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>
18 #include <linux/vs_base.h>
19 #include <linux/vs_memory.h>
21 #include <asm/mmu_context.h>
22 #include <asm/cacheflush.h>
23 #include <asm/tlbflush.h>
25 static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
26 unsigned long addr, pte_t *ptep)
29 struct page *page = NULL;
31 if (pte_present(pte)) {
32 flush_cache_page(vma, addr, pte_pfn(pte));
33 pte = ptep_clear_flush(vma, addr, ptep);
34 page = vm_normal_page(vma, addr, pte);
38 page_remove_rmap(page, vma);
39 page_cache_release(page);
43 free_swap_and_cache(pte_to_swp_entry(pte));
44 pte_clear_not_present_full(mm, addr, ptep, 0);
50 * Install a file page to a given virtual memory address, release any
51 * previously existing mapping.
53 int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
54 unsigned long addr, struct page *page, pgprot_t prot)
63 pte = get_locked_pte(mm, addr, &ptl);
68 * This page may have been truncated. Tell the
72 inode = vma->vm_file->f_mapping->host;
73 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
74 if (!page->mapping || page->index >= size)
77 if (page_mapcount(page) > INT_MAX/2)
79 if (!vx_rss_avail(mm, 1))
82 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
83 inc_mm_counter(mm, file_rss);
85 flush_icache_page(vma, page);
86 pte_val = mk_pte(page, prot);
87 set_pte_at(mm, addr, pte, pte_val);
88 page_add_file_rmap(page);
89 update_mmu_cache(vma, addr, pte_val);
90 lazy_mmu_prot_update(pte_val);
93 pte_unmap_unlock(pte, ptl);
97 EXPORT_SYMBOL(install_page);
100 * Install a file pte to a given virtual memory address, release any
101 * previously existing mapping.
103 int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
104 unsigned long addr, unsigned long pgoff, pgprot_t prot)
110 pte = get_locked_pte(mm, addr, &ptl);
114 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
115 update_hiwater_rss(mm);
116 dec_mm_counter(mm, file_rss);
119 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
121 * We don't need to run update_mmu_cache() here because the "file pte"
122 * being installed by install_file_pte() is not a real pte - it's a
123 * non-present entry (like a swap entry), noting what file offset should
124 * be mapped there when there's a fault (in a non-linear vma where
125 * that's not obvious).
127 pte_unmap_unlock(pte, ptl);
134 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
135 * file within an existing vma.
136 * @start: start of the remapped virtual memory range
137 * @size: size of the remapped virtual memory range
138 * @prot: new protection bits of the range
139 * @pgoff: to be mapped page of the backing store file
140 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
142 * this syscall works purely via pagetables, so it's the most efficient
143 * way to map the same (large) file into a given virtual window. Unlike
144 * mmap()/mremap() it does not create any new vmas. The new mappings are
145 * also safe across swapout.
147 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
148 * protection is used. Arbitrary protections might be implemented in the
151 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
152 unsigned long __prot, unsigned long pgoff, unsigned long flags)
154 struct mm_struct *mm = current->mm;
155 struct address_space *mapping;
156 unsigned long end = start + size;
157 struct vm_area_struct *vma;
159 int has_write_lock = 0;
164 * Sanitize the syscall parameters:
166 start = start & PAGE_MASK;
167 size = size & PAGE_MASK;
169 /* Does the address range wrap, or is the span zero-sized? */
170 if (start + size <= start)
173 /* Can we represent this offset inside this architecture's pte's? */
174 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
175 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
179 /* We need down_write() to change vma->vm_flags. */
180 down_read(&mm->mmap_sem);
182 vma = find_vma(mm, start);
185 * Make sure the vma is shared, that it supports prefaulting,
186 * and that the remapped range is valid and fully within
187 * the single existing vma. vm_private_data is used as a
188 * swapout cursor in a VM_NONLINEAR vma.
190 if (vma && (vma->vm_flags & VM_SHARED) &&
191 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
192 vma->vm_ops && vma->vm_ops->populate &&
193 end > start && start >= vma->vm_start &&
194 end <= vma->vm_end) {
196 /* Must set VM_NONLINEAR before any pages are populated. */
197 if (pgoff != linear_page_index(vma, start) &&
198 !(vma->vm_flags & VM_NONLINEAR)) {
199 if (!has_write_lock) {
200 up_read(&mm->mmap_sem);
201 down_write(&mm->mmap_sem);
205 mapping = vma->vm_file->f_mapping;
206 spin_lock(&mapping->i_mmap_lock);
207 flush_dcache_mmap_lock(mapping);
208 vma->vm_flags |= VM_NONLINEAR;
209 vma_prio_tree_remove(vma, &mapping->i_mmap);
210 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
211 flush_dcache_mmap_unlock(mapping);
212 spin_unlock(&mapping->i_mmap_lock);
215 err = vma->vm_ops->populate(vma, start, size,
217 pgoff, flags & MAP_NONBLOCK);
220 * We can't clear VM_NONLINEAR because we'd have to do
221 * it after ->populate completes, and that would prevent
222 * downgrading the lock. (Locks can't be upgraded).
225 if (likely(!has_write_lock))
226 up_read(&mm->mmap_sem);
228 up_write(&mm->mmap_sem);