mm/dmapool.c: take lock only once in dma_pool_free()
[linux-2.6.git] / mm / mremap.c
1 /*
2  *      mm/mremap.c
3  *
4  *      (C) Copyright 1996 Linus Torvalds
5  *
6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
8  */
9
10 #include <linux/mm.h>
11 #include <linux/hugetlb.h>
12 #include <linux/shm.h>
13 #include <linux/ksm.h>
14 #include <linux/mman.h>
15 #include <linux/swap.h>
16 #include <linux/capability.h>
17 #include <linux/fs.h>
18 #include <linux/highmem.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/mmu_notifier.h>
22
23 #include <asm/uaccess.h>
24 #include <asm/cacheflush.h>
25 #include <asm/tlbflush.h>
26
27 #include "internal.h"
28
29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
30 {
31         pgd_t *pgd;
32         pud_t *pud;
33         pmd_t *pmd;
34
35         pgd = pgd_offset(mm, addr);
36         if (pgd_none_or_clear_bad(pgd))
37                 return NULL;
38
39         pud = pud_offset(pgd, addr);
40         if (pud_none_or_clear_bad(pud))
41                 return NULL;
42
43         pmd = pmd_offset(pud, addr);
44         split_huge_page_pmd(mm, pmd);
45         if (pmd_none_or_clear_bad(pmd))
46                 return NULL;
47
48         return pmd;
49 }
50
51 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
52                             unsigned long addr)
53 {
54         pgd_t *pgd;
55         pud_t *pud;
56         pmd_t *pmd;
57
58         pgd = pgd_offset(mm, addr);
59         pud = pud_alloc(mm, pgd, addr);
60         if (!pud)
61                 return NULL;
62
63         pmd = pmd_alloc(mm, pud, addr);
64         if (!pmd)
65                 return NULL;
66
67         VM_BUG_ON(pmd_trans_huge(*pmd));
68         if (pmd_none(*pmd) && __pte_alloc(mm, vma, pmd, addr))
69                 return NULL;
70
71         return pmd;
72 }
73
74 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
75                 unsigned long old_addr, unsigned long old_end,
76                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
77                 unsigned long new_addr)
78 {
79         struct address_space *mapping = NULL;
80         struct mm_struct *mm = vma->vm_mm;
81         pte_t *old_pte, *new_pte, pte;
82         spinlock_t *old_ptl, *new_ptl;
83         unsigned long old_start;
84
85         old_start = old_addr;
86         mmu_notifier_invalidate_range_start(vma->vm_mm,
87                                             old_start, old_end);
88         if (vma->vm_file) {
89                 /*
90                  * Subtle point from Rajesh Venkatasubramanian: before
91                  * moving file-based ptes, we must lock truncate_pagecache
92                  * out, since it might clean the dst vma before the src vma,
93                  * and we propagate stale pages into the dst afterward.
94                  */
95                 mapping = vma->vm_file->f_mapping;
96                 spin_lock(&mapping->i_mmap_lock);
97                 if (new_vma->vm_truncate_count &&
98                     new_vma->vm_truncate_count != vma->vm_truncate_count)
99                         new_vma->vm_truncate_count = 0;
100         }
101
102         /*
103          * We don't have to worry about the ordering of src and dst
104          * pte locks because exclusive mmap_sem prevents deadlock.
105          */
106         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
107         new_pte = pte_offset_map(new_pmd, new_addr);
108         new_ptl = pte_lockptr(mm, new_pmd);
109         if (new_ptl != old_ptl)
110                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
111         arch_enter_lazy_mmu_mode();
112
113         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
114                                    new_pte++, new_addr += PAGE_SIZE) {
115                 if (pte_none(*old_pte))
116                         continue;
117                 pte = ptep_clear_flush(vma, old_addr, old_pte);
118                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
119                 set_pte_at(mm, new_addr, new_pte, pte);
120         }
121
122         arch_leave_lazy_mmu_mode();
123         if (new_ptl != old_ptl)
124                 spin_unlock(new_ptl);
125         pte_unmap(new_pte - 1);
126         pte_unmap_unlock(old_pte - 1, old_ptl);
127         if (mapping)
128                 spin_unlock(&mapping->i_mmap_lock);
129         mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
130 }
131
132 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
133
134 unsigned long move_page_tables(struct vm_area_struct *vma,
135                 unsigned long old_addr, struct vm_area_struct *new_vma,
136                 unsigned long new_addr, unsigned long len)
137 {
138         unsigned long extent, next, old_end;
139         pmd_t *old_pmd, *new_pmd;
140
141         old_end = old_addr + len;
142         flush_cache_range(vma, old_addr, old_end);
143
144         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
145                 cond_resched();
146                 next = (old_addr + PMD_SIZE) & PMD_MASK;
147                 if (next - 1 > old_end)
148                         next = old_end;
149                 extent = next - old_addr;
150                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
151                 if (!old_pmd)
152                         continue;
153                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
154                 if (!new_pmd)
155                         break;
156                 next = (new_addr + PMD_SIZE) & PMD_MASK;
157                 if (extent > next - new_addr)
158                         extent = next - new_addr;
159                 if (extent > LATENCY_LIMIT)
160                         extent = LATENCY_LIMIT;
161                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
162                                 new_vma, new_pmd, new_addr);
163         }
164
165         return len + old_addr - old_end;        /* how much done */
166 }
167
168 static unsigned long move_vma(struct vm_area_struct *vma,
169                 unsigned long old_addr, unsigned long old_len,
170                 unsigned long new_len, unsigned long new_addr)
171 {
172         struct mm_struct *mm = vma->vm_mm;
173         struct vm_area_struct *new_vma;
174         unsigned long vm_flags = vma->vm_flags;
175         unsigned long new_pgoff;
176         unsigned long moved_len;
177         unsigned long excess = 0;
178         unsigned long hiwater_vm;
179         int split = 0;
180         int err;
181
182         /*
183          * We'd prefer to avoid failure later on in do_munmap:
184          * which may split one vma into three before unmapping.
185          */
186         if (mm->map_count >= sysctl_max_map_count - 3)
187                 return -ENOMEM;
188
189         /*
190          * Advise KSM to break any KSM pages in the area to be moved:
191          * it would be confusing if they were to turn up at the new
192          * location, where they happen to coincide with different KSM
193          * pages recently unmapped.  But leave vma->vm_flags as it was,
194          * so KSM can come around to merge on vma and new_vma afterwards.
195          */
196         err = ksm_madvise(vma, old_addr, old_addr + old_len,
197                                                 MADV_UNMERGEABLE, &vm_flags);
198         if (err)
199                 return err;
200
201         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
202         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
203         if (!new_vma)
204                 return -ENOMEM;
205
206         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
207         if (moved_len < old_len) {
208                 /*
209                  * On error, move entries back from new area to old,
210                  * which will succeed since page tables still there,
211                  * and then proceed to unmap new area instead of old.
212                  */
213                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
214                 vma = new_vma;
215                 old_len = new_len;
216                 old_addr = new_addr;
217                 new_addr = -ENOMEM;
218         }
219
220         /* Conceal VM_ACCOUNT so old reservation is not undone */
221         if (vm_flags & VM_ACCOUNT) {
222                 vma->vm_flags &= ~VM_ACCOUNT;
223                 excess = vma->vm_end - vma->vm_start - old_len;
224                 if (old_addr > vma->vm_start &&
225                     old_addr + old_len < vma->vm_end)
226                         split = 1;
227         }
228
229         /*
230          * If we failed to move page tables we still do total_vm increment
231          * since do_munmap() will decrement it by old_len == new_len.
232          *
233          * Since total_vm is about to be raised artificially high for a
234          * moment, we need to restore high watermark afterwards: if stats
235          * are taken meanwhile, total_vm and hiwater_vm appear too high.
236          * If this were a serious issue, we'd add a flag to do_munmap().
237          */
238         hiwater_vm = mm->hiwater_vm;
239         mm->total_vm += new_len >> PAGE_SHIFT;
240         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
241
242         if (do_munmap(mm, old_addr, old_len) < 0) {
243                 /* OOM: unable to split vma, just get accounts right */
244                 vm_unacct_memory(excess >> PAGE_SHIFT);
245                 excess = 0;
246         }
247         mm->hiwater_vm = hiwater_vm;
248
249         /* Restore VM_ACCOUNT if one or two pieces of vma left */
250         if (excess) {
251                 vma->vm_flags |= VM_ACCOUNT;
252                 if (split)
253                         vma->vm_next->vm_flags |= VM_ACCOUNT;
254         }
255
256         if (vm_flags & VM_LOCKED) {
257                 mm->locked_vm += new_len >> PAGE_SHIFT;
258                 if (new_len > old_len)
259                         mlock_vma_pages_range(new_vma, new_addr + old_len,
260                                                        new_addr + new_len);
261         }
262
263         return new_addr;
264 }
265
266 static struct vm_area_struct *vma_to_resize(unsigned long addr,
267         unsigned long old_len, unsigned long new_len, unsigned long *p)
268 {
269         struct mm_struct *mm = current->mm;
270         struct vm_area_struct *vma = find_vma(mm, addr);
271
272         if (!vma || vma->vm_start > addr)
273                 goto Efault;
274
275         if (is_vm_hugetlb_page(vma))
276                 goto Einval;
277
278         /* We can't remap across vm area boundaries */
279         if (old_len > vma->vm_end - addr)
280                 goto Efault;
281
282         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
283                 if (new_len > old_len)
284                         goto Efault;
285         }
286
287         if (vma->vm_flags & VM_LOCKED) {
288                 unsigned long locked, lock_limit;
289                 locked = mm->locked_vm << PAGE_SHIFT;
290                 lock_limit = rlimit(RLIMIT_MEMLOCK);
291                 locked += new_len - old_len;
292                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
293                         goto Eagain;
294         }
295
296         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
297                 goto Enomem;
298
299         if (vma->vm_flags & VM_ACCOUNT) {
300                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
301                 if (security_vm_enough_memory(charged))
302                         goto Efault;
303                 *p = charged;
304         }
305
306         return vma;
307
308 Efault: /* very odd choice for most of the cases, but... */
309         return ERR_PTR(-EFAULT);
310 Einval:
311         return ERR_PTR(-EINVAL);
312 Enomem:
313         return ERR_PTR(-ENOMEM);
314 Eagain:
315         return ERR_PTR(-EAGAIN);
316 }
317
318 static unsigned long mremap_to(unsigned long addr,
319         unsigned long old_len, unsigned long new_addr,
320         unsigned long new_len)
321 {
322         struct mm_struct *mm = current->mm;
323         struct vm_area_struct *vma;
324         unsigned long ret = -EINVAL;
325         unsigned long charged = 0;
326         unsigned long map_flags;
327
328         if (new_addr & ~PAGE_MASK)
329                 goto out;
330
331         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
332                 goto out;
333
334         /* Check if the location we're moving into overlaps the
335          * old location at all, and fail if it does.
336          */
337         if ((new_addr <= addr) && (new_addr+new_len) > addr)
338                 goto out;
339
340         if ((addr <= new_addr) && (addr+old_len) > new_addr)
341                 goto out;
342
343         ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
344         if (ret)
345                 goto out;
346
347         ret = do_munmap(mm, new_addr, new_len);
348         if (ret)
349                 goto out;
350
351         if (old_len >= new_len) {
352                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
353                 if (ret && old_len != new_len)
354                         goto out;
355                 old_len = new_len;
356         }
357
358         vma = vma_to_resize(addr, old_len, new_len, &charged);
359         if (IS_ERR(vma)) {
360                 ret = PTR_ERR(vma);
361                 goto out;
362         }
363
364         map_flags = MAP_FIXED;
365         if (vma->vm_flags & VM_MAYSHARE)
366                 map_flags |= MAP_SHARED;
367
368         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
369                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
370                                 map_flags);
371         if (ret & ~PAGE_MASK)
372                 goto out1;
373
374         ret = move_vma(vma, addr, old_len, new_len, new_addr);
375         if (!(ret & ~PAGE_MASK))
376                 goto out;
377 out1:
378         vm_unacct_memory(charged);
379
380 out:
381         return ret;
382 }
383
384 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
385 {
386         unsigned long end = vma->vm_end + delta;
387         if (end < vma->vm_end) /* overflow */
388                 return 0;
389         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
390                 return 0;
391         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
392                               0, MAP_FIXED) & ~PAGE_MASK)
393                 return 0;
394         return 1;
395 }
396
397 /*
398  * Expand (or shrink) an existing mapping, potentially moving it at the
399  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
400  *
401  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
402  * This option implies MREMAP_MAYMOVE.
403  */
404 unsigned long do_mremap(unsigned long addr,
405         unsigned long old_len, unsigned long new_len,
406         unsigned long flags, unsigned long new_addr)
407 {
408         struct mm_struct *mm = current->mm;
409         struct vm_area_struct *vma;
410         unsigned long ret = -EINVAL;
411         unsigned long charged = 0;
412
413         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
414                 goto out;
415
416         if (addr & ~PAGE_MASK)
417                 goto out;
418
419         old_len = PAGE_ALIGN(old_len);
420         new_len = PAGE_ALIGN(new_len);
421
422         /*
423          * We allow a zero old-len as a special case
424          * for DOS-emu "duplicate shm area" thing. But
425          * a zero new-len is nonsensical.
426          */
427         if (!new_len)
428                 goto out;
429
430         if (flags & MREMAP_FIXED) {
431                 if (flags & MREMAP_MAYMOVE)
432                         ret = mremap_to(addr, old_len, new_addr, new_len);
433                 goto out;
434         }
435
436         /*
437          * Always allow a shrinking remap: that just unmaps
438          * the unnecessary pages..
439          * do_munmap does all the needed commit accounting
440          */
441         if (old_len >= new_len) {
442                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
443                 if (ret && old_len != new_len)
444                         goto out;
445                 ret = addr;
446                 goto out;
447         }
448
449         /*
450          * Ok, we need to grow..
451          */
452         vma = vma_to_resize(addr, old_len, new_len, &charged);
453         if (IS_ERR(vma)) {
454                 ret = PTR_ERR(vma);
455                 goto out;
456         }
457
458         /* old_len exactly to the end of the area..
459          */
460         if (old_len == vma->vm_end - addr) {
461                 /* can we just expand the current mapping? */
462                 if (vma_expandable(vma, new_len - old_len)) {
463                         int pages = (new_len - old_len) >> PAGE_SHIFT;
464
465                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
466                                        vma->vm_pgoff, NULL)) {
467                                 ret = -ENOMEM;
468                                 goto out;
469                         }
470
471                         mm->total_vm += pages;
472                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
473                         if (vma->vm_flags & VM_LOCKED) {
474                                 mm->locked_vm += pages;
475                                 mlock_vma_pages_range(vma, addr + old_len,
476                                                    addr + new_len);
477                         }
478                         ret = addr;
479                         goto out;
480                 }
481         }
482
483         /*
484          * We weren't able to just expand or shrink the area,
485          * we need to create a new one and move it..
486          */
487         ret = -ENOMEM;
488         if (flags & MREMAP_MAYMOVE) {
489                 unsigned long map_flags = 0;
490                 if (vma->vm_flags & VM_MAYSHARE)
491                         map_flags |= MAP_SHARED;
492
493                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
494                                         vma->vm_pgoff +
495                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
496                                         map_flags);
497                 if (new_addr & ~PAGE_MASK) {
498                         ret = new_addr;
499                         goto out;
500                 }
501
502                 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
503                 if (ret)
504                         goto out;
505                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
506         }
507 out:
508         if (ret & ~PAGE_MASK)
509                 vm_unacct_memory(charged);
510         return ret;
511 }
512
513 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
514                 unsigned long, new_len, unsigned long, flags,
515                 unsigned long, new_addr)
516 {
517         unsigned long ret;
518
519         down_write(&current->mm->mmap_sem);
520         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
521         up_write(&current->mm->mmap_sem);
522         return ret;
523 }