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 inline void dir_put_page(struct page *page) 32 { 33 kunmap(page); 34 put_page(page); 35 } 36 37 static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len) 38 { 39 struct address_space *mapping = page->mapping; 40 struct inode *dir = mapping->host; 41 int err = 0; 42 43 block_write_end(NULL, mapping, pos, len, len, page, NULL); 44 if (pos+len > dir->i_size) { 45 i_size_write(dir, pos+len); 46 mark_inode_dirty(dir); 47 } 48 if (IS_DIRSYNC(dir)) 49 err = write_one_page(page); 50 else 51 unlock_page(page); 52 return err; 53 } 54 55 static struct page * dir_get_page(struct inode *dir, unsigned long n) 56 { 57 struct address_space *mapping = dir->i_mapping; 58 struct page *page = read_mapping_page(mapping, n, NULL); 59 if (!IS_ERR(page)) 60 kmap(page); 61 return page; 62 } 63 64 static int sysv_readdir(struct file *file, struct dir_context *ctx) 65 { 66 unsigned long pos = ctx->pos; 67 struct inode *inode = file_inode(file); 68 struct super_block *sb = inode->i_sb; 69 unsigned long npages = dir_pages(inode); 70 unsigned offset; 71 unsigned long n; 72 73 ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1); 74 if (pos >= inode->i_size) 75 return 0; 76 77 offset = pos & ~PAGE_MASK; 78 n = pos >> PAGE_SHIFT; 79 80 for ( ; n < npages; n++, offset = 0) { 81 char *kaddr, *limit; 82 struct sysv_dir_entry *de; 83 struct page *page = dir_get_page(inode, n); 84 85 if (IS_ERR(page)) 86 continue; 87 kaddr = (char *)page_address(page); 88 de = (struct sysv_dir_entry *)(kaddr+offset); 89 limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE; 90 for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) { 91 char *name = de->name; 92 93 if (!de->inode) 94 continue; 95 96 if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN), 97 fs16_to_cpu(SYSV_SB(sb), de->inode), 98 DT_UNKNOWN)) { 99 dir_put_page(page); 100 return 0; 101 } 102 } 103 dir_put_page(page); 104 } 105 return 0; 106 } 107 108 /* compare strings: name[0..len-1] (not zero-terminated) and 109 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1]) 110 */ 111 static inline int namecompare(int len, int maxlen, 112 const char * name, const char * buffer) 113 { 114 if (len < maxlen && buffer[len]) 115 return 0; 116 return !memcmp(name, buffer, len); 117 } 118 119 /* 120 * sysv_find_entry() 121 * 122 * finds an entry in the specified directory with the wanted name. It 123 * returns the cache buffer in which the entry was found, and the entry 124 * itself (as a parameter - res_dir). It does NOT read the inode of the 125 * entry - you'll have to do that yourself if you want to. 126 */ 127 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page) 128 { 129 const char * name = dentry->d_name.name; 130 int namelen = dentry->d_name.len; 131 struct inode * dir = d_inode(dentry->d_parent); 132 unsigned long start, n; 133 unsigned long npages = dir_pages(dir); 134 struct page *page = NULL; 135 struct sysv_dir_entry *de; 136 137 *res_page = NULL; 138 139 start = SYSV_I(dir)->i_dir_start_lookup; 140 if (start >= npages) 141 start = 0; 142 n = start; 143 144 do { 145 char *kaddr; 146 page = dir_get_page(dir, n); 147 if (!IS_ERR(page)) { 148 kaddr = (char*)page_address(page); 149 de = (struct sysv_dir_entry *) kaddr; 150 kaddr += PAGE_SIZE - SYSV_DIRSIZE; 151 for ( ; (char *) de <= kaddr ; de++) { 152 if (!de->inode) 153 continue; 154 if (namecompare(namelen, SYSV_NAMELEN, 155 name, de->name)) 156 goto found; 157 } 158 dir_put_page(page); 159 } 160 161 if (++n >= npages) 162 n = 0; 163 } while (n != start); 164 165 return NULL; 166 167 found: 168 SYSV_I(dir)->i_dir_start_lookup = n; 169 *res_page = page; 170 return de; 171 } 172 173 int sysv_add_link(struct dentry *dentry, struct inode *inode) 174 { 175 struct inode *dir = d_inode(dentry->d_parent); 176 const char * name = dentry->d_name.name; 177 int namelen = dentry->d_name.len; 178 struct page *page = NULL; 179 struct sysv_dir_entry * de; 180 unsigned long npages = dir_pages(dir); 181 unsigned long n; 182 char *kaddr; 183 loff_t pos; 184 int err; 185 186 /* We take care of directory expansion in the same loop */ 187 for (n = 0; n <= npages; n++) { 188 page = dir_get_page(dir, n); 189 err = PTR_ERR(page); 190 if (IS_ERR(page)) 191 goto out; 192 kaddr = (char*)page_address(page); 193 de = (struct sysv_dir_entry *)kaddr; 194 kaddr += PAGE_SIZE - SYSV_DIRSIZE; 195 while ((char *)de <= kaddr) { 196 if (!de->inode) 197 goto got_it; 198 err = -EEXIST; 199 if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 200 goto out_page; 201 de++; 202 } 203 dir_put_page(page); 204 } 205 BUG(); 206 return -EINVAL; 207 208 got_it: 209 pos = page_offset(page) + 210 (char*)de - (char*)page_address(page); 211 lock_page(page); 212 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE); 213 if (err) 214 goto out_unlock; 215 memcpy (de->name, name, namelen); 216 memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2); 217 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 218 err = dir_commit_chunk(page, pos, SYSV_DIRSIZE); 219 dir->i_mtime = dir->i_ctime = current_time(dir); 220 mark_inode_dirty(dir); 221 out_page: 222 dir_put_page(page); 223 out: 224 return err; 225 out_unlock: 226 unlock_page(page); 227 goto out_page; 228 } 229 230 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page) 231 { 232 struct inode *inode = page->mapping->host; 233 char *kaddr = (char*)page_address(page); 234 loff_t pos = page_offset(page) + (char *)de - kaddr; 235 int err; 236 237 lock_page(page); 238 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE); 239 BUG_ON(err); 240 de->inode = 0; 241 err = dir_commit_chunk(page, pos, SYSV_DIRSIZE); 242 dir_put_page(page); 243 inode->i_ctime = inode->i_mtime = current_time(inode); 244 mark_inode_dirty(inode); 245 return err; 246 } 247 248 int sysv_make_empty(struct inode *inode, struct inode *dir) 249 { 250 struct page *page = grab_cache_page(inode->i_mapping, 0); 251 struct sysv_dir_entry * de; 252 char *base; 253 int err; 254 255 if (!page) 256 return -ENOMEM; 257 err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE); 258 if (err) { 259 unlock_page(page); 260 goto fail; 261 } 262 kmap(page); 263 264 base = (char*)page_address(page); 265 memset(base, 0, PAGE_SIZE); 266 267 de = (struct sysv_dir_entry *) base; 268 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 269 strcpy(de->name,"."); 270 de++; 271 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino); 272 strcpy(de->name,".."); 273 274 kunmap(page); 275 err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE); 276 fail: 277 put_page(page); 278 return err; 279 } 280 281 /* 282 * routine to check that the specified directory is empty (for rmdir) 283 */ 284 int sysv_empty_dir(struct inode * inode) 285 { 286 struct super_block *sb = inode->i_sb; 287 struct page *page = NULL; 288 unsigned long i, npages = dir_pages(inode); 289 290 for (i = 0; i < npages; i++) { 291 char *kaddr; 292 struct sysv_dir_entry * de; 293 page = dir_get_page(inode, i); 294 295 if (IS_ERR(page)) 296 continue; 297 298 kaddr = (char *)page_address(page); 299 de = (struct sysv_dir_entry *)kaddr; 300 kaddr += PAGE_SIZE-SYSV_DIRSIZE; 301 302 for ( ;(char *)de <= kaddr; de++) { 303 if (!de->inode) 304 continue; 305 /* check for . and .. */ 306 if (de->name[0] != '.') 307 goto not_empty; 308 if (!de->name[1]) { 309 if (de->inode == cpu_to_fs16(SYSV_SB(sb), 310 inode->i_ino)) 311 continue; 312 goto not_empty; 313 } 314 if (de->name[1] != '.' || de->name[2]) 315 goto not_empty; 316 } 317 dir_put_page(page); 318 } 319 return 1; 320 321 not_empty: 322 dir_put_page(page); 323 return 0; 324 } 325 326 /* Releases the page */ 327 void sysv_set_link(struct sysv_dir_entry *de, struct page *page, 328 struct inode *inode) 329 { 330 struct inode *dir = page->mapping->host; 331 loff_t pos = page_offset(page) + 332 (char *)de-(char*)page_address(page); 333 int err; 334 335 lock_page(page); 336 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE); 337 BUG_ON(err); 338 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino); 339 err = dir_commit_chunk(page, pos, SYSV_DIRSIZE); 340 dir_put_page(page); 341 dir->i_mtime = dir->i_ctime = current_time(dir); 342 mark_inode_dirty(dir); 343 } 344 345 struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p) 346 { 347 struct page *page = dir_get_page(dir, 0); 348 struct sysv_dir_entry *de = NULL; 349 350 if (!IS_ERR(page)) { 351 de = (struct sysv_dir_entry*) page_address(page) + 1; 352 *p = page; 353 } 354 return de; 355 } 356 357 ino_t sysv_inode_by_name(struct dentry *dentry) 358 { 359 struct page *page; 360 struct sysv_dir_entry *de = sysv_find_entry (dentry, &page); 361 ino_t res = 0; 362 363 if (de) { 364 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode); 365 dir_put_page(page); 366 } 367 return res; 368 } 369