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 25 #include <asm/uaccess.h> 26 #include "internal.h" 27 28 static int ramfs_nommu_setattr(struct dentry *, struct iattr *); 29 30 const struct address_space_operations ramfs_aops = { 31 .readpage = simple_readpage, 32 .write_begin = simple_write_begin, 33 .write_end = simple_write_end, 34 .set_page_dirty = __set_page_dirty_no_writeback, 35 }; 36 37 const struct file_operations ramfs_file_operations = { 38 .mmap = ramfs_nommu_mmap, 39 .get_unmapped_area = ramfs_nommu_get_unmapped_area, 40 .read = do_sync_read, 41 .aio_read = generic_file_aio_read, 42 .write = do_sync_write, 43 .aio_write = generic_file_aio_write, 44 .fsync = simple_sync_file, 45 .splice_read = generic_file_splice_read, 46 .splice_write = generic_file_splice_write, 47 .llseek = generic_file_llseek, 48 }; 49 50 const struct inode_operations ramfs_file_inode_operations = { 51 .setattr = ramfs_nommu_setattr, 52 .getattr = simple_getattr, 53 }; 54 55 /*****************************************************************************/ 56 /* 57 * add a contiguous set of pages into a ramfs inode when it's truncated from 58 * size 0 on the assumption that it's going to be used for an mmap of shared 59 * memory 60 */ 61 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 62 { 63 unsigned long npages, xpages, loop, limit; 64 struct page *pages; 65 unsigned order; 66 void *data; 67 int ret; 68 69 /* make various checks */ 70 order = get_order(newsize); 71 if (unlikely(order >= MAX_ORDER)) 72 goto too_big; 73 74 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 75 if (limit != RLIM_INFINITY && newsize > limit) 76 goto fsize_exceeded; 77 78 if (newsize > inode->i_sb->s_maxbytes) 79 goto too_big; 80 81 i_size_write(inode, newsize); 82 83 /* allocate enough contiguous pages to be able to satisfy the 84 * request */ 85 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); 86 if (!pages) 87 return -ENOMEM; 88 89 /* split the high-order page into an array of single pages */ 90 xpages = 1UL << order; 91 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; 92 93 split_page(pages, order); 94 95 /* trim off any pages we don't actually require */ 96 for (loop = npages; loop < xpages; loop++) 97 __free_page(pages + loop); 98 99 /* clear the memory we allocated */ 100 newsize = PAGE_SIZE * npages; 101 data = page_address(pages); 102 memset(data, 0, newsize); 103 104 /* attach all the pages to the inode's address space */ 105 for (loop = 0; loop < npages; loop++) { 106 struct page *page = pages + loop; 107 108 ret = add_to_page_cache_lru(page, inode->i_mapping, loop, 109 GFP_KERNEL); 110 if (ret < 0) 111 goto add_error; 112 113 /* prevent the page from being discarded on memory pressure */ 114 SetPageDirty(page); 115 116 unlock_page(page); 117 } 118 119 return 0; 120 121 fsize_exceeded: 122 send_sig(SIGXFSZ, current, 0); 123 too_big: 124 return -EFBIG; 125 126 add_error: 127 while (loop < npages) 128 __free_page(pages + loop++); 129 return ret; 130 } 131 132 /*****************************************************************************/ 133 /* 134 * check that file shrinkage doesn't leave any VMAs dangling in midair 135 */ 136 static int ramfs_nommu_check_mappings(struct inode *inode, 137 size_t newsize, size_t size) 138 { 139 struct vm_area_struct *vma; 140 struct prio_tree_iter iter; 141 142 /* search for VMAs that fall within the dead zone */ 143 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, 144 newsize >> PAGE_SHIFT, 145 (size + PAGE_SIZE - 1) >> PAGE_SHIFT 146 ) { 147 /* found one - only interested if it's shared out of the page 148 * cache */ 149 if (vma->vm_flags & VM_SHARED) 150 return -ETXTBSY; /* not quite true, but near enough */ 151 } 152 153 return 0; 154 } 155 156 /*****************************************************************************/ 157 /* 158 * 159 */ 160 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 161 { 162 int ret; 163 164 /* assume a truncate from zero size is going to be for the purposes of 165 * shared mmap */ 166 if (size == 0) { 167 if (unlikely(newsize >> 32)) 168 return -EFBIG; 169 170 return ramfs_nommu_expand_for_mapping(inode, newsize); 171 } 172 173 /* check that a decrease in size doesn't cut off any shared mappings */ 174 if (newsize < size) { 175 ret = ramfs_nommu_check_mappings(inode, newsize, size); 176 if (ret < 0) 177 return ret; 178 } 179 180 ret = vmtruncate(inode, newsize); 181 182 return ret; 183 } 184 185 /*****************************************************************************/ 186 /* 187 * handle a change of attributes 188 * - we're specifically interested in a change of size 189 */ 190 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 191 { 192 struct inode *inode = dentry->d_inode; 193 unsigned int old_ia_valid = ia->ia_valid; 194 int ret = 0; 195 196 /* POSIX UID/GID verification for setting inode attributes */ 197 ret = inode_change_ok(inode, ia); 198 if (ret) 199 return ret; 200 201 /* pick out size-changing events */ 202 if (ia->ia_valid & ATTR_SIZE) { 203 loff_t size = i_size_read(inode); 204 if (ia->ia_size != size) { 205 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 206 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 207 goto out; 208 } else { 209 /* we skipped the truncate but must still update 210 * timestamps 211 */ 212 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 213 } 214 } 215 216 ret = inode_setattr(inode, ia); 217 out: 218 ia->ia_valid = old_ia_valid; 219 return ret; 220 } 221 222 /*****************************************************************************/ 223 /* 224 * try to determine where a shared mapping can be made 225 * - we require that: 226 * - the pages to be mapped must exist 227 * - the pages be physically contiguous in sequence 228 */ 229 unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 230 unsigned long addr, unsigned long len, 231 unsigned long pgoff, unsigned long flags) 232 { 233 unsigned long maxpages, lpages, nr, loop, ret; 234 struct inode *inode = file->f_path.dentry->d_inode; 235 struct page **pages = NULL, **ptr, *page; 236 loff_t isize; 237 238 if (!(flags & MAP_SHARED)) 239 return addr; 240 241 /* the mapping mustn't extend beyond the EOF */ 242 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 243 isize = i_size_read(inode); 244 245 ret = -EINVAL; 246 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 247 if (pgoff >= maxpages) 248 goto out; 249 250 if (maxpages - pgoff < lpages) 251 goto out; 252 253 /* gang-find the pages */ 254 ret = -ENOMEM; 255 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); 256 if (!pages) 257 goto out_free; 258 259 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 260 if (nr != lpages) 261 goto out_free_pages; /* leave if some pages were missing */ 262 263 /* check the pages for physical adjacency */ 264 ptr = pages; 265 page = *ptr++; 266 page++; 267 for (loop = lpages; loop > 1; loop--) 268 if (*ptr++ != page++) 269 goto out_free_pages; 270 271 /* okay - all conditions fulfilled */ 272 ret = (unsigned long) page_address(pages[0]); 273 274 out_free_pages: 275 ptr = pages; 276 for (loop = nr; loop > 0; loop--) 277 put_page(*ptr++); 278 out_free: 279 kfree(pages); 280 out: 281 return ret; 282 } 283 284 /*****************************************************************************/ 285 /* 286 * set up a mapping for shared memory segments 287 */ 288 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 289 { 290 if (!(vma->vm_flags & VM_SHARED)) 291 return -ENOSYS; 292 293 file_accessed(file); 294 vma->vm_ops = &generic_file_vm_ops; 295 return 0; 296 } 297