4 * Explicit pagetable population and nonlinear (random) mappings support.
6 * started by Ingo Molnar, Copyright (C) 2002, 2003
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>
19 #include <asm/mmu_context.h>
20 #include <asm/cacheflush.h>
21 #include <asm/tlbflush.h>
23 static inline void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
24 unsigned long addr, pte_t *ptep)
30 if (pte_present(pte)) {
31 unsigned long pfn = pte_pfn(pte);
33 flush_cache_page(vma, addr);
34 pte = ptep_clear_flush(vma, addr, ptep);
36 struct page *page = pfn_to_page(pfn);
37 if (!PageReserved(page)) {
40 page_remove_rmap(page);
41 page_cache_release(page);
47 free_swap_and_cache(pte_to_swp_entry(pte));
53 * Install a file page to a given virtual memory address, release any
54 * previously existing mapping.
56 int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
57 unsigned long addr, struct page *page, pgprot_t prot)
67 pgd = pgd_offset(mm, addr);
68 spin_lock(&mm->page_table_lock);
70 pmd = pmd_alloc(mm, pgd, addr);
74 pte = pte_alloc_map(mm, pmd, addr);
79 * This page may have been truncated. Tell the
83 inode = vma->vm_file->f_mapping->host;
84 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
85 if (!page->mapping || page->index >= size)
88 zap_pte(mm, vma, addr, pte);
91 flush_icache_page(vma, page);
92 set_pte(pte, mk_pte(page, prot));
93 page_add_file_rmap(page);
96 update_mmu_cache(vma, addr, pte_val);
100 spin_unlock(&mm->page_table_lock);
103 EXPORT_SYMBOL(install_page);
107 * Install a file pte to a given virtual memory address, release any
108 * previously existing mapping.
110 int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
111 unsigned long addr, unsigned long pgoff, pgprot_t prot)
119 pgd = pgd_offset(mm, addr);
120 spin_lock(&mm->page_table_lock);
122 pmd = pmd_alloc(mm, pgd, addr);
126 pte = pte_alloc_map(mm, pmd, addr);
130 zap_pte(mm, vma, addr, pte);
132 set_pte(pte, pgoff_to_pte(pgoff));
135 update_mmu_cache(vma, addr, pte_val);
136 spin_unlock(&mm->page_table_lock);
140 spin_unlock(&mm->page_table_lock);
146 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
147 * file within an existing vma.
148 * @start: start of the remapped virtual memory range
149 * @size: size of the remapped virtual memory range
150 * @prot: new protection bits of the range
151 * @pgoff: to be mapped page of the backing store file
152 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
154 * this syscall works purely via pagetables, so it's the most efficient
155 * way to map the same (large) file into a given virtual window. Unlike
156 * mmap()/mremap() it does not create any new vmas. The new mappings are
157 * also safe across swapout.
159 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
160 * protection is used. Arbitrary protections might be implemented in the
163 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
164 unsigned long __prot, unsigned long pgoff, unsigned long flags)
166 struct mm_struct *mm = current->mm;
167 struct address_space *mapping;
168 unsigned long end = start + size;
169 struct vm_area_struct *vma;
171 int has_write_lock = 0;
176 * Sanitize the syscall parameters:
178 start = start & PAGE_MASK;
179 size = size & PAGE_MASK;
181 /* Does the address range wrap, or is the span zero-sized? */
182 if (start + size <= start)
185 /* Can we represent this offset inside this architecture's pte's? */
186 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
187 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
191 /* We need down_write() to change vma->vm_flags. */
192 down_read(&mm->mmap_sem);
194 vma = find_vma(mm, start);
197 * Make sure the vma is shared, that it supports prefaulting,
198 * and that the remapped range is valid and fully within
199 * the single existing vma. vm_private_data is used as a
200 * swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED
201 * or VM_LOCKED, but VM_LOCKED could be revoked later on).
203 if (vma && (vma->vm_flags & VM_SHARED) &&
204 (!vma->vm_private_data ||
205 (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) &&
206 vma->vm_ops && vma->vm_ops->populate &&
207 end > start && start >= vma->vm_start &&
208 end <= vma->vm_end) {
210 /* Must set VM_NONLINEAR before any pages are populated. */
211 if (pgoff != linear_page_index(vma, start) &&
212 !(vma->vm_flags & VM_NONLINEAR)) {
213 if (!has_write_lock) {
214 up_read(&mm->mmap_sem);
215 down_write(&mm->mmap_sem);
219 mapping = vma->vm_file->f_mapping;
220 spin_lock(&mapping->i_mmap_lock);
221 flush_dcache_mmap_lock(mapping);
222 vma->vm_flags |= VM_NONLINEAR;
223 vma_prio_tree_remove(vma, &mapping->i_mmap);
224 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
225 flush_dcache_mmap_unlock(mapping);
226 spin_unlock(&mapping->i_mmap_lock);
229 err = vma->vm_ops->populate(vma, start, size,
231 pgoff, flags & MAP_NONBLOCK);
234 * We can't clear VM_NONLINEAR because we'd have to do
235 * it after ->populate completes, and that would prevent
236 * downgrading the lock. (Locks can't be upgraded).
239 if (likely(!has_write_lock))
240 up_read(&mm->mmap_sem);
242 up_write(&mm->mmap_sem);