blob: 3235fb77c1331499c18510ceda2dd87867a73a23 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
9#include <linux/mm.h>
10#include <linux/swap.h>
11#include <linux/file.h>
12#include <linux/mman.h>
13#include <linux/pagemap.h>
14#include <linux/swapops.h>
15#include <linux/rmap.h>
16#include <linux/module.h>
17#include <linux/syscalls.h>
18
19#include <asm/mmu_context.h>
20#include <asm/cacheflush.h>
21#include <asm/tlbflush.h>
22
23static inline void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
24 unsigned long addr, pte_t *ptep)
25{
26 pte_t pte = *ptep;
27
28 if (pte_none(pte))
29 return;
30 if (pte_present(pte)) {
31 unsigned long pfn = pte_pfn(pte);
32
33 flush_cache_page(vma, addr, pfn);
34 pte = ptep_clear_flush(vma, addr, ptep);
35 if (pfn_valid(pfn)) {
36 struct page *page = pfn_to_page(pfn);
37 if (!PageReserved(page)) {
38 if (pte_dirty(pte))
39 set_page_dirty(page);
40 page_remove_rmap(page);
41 page_cache_release(page);
42 dec_mm_counter(mm, rss);
43 }
44 }
45 } else {
46 if (!pte_file(pte))
47 free_swap_and_cache(pte_to_swp_entry(pte));
48 pte_clear(mm, addr, ptep);
49 }
50}
51
52/*
53 * Install a file page to a given virtual memory address, release any
54 * previously existing mapping.
55 */
56int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
57 unsigned long addr, struct page *page, pgprot_t prot)
58{
59 struct inode *inode;
60 pgoff_t size;
61 int err = -ENOMEM;
62 pte_t *pte;
63 pmd_t *pmd;
64 pud_t *pud;
65 pgd_t *pgd;
66 pte_t pte_val;
67
68 pgd = pgd_offset(mm, addr);
69 spin_lock(&mm->page_table_lock);
70
71 pud = pud_alloc(mm, pgd, addr);
72 if (!pud)
73 goto err_unlock;
74
75 pmd = pmd_alloc(mm, pud, addr);
76 if (!pmd)
77 goto err_unlock;
78
79 pte = pte_alloc_map(mm, pmd, addr);
80 if (!pte)
81 goto err_unlock;
82
83 /*
84 * This page may have been truncated. Tell the
85 * caller about it.
86 */
87 err = -EINVAL;
88 inode = vma->vm_file->f_mapping->host;
89 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
90 if (!page->mapping || page->index >= size)
91 goto err_unlock;
92
93 zap_pte(mm, vma, addr, pte);
94
95 inc_mm_counter(mm,rss);
96 flush_icache_page(vma, page);
97 set_pte_at(mm, addr, pte, mk_pte(page, prot));
98 page_add_file_rmap(page);
99 pte_val = *pte;
100 pte_unmap(pte);
101 update_mmu_cache(vma, addr, pte_val);
102
103 err = 0;
104err_unlock:
105 spin_unlock(&mm->page_table_lock);
106 return err;
107}
108EXPORT_SYMBOL(install_page);
109
110
111/*
112 * Install a file pte to a given virtual memory address, release any
113 * previously existing mapping.
114 */
115int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
116 unsigned long addr, unsigned long pgoff, pgprot_t prot)
117{
118 int err = -ENOMEM;
119 pte_t *pte;
120 pmd_t *pmd;
121 pud_t *pud;
122 pgd_t *pgd;
123 pte_t pte_val;
124
125 pgd = pgd_offset(mm, addr);
126 spin_lock(&mm->page_table_lock);
127
128 pud = pud_alloc(mm, pgd, addr);
129 if (!pud)
130 goto err_unlock;
131
132 pmd = pmd_alloc(mm, pud, addr);
133 if (!pmd)
134 goto err_unlock;
135
136 pte = pte_alloc_map(mm, pmd, addr);
137 if (!pte)
138 goto err_unlock;
139
140 zap_pte(mm, vma, addr, pte);
141
142 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
143 pte_val = *pte;
144 pte_unmap(pte);
145 update_mmu_cache(vma, addr, pte_val);
146 spin_unlock(&mm->page_table_lock);
147 return 0;
148
149err_unlock:
150 spin_unlock(&mm->page_table_lock);
151 return err;
152}
153
154
155/***
156 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
157 * file within an existing vma.
158 * @start: start of the remapped virtual memory range
159 * @size: size of the remapped virtual memory range
160 * @prot: new protection bits of the range
161 * @pgoff: to be mapped page of the backing store file
162 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
163 *
164 * this syscall works purely via pagetables, so it's the most efficient
165 * way to map the same (large) file into a given virtual window. Unlike
166 * mmap()/mremap() it does not create any new vmas. The new mappings are
167 * also safe across swapout.
168 *
169 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
170 * protection is used. Arbitrary protections might be implemented in the
171 * future.
172 */
173asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
174 unsigned long __prot, unsigned long pgoff, unsigned long flags)
175{
176 struct mm_struct *mm = current->mm;
177 struct address_space *mapping;
178 unsigned long end = start + size;
179 struct vm_area_struct *vma;
180 int err = -EINVAL;
181 int has_write_lock = 0;
182
183 if (__prot)
184 return err;
185 /*
186 * Sanitize the syscall parameters:
187 */
188 start = start & PAGE_MASK;
189 size = size & PAGE_MASK;
190
191 /* Does the address range wrap, or is the span zero-sized? */
192 if (start + size <= start)
193 return err;
194
195 /* Can we represent this offset inside this architecture's pte's? */
196#if PTE_FILE_MAX_BITS < BITS_PER_LONG
197 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
198 return err;
199#endif
200
201 /* We need down_write() to change vma->vm_flags. */
202 down_read(&mm->mmap_sem);
203 retry:
204 vma = find_vma(mm, start);
205
206 /*
207 * Make sure the vma is shared, that it supports prefaulting,
208 * and that the remapped range is valid and fully within
209 * the single existing vma. vm_private_data is used as a
210 * swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED
211 * or VM_LOCKED, but VM_LOCKED could be revoked later on).
212 */
213 if (vma && (vma->vm_flags & VM_SHARED) &&
214 (!vma->vm_private_data ||
215 (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) &&
216 vma->vm_ops && vma->vm_ops->populate &&
217 end > start && start >= vma->vm_start &&
218 end <= vma->vm_end) {
219
220 /* Must set VM_NONLINEAR before any pages are populated. */
221 if (pgoff != linear_page_index(vma, start) &&
222 !(vma->vm_flags & VM_NONLINEAR)) {
223 if (!has_write_lock) {
224 up_read(&mm->mmap_sem);
225 down_write(&mm->mmap_sem);
226 has_write_lock = 1;
227 goto retry;
228 }
229 mapping = vma->vm_file->f_mapping;
230 spin_lock(&mapping->i_mmap_lock);
231 flush_dcache_mmap_lock(mapping);
232 vma->vm_flags |= VM_NONLINEAR;
233 vma_prio_tree_remove(vma, &mapping->i_mmap);
234 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
235 flush_dcache_mmap_unlock(mapping);
236 spin_unlock(&mapping->i_mmap_lock);
237 }
238
239 err = vma->vm_ops->populate(vma, start, size,
240 vma->vm_page_prot,
241 pgoff, flags & MAP_NONBLOCK);
242
243 /*
244 * We can't clear VM_NONLINEAR because we'd have to do
245 * it after ->populate completes, and that would prevent
246 * downgrading the lock. (Locks can't be upgraded).
247 */
248 }
249 if (likely(!has_write_lock))
250 up_read(&mm->mmap_sem);
251 else
252 up_write(&mm->mmap_sem);
253
254 return err;
255}
256