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