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