Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux...
[sfrench/cifs-2.6.git] / mm / fremap.c
1 /*
2  *   linux/mm/fremap.c
3  * 
4  * Explicit pagetable population and nonlinear (random) mappings support.
5  *
6  * started by Ingo Molnar, Copyright (C) 2002, 2003
7  */
8 #include <linux/export.h>
9 #include <linux/backing-dev.h>
10 #include <linux/mm.h>
11 #include <linux/swap.h>
12 #include <linux/file.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swapops.h>
16 #include <linux/rmap.h>
17 #include <linux/syscalls.h>
18 #include <linux/mmu_notifier.h>
19
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/tlbflush.h>
23
24 #include "internal.h"
25
26 static int mm_counter(struct page *page)
27 {
28         return PageAnon(page) ? MM_ANONPAGES : MM_FILEPAGES;
29 }
30
31 static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
32                         unsigned long addr, pte_t *ptep)
33 {
34         pte_t pte = *ptep;
35         struct page *page;
36         swp_entry_t entry;
37
38         if (pte_present(pte)) {
39                 flush_cache_page(vma, addr, pte_pfn(pte));
40                 pte = ptep_clear_flush(vma, addr, ptep);
41                 page = vm_normal_page(vma, addr, pte);
42                 if (page) {
43                         if (pte_dirty(pte))
44                                 set_page_dirty(page);
45                         update_hiwater_rss(mm);
46                         dec_mm_counter(mm, mm_counter(page));
47                         page_remove_rmap(page);
48                         page_cache_release(page);
49                 }
50         } else {        /* zap_pte() is not called when pte_none() */
51                 if (!pte_file(pte)) {
52                         update_hiwater_rss(mm);
53                         entry = pte_to_swp_entry(pte);
54                         if (non_swap_entry(entry)) {
55                                 if (is_migration_entry(entry)) {
56                                         page = migration_entry_to_page(entry);
57                                         dec_mm_counter(mm, mm_counter(page));
58                                 }
59                         } else {
60                                 free_swap_and_cache(entry);
61                                 dec_mm_counter(mm, MM_SWAPENTS);
62                         }
63                 }
64                 pte_clear_not_present_full(mm, addr, ptep, 0);
65         }
66 }
67
68 /*
69  * Install a file pte to a given virtual memory address, release any
70  * previously existing mapping.
71  */
72 static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
73                 unsigned long addr, unsigned long pgoff, pgprot_t prot)
74 {
75         int err = -ENOMEM;
76         pte_t *pte, ptfile;
77         spinlock_t *ptl;
78
79         pte = get_locked_pte(mm, addr, &ptl);
80         if (!pte)
81                 goto out;
82
83         ptfile = pgoff_to_pte(pgoff);
84
85         if (!pte_none(*pte))
86                 zap_pte(mm, vma, addr, pte);
87
88         set_pte_at(mm, addr, pte, pte_file_mksoft_dirty(ptfile));
89         /*
90          * We don't need to run update_mmu_cache() here because the "file pte"
91          * being installed by install_file_pte() is not a real pte - it's a
92          * non-present entry (like a swap entry), noting what file offset should
93          * be mapped there when there's a fault (in a non-linear vma where
94          * that's not obvious).
95          */
96         pte_unmap_unlock(pte, ptl);
97         err = 0;
98 out:
99         return err;
100 }
101
102 int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr,
103                              unsigned long size, pgoff_t pgoff)
104 {
105         struct mm_struct *mm = vma->vm_mm;
106         int err;
107
108         do {
109                 err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
110                 if (err)
111                         return err;
112
113                 size -= PAGE_SIZE;
114                 addr += PAGE_SIZE;
115                 pgoff++;
116         } while (size);
117
118         return 0;
119 }
120 EXPORT_SYMBOL(generic_file_remap_pages);
121
122 /**
123  * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
124  * @start: start of the remapped virtual memory range
125  * @size: size of the remapped virtual memory range
126  * @prot: new protection bits of the range (see NOTE)
127  * @pgoff: to-be-mapped page of the backing store file
128  * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
129  *
130  * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
131  * (shared backing store file).
132  *
133  * This syscall works purely via pagetables, so it's the most efficient
134  * way to map the same (large) file into a given virtual window. Unlike
135  * mmap()/mremap() it does not create any new vmas. The new mappings are
136  * also safe across swapout.
137  *
138  * NOTE: the @prot parameter right now is ignored (but must be zero),
139  * and the vma's default protection is used. Arbitrary protections
140  * might be implemented in the future.
141  */
142 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
143                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
144 {
145         struct mm_struct *mm = current->mm;
146         struct address_space *mapping;
147         struct vm_area_struct *vma;
148         int err = -EINVAL;
149         int has_write_lock = 0;
150         vm_flags_t vm_flags = 0;
151
152         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. "
153                         "See Documentation/vm/remap_file_pages.txt.\n",
154                         current->comm, current->pid);
155
156         if (prot)
157                 return err;
158         /*
159          * Sanitize the syscall parameters:
160          */
161         start = start & PAGE_MASK;
162         size = size & PAGE_MASK;
163
164         /* Does the address range wrap, or is the span zero-sized? */
165         if (start + size <= start)
166                 return err;
167
168         /* Does pgoff wrap? */
169         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
170                 return err;
171
172         /* Can we represent this offset inside this architecture's pte's? */
173 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
174         if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
175                 return err;
176 #endif
177
178         /* We need down_write() to change vma->vm_flags. */
179         down_read(&mm->mmap_sem);
180  retry:
181         vma = find_vma(mm, start);
182
183         /*
184          * Make sure the vma is shared, that it supports prefaulting,
185          * and that the remapped range is valid and fully within
186          * the single existing vma.
187          */
188         if (!vma || !(vma->vm_flags & VM_SHARED))
189                 goto out;
190
191         if (!vma->vm_ops || !vma->vm_ops->remap_pages)
192                 goto out;
193
194         if (start < vma->vm_start || start + size > vma->vm_end)
195                 goto out;
196
197         /* Must set VM_NONLINEAR before any pages are populated. */
198         if (!(vma->vm_flags & VM_NONLINEAR)) {
199                 /*
200                  * vm_private_data is used as a swapout cursor
201                  * in a VM_NONLINEAR vma.
202                  */
203                 if (vma->vm_private_data)
204                         goto out;
205
206                 /* Don't need a nonlinear mapping, exit success */
207                 if (pgoff == linear_page_index(vma, start)) {
208                         err = 0;
209                         goto out;
210                 }
211
212                 if (!has_write_lock) {
213 get_write_lock:
214                         up_read(&mm->mmap_sem);
215                         down_write(&mm->mmap_sem);
216                         has_write_lock = 1;
217                         goto retry;
218                 }
219                 mapping = vma->vm_file->f_mapping;
220                 /*
221                  * page_mkclean doesn't work on nonlinear vmas, so if
222                  * dirty pages need to be accounted, emulate with linear
223                  * vmas.
224                  */
225                 if (mapping_cap_account_dirty(mapping)) {
226                         unsigned long addr;
227                         struct file *file = get_file(vma->vm_file);
228                         /* mmap_region may free vma; grab the info now */
229                         vm_flags = vma->vm_flags;
230
231                         addr = mmap_region(file, start, size, vm_flags, pgoff);
232                         fput(file);
233                         if (IS_ERR_VALUE(addr)) {
234                                 err = addr;
235                         } else {
236                                 BUG_ON(addr != start);
237                                 err = 0;
238                         }
239                         goto out_freed;
240                 }
241                 mutex_lock(&mapping->i_mmap_mutex);
242                 flush_dcache_mmap_lock(mapping);
243                 vma->vm_flags |= VM_NONLINEAR;
244                 vma_interval_tree_remove(vma, &mapping->i_mmap);
245                 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
246                 flush_dcache_mmap_unlock(mapping);
247                 mutex_unlock(&mapping->i_mmap_mutex);
248         }
249
250         if (vma->vm_flags & VM_LOCKED) {
251                 /*
252                  * drop PG_Mlocked flag for over-mapped range
253                  */
254                 if (!has_write_lock)
255                         goto get_write_lock;
256                 vm_flags = vma->vm_flags;
257                 munlock_vma_pages_range(vma, start, start + size);
258                 vma->vm_flags = vm_flags;
259         }
260
261         mmu_notifier_invalidate_range_start(mm, start, start + size);
262         err = vma->vm_ops->remap_pages(vma, start, size, pgoff);
263         mmu_notifier_invalidate_range_end(mm, start, start + size);
264
265         /*
266          * We can't clear VM_NONLINEAR because we'd have to do
267          * it after ->populate completes, and that would prevent
268          * downgrading the lock.  (Locks can't be upgraded).
269          */
270
271 out:
272         if (vma)
273                 vm_flags = vma->vm_flags;
274 out_freed:
275         if (likely(!has_write_lock))
276                 up_read(&mm->mmap_sem);
277         else
278                 up_write(&mm->mmap_sem);
279         if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK)))
280                 mm_populate(start, size);
281
282         return err;
283 }