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 int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
24 unsigned long addr, pte_t *ptep)
27 struct page *page = NULL;
29 if (pte_present(pte)) {
30 flush_cache_page(vma, addr, pte_pfn(pte));
31 pte = ptep_clear_flush(vma, addr, ptep);
32 page = vm_normal_page(vma, addr, pte);
36 page_remove_rmap(page);
37 page_cache_release(page);
41 free_swap_and_cache(pte_to_swp_entry(pte));
42 pte_clear(mm, addr, ptep);
48 * Install a file page to a given virtual memory address, release any
49 * previously existing mapping.
51 int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
52 unsigned long addr, struct page *page, pgprot_t prot)
64 pgd = pgd_offset(mm, addr);
65 pud = pud_alloc(mm, pgd, addr);
68 pmd = pmd_alloc(mm, pud, addr);
71 pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
76 * This page may have been truncated. Tell the
80 inode = vma->vm_file->f_mapping->host;
81 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
82 if (!page->mapping || page->index >= size)
85 if (page_mapcount(page) > INT_MAX/2)
88 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
89 inc_mm_counter(mm, file_rss);
91 flush_icache_page(vma, page);
92 set_pte_at(mm, addr, pte, mk_pte(page, prot));
93 page_add_file_rmap(page);
95 update_mmu_cache(vma, addr, pte_val);
98 pte_unmap_unlock(pte, ptl);
102 EXPORT_SYMBOL(install_page);
105 * Install a file pte to a given virtual memory address, release any
106 * previously existing mapping.
108 int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
109 unsigned long addr, unsigned long pgoff, pgprot_t prot)
119 pgd = pgd_offset(mm, addr);
120 pud = pud_alloc(mm, pgd, addr);
123 pmd = pmd_alloc(mm, pud, addr);
126 pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
130 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
131 update_hiwater_rss(mm);
132 dec_mm_counter(mm, file_rss);
135 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
137 update_mmu_cache(vma, addr, pte_val);
138 pte_unmap_unlock(pte, ptl);
145 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
146 * file within an existing vma.
147 * @start: start of the remapped virtual memory range
148 * @size: size of the remapped virtual memory range
149 * @prot: new protection bits of the range
150 * @pgoff: to be mapped page of the backing store file
151 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
153 * this syscall works purely via pagetables, so it's the most efficient
154 * way to map the same (large) file into a given virtual window. Unlike
155 * mmap()/mremap() it does not create any new vmas. The new mappings are
156 * also safe across swapout.
158 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
159 * protection is used. Arbitrary protections might be implemented in the
162 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
163 unsigned long __prot, unsigned long pgoff, unsigned long flags)
165 struct mm_struct *mm = current->mm;
166 struct address_space *mapping;
167 unsigned long end = start + size;
168 struct vm_area_struct *vma;
170 int has_write_lock = 0;
175 * Sanitize the syscall parameters:
177 start = start & PAGE_MASK;
178 size = size & PAGE_MASK;
180 /* Does the address range wrap, or is the span zero-sized? */
181 if (start + size <= start)
184 /* Can we represent this offset inside this architecture's pte's? */
185 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
186 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
190 /* We need down_write() to change vma->vm_flags. */
191 down_read(&mm->mmap_sem);
193 vma = find_vma(mm, start);
196 * Make sure the vma is shared, that it supports prefaulting,
197 * and that the remapped range is valid and fully within
198 * the single existing vma. vm_private_data is used as a
199 * swapout cursor in a VM_NONLINEAR vma.
201 if (vma && (vma->vm_flags & VM_SHARED) &&
202 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
203 vma->vm_ops && vma->vm_ops->populate &&
204 end > start && start >= vma->vm_start &&
205 end <= vma->vm_end) {
207 /* Must set VM_NONLINEAR before any pages are populated. */
208 if (pgoff != linear_page_index(vma, start) &&
209 !(vma->vm_flags & VM_NONLINEAR)) {
210 if (!has_write_lock) {
211 up_read(&mm->mmap_sem);
212 down_write(&mm->mmap_sem);
216 mapping = vma->vm_file->f_mapping;
217 spin_lock(&mapping->i_mmap_lock);
218 flush_dcache_mmap_lock(mapping);
219 vma->vm_flags |= VM_NONLINEAR;
220 vma_prio_tree_remove(vma, &mapping->i_mmap);
221 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
222 flush_dcache_mmap_unlock(mapping);
223 spin_unlock(&mapping->i_mmap_lock);
226 err = vma->vm_ops->populate(vma, start, size,
228 pgoff, flags & MAP_NONBLOCK);
231 * We can't clear VM_NONLINEAR because we'd have to do
232 * it after ->populate completes, and that would prevent
233 * downgrading the lock. (Locks can't be upgraded).
236 if (likely(!has_write_lock))
237 up_read(&mm->mmap_sem);
239 up_write(&mm->mmap_sem);