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 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_cache_page(mapping, n,
  64                                 (filler_t*)mapping->a_ops->readpage, NULL);
  65         if (!IS_ERR(page)) {
  66                 wait_on_page_locked(page);
  67                 kmap(page);
  68                 if (!PageUptodate(page))
  69                         goto fail;
  70         }
  71         return page;
  72
  73 fail:
  74         dir_put_page(page);
  75         return ERR_PTR(-EIO);
  76 }
  77
  78 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
  79 {
  80         return (void*)((char*)de + sbi->s_dirsize);
  81 }
  82
  83 static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)
  84 {
  85         unsigned long pos = filp->f_pos;
  86         struct inode *inode = filp->f_dentry->d_inode;
  87         struct super_block *sb = inode->i_sb;
  88         unsigned offset = pos & ~PAGE_CACHE_MASK;
  89         unsigned long n = pos >> PAGE_CACHE_SHIFT;
  90         unsigned long npages = dir_pages(inode);
  91         struct minix_sb_info *sbi = minix_sb(sb);
  92         unsigned chunk_size = sbi->s_dirsize;
  93
  94         lock_kernel();
  95
  96         pos = (pos + chunk_size-1) & ~(chunk_size-1);
  97         if (pos >= inode->i_size)
  98                 goto done;
  99
 100         for ( ; n < npages; n++, offset = 0) {
 101                 char *p, *kaddr, *limit;
 102                 struct page *page = dir_get_page(inode, n);
 103
 104                 if (IS_ERR(page))
 105                         continue;
 106                 kaddr = (char *)page_address(page);
 107                 p = kaddr+offset;
 108                 limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 109                 for ( ; p <= limit ; p = minix_next_entry(p, sbi)) {
 110                         minix_dirent *de = (minix_dirent *)p;
 111                         if (de->inode) {
 112                                 int over;
 113                                 unsigned l = strnlen(de->name,sbi->s_namelen);
 114
 115                                 offset = p - kaddr;
 116                                 over = filldir(dirent, de->name, l,
 117                                                 (n<<PAGE_CACHE_SHIFT) | offset,
 118                                                 de->inode, DT_UNKNOWN);
 119                                 if (over) {
 120                                         dir_put_page(page);
 121                                         goto done;
 122                                 }
 123                         }
 124                 }
 125                 dir_put_page(page);
 126         }
 127
 128 done:
 129         filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
 130         unlock_kernel();
 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 = dentry->d_parent->d_inode;
 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         struct minix_dir_entry *de;
 161
 162         *res_page = NULL;
 163
 164         for (n = 0; n < npages; n++) {
 165                 char *kaddr;
 166                 page = dir_get_page(dir, n);
 167                 if (IS_ERR(page))
 168                         continue;
 169
 170                 kaddr = (char*)page_address(page);
 171                 de = (struct minix_dir_entry *) kaddr;
 172                 kaddr += minix_last_byte(dir, n) - sbi->s_dirsize;
 173                 for ( ; (char *) de <= kaddr ; de = minix_next_entry(de,sbi)) {
 174                         if (!de->inode)
 175                                 continue;
 176                         if (namecompare(namelen,sbi->s_namelen,name,de->name))
 177                                 goto found;
 178                 }
 179                 dir_put_page(page);
 180         }
 181         return NULL;
 182
 183 found:
 184         *res_page = page;
 185         return de;
 186 }
 187
 188 int minix_add_link(struct dentry *dentry, struct inode *inode)
 189 {
 190         struct inode *dir = dentry->d_parent->d_inode;
 191         const char * name = dentry->d_name.name;
 192         int namelen = dentry->d_name.len;
 193         struct super_block * sb = dir->i_sb;
 194         struct minix_sb_info * sbi = minix_sb(sb);
 195         struct page *page = NULL;
 196         struct minix_dir_entry * de;
 197         unsigned long npages = dir_pages(dir);
 198         unsigned long n;
 199         char *kaddr;
 200         unsigned from, to;
 201         int err;
 202
 203         /*
 204          * We take care of directory expansion in the same loop
 205          * This code plays outside i_size, so it locks the page
 206          * to protect that region.
 207          */
 208         for (n = 0; n <= npages; n++) {
 209                 char *dir_end;
 210
 211                 page = dir_get_page(dir, n);
 212                 err = PTR_ERR(page);
 213                 if (IS_ERR(page))
 214                         goto out;
 215                 lock_page(page);
 216                 kaddr = (char*)page_address(page);
 217                 dir_end = kaddr + minix_last_byte(dir, n);
 218                 de = (minix_dirent *)kaddr;
 219                 kaddr += PAGE_CACHE_SIZE - sbi->s_dirsize;
 220                 while ((char *)de <= kaddr) {
 221                         if ((char *)de == dir_end) {
 222                                 /* We hit i_size */
 223                                 de->inode = 0;
 224                                 goto got_it;
 225                         }
 226                         if (!de->inode)
 227                                 goto got_it;
 228                         err = -EEXIST;
 229                         if (namecompare(namelen,sbi->s_namelen,name,de->name))
 230                                 goto out_unlock;
 231                         de = minix_next_entry(de, sbi);
 232                 }
 233                 unlock_page(page);
 234                 dir_put_page(page);
 235         }
 236         BUG();
 237         return -EINVAL;
 238
 239 got_it:
 240         from = (char*)de - (char*)page_address(page);
 241         to = from + sbi->s_dirsize;
 242         err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
 243         if (err)
 244                 goto out_unlock;
 245         memcpy (de->name, name, namelen);
 246         memset (de->name + namelen, 0, sbi->s_dirsize - namelen - 2);
 247         de->inode = inode->i_ino;
 248         err = dir_commit_chunk(page, from, to);
 249         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 250         mark_inode_dirty(dir);
 251 out_put:
 252         dir_put_page(page);
 253 out:
 254         return err;
 255 out_unlock:
 256         unlock_page(page);
 257         goto out_put;
 258 }
 259
 260 int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 261 {
 262         struct address_space *mapping = page->mapping;
 263         struct inode *inode = (struct inode*)mapping->host;
 264         char *kaddr = page_address(page);
 265         unsigned from = (char*)de - kaddr;
 266         unsigned to = from + minix_sb(inode->i_sb)->s_dirsize;
 267         int err;
 268
 269         lock_page(page);
 270         err = mapping->a_ops->prepare_write(NULL, page, from, to);
 271         if (err == 0) {
 272                 de->inode = 0;
 273                 err = dir_commit_chunk(page, from, to);
 274         } else {
 275                 unlock_page(page);
 276         }
 277         dir_put_page(page);
 278         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 279         mark_inode_dirty(inode);
 280         return err;
 281 }
 282
 283 int minix_make_empty(struct inode *inode, struct inode *dir)
 284 {
 285         struct address_space *mapping = inode->i_mapping;
 286         struct page *page = grab_cache_page(mapping, 0);
 287         struct minix_sb_info * sbi = minix_sb(inode->i_sb);
 288         struct minix_dir_entry * de;
 289         char *kaddr;
 290         int err;
 291
 292         if (!page)
 293                 return -ENOMEM;
 294         err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * sbi->s_dirsize);
 295         if (err) {
 296                 unlock_page(page);
 297                 goto fail;
 298         }
 299
 300         kaddr = kmap_atomic(page, KM_USER0);
 301         memset(kaddr, 0, PAGE_CACHE_SIZE);
 302
 303         de = (struct minix_dir_entry *)kaddr;
 304         de->inode = inode->i_ino;
 305         strcpy(de->name,".");
 306         de = minix_next_entry(de, sbi);
 307         de->inode = dir->i_ino;
 308         strcpy(de->name,"..");
 309         kunmap_atomic(kaddr, KM_USER0);
 310
 311         err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
 312 fail:
 313         page_cache_release(page);
 314         return err;
 315 }
 316
 317 /*
 318  * routine to check that the specified directory is empty (for rmdir)
 319  */
 320 int minix_empty_dir(struct inode * inode)
 321 {
 322         struct page *page = NULL;
 323         unsigned long i, npages = dir_pages(inode);
 324         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 325
 326         for (i = 0; i < npages; i++) {
 327                 char *kaddr;
 328                 minix_dirent * de;
 329                 page = dir_get_page(inode, i);
 330
 331                 if (IS_ERR(page))
 332                         continue;
 333
 334                 kaddr = (char *)page_address(page);
 335                 de = (minix_dirent *)kaddr;
 336                 kaddr += minix_last_byte(inode, i) - sbi->s_dirsize;
 337
 338                 while ((char *)de <= kaddr) {
 339                         if (de->inode != 0) {
 340                                 /* check for . and .. */
 341                                 if (de->name[0] != '.')
 342                                         goto not_empty;
 343                                 if (!de->name[1]) {
 344                                         if (de->inode != inode->i_ino)
 345                                                 goto not_empty;
 346                                 } else if (de->name[1] != '.')
 347                                         goto not_empty;
 348                                 else if (de->name[2])
 349                                         goto not_empty;
 350                         }
 351                         de = minix_next_entry(de, sbi);
 352                 }
 353                 dir_put_page(page);
 354         }
 355         return 1;
 356
 357 not_empty:
 358         dir_put_page(page);
 359         return 0;
 360 }
 361
 362 /* Releases the page */
 363 void minix_set_link(struct minix_dir_entry *de, struct page *page,
 364         struct inode *inode)
 365 {
 366         struct inode *dir = (struct inode*)page->mapping->host;
 367         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 368         unsigned from = (char *)de-(char*)page_address(page);
 369         unsigned to = from + sbi->s_dirsize;
 370         int err;
 371
 372         lock_page(page);
 373         err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
 374         if (err == 0) {
 375                 de->inode = inode->i_ino;
 376                 err = dir_commit_chunk(page, from, to);
 377         } else {
 378                 unlock_page(page);
 379         }
 380         dir_put_page(page);
 381         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 382         mark_inode_dirty(dir);
 383 }
 384
 385 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
 386 {
 387         struct page *page = dir_get_page(dir, 0);
 388         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 389         struct minix_dir_entry *de = NULL;
 390
 391         if (!IS_ERR(page)) {
 392                 de = minix_next_entry(page_address(page), sbi);
 393                 *p = page;
 394         }
 395         return de;
 396 }
 397
 398 ino_t minix_inode_by_name(struct dentry *dentry)
 399 {
 400         struct page *page;
 401         struct minix_dir_entry *de = minix_find_entry(dentry, &page);
 402         ino_t res = 0;
 403
 404         if (de) {
 405                 res = de->inode;
 406                 dir_put_page(page);
 407         }
 408         return res;
 409 }