1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/sysv/dir.c 4 * 5 * minix/dir.c 6 * Copyright (C) 1991, 1992 Linus Torvalds 7 * 8 * coh/dir.c 9 * Copyright (C) 1993 Pascal Haible, Bruno Haible 10 * 11 * sysv/dir.c 12 * Copyright (C) 1993 Bruno Haible 13 * 14 * SystemV/Coherent directory handling functions 15 */ 16 17 #include <linux/pagemap.h> 18 #include <linux/highmem.h> 19 #include <linux/swap.h> 20 #include "sysv.h" 21 22 static int sysv_readdir(struct file *, struct dir_context *); 23 24 const struct file_operations sysv_dir_operations = { 25 .llseek = generic_file_llseek, 26 .read = generic_read_dir, 27 .iterate_shared = sysv_readdir, 28 .fsync = generic_file_fsync, 29 }; 30 31 static void dir_commit_chunk(struct folio *folio, loff_t pos, unsigned len) 32 { 33 struct address_space *mapping = folio->mapping; 34 struct inode *dir = mapping->host; 35 36 block_write_end(NULL, mapping, pos, len, len, folio, NULL); 37 if (pos+len > dir->i_size) { 38 i_size_write(dir, pos+len); 39 mark_inode_dirty(dir); 40 } 41 folio_unlock(folio); 42 } 43 44 static int sysv_handle_dirsync(struct inode *dir) 45 { 46 int err; 47 48 err = filemap_write_and_wait(dir->i_mapping); 49 if (!err) 50 err = sync_inode_metadata(dir, 1); 51 return err; 52 } 53 54 /* 55 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the 56 * rules documented in mm/highmem.rst. 57 * 58 * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_folio() 59 * and must be treated accordingly for nesting purposes. 60 */ 61 static void *dir_get_folio(struct inode *dir, unsigned long n, 62 struct folio **foliop) 63 { 64 struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL); 65 66 if (IS_ERR(folio)) 67 return ERR_CAST(folio); 68 *foliop = folio; 69 return kmap_local_folio(folio, 0); 70 } 71 72 static int sysv_readdir(struct file *file, struct dir_context *ctx) 73 { 74 unsigned long pos = ctx->pos; 75 struct inode *inode = file_inode(file); 76 struct super_block *sb = inode->i_sb; 77 unsigned long npages = dir_pages(inode); 78 unsigned offset; 79 unsigned long n; 80 81 ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1); 82 if (pos >= inode->i_size) 83 return 0; 84 85 offset = pos & ~PAGE_MASK; 86 n = pos >> PAGE_SHIFT; 87 88 for ( ; n < npages; n++, offset = 0) { 89 char *kaddr, *limit; 90 struct sysv_dir_entry *de; 91 struct folio *folio; 92 93 kaddr = dir_get_folio(inode, n, &folio); 94 if (IS_ERR(kaddr)) 95 continue; 96 de = (struct sysv_dir_entry *)(kaddr+offset); 97 limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE; 98 for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) { 99 char *name = de->name; 100 101 if (!de->inode) 102 continue; 103 104 if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN), 105 fs16_to_cpu(SYSV_SB(sb), de->inode), 106 DT_UNKNOWN)) { 107 folio_release_kmap(folio, kaddr); 108 return 0; 109 } 110 } 111 folio_release_kmap(folio, kaddr); 112 } 113 return 0; 114 } 115 116 /* compare strings: name[0..len-1] (not zero-terminated) and 117 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1]) 118 */ 119 static inline int namecompare(int len, int maxlen, 120 const char * name, const char * buffer) 121 { 122 if (len < maxlen && buffer[len]) 123 return 0; 124 return !memcmp(name, buffer, len); 125 } 126 127 /* 128 * sysv_find_entry() 129 * 130 * finds an entry in the specified directory with the wanted name. 131 * It does NOT read the inode of the 132 * entry - you'll have to do that yourself if you want to. 133 * 134 * On Success folio_release_kmap() should be called on *foliop. 135 * 136 * sysv_find_entry() acts as a call to dir_get_folio() and must be treated 137 * accordingly for nesting purposes. 138 */ 139 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct folio **foliop) 140 { 141 const char * name = dentry->d_name.name; 142 int namelen = dentry->d_name.len; 143 struct inode * dir = d_inode(dentry->d_parent); 144 unsigned long start, n; 145 unsigned long npages = dir_pages(dir); 146 struct sysv_dir_entry *de; 147 148 start = SYSV_I(dir)->i_dir_start_lookup; 149 if (start >= npages) 150 start = 0; 151 n = start; 152 153 do { 154 char *kaddr = dir_get_folio(dir, n, foliop); 155 156 if (!IS_ERR(kaddr)) { 157 de = (struct sysv_dir_entry *)kaddr; 158 kaddr += folio_size(*foliop) - SYSV_DIRSIZE; 159 for ( ; (char *) de <= kaddr ; de++) { 160 if (!de->inode) 161 continue; 162 if (namecompare(namelen, SYSV_NAMELEN, 163 name, de->name)) 164 goto found; 165 } 166 folio_release_kmap(*foliop, kaddr); 167 } 168 169 if (++n >= npages) 170 n = 0; 171 } while (n != start); 172 173 return NULL; 174 175 found: 176 SYSV_I(dir)->i_dir_start_lookup = n; 177 return de; 178 } 179 180 int sysv_add_link(struct dentry *dentry, struct inode *inode) 181 { 182 struct inode *dir = d_inode(dentry->d_parent); 183 const char * name = dentry->d_name.name; 184 int namelen = dentry->d_name.len; 185 struct folio *folio = NULL; 186 struct sysv_dir_entry * de; 187 unsigned long npages = dir_pages(dir); 188 unsigned long n; 189 char *kaddr; 190 loff_t pos; 191 int err; 192 193 /* We take care of directory expansion in the same loop */ 194 for (n = 0; n <= npages; n++) { 195 kaddr = dir_get_folio(dir, n, &folio); 196 if (IS_ERR(kaddr)) 197 return PTR_ERR(kaddr); 198 de = (struct sysv_dir_entry *)kaddr; 199 kaddr += PAGE_SIZE - SYSV_DIRSIZE; 200 while ((char *)de <= kaddr) { 201 if (!de->inode) 202 goto got_it; 203 err = -EEXIST; 204 if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 205 goto out_folio; 206 de++; 207 } 208 folio_release_kmap(folio, kaddr); 209 } 210 BUG(); 211 return -EINVAL; 212 213 got_it: 214 pos = folio_pos(folio) + offset_in_folio(folio, de); 215 folio_lock(folio); 216 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE); 217 if (err) 218 goto out_unlock; 219 memcpy (de->name, name, namelen); 220 memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2); 221 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 222 dir_commit_chunk(folio, pos, SYSV_DIRSIZE); 223 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 224 mark_inode_dirty(dir); 225 err = sysv_handle_dirsync(dir); 226 out_folio: 227 folio_release_kmap(folio, kaddr); 228 return err; 229 out_unlock: 230 folio_unlock(folio); 231 goto out_folio; 232 } 233 234 int sysv_delete_entry(struct sysv_dir_entry *de, struct folio *folio) 235 { 236 struct inode *inode = folio->mapping->host; 237 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de); 238 int err; 239 240 folio_lock(folio); 241 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE); 242 if (err) { 243 folio_unlock(folio); 244 return err; 245 } 246 de->inode = 0; 247 dir_commit_chunk(folio, pos, SYSV_DIRSIZE); 248 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode)); 249 mark_inode_dirty(inode); 250 return sysv_handle_dirsync(inode); 251 } 252 253 int sysv_make_empty(struct inode *inode, struct inode *dir) 254 { 255 struct folio *folio = filemap_grab_folio(inode->i_mapping, 0); 256 struct sysv_dir_entry * de; 257 char *kaddr; 258 int err; 259 260 if (IS_ERR(folio)) 261 return PTR_ERR(folio); 262 err = sysv_prepare_chunk(folio, 0, 2 * SYSV_DIRSIZE); 263 if (err) { 264 folio_unlock(folio); 265 goto fail; 266 } 267 kaddr = kmap_local_folio(folio, 0); 268 memset(kaddr, 0, folio_size(folio)); 269 270 de = (struct sysv_dir_entry *)kaddr; 271 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 272 strcpy(de->name,"."); 273 de++; 274 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino); 275 strcpy(de->name,".."); 276 277 kunmap_local(kaddr); 278 dir_commit_chunk(folio, 0, 2 * SYSV_DIRSIZE); 279 err = sysv_handle_dirsync(inode); 280 fail: 281 folio_put(folio); 282 return err; 283 } 284 285 /* 286 * routine to check that the specified directory is empty (for rmdir) 287 */ 288 int sysv_empty_dir(struct inode * inode) 289 { 290 struct super_block *sb = inode->i_sb; 291 struct folio *folio = NULL; 292 unsigned long i, npages = dir_pages(inode); 293 char *kaddr; 294 295 for (i = 0; i < npages; i++) { 296 struct sysv_dir_entry *de; 297 298 kaddr = dir_get_folio(inode, i, &folio); 299 if (IS_ERR(kaddr)) 300 continue; 301 302 de = (struct sysv_dir_entry *)kaddr; 303 kaddr += folio_size(folio) - SYSV_DIRSIZE; 304 305 for ( ;(char *)de <= kaddr; de++) { 306 if (!de->inode) 307 continue; 308 /* check for . and .. */ 309 if (de->name[0] != '.') 310 goto not_empty; 311 if (!de->name[1]) { 312 if (de->inode == cpu_to_fs16(SYSV_SB(sb), 313 inode->i_ino)) 314 continue; 315 goto not_empty; 316 } 317 if (de->name[1] != '.' || de->name[2]) 318 goto not_empty; 319 } 320 folio_release_kmap(folio, kaddr); 321 } 322 return 1; 323 324 not_empty: 325 folio_release_kmap(folio, kaddr); 326 return 0; 327 } 328 329 /* Releases the page */ 330 int sysv_set_link(struct sysv_dir_entry *de, struct folio *folio, 331 struct inode *inode) 332 { 333 struct inode *dir = folio->mapping->host; 334 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de); 335 int err; 336 337 folio_lock(folio); 338 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE); 339 if (err) { 340 folio_unlock(folio); 341 return err; 342 } 343 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 344 dir_commit_chunk(folio, pos, SYSV_DIRSIZE); 345 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 346 mark_inode_dirty(dir); 347 return sysv_handle_dirsync(inode); 348 } 349 350 /* 351 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the 352 * rules documented in mm/highmem.rst. 353 * 354 * sysv_dotdot() acts as a call to dir_get_folio() and must be treated 355 * accordingly for nesting purposes. 356 */ 357 struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct folio **foliop) 358 { 359 struct sysv_dir_entry *de = dir_get_folio(dir, 0, foliop); 360 361 if (IS_ERR(de)) 362 return NULL; 363 /* ".." is the second directory entry */ 364 return de + 1; 365 } 366 367 ino_t sysv_inode_by_name(struct dentry *dentry) 368 { 369 struct folio *folio; 370 struct sysv_dir_entry *de = sysv_find_entry (dentry, &folio); 371 ino_t res = 0; 372 373 if (de) { 374 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode); 375 folio_release_kmap(folio, de); 376 } 377 return res; 378 } 379