[PATCH] mm: vm_stat_account unshackled
[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@redhat.com>
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/slab.h>
13 #include <linux/shm.h>
14 #include <linux/mman.h>
15 #include <linux/swap.h>
16 #include <linux/fs.h>
17 #include <linux/highmem.h>
18 #include <linux/security.h>
19 #include <linux/syscalls.h>
20
21 #include <asm/uaccess.h>
22 #include <asm/cacheflush.h>
23 #include <asm/tlbflush.h>
24
25 static pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr)
26 {
27         pgd_t *pgd;
28         pud_t *pud;
29         pmd_t *pmd;
30         pte_t *pte = NULL;
31
32         pgd = pgd_offset(mm, addr);
33         if (pgd_none_or_clear_bad(pgd))
34                 goto end;
35
36         pud = pud_offset(pgd, addr);
37         if (pud_none_or_clear_bad(pud))
38                 goto end;
39
40         pmd = pmd_offset(pud, addr);
41         if (pmd_none_or_clear_bad(pmd))
42                 goto end;
43
44         pte = pte_offset_map_nested(pmd, addr);
45         if (pte_none(*pte)) {
46                 pte_unmap_nested(pte);
47                 pte = NULL;
48         }
49 end:
50         return pte;
51 }
52
53 static pte_t *get_one_pte_map(struct mm_struct *mm, unsigned long addr)
54 {
55         pgd_t *pgd;
56         pud_t *pud;
57         pmd_t *pmd;
58
59         pgd = pgd_offset(mm, addr);
60         if (pgd_none_or_clear_bad(pgd))
61                 return NULL;
62
63         pud = pud_offset(pgd, addr);
64         if (pud_none_or_clear_bad(pud))
65                 return NULL;
66
67         pmd = pmd_offset(pud, addr);
68         if (pmd_none_or_clear_bad(pmd))
69                 return NULL;
70
71         return pte_offset_map(pmd, addr);
72 }
73
74 static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr)
75 {
76         pgd_t *pgd;
77         pud_t *pud;
78         pmd_t *pmd;
79         pte_t *pte = NULL;
80
81         pgd = pgd_offset(mm, addr);
82
83         pud = pud_alloc(mm, pgd, addr);
84         if (!pud)
85                 return NULL;
86         pmd = pmd_alloc(mm, pud, addr);
87         if (pmd)
88                 pte = pte_alloc_map(mm, pmd, addr);
89         return pte;
90 }
91
92 static int
93 move_one_page(struct vm_area_struct *vma, unsigned long old_addr,
94                 struct vm_area_struct *new_vma, unsigned long new_addr)
95 {
96         struct address_space *mapping = NULL;
97         struct mm_struct *mm = vma->vm_mm;
98         int error = 0;
99         pte_t *src, *dst;
100
101         if (vma->vm_file) {
102                 /*
103                  * Subtle point from Rajesh Venkatasubramanian: before
104                  * moving file-based ptes, we must lock vmtruncate out,
105                  * since it might clean the dst vma before the src vma,
106                  * and we propagate stale pages into the dst afterward.
107                  */
108                 mapping = vma->vm_file->f_mapping;
109                 spin_lock(&mapping->i_mmap_lock);
110                 if (new_vma->vm_truncate_count &&
111                     new_vma->vm_truncate_count != vma->vm_truncate_count)
112                         new_vma->vm_truncate_count = 0;
113         }
114         spin_lock(&mm->page_table_lock);
115
116         src = get_one_pte_map_nested(mm, old_addr);
117         if (src) {
118                 /*
119                  * Look to see whether alloc_one_pte_map needs to perform a
120                  * memory allocation.  If it does then we need to drop the
121                  * atomic kmap
122                  */
123                 dst = get_one_pte_map(mm, new_addr);
124                 if (unlikely(!dst)) {
125                         pte_unmap_nested(src);
126                         if (mapping)
127                                 spin_unlock(&mapping->i_mmap_lock);
128                         dst = alloc_one_pte_map(mm, new_addr);
129                         if (mapping && !spin_trylock(&mapping->i_mmap_lock)) {
130                                 spin_unlock(&mm->page_table_lock);
131                                 spin_lock(&mapping->i_mmap_lock);
132                                 spin_lock(&mm->page_table_lock);
133                         }
134                         src = get_one_pte_map_nested(mm, old_addr);
135                 }
136                 /*
137                  * Since alloc_one_pte_map can drop and re-acquire
138                  * page_table_lock, we should re-check the src entry...
139                  */
140                 if (src) {
141                         if (dst) {
142                                 pte_t pte;
143                                 pte = ptep_clear_flush(vma, old_addr, src);
144
145                                 /* ZERO_PAGE can be dependant on virtual addr */
146                                 pte = move_pte(pte, new_vma->vm_page_prot,
147                                                         old_addr, new_addr);
148                                 set_pte_at(mm, new_addr, dst, pte);
149                         } else
150                                 error = -ENOMEM;
151                         pte_unmap_nested(src);
152                 }
153                 if (dst)
154                         pte_unmap(dst);
155         }
156         spin_unlock(&mm->page_table_lock);
157         if (mapping)
158                 spin_unlock(&mapping->i_mmap_lock);
159         return error;
160 }
161
162 static unsigned long move_page_tables(struct vm_area_struct *vma,
163                 unsigned long old_addr, struct vm_area_struct *new_vma,
164                 unsigned long new_addr, unsigned long len)
165 {
166         unsigned long offset;
167
168         flush_cache_range(vma, old_addr, old_addr + len);
169
170         /*
171          * This is not the clever way to do this, but we're taking the
172          * easy way out on the assumption that most remappings will be
173          * only a few pages.. This also makes error recovery easier.
174          */
175         for (offset = 0; offset < len; offset += PAGE_SIZE) {
176                 if (move_one_page(vma, old_addr + offset,
177                                 new_vma, new_addr + offset) < 0)
178                         break;
179                 cond_resched();
180         }
181         return offset;
182 }
183
184 static unsigned long move_vma(struct vm_area_struct *vma,
185                 unsigned long old_addr, unsigned long old_len,
186                 unsigned long new_len, unsigned long new_addr)
187 {
188         struct mm_struct *mm = vma->vm_mm;
189         struct vm_area_struct *new_vma;
190         unsigned long vm_flags = vma->vm_flags;
191         unsigned long new_pgoff;
192         unsigned long moved_len;
193         unsigned long excess = 0;
194         int split = 0;
195
196         /*
197          * We'd prefer to avoid failure later on in do_munmap:
198          * which may split one vma into three before unmapping.
199          */
200         if (mm->map_count >= sysctl_max_map_count - 3)
201                 return -ENOMEM;
202
203         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
204         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
205         if (!new_vma)
206                 return -ENOMEM;
207
208         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
209         if (moved_len < old_len) {
210                 /*
211                  * On error, move entries back from new area to old,
212                  * which will succeed since page tables still there,
213                  * and then proceed to unmap new area instead of old.
214                  */
215                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
216                 vma = new_vma;
217                 old_len = new_len;
218                 old_addr = new_addr;
219                 new_addr = -ENOMEM;
220         }
221
222         /* Conceal VM_ACCOUNT so old reservation is not undone */
223         if (vm_flags & VM_ACCOUNT) {
224                 vma->vm_flags &= ~VM_ACCOUNT;
225                 excess = vma->vm_end - vma->vm_start - old_len;
226                 if (old_addr > vma->vm_start &&
227                     old_addr + old_len < vma->vm_end)
228                         split = 1;
229         }
230
231         /*
232          * if we failed to move page tables we still do total_vm increment
233          * since do_munmap() will decrement it by old_len == new_len
234          */
235         mm->total_vm += new_len >> PAGE_SHIFT;
236         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
237
238         if (do_munmap(mm, old_addr, old_len) < 0) {
239                 /* OOM: unable to split vma, just get accounts right */
240                 vm_unacct_memory(excess >> PAGE_SHIFT);
241                 excess = 0;
242         }
243
244         /* Restore VM_ACCOUNT if one or two pieces of vma left */
245         if (excess) {
246                 vma->vm_flags |= VM_ACCOUNT;
247                 if (split)
248                         vma->vm_next->vm_flags |= VM_ACCOUNT;
249         }
250
251         if (vm_flags & VM_LOCKED) {
252                 mm->locked_vm += new_len >> PAGE_SHIFT;
253                 if (new_len > old_len)
254                         make_pages_present(new_addr + old_len,
255                                            new_addr + new_len);
256         }
257
258         return new_addr;
259 }
260
261 /*
262  * Expand (or shrink) an existing mapping, potentially moving it at the
263  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
264  *
265  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
266  * This option implies MREMAP_MAYMOVE.
267  */
268 unsigned long do_mremap(unsigned long addr,
269         unsigned long old_len, unsigned long new_len,
270         unsigned long flags, unsigned long new_addr)
271 {
272         struct vm_area_struct *vma;
273         unsigned long ret = -EINVAL;
274         unsigned long charged = 0;
275
276         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
277                 goto out;
278
279         if (addr & ~PAGE_MASK)
280                 goto out;
281
282         old_len = PAGE_ALIGN(old_len);
283         new_len = PAGE_ALIGN(new_len);
284
285         /*
286          * We allow a zero old-len as a special case
287          * for DOS-emu "duplicate shm area" thing. But
288          * a zero new-len is nonsensical.
289          */
290         if (!new_len)
291                 goto out;
292
293         /* new_addr is only valid if MREMAP_FIXED is specified */
294         if (flags & MREMAP_FIXED) {
295                 if (new_addr & ~PAGE_MASK)
296                         goto out;
297                 if (!(flags & MREMAP_MAYMOVE))
298                         goto out;
299
300                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
301                         goto out;
302
303                 /* Check if the location we're moving into overlaps the
304                  * old location at all, and fail if it does.
305                  */
306                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
307                         goto out;
308
309                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
310                         goto out;
311
312                 ret = do_munmap(current->mm, new_addr, new_len);
313                 if (ret)
314                         goto out;
315         }
316
317         /*
318          * Always allow a shrinking remap: that just unmaps
319          * the unnecessary pages..
320          * do_munmap does all the needed commit accounting
321          */
322         if (old_len >= new_len) {
323                 ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
324                 if (ret && old_len != new_len)
325                         goto out;
326                 ret = addr;
327                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
328                         goto out;
329                 old_len = new_len;
330         }
331
332         /*
333          * Ok, we need to grow..  or relocate.
334          */
335         ret = -EFAULT;
336         vma = find_vma(current->mm, addr);
337         if (!vma || vma->vm_start > addr)
338                 goto out;
339         if (is_vm_hugetlb_page(vma)) {
340                 ret = -EINVAL;
341                 goto out;
342         }
343         /* We can't remap across vm area boundaries */
344         if (old_len > vma->vm_end - addr)
345                 goto out;
346         if (vma->vm_flags & VM_DONTEXPAND) {
347                 if (new_len > old_len)
348                         goto out;
349         }
350         if (vma->vm_flags & VM_LOCKED) {
351                 unsigned long locked, lock_limit;
352                 locked = current->mm->locked_vm << PAGE_SHIFT;
353                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
354                 locked += new_len - old_len;
355                 ret = -EAGAIN;
356                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
357                         goto out;
358         }
359         if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) {
360                 ret = -ENOMEM;
361                 goto out;
362         }
363
364         if (vma->vm_flags & VM_ACCOUNT) {
365                 charged = (new_len - old_len) >> PAGE_SHIFT;
366                 if (security_vm_enough_memory(charged))
367                         goto out_nc;
368         }
369
370         /* old_len exactly to the end of the area..
371          * And we're not relocating the area.
372          */
373         if (old_len == vma->vm_end - addr &&
374             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
375             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
376                 unsigned long max_addr = TASK_SIZE;
377                 if (vma->vm_next)
378                         max_addr = vma->vm_next->vm_start;
379                 /* can we just expand the current mapping? */
380                 if (max_addr - addr >= new_len) {
381                         int pages = (new_len - old_len) >> PAGE_SHIFT;
382
383                         vma_adjust(vma, vma->vm_start,
384                                 addr + new_len, vma->vm_pgoff, NULL);
385
386                         current->mm->total_vm += pages;
387                         vm_stat_account(vma->vm_mm, vma->vm_flags,
388                                                         vma->vm_file, pages);
389                         if (vma->vm_flags & VM_LOCKED) {
390                                 current->mm->locked_vm += pages;
391                                 make_pages_present(addr + old_len,
392                                                    addr + new_len);
393                         }
394                         ret = addr;
395                         goto out;
396                 }
397         }
398
399         /*
400          * We weren't able to just expand or shrink the area,
401          * we need to create a new one and move it..
402          */
403         ret = -ENOMEM;
404         if (flags & MREMAP_MAYMOVE) {
405                 if (!(flags & MREMAP_FIXED)) {
406                         unsigned long map_flags = 0;
407                         if (vma->vm_flags & VM_MAYSHARE)
408                                 map_flags |= MAP_SHARED;
409
410                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
411                                                 vma->vm_pgoff, map_flags);
412                         ret = new_addr;
413                         if (new_addr & ~PAGE_MASK)
414                                 goto out;
415                 }
416                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
417         }
418 out:
419         if (ret & ~PAGE_MASK)
420                 vm_unacct_memory(charged);
421 out_nc:
422         return ret;
423 }
424
425 asmlinkage unsigned long sys_mremap(unsigned long addr,
426         unsigned long old_len, unsigned long new_len,
427         unsigned long flags, unsigned long new_addr)
428 {
429         unsigned long ret;
430
431         down_write(&current->mm->mmap_sem);
432         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
433         up_write(&current->mm->mmap_sem);
434         return ret;
435 }