1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/minix/dir.c 4 * 5 * Copyright (C) 1991, 1992 Linus Torvalds 6 * 7 * minix directory handling functions 8 * 9 * Updated to filesystem version 3 by Daniel Aragones 10 */ 11 12 #include "minix.h" 13 #include <linux/buffer_head.h> 14 #include <linux/highmem.h> 15 #include <linux/swap.h> 16 17 typedef struct minix_dir_entry minix_dirent; 18 typedef struct minix3_dir_entry minix3_dirent; 19 20 static int minix_readdir(struct file *, struct dir_context *); 21 22 const struct file_operations minix_dir_operations = { 23 .llseek = generic_file_llseek, 24 .read = generic_read_dir, 25 .iterate_shared = minix_readdir, 26 .fsync = generic_file_fsync, 27 }; 28 29 static inline void dir_put_page(struct page *page) 30 { 31 kunmap(page); 32 put_page(page); 33 } 34 35 /* 36 * Return the offset into page `page_nr' of the last valid 37 * byte in that page, plus one. 38 */ 39 static unsigned 40 minix_last_byte(struct inode *inode, unsigned long page_nr) 41 { 42 unsigned last_byte = PAGE_SIZE; 43 44 if (page_nr == (inode->i_size >> PAGE_SHIFT)) 45 last_byte = inode->i_size & (PAGE_SIZE - 1); 46 return last_byte; 47 } 48 49 static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len) 50 { 51 struct address_space *mapping = page->mapping; 52 struct inode *dir = mapping->host; 53 54 block_write_end(NULL, mapping, pos, len, len, page, NULL); 55 56 if (pos+len > dir->i_size) { 57 i_size_write(dir, pos+len); 58 mark_inode_dirty(dir); 59 } 60 unlock_page(page); 61 } 62 63 static int minix_handle_dirsync(struct inode *dir) 64 { 65 int err; 66 67 err = filemap_write_and_wait(dir->i_mapping); 68 if (!err) 69 err = sync_inode_metadata(dir, 1); 70 return err; 71 } 72 73 static struct page * dir_get_page(struct inode *dir, unsigned long n) 74 { 75 struct address_space *mapping = dir->i_mapping; 76 struct page *page = read_mapping_page(mapping, n, NULL); 77 if (!IS_ERR(page)) 78 kmap(page); 79 return page; 80 } 81 82 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi) 83 { 84 return (void*)((char*)de + sbi->s_dirsize); 85 } 86 87 static int minix_readdir(struct file *file, struct dir_context *ctx) 88 { 89 struct inode *inode = file_inode(file); 90 struct super_block *sb = inode->i_sb; 91 struct minix_sb_info *sbi = minix_sb(sb); 92 unsigned chunk_size = sbi->s_dirsize; 93 unsigned long npages = dir_pages(inode); 94 unsigned long pos = ctx->pos; 95 unsigned offset; 96 unsigned long n; 97 98 ctx->pos = pos = ALIGN(pos, chunk_size); 99 if (pos >= inode->i_size) 100 return 0; 101 102 offset = pos & ~PAGE_MASK; 103 n = pos >> PAGE_SHIFT; 104 105 for ( ; n < npages; n++, offset = 0) { 106 char *p, *kaddr, *limit; 107 struct page *page = dir_get_page(inode, n); 108 109 if (IS_ERR(page)) 110 continue; 111 kaddr = (char *)page_address(page); 112 p = kaddr+offset; 113 limit = kaddr + minix_last_byte(inode, n) - chunk_size; 114 for ( ; p <= limit; p = minix_next_entry(p, sbi)) { 115 const char *name; 116 __u32 inumber; 117 if (sbi->s_version == MINIX_V3) { 118 minix3_dirent *de3 = (minix3_dirent *)p; 119 name = de3->name; 120 inumber = de3->inode; 121 } else { 122 minix_dirent *de = (minix_dirent *)p; 123 name = de->name; 124 inumber = de->inode; 125 } 126 if (inumber) { 127 unsigned l = strnlen(name, sbi->s_namelen); 128 if (!dir_emit(ctx, name, l, 129 inumber, DT_UNKNOWN)) { 130 dir_put_page(page); 131 return 0; 132 } 133 } 134 ctx->pos += chunk_size; 135 } 136 dir_put_page(page); 137 } 138 return 0; 139 } 140 141 static inline int namecompare(int len, int maxlen, 142 const char * name, const char * buffer) 143 { 144 if (len < maxlen && buffer[len]) 145 return 0; 146 return !memcmp(name, buffer, len); 147 } 148 149 /* 150 * minix_find_entry() 151 * 152 * finds an entry in the specified directory with the wanted name. It 153 * returns the cache buffer in which the entry was found, and the entry 154 * itself (as a parameter - res_dir). It does NOT read the inode of the 155 * entry - you'll have to do that yourself if you want to. 156 */ 157 minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page) 158 { 159 const char * name = dentry->d_name.name; 160 int namelen = dentry->d_name.len; 161 struct inode * dir = d_inode(dentry->d_parent); 162 struct super_block * sb = dir->i_sb; 163 struct minix_sb_info * sbi = minix_sb(sb); 164 unsigned long n; 165 unsigned long npages = dir_pages(dir); 166 struct page *page = NULL; 167 char *p; 168 169 char *namx; 170 __u32 inumber; 171 *res_page = NULL; 172 173 for (n = 0; n < npages; n++) { 174 char *kaddr, *limit; 175 176 page = dir_get_page(dir, n); 177 if (IS_ERR(page)) 178 continue; 179 180 kaddr = (char*)page_address(page); 181 limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize; 182 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) { 183 if (sbi->s_version == MINIX_V3) { 184 minix3_dirent *de3 = (minix3_dirent *)p; 185 namx = de3->name; 186 inumber = de3->inode; 187 } else { 188 minix_dirent *de = (minix_dirent *)p; 189 namx = de->name; 190 inumber = de->inode; 191 } 192 if (!inumber) 193 continue; 194 if (namecompare(namelen, sbi->s_namelen, name, namx)) 195 goto found; 196 } 197 dir_put_page(page); 198 } 199 return NULL; 200 201 found: 202 *res_page = page; 203 return (minix_dirent *)p; 204 } 205 206 int minix_add_link(struct dentry *dentry, struct inode *inode) 207 { 208 struct inode *dir = d_inode(dentry->d_parent); 209 const char * name = dentry->d_name.name; 210 int namelen = dentry->d_name.len; 211 struct super_block * sb = dir->i_sb; 212 struct minix_sb_info * sbi = minix_sb(sb); 213 struct page *page = NULL; 214 unsigned long npages = dir_pages(dir); 215 unsigned long n; 216 char *kaddr, *p; 217 minix_dirent *de; 218 minix3_dirent *de3; 219 loff_t pos; 220 int err; 221 char *namx = NULL; 222 __u32 inumber; 223 224 /* 225 * We take care of directory expansion in the same loop 226 * This code plays outside i_size, so it locks the page 227 * to protect that region. 228 */ 229 for (n = 0; n <= npages; n++) { 230 char *limit, *dir_end; 231 232 page = dir_get_page(dir, n); 233 err = PTR_ERR(page); 234 if (IS_ERR(page)) 235 goto out; 236 lock_page(page); 237 kaddr = (char*)page_address(page); 238 dir_end = kaddr + minix_last_byte(dir, n); 239 limit = kaddr + PAGE_SIZE - sbi->s_dirsize; 240 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) { 241 de = (minix_dirent *)p; 242 de3 = (minix3_dirent *)p; 243 if (sbi->s_version == MINIX_V3) { 244 namx = de3->name; 245 inumber = de3->inode; 246 } else { 247 namx = de->name; 248 inumber = de->inode; 249 } 250 if (p == dir_end) { 251 /* We hit i_size */ 252 if (sbi->s_version == MINIX_V3) 253 de3->inode = 0; 254 else 255 de->inode = 0; 256 goto got_it; 257 } 258 if (!inumber) 259 goto got_it; 260 err = -EEXIST; 261 if (namecompare(namelen, sbi->s_namelen, name, namx)) 262 goto out_unlock; 263 } 264 unlock_page(page); 265 dir_put_page(page); 266 } 267 BUG(); 268 return -EINVAL; 269 270 got_it: 271 pos = page_offset(page) + p - (char *)page_address(page); 272 err = minix_prepare_chunk(page, pos, sbi->s_dirsize); 273 if (err) 274 goto out_unlock; 275 memcpy (namx, name, namelen); 276 if (sbi->s_version == MINIX_V3) { 277 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4); 278 de3->inode = inode->i_ino; 279 } else { 280 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2); 281 de->inode = inode->i_ino; 282 } 283 dir_commit_chunk(page, pos, sbi->s_dirsize); 284 dir->i_mtime = inode_set_ctime_current(dir); 285 mark_inode_dirty(dir); 286 err = minix_handle_dirsync(dir); 287 out_put: 288 dir_put_page(page); 289 out: 290 return err; 291 out_unlock: 292 unlock_page(page); 293 goto out_put; 294 } 295 296 int minix_delete_entry(struct minix_dir_entry *de, struct page *page) 297 { 298 struct inode *inode = page->mapping->host; 299 char *kaddr = page_address(page); 300 loff_t pos = page_offset(page) + (char*)de - kaddr; 301 struct minix_sb_info *sbi = minix_sb(inode->i_sb); 302 unsigned len = sbi->s_dirsize; 303 int err; 304 305 lock_page(page); 306 err = minix_prepare_chunk(page, pos, len); 307 if (err) { 308 unlock_page(page); 309 return err; 310 } 311 if (sbi->s_version == MINIX_V3) 312 ((minix3_dirent *)de)->inode = 0; 313 else 314 de->inode = 0; 315 dir_commit_chunk(page, pos, len); 316 inode->i_mtime = inode_set_ctime_current(inode); 317 mark_inode_dirty(inode); 318 return minix_handle_dirsync(inode); 319 } 320 321 int minix_make_empty(struct inode *inode, struct inode *dir) 322 { 323 struct page *page = grab_cache_page(inode->i_mapping, 0); 324 struct minix_sb_info *sbi = minix_sb(inode->i_sb); 325 char *kaddr; 326 int err; 327 328 if (!page) 329 return -ENOMEM; 330 err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize); 331 if (err) { 332 unlock_page(page); 333 goto fail; 334 } 335 336 kaddr = kmap_atomic(page); 337 memset(kaddr, 0, PAGE_SIZE); 338 339 if (sbi->s_version == MINIX_V3) { 340 minix3_dirent *de3 = (minix3_dirent *)kaddr; 341 342 de3->inode = inode->i_ino; 343 strcpy(de3->name, "."); 344 de3 = minix_next_entry(de3, sbi); 345 de3->inode = dir->i_ino; 346 strcpy(de3->name, ".."); 347 } else { 348 minix_dirent *de = (minix_dirent *)kaddr; 349 350 de->inode = inode->i_ino; 351 strcpy(de->name, "."); 352 de = minix_next_entry(de, sbi); 353 de->inode = dir->i_ino; 354 strcpy(de->name, ".."); 355 } 356 kunmap_atomic(kaddr); 357 358 dir_commit_chunk(page, 0, 2 * sbi->s_dirsize); 359 err = minix_handle_dirsync(inode); 360 fail: 361 put_page(page); 362 return err; 363 } 364 365 /* 366 * routine to check that the specified directory is empty (for rmdir) 367 */ 368 int minix_empty_dir(struct inode * inode) 369 { 370 struct page *page = NULL; 371 unsigned long i, npages = dir_pages(inode); 372 struct minix_sb_info *sbi = minix_sb(inode->i_sb); 373 char *name; 374 __u32 inumber; 375 376 for (i = 0; i < npages; i++) { 377 char *p, *kaddr, *limit; 378 379 page = dir_get_page(inode, i); 380 if (IS_ERR(page)) 381 continue; 382 383 kaddr = (char *)page_address(page); 384 limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize; 385 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) { 386 if (sbi->s_version == MINIX_V3) { 387 minix3_dirent *de3 = (minix3_dirent *)p; 388 name = de3->name; 389 inumber = de3->inode; 390 } else { 391 minix_dirent *de = (minix_dirent *)p; 392 name = de->name; 393 inumber = de->inode; 394 } 395 396 if (inumber != 0) { 397 /* check for . and .. */ 398 if (name[0] != '.') 399 goto not_empty; 400 if (!name[1]) { 401 if (inumber != inode->i_ino) 402 goto not_empty; 403 } else if (name[1] != '.') 404 goto not_empty; 405 else if (name[2]) 406 goto not_empty; 407 } 408 } 409 dir_put_page(page); 410 } 411 return 1; 412 413 not_empty: 414 dir_put_page(page); 415 return 0; 416 } 417 418 /* Releases the page */ 419 int minix_set_link(struct minix_dir_entry *de, struct page *page, 420 struct inode *inode) 421 { 422 struct inode *dir = page->mapping->host; 423 struct minix_sb_info *sbi = minix_sb(dir->i_sb); 424 loff_t pos = page_offset(page) + 425 (char *)de-(char*)page_address(page); 426 int err; 427 428 lock_page(page); 429 err = minix_prepare_chunk(page, pos, sbi->s_dirsize); 430 if (err) { 431 unlock_page(page); 432 return err; 433 } 434 if (sbi->s_version == MINIX_V3) 435 ((minix3_dirent *)de)->inode = inode->i_ino; 436 else 437 de->inode = inode->i_ino; 438 dir_commit_chunk(page, pos, sbi->s_dirsize); 439 dir->i_mtime = inode_set_ctime_current(dir); 440 mark_inode_dirty(dir); 441 return minix_handle_dirsync(dir); 442 } 443 444 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p) 445 { 446 struct page *page = dir_get_page(dir, 0); 447 struct minix_sb_info *sbi = minix_sb(dir->i_sb); 448 struct minix_dir_entry *de = NULL; 449 450 if (!IS_ERR(page)) { 451 de = minix_next_entry(page_address(page), sbi); 452 *p = page; 453 } 454 return de; 455 } 456 457 ino_t minix_inode_by_name(struct dentry *dentry) 458 { 459 struct page *page; 460 struct minix_dir_entry *de = minix_find_entry(dentry, &page); 461 ino_t res = 0; 462 463 if (de) { 464 struct address_space *mapping = page->mapping; 465 struct inode *inode = mapping->host; 466 struct minix_sb_info *sbi = minix_sb(inode->i_sb); 467 468 if (sbi->s_version == MINIX_V3) 469 res = ((minix3_dirent *) de)->inode; 470 else 471 res = de->inode; 472 dir_put_page(page); 473 } 474 return res; 475 } 476