1 /* file-nommu.c: no-MMU version of ramfs 2 * 3 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/fs.h> 14 #include <linux/mm.h> 15 #include <linux/pagemap.h> 16 #include <linux/highmem.h> 17 #include <linux/init.h> 18 #include <linux/string.h> 19 #include <linux/backing-dev.h> 20 #include <linux/ramfs.h> 21 #include <linux/pagevec.h> 22 #include <linux/mman.h> 23 #include <linux/sched.h> 24 #include <linux/slab.h> 25 26 #include <asm/uaccess.h> 27 #include "internal.h" 28 29 static int ramfs_nommu_setattr(struct dentry *, struct iattr *); 30 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 31 unsigned long addr, 32 unsigned long len, 33 unsigned long pgoff, 34 unsigned long flags); 35 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma); 36 37 static unsigned ramfs_mmap_capabilities(struct file *file) 38 { 39 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ | 40 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC; 41 } 42 43 const struct file_operations ramfs_file_operations = { 44 .mmap_capabilities = ramfs_mmap_capabilities, 45 .mmap = ramfs_nommu_mmap, 46 .get_unmapped_area = ramfs_nommu_get_unmapped_area, 47 .read = new_sync_read, 48 .read_iter = generic_file_read_iter, 49 .write = new_sync_write, 50 .write_iter = generic_file_write_iter, 51 .fsync = noop_fsync, 52 .splice_read = generic_file_splice_read, 53 .splice_write = iter_file_splice_write, 54 .llseek = generic_file_llseek, 55 }; 56 57 const struct inode_operations ramfs_file_inode_operations = { 58 .setattr = ramfs_nommu_setattr, 59 .getattr = simple_getattr, 60 }; 61 62 /*****************************************************************************/ 63 /* 64 * add a contiguous set of pages into a ramfs inode when it's truncated from 65 * size 0 on the assumption that it's going to be used for an mmap of shared 66 * memory 67 */ 68 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 69 { 70 unsigned long npages, xpages, loop; 71 struct page *pages; 72 unsigned order; 73 void *data; 74 int ret; 75 76 /* make various checks */ 77 order = get_order(newsize); 78 if (unlikely(order >= MAX_ORDER)) 79 return -EFBIG; 80 81 ret = inode_newsize_ok(inode, newsize); 82 if (ret) 83 return ret; 84 85 i_size_write(inode, newsize); 86 87 /* allocate enough contiguous pages to be able to satisfy the 88 * request */ 89 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); 90 if (!pages) 91 return -ENOMEM; 92 93 /* split the high-order page into an array of single pages */ 94 xpages = 1UL << order; 95 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; 96 97 split_page(pages, order); 98 99 /* trim off any pages we don't actually require */ 100 for (loop = npages; loop < xpages; loop++) 101 __free_page(pages + loop); 102 103 /* clear the memory we allocated */ 104 newsize = PAGE_SIZE * npages; 105 data = page_address(pages); 106 memset(data, 0, newsize); 107 108 /* attach all the pages to the inode's address space */ 109 for (loop = 0; loop < npages; loop++) { 110 struct page *page = pages + loop; 111 112 ret = add_to_page_cache_lru(page, inode->i_mapping, loop, 113 GFP_KERNEL); 114 if (ret < 0) 115 goto add_error; 116 117 /* prevent the page from being discarded on memory pressure */ 118 SetPageDirty(page); 119 SetPageUptodate(page); 120 121 unlock_page(page); 122 put_page(page); 123 } 124 125 return 0; 126 127 add_error: 128 while (loop < npages) 129 __free_page(pages + loop++); 130 return ret; 131 } 132 133 /*****************************************************************************/ 134 /* 135 * 136 */ 137 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 138 { 139 int ret; 140 141 /* assume a truncate from zero size is going to be for the purposes of 142 * shared mmap */ 143 if (size == 0) { 144 if (unlikely(newsize >> 32)) 145 return -EFBIG; 146 147 return ramfs_nommu_expand_for_mapping(inode, newsize); 148 } 149 150 /* check that a decrease in size doesn't cut off any shared mappings */ 151 if (newsize < size) { 152 ret = nommu_shrink_inode_mappings(inode, size, newsize); 153 if (ret < 0) 154 return ret; 155 } 156 157 truncate_setsize(inode, newsize); 158 return 0; 159 } 160 161 /*****************************************************************************/ 162 /* 163 * handle a change of attributes 164 * - we're specifically interested in a change of size 165 */ 166 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 167 { 168 struct inode *inode = dentry->d_inode; 169 unsigned int old_ia_valid = ia->ia_valid; 170 int ret = 0; 171 172 /* POSIX UID/GID verification for setting inode attributes */ 173 ret = inode_change_ok(inode, ia); 174 if (ret) 175 return ret; 176 177 /* pick out size-changing events */ 178 if (ia->ia_valid & ATTR_SIZE) { 179 loff_t size = inode->i_size; 180 181 if (ia->ia_size != size) { 182 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 183 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 184 goto out; 185 } else { 186 /* we skipped the truncate but must still update 187 * timestamps 188 */ 189 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 190 } 191 } 192 193 setattr_copy(inode, ia); 194 out: 195 ia->ia_valid = old_ia_valid; 196 return ret; 197 } 198 199 /*****************************************************************************/ 200 /* 201 * try to determine where a shared mapping can be made 202 * - we require that: 203 * - the pages to be mapped must exist 204 * - the pages be physically contiguous in sequence 205 */ 206 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 207 unsigned long addr, unsigned long len, 208 unsigned long pgoff, unsigned long flags) 209 { 210 unsigned long maxpages, lpages, nr, loop, ret; 211 struct inode *inode = file_inode(file); 212 struct page **pages = NULL, **ptr, *page; 213 loff_t isize; 214 215 if (!(flags & MAP_SHARED)) 216 return addr; 217 218 /* the mapping mustn't extend beyond the EOF */ 219 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 220 isize = i_size_read(inode); 221 222 ret = -EINVAL; 223 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 224 if (pgoff >= maxpages) 225 goto out; 226 227 if (maxpages - pgoff < lpages) 228 goto out; 229 230 /* gang-find the pages */ 231 ret = -ENOMEM; 232 pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL); 233 if (!pages) 234 goto out_free; 235 236 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 237 if (nr != lpages) 238 goto out_free_pages; /* leave if some pages were missing */ 239 240 /* check the pages for physical adjacency */ 241 ptr = pages; 242 page = *ptr++; 243 page++; 244 for (loop = lpages; loop > 1; loop--) 245 if (*ptr++ != page++) 246 goto out_free_pages; 247 248 /* okay - all conditions fulfilled */ 249 ret = (unsigned long) page_address(pages[0]); 250 251 out_free_pages: 252 ptr = pages; 253 for (loop = nr; loop > 0; loop--) 254 put_page(*ptr++); 255 out_free: 256 kfree(pages); 257 out: 258 return ret; 259 } 260 261 /*****************************************************************************/ 262 /* 263 * set up a mapping for shared memory segments 264 */ 265 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 266 { 267 if (!(vma->vm_flags & VM_SHARED)) 268 return -ENOSYS; 269 270 file_accessed(file); 271 vma->vm_ops = &generic_file_vm_ops; 272 return 0; 273 } 274