4 * Explicit pagetable population and nonlinear (random) mappings support.
6 * started by Ingo Molnar, Copyright (C) 2002, 2003
8 #include <linux/export.h>
9 #include <linux/backing-dev.h>
11 #include <linux/swap.h>
12 #include <linux/file.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swapops.h>
16 #include <linux/rmap.h>
17 #include <linux/syscalls.h>
18 #include <linux/mmu_notifier.h>
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/tlbflush.h>
26 static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
27 unsigned long addr, pte_t *ptep)
31 if (pte_present(pte)) {
34 flush_cache_page(vma, addr, pte_pfn(pte));
35 pte = ptep_clear_flush(vma, addr, ptep);
36 page = vm_normal_page(vma, addr, pte);
40 page_remove_rmap(page);
41 page_cache_release(page);
42 update_hiwater_rss(mm);
43 dec_mm_counter(mm, MM_FILEPAGES);
47 free_swap_and_cache(pte_to_swp_entry(pte));
48 pte_clear_not_present_full(mm, addr, ptep, 0);
53 * Install a file pte to a given virtual memory address, release any
54 * previously existing mapping.
56 static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
57 unsigned long addr, unsigned long pgoff, pgprot_t prot)
63 pte = get_locked_pte(mm, addr, &ptl);
67 ptfile = pgoff_to_pte(pgoff);
69 if (!pte_none(*pte)) {
70 if (pte_present(*pte) && pte_soft_dirty(*pte))
71 pte_file_mksoft_dirty(ptfile);
72 zap_pte(mm, vma, addr, pte);
75 set_pte_at(mm, addr, pte, ptfile);
77 * We don't need to run update_mmu_cache() here because the "file pte"
78 * being installed by install_file_pte() is not a real pte - it's a
79 * non-present entry (like a swap entry), noting what file offset should
80 * be mapped there when there's a fault (in a non-linear vma where
81 * that's not obvious).
83 pte_unmap_unlock(pte, ptl);
89 int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr,
90 unsigned long size, pgoff_t pgoff)
92 struct mm_struct *mm = vma->vm_mm;
96 err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
107 EXPORT_SYMBOL(generic_file_remap_pages);
110 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
111 * @start: start of the remapped virtual memory range
112 * @size: size of the remapped virtual memory range
113 * @prot: new protection bits of the range (see NOTE)
114 * @pgoff: to-be-mapped page of the backing store file
115 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
117 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
118 * (shared backing store file).
120 * This syscall works purely via pagetables, so it's the most efficient
121 * way to map the same (large) file into a given virtual window. Unlike
122 * mmap()/mremap() it does not create any new vmas. The new mappings are
123 * also safe across swapout.
125 * NOTE: the @prot parameter right now is ignored (but must be zero),
126 * and the vma's default protection is used. Arbitrary protections
127 * might be implemented in the future.
129 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
130 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
132 struct mm_struct *mm = current->mm;
133 struct address_space *mapping;
134 struct vm_area_struct *vma;
136 int has_write_lock = 0;
137 vm_flags_t vm_flags = 0;
142 * Sanitize the syscall parameters:
144 start = start & PAGE_MASK;
145 size = size & PAGE_MASK;
147 /* Does the address range wrap, or is the span zero-sized? */
148 if (start + size <= start)
151 /* Does pgoff wrap? */
152 if (pgoff + (size >> PAGE_SHIFT) < pgoff)
155 /* Can we represent this offset inside this architecture's pte's? */
156 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
157 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
161 /* We need down_write() to change vma->vm_flags. */
162 down_read(&mm->mmap_sem);
164 vma = find_vma(mm, start);
167 * Make sure the vma is shared, that it supports prefaulting,
168 * and that the remapped range is valid and fully within
169 * the single existing vma.
171 if (!vma || !(vma->vm_flags & VM_SHARED))
174 if (!vma->vm_ops || !vma->vm_ops->remap_pages)
177 if (start < vma->vm_start || start + size > vma->vm_end)
180 /* Must set VM_NONLINEAR before any pages are populated. */
181 if (!(vma->vm_flags & VM_NONLINEAR)) {
183 * vm_private_data is used as a swapout cursor
184 * in a VM_NONLINEAR vma.
186 if (vma->vm_private_data)
189 /* Don't need a nonlinear mapping, exit success */
190 if (pgoff == linear_page_index(vma, start)) {
195 if (!has_write_lock) {
197 up_read(&mm->mmap_sem);
198 down_write(&mm->mmap_sem);
202 mapping = vma->vm_file->f_mapping;
204 * page_mkclean doesn't work on nonlinear vmas, so if
205 * dirty pages need to be accounted, emulate with linear
208 if (mapping_cap_account_dirty(mapping)) {
210 struct file *file = get_file(vma->vm_file);
212 addr = mmap_region(file, start, size,
213 vma->vm_flags, pgoff);
215 if (IS_ERR_VALUE(addr)) {
218 BUG_ON(addr != start);
223 mutex_lock(&mapping->i_mmap_mutex);
224 flush_dcache_mmap_lock(mapping);
225 vma->vm_flags |= VM_NONLINEAR;
226 vma_interval_tree_remove(vma, &mapping->i_mmap);
227 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
228 flush_dcache_mmap_unlock(mapping);
229 mutex_unlock(&mapping->i_mmap_mutex);
232 if (vma->vm_flags & VM_LOCKED) {
234 * drop PG_Mlocked flag for over-mapped range
238 vm_flags = vma->vm_flags;
239 munlock_vma_pages_range(vma, start, start + size);
240 vma->vm_flags = vm_flags;
243 mmu_notifier_invalidate_range_start(mm, start, start + size);
244 err = vma->vm_ops->remap_pages(vma, start, size, pgoff);
245 mmu_notifier_invalidate_range_end(mm, start, start + size);
248 * We can't clear VM_NONLINEAR because we'd have to do
249 * it after ->populate completes, and that would prevent
250 * downgrading the lock. (Locks can't be upgraded).
255 vm_flags = vma->vm_flags;
256 if (likely(!has_write_lock))
257 up_read(&mm->mmap_sem);
259 up_write(&mm->mmap_sem);
260 if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK)))
261 mm_populate(start, size);