fremap.c revision 9888a1cae3f859db38b9604e3df1c02177161bb0
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 int 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 struct page *page = NULL; 28 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); 33 if (page) { 34 if (pte_dirty(pte)) 35 set_page_dirty(page); 36 page_remove_rmap(page); 37 page_cache_release(page); 38 } 39 } else { 40 if (!pte_file(pte)) 41 free_swap_and_cache(pte_to_swp_entry(pte)); 42 pte_clear_not_present_full(mm, addr, ptep, 0); 43 } 44 return !!page; 45} 46 47/* 48 * Install a file page to a given virtual memory address, release any 49 * previously existing mapping. 50 */ 51int install_page(struct mm_struct *mm, struct vm_area_struct *vma, 52 unsigned long addr, struct page *page, pgprot_t prot) 53{ 54 struct inode *inode; 55 pgoff_t size; 56 int err = -ENOMEM; 57 pte_t *pte; 58 pte_t pte_val; 59 spinlock_t *ptl; 60 61 pte = get_locked_pte(mm, addr, &ptl); 62 if (!pte) 63 goto out; 64 65 /* 66 * This page may have been truncated. Tell the 67 * caller about it. 68 */ 69 err = -EINVAL; 70 inode = vma->vm_file->f_mapping->host; 71 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 72 if (!page->mapping || page->index >= size) 73 goto unlock; 74 err = -ENOMEM; 75 if (page_mapcount(page) > INT_MAX/2) 76 goto unlock; 77 78 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte)) 79 inc_mm_counter(mm, file_rss); 80 81 flush_icache_page(vma, page); 82 pte_val = mk_pte(page, prot); 83 set_pte_at(mm, addr, pte, pte_val); 84 page_add_file_rmap(page); 85 update_mmu_cache(vma, addr, pte_val); 86 lazy_mmu_prot_update(pte_val); 87 err = 0; 88unlock: 89 pte_unmap_unlock(pte, ptl); 90out: 91 return err; 92} 93EXPORT_SYMBOL(install_page); 94 95/* 96 * Install a file pte to a given virtual memory address, release any 97 * previously existing mapping. 98 */ 99int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, 100 unsigned long addr, unsigned long pgoff, pgprot_t prot) 101{ 102 int err = -ENOMEM; 103 pte_t *pte; 104 pte_t pte_val; 105 spinlock_t *ptl; 106 107 pte = get_locked_pte(mm, addr, &ptl); 108 if (!pte) 109 goto out; 110 111 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) { 112 update_hiwater_rss(mm); 113 dec_mm_counter(mm, file_rss); 114 } 115 116 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); 117 pte_val = *pte; 118 /* 119 * We don't need to run update_mmu_cache() here because the "file pte" 120 * being installed by install_file_pte() is not a real pte - it's a 121 * non-present entry (like a swap entry), noting what file offset should 122 * be mapped there when there's a fault (in a non-linear vma where 123 * that's not obvious). 124 */ 125 pte_unmap_unlock(pte, ptl); 126 err = 0; 127out: 128 return err; 129} 130 131/*** 132 * sys_remap_file_pages - remap arbitrary pages of a shared backing store 133 * file within an existing vma. 134 * @start: start of the remapped virtual memory range 135 * @size: size of the remapped virtual memory range 136 * @prot: new protection bits of the range 137 * @pgoff: to be mapped page of the backing store file 138 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. 139 * 140 * this syscall works purely via pagetables, so it's the most efficient 141 * way to map the same (large) file into a given virtual window. Unlike 142 * mmap()/mremap() it does not create any new vmas. The new mappings are 143 * also safe across swapout. 144 * 145 * NOTE: the 'prot' parameter right now is ignored, and the vma's default 146 * protection is used. Arbitrary protections might be implemented in the 147 * future. 148 */ 149asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, 150 unsigned long __prot, unsigned long pgoff, unsigned long flags) 151{ 152 struct mm_struct *mm = current->mm; 153 struct address_space *mapping; 154 unsigned long end = start + size; 155 struct vm_area_struct *vma; 156 int err = -EINVAL; 157 int has_write_lock = 0; 158 159 if (__prot) 160 return err; 161 /* 162 * Sanitize the syscall parameters: 163 */ 164 start = start & PAGE_MASK; 165 size = size & PAGE_MASK; 166 167 /* Does the address range wrap, or is the span zero-sized? */ 168 if (start + size <= start) 169 return err; 170 171 /* Can we represent this offset inside this architecture's pte's? */ 172#if PTE_FILE_MAX_BITS < BITS_PER_LONG 173 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) 174 return err; 175#endif 176 177 /* We need down_write() to change vma->vm_flags. */ 178 down_read(&mm->mmap_sem); 179 retry: 180 vma = find_vma(mm, start); 181 182 /* 183 * Make sure the vma is shared, that it supports prefaulting, 184 * and that the remapped range is valid and fully within 185 * the single existing vma. vm_private_data is used as a 186 * swapout cursor in a VM_NONLINEAR vma. 187 */ 188 if (vma && (vma->vm_flags & VM_SHARED) && 189 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) && 190 vma->vm_ops && vma->vm_ops->populate && 191 end > start && start >= vma->vm_start && 192 end <= vma->vm_end) { 193 194 /* Must set VM_NONLINEAR before any pages are populated. */ 195 if (pgoff != linear_page_index(vma, start) && 196 !(vma->vm_flags & VM_NONLINEAR)) { 197 if (!has_write_lock) { 198 up_read(&mm->mmap_sem); 199 down_write(&mm->mmap_sem); 200 has_write_lock = 1; 201 goto retry; 202 } 203 mapping = vma->vm_file->f_mapping; 204 spin_lock(&mapping->i_mmap_lock); 205 flush_dcache_mmap_lock(mapping); 206 vma->vm_flags |= VM_NONLINEAR; 207 vma_prio_tree_remove(vma, &mapping->i_mmap); 208 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); 209 flush_dcache_mmap_unlock(mapping); 210 spin_unlock(&mapping->i_mmap_lock); 211 } 212 213 err = vma->vm_ops->populate(vma, start, size, 214 vma->vm_page_prot, 215 pgoff, flags & MAP_NONBLOCK); 216 217 /* 218 * We can't clear VM_NONLINEAR because we'd have to do 219 * it after ->populate completes, and that would prevent 220 * downgrading the lock. (Locks can't be upgraded). 221 */ 222 } 223 if (likely(!has_write_lock)) 224 up_read(&mm->mmap_sem); 225 else 226 up_write(&mm->mmap_sem); 227 228 return err; 229} 230 231