blob: 4e3f53dd5fd448d20a23296dfb398dd1d281fee0 [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
Hugh Dickins861f2fb2005-10-29 18:16:17 -070023static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
Linus Torvalds1da177e2005-04-16 15:20:36 -070024 unsigned long addr, pte_t *ptep)
25{
26 pte_t pte = *ptep;
Hugh Dickins861f2fb2005-10-29 18:16:17 -070027 struct page *page = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
Linus Torvalds1da177e2005-04-16 15:20:36 -070029 if (pte_present(pte)) {
Linus Torvalds6aab3412005-11-28 14:34:23 -080030 flush_cache_page(vma, addr, pte_pfn(pte));
Linus Torvalds1da177e2005-04-16 15:20:36 -070031 pte = ptep_clear_flush(vma, addr, ptep);
Linus Torvalds6aab3412005-11-28 14:34:23 -080032 page = vm_normal_page(vma, addr, pte);
33 if (page) {
34 if (pte_dirty(pte))
35 set_page_dirty(page);
Nick Piggin7de6b802006-12-22 01:09:33 -080036 page_remove_rmap(page, vma);
Linus Torvalds6aab3412005-11-28 14:34:23 -080037 page_cache_release(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 }
39 } else {
40 if (!pte_file(pte))
41 free_swap_and_cache(pte_to_swp_entry(pte));
Zachary Amsden9888a1c2006-09-30 23:29:31 -070042 pte_clear_not_present_full(mm, addr, ptep, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 }
Hugh Dickins861f2fb2005-10-29 18:16:17 -070044 return !!page;
Linus Torvalds1da177e2005-04-16 15:20:36 -070045}
46
47/*
48 * Install a file page to a given virtual memory address, release any
49 * previously existing mapping.
50 */
51int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
52 unsigned long addr, struct page *page, pgprot_t prot)
53{
54 struct inode *inode;
55 pgoff_t size;
56 int err = -ENOMEM;
57 pte_t *pte;
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 pte_t pte_val;
Hugh Dickinsc74df322005-10-29 18:16:23 -070059 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Linus Torvaldsc9cfcdd2005-11-29 14:03:14 -080061 pte = get_locked_pte(mm, addr, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 if (!pte)
Hugh Dickinsc74df322005-10-29 18:16:23 -070063 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -070064
65 /*
66 * This page may have been truncated. Tell the
67 * caller about it.
68 */
69 err = -EINVAL;
70 inode = vma->vm_file->f_mapping->host;
71 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
72 if (!page->mapping || page->index >= size)
Hugh Dickinsc74df322005-10-29 18:16:23 -070073 goto unlock;
Hugh Dickinsf5154a92005-10-11 19:16:26 +010074 err = -ENOMEM;
75 if (page_mapcount(page) > INT_MAX/2)
Hugh Dickinsc74df322005-10-29 18:16:23 -070076 goto unlock;
Linus Torvalds1da177e2005-04-16 15:20:36 -070077
Hugh Dickins861f2fb2005-10-29 18:16:17 -070078 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
79 inc_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -070080
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 flush_icache_page(vma, page);
Peter Zijlstrae88dd6c2006-09-25 23:30:59 -070082 pte_val = mk_pte(page, prot);
83 set_pte_at(mm, addr, pte, pte_val);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 page_add_file_rmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 update_mmu_cache(vma, addr, pte_val);
Hugh Dickins668e0d82006-06-23 02:03:45 -070086 lazy_mmu_prot_update(pte_val);
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 err = 0;
Hugh Dickinsc74df322005-10-29 18:16:23 -070088unlock:
89 pte_unmap_unlock(pte, ptl);
90out:
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 return err;
92}
93EXPORT_SYMBOL(install_page);
94
Linus Torvalds1da177e2005-04-16 15:20:36 -070095/*
96 * Install a file pte to a given virtual memory address, release any
97 * previously existing mapping.
98 */
99int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
100 unsigned long addr, unsigned long pgoff, pgprot_t prot)
101{
102 int err = -ENOMEM;
103 pte_t *pte;
Hugh Dickinsc74df322005-10-29 18:16:23 -0700104 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105
Linus Torvaldsc9cfcdd2005-11-29 14:03:14 -0800106 pte = get_locked_pte(mm, addr, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 if (!pte)
Hugh Dickinsc74df322005-10-29 18:16:23 -0700108 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
Hugh Dickins365e9c872005-10-29 18:16:18 -0700110 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
111 update_hiwater_rss(mm);
Hugh Dickins861f2fb2005-10-29 18:16:17 -0700112 dec_mm_counter(mm, file_rss);
Hugh Dickins365e9c872005-10-29 18:16:18 -0700113 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114
115 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
Hugh Dickins668e0d82006-06-23 02:03:45 -0700116 /*
117 * We don't need to run update_mmu_cache() here because the "file pte"
118 * being installed by install_file_pte() is not a real pte - it's a
119 * non-present entry (like a swap entry), noting what file offset should
120 * be mapped there when there's a fault (in a non-linear vma where
121 * that's not obvious).
122 */
Hugh Dickinsc74df322005-10-29 18:16:23 -0700123 pte_unmap_unlock(pte, ptl);
124 err = 0;
125out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126 return err;
127}
128
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129/***
130 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
131 * file within an existing vma.
132 * @start: start of the remapped virtual memory range
133 * @size: size of the remapped virtual memory range
134 * @prot: new protection bits of the range
135 * @pgoff: to be mapped page of the backing store file
136 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
137 *
138 * this syscall works purely via pagetables, so it's the most efficient
139 * way to map the same (large) file into a given virtual window. Unlike
140 * mmap()/mremap() it does not create any new vmas. The new mappings are
141 * also safe across swapout.
142 *
143 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
144 * protection is used. Arbitrary protections might be implemented in the
145 * future.
146 */
147asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
148 unsigned long __prot, unsigned long pgoff, unsigned long flags)
149{
150 struct mm_struct *mm = current->mm;
151 struct address_space *mapping;
152 unsigned long end = start + size;
153 struct vm_area_struct *vma;
154 int err = -EINVAL;
155 int has_write_lock = 0;
156
157 if (__prot)
158 return err;
159 /*
160 * Sanitize the syscall parameters:
161 */
162 start = start & PAGE_MASK;
163 size = size & PAGE_MASK;
164
165 /* Does the address range wrap, or is the span zero-sized? */
166 if (start + size <= start)
167 return err;
168
169 /* Can we represent this offset inside this architecture's pte's? */
170#if PTE_FILE_MAX_BITS < BITS_PER_LONG
171 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
172 return err;
173#endif
174
175 /* We need down_write() to change vma->vm_flags. */
176 down_read(&mm->mmap_sem);
177 retry:
178 vma = find_vma(mm, start);
179
180 /*
181 * Make sure the vma is shared, that it supports prefaulting,
182 * and that the remapped range is valid and fully within
183 * the single existing vma. vm_private_data is used as a
Hugh Dickins101d2be2005-11-21 21:32:16 -0800184 * swapout cursor in a VM_NONLINEAR vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 */
186 if (vma && (vma->vm_flags & VM_SHARED) &&
Hugh Dickins101d2be2005-11-21 21:32:16 -0800187 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188 vma->vm_ops && vma->vm_ops->populate &&
189 end > start && start >= vma->vm_start &&
190 end <= vma->vm_end) {
191
192 /* Must set VM_NONLINEAR before any pages are populated. */
193 if (pgoff != linear_page_index(vma, start) &&
194 !(vma->vm_flags & VM_NONLINEAR)) {
195 if (!has_write_lock) {
196 up_read(&mm->mmap_sem);
197 down_write(&mm->mmap_sem);
198 has_write_lock = 1;
199 goto retry;
200 }
201 mapping = vma->vm_file->f_mapping;
202 spin_lock(&mapping->i_mmap_lock);
203 flush_dcache_mmap_lock(mapping);
204 vma->vm_flags |= VM_NONLINEAR;
205 vma_prio_tree_remove(vma, &mapping->i_mmap);
206 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
207 flush_dcache_mmap_unlock(mapping);
208 spin_unlock(&mapping->i_mmap_lock);
209 }
210
211 err = vma->vm_ops->populate(vma, start, size,
212 vma->vm_page_prot,
213 pgoff, flags & MAP_NONBLOCK);
214
215 /*
216 * We can't clear VM_NONLINEAR because we'd have to do
217 * it after ->populate completes, and that would prevent
218 * downgrading the lock. (Locks can't be upgraded).
219 */
220 }
221 if (likely(!has_write_lock))
222 up_read(&mm->mmap_sem);
223 else
224 up_write(&mm->mmap_sem);
225
226 return err;
227}
228