fs/minix/dir.c

   1 /*
   2  *  linux/fs/minix/dir.c
   3  *
   4  *  Copyright (C) 1991, 1992 Linus Torvalds
   5  *
   6  *  minix directory handling functions
   7  *
   8  *  Updated to filesystem version 3 by Daniel Aragones
   9  */
  10
  11 #include "minix.h"
  12 #include <linux/buffer_head.h>
  13 #include <linux/highmem.h>
  14 #include <linux/swap.h>
  15
  16 typedef struct minix_dir_entry minix_dirent;
  17 typedef struct minix3_dir_entry minix3_dirent;
  18
  19 static int minix_readdir(struct file *, void *, filldir_t);
  20
  21 const struct file_operations minix_dir_operations = {
  22         .llseek         = generic_file_llseek,
  23         .read           = generic_read_dir,
  24         .readdir        = minix_readdir,
  25         .fsync          = generic_file_fsync,
  26 };
  27
  28 static inline void dir_put_page(struct page *page)
  29 {
  30         kunmap(page);
  31         page_cache_release(page);
  32 }
  33
  34 /*
  35  * Return the offset into page `page_nr' of the last valid
  36  * byte in that page, plus one.
  37  */
  38 static unsigned
  39 minix_last_byte(struct inode *inode, unsigned long page_nr)
  40 {
  41         unsigned last_byte = PAGE_CACHE_SIZE;
  42
  43         if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
  44                 last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
  45         return last_byte;
  46 }
  47
  48 static inline unsigned long dir_pages(struct inode *inode)
  49 {
  50         return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  51 }
  52
  53 static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
  54 {
  55         struct address_space *mapping = page->mapping;
  56         struct inode *dir = mapping->host;
  57         int err = 0;
  58         block_write_end(NULL, mapping, pos, len, len, page, NULL);
  59
  60         if (pos+len > dir->i_size) {
  61                 i_size_write(dir, pos+len);
  62                 mark_inode_dirty(dir);
  63         }
  64         if (IS_DIRSYNC(dir))
  65                 err = write_one_page(page, 1);
  66         else
  67                 unlock_page(page);
  68         return err;
  69 }
  70
  71 static struct page * dir_get_page(struct inode *dir, unsigned long n)
  72 {
  73         struct address_space *mapping = dir->i_mapping;
  74         struct page *page = read_mapping_page(mapping, n, NULL);
  75         if (!IS_ERR(page))
  76                 kmap(page);
  77         return page;
  78 }
  79
  80 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
  81 {
  82         return (void*)((char*)de + sbi->s_dirsize);
  83 }
  84
  85 static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)
  86 {
  87         unsigned long pos = filp->f_pos;
  88         struct inode *inode = filp->f_path.dentry->d_inode;
  89         struct super_block *sb = inode->i_sb;
  90         unsigned offset = pos & ~PAGE_CACHE_MASK;
  91         unsigned long n = pos >> PAGE_CACHE_SHIFT;
  92         unsigned long npages = dir_pages(inode);
  93         struct minix_sb_info *sbi = minix_sb(sb);
  94         unsigned chunk_size = sbi->s_dirsize;
  95         char *name;
  96         __u32 inumber;
  97
  98         pos = (pos + chunk_size-1) & ~(chunk_size-1);
  99         if (pos >= inode->i_size)
 100                 goto done;
 101
 102         for ( ; n < npages; n++, offset = 0) {
 103                 char *p, *kaddr, *limit;
 104                 struct page *page = dir_get_page(inode, n);
 105
 106                 if (IS_ERR(page))
 107                         continue;
 108                 kaddr = (char *)page_address(page);
 109                 p = kaddr+offset;
 110                 limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 111                 for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
 112                         if (sbi->s_version == MINIX_V3) {
 113                                 minix3_dirent *de3 = (minix3_dirent *)p;
 114                                 name = de3->name;
 115                                 inumber = de3->inode;
 116                         } else {
 117                                 minix_dirent *de = (minix_dirent *)p;
 118                                 name = de->name;
 119                                 inumber = de->inode;
 120                         }
 121                         if (inumber) {
 122                                 int over;
 123
 124                                 unsigned l = strnlen(name, sbi->s_namelen);
 125                                 offset = p - kaddr;
 126                                 over = filldir(dirent, name, l,
 127                                         (n << PAGE_CACHE_SHIFT) | offset,
 128                                         inumber, DT_UNKNOWN);
 129                                 if (over) {
 130                                         dir_put_page(page);
 131                                         goto done;
 132                                 }
 133                         }
 134                 }
 135                 dir_put_page(page);
 136         }
 137
 138 done:
 139         filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
 140         return 0;
 141 }
 142
 143 static inline int namecompare(int len, int maxlen,
 144         const char * name, const char * buffer)
 145 {
 146         if (len < maxlen && buffer[len])
 147                 return 0;
 148         return !memcmp(name, buffer, len);
 149 }
 150
 151 /*
 152  *      minix_find_entry()
 153  *
 154  * finds an entry in the specified directory with the wanted name. It
 155  * returns the cache buffer in which the entry was found, and the entry
 156  * itself (as a parameter - res_dir). It does NOT read the inode of the
 157  * entry - you'll have to do that yourself if you want to.
 158  */
 159 minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
 160 {
 161         const char * name = dentry->d_name.name;
 162         int namelen = dentry->d_name.len;
 163         struct inode * dir = dentry->d_parent->d_inode;
 164         struct super_block * sb = dir->i_sb;
 165         struct minix_sb_info * sbi = minix_sb(sb);
 166         unsigned long n;
 167         unsigned long npages = dir_pages(dir);
 168         struct page *page = NULL;
 169         char *p;
 170
 171         char *namx;
 172         __u32 inumber;
 173         *res_page = NULL;
 174
 175         for (n = 0; n < npages; n++) {
 176                 char *kaddr, *limit;
 177
 178                 page = dir_get_page(dir, n);
 179                 if (IS_ERR(page))
 180                         continue;
 181
 182                 kaddr = (char*)page_address(page);
 183                 limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
 184                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 185                         if (sbi->s_version == MINIX_V3) {
 186                                 minix3_dirent *de3 = (minix3_dirent *)p;
 187                                 namx = de3->name;
 188                                 inumber = de3->inode;
 189                         } else {
 190                                 minix_dirent *de = (minix_dirent *)p;
 191                                 namx = de->name;
 192                                 inumber = de->inode;
 193                         }
 194                         if (!inumber)
 195                                 continue;
 196                         if (namecompare(namelen, sbi->s_namelen, name, namx))
 197                                 goto found;
 198                 }
 199                 dir_put_page(page);
 200         }
 201         return NULL;
 202
 203 found:
 204         *res_page = page;
 205         return (minix_dirent *)p;
 206 }
 207
 208 int minix_add_link(struct dentry *dentry, struct inode *inode)
 209 {
 210         struct inode *dir = dentry->d_parent->d_inode;
 211         const char * name = dentry->d_name.name;
 212         int namelen = dentry->d_name.len;
 213         struct super_block * sb = dir->i_sb;
 214         struct minix_sb_info * sbi = minix_sb(sb);
 215         struct page *page = NULL;
 216         unsigned long npages = dir_pages(dir);
 217         unsigned long n;
 218         char *kaddr, *p;
 219         minix_dirent *de;
 220         minix3_dirent *de3;
 221         loff_t pos;
 222         int err;
 223         char *namx = NULL;
 224         __u32 inumber;
 225
 226         /*
 227          * We take care of directory expansion in the same loop
 228          * This code plays outside i_size, so it locks the page
 229          * to protect that region.
 230          */
 231         for (n = 0; n <= npages; n++) {
 232                 char *limit, *dir_end;
 233
 234                 page = dir_get_page(dir, n);
 235                 err = PTR_ERR(page);
 236                 if (IS_ERR(page))
 237                         goto out;
 238                 lock_page(page);
 239                 kaddr = (char*)page_address(page);
 240                 dir_end = kaddr + minix_last_byte(dir, n);
 241                 limit = kaddr + PAGE_CACHE_SIZE - sbi->s_dirsize;
 242                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 243                         de = (minix_dirent *)p;
 244                         de3 = (minix3_dirent *)p;
 245                         if (sbi->s_version == MINIX_V3) {
 246                                 namx = de3->name;
 247                                 inumber = de3->inode;
 248                         } else {
 249                                 namx = de->name;
 250                                 inumber = de->inode;
 251                         }
 252                         if (p == dir_end) {
 253                                 /* We hit i_size */
 254                                 if (sbi->s_version == MINIX_V3)
 255                                         de3->inode = 0;
 256                                 else
 257                                         de->inode = 0;
 258                                 goto got_it;
 259                         }
 260                         if (!inumber)
 261                                 goto got_it;
 262                         err = -EEXIST;
 263                         if (namecompare(namelen, sbi->s_namelen, name, namx))
 264                                 goto out_unlock;
 265                 }
 266                 unlock_page(page);
 267                 dir_put_page(page);
 268         }
 269         BUG();
 270         return -EINVAL;
 271
 272 got_it:
 273         pos = page_offset(page) + p - (char *)page_address(page);
 274         err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
 275         if (err)
 276                 goto out_unlock;
 277         memcpy (namx, name, namelen);
 278         if (sbi->s_version == MINIX_V3) {
 279                 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
 280                 de3->inode = inode->i_ino;
 281         } else {
 282                 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
 283                 de->inode = inode->i_ino;
 284         }
 285         err = dir_commit_chunk(page, pos, sbi->s_dirsize);
 286         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 287         mark_inode_dirty(dir);
 288 out_put:
 289         dir_put_page(page);
 290 out:
 291         return err;
 292 out_unlock:
 293         unlock_page(page);
 294         goto out_put;
 295 }
 296
 297 int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 298 {
 299         struct inode *inode = page->mapping->host;
 300         char *kaddr = page_address(page);
 301         loff_t pos = page_offset(page) + (char*)de - kaddr;
 302         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 303         unsigned len = sbi->s_dirsize;
 304         int err;
 305
 306         lock_page(page);
 307         err = minix_prepare_chunk(page, pos, len);
 308         if (err == 0) {
 309                 if (sbi->s_version == MINIX_V3)
 310                         ((minix3_dirent *) de)->inode = 0;
 311                 else
 312                         de->inode = 0;
 313                 err = dir_commit_chunk(page, pos, len);
 314         } else {
 315                 unlock_page(page);
 316         }
 317         dir_put_page(page);
 318         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 319         mark_inode_dirty(inode);
 320         return err;
 321 }
 322
 323 int minix_make_empty(struct inode *inode, struct inode *dir)
 324 {
 325         struct page *page = grab_cache_page(inode->i_mapping, 0);
 326         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 327         char *kaddr;
 328         int err;
 329
 330         if (!page)
 331                 return -ENOMEM;
 332         err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize);
 333         if (err) {
 334                 unlock_page(page);
 335                 goto fail;
 336         }
 337
 338         kaddr = kmap_atomic(page, KM_USER0);
 339         memset(kaddr, 0, PAGE_CACHE_SIZE);
 340
 341         if (sbi->s_version == MINIX_V3) {
 342                 minix3_dirent *de3 = (minix3_dirent *)kaddr;
 343
 344                 de3->inode = inode->i_ino;
 345                 strcpy(de3->name, ".");
 346                 de3 = minix_next_entry(de3, sbi);
 347                 de3->inode = dir->i_ino;
 348                 strcpy(de3->name, "..");
 349         } else {
 350                 minix_dirent *de = (minix_dirent *)kaddr;
 351
 352                 de->inode = inode->i_ino;
 353                 strcpy(de->name, ".");
 354                 de = minix_next_entry(de, sbi);
 355                 de->inode = dir->i_ino;
 356                 strcpy(de->name, "..");
 357         }
 358         kunmap_atomic(kaddr, KM_USER0);
 359
 360         err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
 361 fail:
 362         page_cache_release(page);
 363         return err;
 364 }
 365
 366 /*
 367  * routine to check that the specified directory is empty (for rmdir)
 368  */
 369 int minix_empty_dir(struct inode * inode)
 370 {
 371         struct page *page = NULL;
 372         unsigned long i, npages = dir_pages(inode);
 373         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 374         char *name;
 375         __u32 inumber;
 376
 377         for (i = 0; i < npages; i++) {
 378                 char *p, *kaddr, *limit;
 379
 380                 page = dir_get_page(inode, i);
 381                 if (IS_ERR(page))
 382                         continue;
 383
 384                 kaddr = (char *)page_address(page);
 385                 limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
 386                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 387                         if (sbi->s_version == MINIX_V3) {
 388                                 minix3_dirent *de3 = (minix3_dirent *)p;
 389                                 name = de3->name;
 390                                 inumber = de3->inode;
 391                         } else {
 392                                 minix_dirent *de = (minix_dirent *)p;
 393                                 name = de->name;
 394                                 inumber = de->inode;
 395                         }
 396
 397                         if (inumber != 0) {
 398                                 /* check for . and .. */
 399                                 if (name[0] != '.')
 400                                         goto not_empty;
 401                                 if (!name[1]) {
 402                                         if (inumber != inode->i_ino)
 403                                                 goto not_empty;
 404                                 } else if (name[1] != '.')
 405                                         goto not_empty;
 406                                 else if (name[2])
 407                                         goto not_empty;
 408                         }
 409                 }
 410                 dir_put_page(page);
 411         }
 412         return 1;
 413
 414 not_empty:
 415         dir_put_page(page);
 416         return 0;
 417 }
 418
 419 /* Releases the page */
 420 void minix_set_link(struct minix_dir_entry *de, struct page *page,
 421         struct inode *inode)
 422 {
 423         struct inode *dir = page->mapping->host;
 424         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 425         loff_t pos = page_offset(page) +
 426                         (char *)de-(char*)page_address(page);
 427         int err;
 428
 429         lock_page(page);
 430
 431         err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
 432         if (err == 0) {
 433                 if (sbi->s_version == MINIX_V3)
 434                         ((minix3_dirent *) de)->inode = inode->i_ino;
 435                 else
 436                         de->inode = inode->i_ino;
 437                 err = dir_commit_chunk(page, pos, sbi->s_dirsize);
 438         } else {
 439                 unlock_page(page);
 440         }
 441         dir_put_page(page);
 442         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 443         mark_inode_dirty(dir);
 444 }
 445
 446 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
 447 {
 448         struct page *page = dir_get_page(dir, 0);
 449         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 450         struct minix_dir_entry *de = NULL;
 451
 452         if (!IS_ERR(page)) {
 453                 de = minix_next_entry(page_address(page), sbi);
 454                 *p = page;
 455         }
 456         return de;
 457 }
 458
 459 ino_t minix_inode_by_name(struct dentry *dentry)
 460 {
 461         struct page *page;
 462         struct minix_dir_entry *de = minix_find_entry(dentry, &page);
 463         ino_t res = 0;
 464
 465         if (de) {
 466                 struct address_space *mapping = page->mapping;
 467                 struct inode *inode = mapping->host;
 468                 struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 469
 470                 if (sbi->s_version == MINIX_V3)
 471                         res = ((minix3_dirent *) de)->inode;
 472                 else
 473                         res = de->inode;
 474                 dir_put_page(page);
 475         }
 476         return res;
 477 }