_to_unmap, and all page faults.
2530  *
2531  * The caller must take the mmap_sem in write mode before calling
2532  * mm_take_all_locks(). The caller isn't allowed to release the
2533  * mmap_sem until mm_drop_all_locks() returns.
2534  *
2535  * mmap_sem in write mode is required in order to block all operations
2536  * that could modify pagetables and free pages without need of
2537  * altering the vma layout (for example populate_range() with
2538  * nonlinear vmas). It's also needed in write mode to avoid new
2539  * anon_vmas to be associated with existing vmas.
2540  *
2541  * A single task can't take more than one mm_take_all_locks() in a row
2542  * or it would deadlock.
2543  *
2544  * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in
2545  * mapping->flags avoid to take the same lock twice, if more than one
2546  * vma in this mm is backed by the same anon_vma or address_space.
2547  *
2548  * We can take all the locks in random order because the VM code
2549  * taking i_mmap_mutex or anon_vma->mutex outside the mmap_sem never
2550  * takes more than one of them in a row. Secondly we're protected
2551  * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2552  *
2553  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2554  * that may have to take thousand of locks.
2555  *
2556  * mm_take_all_locks() can fail if it's interrupted by signals.
2557  */
2558 int mm_take_all_locks(struct mm_struct *mm)
2559 {
2560         struct vm_area_struct *vma;
2561         struct anon_vma_chain *avc;
2562
2563         BUG_ON(down_read_trylock(&mm->mmap_sem));
2564
2565         mutex_lock(&mm_all_locks_mutex);
2566
2567         for (vma = mm->mmap; vma; vma = vma->vm_next) {
2568                 if (signal_pending(current))
2569                         goto out_unlock;
2570                 if (vma->vm_file && vma->vm_file->f_mapping)
2571                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
2572         }
2573
2574         for (vma = mm->mmap; vma; vma = vma->vm_next) {
2575                 if (signal_pending(current))
2576                         goto out_unlock;
2577                 if (vma->anon_vma)
2578                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2579                                 vm_lock_anon_vma(mm, avc->anon_vma);
2580         }
2581
2582         return 0;
2583
2584 out_unlock:
2585         mm_drop_all_locks(mm);
2586         return -EINTR;
2587 }
2588
2589 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2590 {
2591         if (test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2592                 /*
2593                  * The LSB of head.next can't change to 0 from under
2594                  * us because we hold the mm_all_locks_mutex.
2595                  *
2596                  * We must however clear the bitflag before unlocking
2597                  * the vma so the users using the anon_vma->head will
2598                  * never see our bitflag.
2599                  *
2600                  * No need of atomic instructions here, head.next
2601                  * can't change from under us until we release the
2602                  * anon_vma->root->mutex.
2603                  */
2604                 if (!__test_and_clear_bit(0, (unsigned long *)
2605                                           &anon_vma->root->head.next))
2606                         BUG();
2607                 anon_vma_unlock(anon_vma);
2608         }
2609 }
2610
2611 static void vm_unlock_mapping(struct address_space *mapping)
2612 {
2613         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2614                 /*
2615                  * AS_MM_ALL_LOCKS can't change to 0 from under us
2616                  * because we hold the mm_all_locks_mutex.
2617                  */
2618                 mutex_unlock(&mapping->i_mmap_mutex);
2619                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2620                                         &mapping->flags))
2621                         BUG();
2622         }
2623 }
2624
2625 /*
2626  * The mmap_sem cannot be released by the caller until
2627  * mm_drop_all_locks() returns.
2628  */
2629 void mm_drop_all_locks(struct mm_struct *mm)
2630 {
2631         struct vm_area_struct *vma;
2632         struct anon_vma_chain *avc;
2633
2634         BUG_ON(down_read_trylock(&mm->mmap_sem));
2635         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2636
2637         for (vma = mm->mmap; vma; vma = vma->vm_next) {
2638                 if (vma->anon_vma)
2639                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2640                                 vm_unlock_anon_vma(avc->anon_vma);
2641                 if (vma->vm_file && vma->vm_file->f_mapping)
2642                         vm_unlock_mapping(vma->vm_file->f_mapping);
2643         }
2644
2645         mutex_unlock(&mm_all_locks_mutex);
2646 }
2647
2648 /*
2649  * initialise the VMA slab
2650  */
2651 void __init mmap_init(void)
2652 {
2653         int ret;
2654
2655         ret = percpu_counter_init(&vm_committed_as, 0);
2656         VM_BUG_ON(ret);
2657 }