fremap.c revision f5154a98a1931641f0448f6512294a15279110d7
1/* 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 23static inline void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, 24 unsigned long addr, pte_t *ptep) 25{ 26 pte_t pte = *ptep; 27 28 if (pte_none(pte)) 29 return; 30 if (pte_present(pte)) { 31 unsigned long pfn = pte_pfn(pte); 32 33 flush_cache_page(vma, addr, pfn); 34 pte = ptep_clear_flush(vma, addr, ptep); 35 if (pfn_valid(pfn)) { 36 struct page *page = pfn_to_page(pfn); 37 if (!PageReserved(page)) { 38 if (pte_dirty(pte)) 39 set_page_dirty(page); 40 page_remove_rmap(page); 41 page_cache_release(page); 42 dec_mm_counter(mm, rss); 43 } 44 } 45 } else { 46 if (!pte_file(pte)) 47 free_swap_and_cache(pte_to_swp_entry(pte)); 48 pte_clear(mm, addr, ptep); 49 } 50} 51 52/* 53 * Install a file page to a given virtual memory address, release any 54 * previously existing mapping. 55 */ 56int install_page(struct mm_struct *mm, struct vm_area_struct *vma, 57 unsigned long addr, struct page *page, pgprot_t prot) 58{ 59 struct inode *inode; 60 pgoff_t size; 61 int err = -ENOMEM; 62 pte_t *pte; 63 pmd_t *pmd; 64 pud_t *pud; 65 pgd_t *pgd; 66 pte_t pte_val; 67 68 pgd = pgd_offset(mm, addr); 69 spin_lock(&mm->page_table_lock); 70 71 pud = pud_alloc(mm, pgd, addr); 72 if (!pud) 73 goto err_unlock; 74 75 pmd = pmd_alloc(mm, pud, addr); 76 if (!pmd) 77 goto err_unlock; 78 79 pte = pte_alloc_map(mm, pmd, addr); 80 if (!pte) 81 goto err_unlock; 82 83 /* 84 * This page may have been truncated. Tell the 85 * caller about it. 86 */ 87 err = -EINVAL; 88 inode = vma->vm_file->f_mapping->host; 89 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 90 if (!page->mapping || page->index >= size) 91 goto err_unlock; 92 err = -ENOMEM; 93 if (page_mapcount(page) > INT_MAX/2) 94 goto err_unlock; 95 96 zap_pte(mm, vma, addr, pte); 97 98 inc_mm_counter(mm,rss); 99 flush_icache_page(vma, page); 100 set_pte_at(mm, addr, pte, mk_pte(page, prot)); 101 page_add_file_rmap(page); 102 pte_val = *pte; 103 pte_unmap(pte); 104 update_mmu_cache(vma, addr, pte_val); 105 106 err = 0; 107err_unlock: 108 spin_unlock(&mm->page_table_lock); 109 return err; 110} 111EXPORT_SYMBOL(install_page); 112 113 114/* 115 * Install a file pte to a given virtual memory address, release any 116 * previously existing mapping. 117 */ 118int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, 119 unsigned long addr, unsigned long pgoff, pgprot_t prot) 120{ 121 int err = -ENOMEM; 122 pte_t *pte; 123 pmd_t *pmd; 124 pud_t *pud; 125 pgd_t *pgd; 126 pte_t pte_val; 127 128 pgd = pgd_offset(mm, addr); 129 spin_lock(&mm->page_table_lock); 130 131 pud = pud_alloc(mm, pgd, addr); 132 if (!pud) 133 goto err_unlock; 134 135 pmd = pmd_alloc(mm, pud, addr); 136 if (!pmd) 137 goto err_unlock; 138 139 pte = pte_alloc_map(mm, pmd, addr); 140 if (!pte) 141 goto err_unlock; 142 143 zap_pte(mm, vma, addr, pte); 144 145 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); 146 pte_val = *pte; 147 pte_unmap(pte); 148 update_mmu_cache(vma, addr, pte_val); 149 spin_unlock(&mm->page_table_lock); 150 return 0; 151 152err_unlock: 153 spin_unlock(&mm->page_table_lock); 154 return err; 155} 156 157 158/*** 159 * sys_remap_file_pages - remap arbitrary pages of a shared backing store 160 * file within an existing vma. 161 * @start: start of the remapped virtual memory range 162 * @size: size of the remapped virtual memory range 163 * @prot: new protection bits of the range 164 * @pgoff: to be mapped page of the backing store file 165 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. 166 * 167 * this syscall works purely via pagetables, so it's the most efficient 168 * way to map the same (large) file into a given virtual window. Unlike 169 * mmap()/mremap() it does not create any new vmas. The new mappings are 170 * also safe across swapout. 171 * 172 * NOTE: the 'prot' parameter right now is ignored, and the vma's default 173 * protection is used. Arbitrary protections might be implemented in the 174 * future. 175 */ 176asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, 177 unsigned long __prot, unsigned long pgoff, unsigned long flags) 178{ 179 struct mm_struct *mm = current->mm; 180 struct address_space *mapping; 181 unsigned long end = start + size; 182 struct vm_area_struct *vma; 183 int err = -EINVAL; 184 int has_write_lock = 0; 185 186 if (__prot) 187 return err; 188 /* 189 * Sanitize the syscall parameters: 190 */ 191 start = start & PAGE_MASK; 192 size = size & PAGE_MASK; 193 194 /* Does the address range wrap, or is the span zero-sized? */ 195 if (start + size <= start) 196 return err; 197 198 /* Can we represent this offset inside this architecture's pte's? */ 199#if PTE_FILE_MAX_BITS < BITS_PER_LONG 200 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) 201 return err; 202#endif 203 204 /* We need down_write() to change vma->vm_flags. */ 205 down_read(&mm->mmap_sem); 206 retry: 207 vma = find_vma(mm, start); 208 209 /* 210 * Make sure the vma is shared, that it supports prefaulting, 211 * and that the remapped range is valid and fully within 212 * the single existing vma. vm_private_data is used as a 213 * swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED 214 * or VM_LOCKED, but VM_LOCKED could be revoked later on). 215 */ 216 if (vma && (vma->vm_flags & VM_SHARED) && 217 (!vma->vm_private_data || 218 (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) && 219 vma->vm_ops && vma->vm_ops->populate && 220 end > start && start >= vma->vm_start && 221 end <= vma->vm_end) { 222 223 /* Must set VM_NONLINEAR before any pages are populated. */ 224 if (pgoff != linear_page_index(vma, start) && 225 !(vma->vm_flags & VM_NONLINEAR)) { 226 if (!has_write_lock) { 227 up_read(&mm->mmap_sem); 228 down_write(&mm->mmap_sem); 229 has_write_lock = 1; 230 goto retry; 231 } 232 mapping = vma->vm_file->f_mapping; 233 spin_lock(&mapping->i_mmap_lock); 234 flush_dcache_mmap_lock(mapping); 235 vma->vm_flags |= VM_NONLINEAR; 236 vma_prio_tree_remove(vma, &mapping->i_mmap); 237 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); 238 flush_dcache_mmap_unlock(mapping); 239 spin_unlock(&mapping->i_mmap_lock); 240 } 241 242 err = vma->vm_ops->populate(vma, start, size, 243 vma->vm_page_prot, 244 pgoff, flags & MAP_NONBLOCK); 245 246 /* 247 * We can't clear VM_NONLINEAR because we'd have to do 248 * it after ->populate completes, and that would prevent 249 * downgrading the lock. (Locks can't be upgraded). 250 */ 251 } 252 if (likely(!has_write_lock)) 253 up_read(&mm->mmap_sem); 254 else 255 up_write(&mm->mmap_sem); 256 257 return err; 258} 259 260