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/quotaops.h> 22 #include <linux/pagevec.h> 23 #include <linux/mman.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 .llseek = generic_file_llseek, 47 }; 48 49 const struct inode_operations ramfs_file_inode_operations = { 50 .setattr = ramfs_nommu_setattr, 51 .getattr = simple_getattr, 52 }; 53 54 /*****************************************************************************/ 55 /* 56 * add a contiguous set of pages into a ramfs inode when it's truncated from 57 * size 0 on the assumption that it's going to be used for an mmap of shared 58 * memory 59 */ 60 static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 61 { 62 struct pagevec lru_pvec; 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 pagevec_init(&lru_pvec, 0); 106 for (loop = 0; loop < npages; loop++) { 107 struct page *page = pages + loop; 108 109 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL); 110 if (ret < 0) 111 goto add_error; 112 113 if (!pagevec_add(&lru_pvec, page)) 114 __pagevec_lru_add(&lru_pvec); 115 116 unlock_page(page); 117 } 118 119 pagevec_lru_add(&lru_pvec); 120 return 0; 121 122 fsize_exceeded: 123 send_sig(SIGXFSZ, current, 0); 124 too_big: 125 return -EFBIG; 126 127 add_error: 128 page_cache_release(pages + loop); 129 for (loop++; loop < npages; loop++) 130 __free_page(pages + loop); 131 return ret; 132 } 133 134 /*****************************************************************************/ 135 /* 136 * check that file shrinkage doesn't leave any VMAs dangling in midair 137 */ 138 static int ramfs_nommu_check_mappings(struct inode *inode, 139 size_t newsize, size_t size) 140 { 141 struct vm_area_struct *vma; 142 struct prio_tree_iter iter; 143 144 /* search for VMAs that fall within the dead zone */ 145 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, 146 newsize >> PAGE_SHIFT, 147 (size + PAGE_SIZE - 1) >> PAGE_SHIFT 148 ) { 149 /* found one - only interested if it's shared out of the page 150 * cache */ 151 if (vma->vm_flags & VM_SHARED) 152 return -ETXTBSY; /* not quite true, but near enough */ 153 } 154 155 return 0; 156 } 157 158 /*****************************************************************************/ 159 /* 160 * 161 */ 162 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 163 { 164 int ret; 165 166 /* assume a truncate from zero size is going to be for the purposes of 167 * shared mmap */ 168 if (size == 0) { 169 if (unlikely(newsize >> 32)) 170 return -EFBIG; 171 172 return ramfs_nommu_expand_for_mapping(inode, newsize); 173 } 174 175 /* check that a decrease in size doesn't cut off any shared mappings */ 176 if (newsize < size) { 177 ret = ramfs_nommu_check_mappings(inode, newsize, size); 178 if (ret < 0) 179 return ret; 180 } 181 182 ret = vmtruncate(inode, newsize); 183 184 return ret; 185 } 186 187 /*****************************************************************************/ 188 /* 189 * handle a change of attributes 190 * - we're specifically interested in a change of size 191 */ 192 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 193 { 194 struct inode *inode = dentry->d_inode; 195 unsigned int old_ia_valid = ia->ia_valid; 196 int ret = 0; 197 198 /* POSIX UID/GID verification for setting inode attributes */ 199 ret = inode_change_ok(inode, ia); 200 if (ret) 201 return ret; 202 203 /* by providing our own setattr() method, we skip this quotaism */ 204 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) || 205 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid)) 206 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0; 207 208 /* pick out size-changing events */ 209 if (ia->ia_valid & ATTR_SIZE) { 210 loff_t size = i_size_read(inode); 211 if (ia->ia_size != size) { 212 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 213 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 214 goto out; 215 } else { 216 /* we skipped the truncate but must still update 217 * timestamps 218 */ 219 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 220 } 221 } 222 223 ret = inode_setattr(inode, ia); 224 out: 225 ia->ia_valid = old_ia_valid; 226 return ret; 227 } 228 229 /*****************************************************************************/ 230 /* 231 * try to determine where a shared mapping can be made 232 * - we require that: 233 * - the pages to be mapped must exist 234 * - the pages be physically contiguous in sequence 235 */ 236 unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 237 unsigned long addr, unsigned long len, 238 unsigned long pgoff, unsigned long flags) 239 { 240 unsigned long maxpages, lpages, nr, loop, ret; 241 struct inode *inode = file->f_path.dentry->d_inode; 242 struct page **pages = NULL, **ptr, *page; 243 loff_t isize; 244 245 if (!(flags & MAP_SHARED)) 246 return addr; 247 248 /* the mapping mustn't extend beyond the EOF */ 249 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 250 isize = i_size_read(inode); 251 252 ret = -EINVAL; 253 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 254 if (pgoff >= maxpages) 255 goto out; 256 257 if (maxpages - pgoff < lpages) 258 goto out; 259 260 /* gang-find the pages */ 261 ret = -ENOMEM; 262 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); 263 if (!pages) 264 goto out; 265 266 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 267 if (nr != lpages) 268 goto out; /* leave if some pages were missing */ 269 270 /* check the pages for physical adjacency */ 271 ptr = pages; 272 page = *ptr++; 273 page++; 274 for (loop = lpages; loop > 1; loop--) 275 if (*ptr++ != page++) 276 goto out; 277 278 /* okay - all conditions fulfilled */ 279 ret = (unsigned long) page_address(pages[0]); 280 281 out: 282 if (pages) { 283 ptr = pages; 284 for (loop = lpages; loop > 0; loop--) 285 put_page(*ptr++); 286 kfree(pages); 287 } 288 289 return ret; 290 } 291 292 /*****************************************************************************/ 293 /* 294 * set up a mapping for shared memory segments 295 */ 296 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 297 { 298 if (!(vma->vm_flags & VM_SHARED)) 299 return -ENOSYS; 300 301 file_accessed(file); 302 vma->vm_ops = &generic_file_vm_ops; 303 return 0; 304 } 305