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