fs/sysv/dir.c

   1 /*
   2  *  linux/fs/sysv/dir.c
   3  *
   4  *  minix/dir.c
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  *
   7  *  coh/dir.c
   8  *  Copyright (C) 1993  Pascal Haible, Bruno Haible
   9  *
  10  *  sysv/dir.c
  11  *  Copyright (C) 1993  Bruno Haible
  12  *
  13  *  SystemV/Coherent directory handling functions
  14  */
  15
  16 #include <linux/pagemap.h>
  17 #include <linux/highmem.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/swap.h>
  20 #include "sysv.h"
  21
  22 static int sysv_readdir(struct file *, void *, filldir_t);
  23
  24 const struct file_operations sysv_dir_operations = {
  25         .read           = generic_read_dir,
  26         .readdir        = sysv_readdir,
  27         .fsync          = sysv_sync_file,
  28 };
  29
  30 static inline void dir_put_page(struct page *page)
  31 {
  32         kunmap(page);
  33         page_cache_release(page);
  34 }
  35
  36 static inline unsigned long dir_pages(struct inode *inode)
  37 {
  38         return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  39 }
  40
  41 static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
  42 {
  43         struct address_space *mapping = page->mapping;
  44         struct inode *dir = mapping->host;
  45         int err = 0;
  46
  47         block_write_end(NULL, mapping, pos, len, len, page, NULL);
  48         if (pos+len > dir->i_size) {
  49                 i_size_write(dir, pos+len);
  50                 mark_inode_dirty(dir);
  51         }
  52         if (IS_DIRSYNC(dir))
  53                 err = write_one_page(page, 1);
  54         else
  55                 unlock_page(page);
  56         return err;
  57 }
  58
  59 static struct page * dir_get_page(struct inode *dir, unsigned long n)
  60 {
  61         struct address_space *mapping = dir->i_mapping;
  62         struct page *page = read_mapping_page(mapping, n, NULL);
  63         if (!IS_ERR(page))
  64                 kmap(page);
  65         return page;
  66 }
  67
  68 static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
  69 {
  70         unsigned long pos = filp->f_pos;
  71         struct inode *inode = filp->f_path.dentry->d_inode;
  72         struct super_block *sb = inode->i_sb;
  73         unsigned offset = pos & ~PAGE_CACHE_MASK;
  74         unsigned long n = pos >> PAGE_CACHE_SHIFT;
  75         unsigned long npages = dir_pages(inode);
  76
  77         lock_kernel();
  78
  79         pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
  80         if (pos >= inode->i_size)
  81                 goto done;
  82
  83         for ( ; n < npages; n++, offset = 0) {
  84                 char *kaddr, *limit;
  85                 struct sysv_dir_entry *de;
  86                 struct page *page = dir_get_page(inode, n);
  87
  88                 if (IS_ERR(page))
  89                         continue;
  90                 kaddr = (char *)page_address(page);
  91                 de = (struct sysv_dir_entry *)(kaddr+offset);
  92                 limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
  93                 for ( ;(char*)de <= limit; de++) {
  94                         char *name = de->name;
  95                         int over;
  96
  97                         if (!de->inode)
  98                                 continue;
  99
 100                         offset = (char *)de - kaddr;
 101
 102                         over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
 103                                         ((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
 104                                         fs16_to_cpu(SYSV_SB(sb), de->inode),
 105                                         DT_UNKNOWN);
 106                         if (over) {
 107                                 dir_put_page(page);
 108                                 goto done;
 109                         }
 110                 }
 111                 dir_put_page(page);
 112         }
 113
 114 done:
 115         filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
 116         unlock_kernel();
 117         return 0;
 118 }
 119
 120 /* compare strings: name[0..len-1] (not zero-terminated) and
 121  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 122  */
 123 static inline int namecompare(int len, int maxlen,
 124         const char * name, const char * buffer)
 125 {
 126         if (len < maxlen && buffer[len])
 127                 return 0;
 128         return !memcmp(name, buffer, len);
 129 }
 130
 131 /*
 132  *      sysv_find_entry()
 133  *
 134  * finds an entry in the specified directory with the wanted name. It
 135  * returns the cache buffer in which the entry was found, and the entry
 136  * itself (as a parameter - res_dir). It does NOT read the inode of the
 137  * entry - you'll have to do that yourself if you want to.
 138  */
 139 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
 140 {
 141         const char * name = dentry->d_name.name;
 142         int namelen = dentry->d_name.len;
 143         struct inode * dir = dentry->d_parent->d_inode;
 144         unsigned long start, n;
 145         unsigned long npages = dir_pages(dir);
 146         struct page *page = NULL;
 147         struct sysv_dir_entry *de;
 148
 149         *res_page = NULL;
 150
 151         start = SYSV_I(dir)->i_dir_start_lookup;
 152         if (start >= npages)
 153                 start = 0;
 154         n = start;
 155
 156         do {
 157                 char *kaddr;
 158                 page = dir_get_page(dir, n);
 159                 if (!IS_ERR(page)) {
 160                         kaddr = (char*)page_address(page);
 161                         de = (struct sysv_dir_entry *) kaddr;
 162                         kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 163                         for ( ; (char *) de <= kaddr ; de++) {
 164                                 if (!de->inode)
 165                                         continue;
 166                                 if (namecompare(namelen, SYSV_NAMELEN,
 167                                                         name, de->name))
 168                                         goto found;
 169                         }
 170                 }
 171                 dir_put_page(page);
 172
 173                 if (++n >= npages)
 174                         n = 0;
 175         } while (n != start);
 176
 177         return NULL;
 178
 179 found:
 180         SYSV_I(dir)->i_dir_start_lookup = n;
 181         *res_page = page;
 182         return de;
 183 }
 184
 185 int sysv_add_link(struct dentry *dentry, struct inode *inode)
 186 {
 187         struct inode *dir = dentry->d_parent->d_inode;
 188         const char * name = dentry->d_name.name;
 189         int namelen = dentry->d_name.len;
 190         struct page *page = NULL;
 191         struct sysv_dir_entry * de;
 192         unsigned long npages = dir_pages(dir);
 193         unsigned long n;
 194         char *kaddr;
 195         loff_t pos;
 196         int err;
 197
 198         /* We take care of directory expansion in the same loop */
 199         for (n = 0; n <= npages; n++) {
 200                 page = dir_get_page(dir, n);
 201                 err = PTR_ERR(page);
 202                 if (IS_ERR(page))
 203                         goto out;
 204                 kaddr = (char*)page_address(page);
 205                 de = (struct sysv_dir_entry *)kaddr;
 206                 kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 207                 while ((char *)de <= kaddr) {
 208                         if (!de->inode)
 209                                 goto got_it;
 210                         err = -EEXIST;
 211                         if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
 212                                 goto out_page;
 213                         de++;
 214                 }
 215                 dir_put_page(page);
 216         }
 217         BUG();
 218         return -EINVAL;
 219
 220 got_it:
 221         pos = page_offset(page) +
 222                         (char*)de - (char*)page_address(page);
 223         lock_page(page);
 224         err = __sysv_write_begin(NULL, page->mapping, pos, SYSV_DIRSIZE,
 225                                 AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 226         if (err)
 227                 goto out_unlock;
 228         memcpy (de->name, name, namelen);
 229         memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
 230         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 231         err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 232         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 233         mark_inode_dirty(dir);
 234 out_page:
 235         dir_put_page(page);
 236 out:
 237         return err;
 238 out_unlock:
 239         unlock_page(page);
 240         goto out_page;
 241 }
 242
 243 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
 244 {
 245         struct address_space *mapping = page->mapping;
 246         struct inode *inode = (struct inode*)mapping->host;
 247         char *kaddr = (char*)page_address(page);
 248         loff_t pos = page_offset(page) + (char *)de - kaddr;
 249         int err;
 250
 251         lock_page(page);
 252         err = __sysv_write_begin(NULL, mapping, pos, SYSV_DIRSIZE,
 253                                 AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 254         BUG_ON(err);
 255         de->inode = 0;
 256         err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 257         dir_put_page(page);
 258         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 259         mark_inode_dirty(inode);
 260         return err;
 261 }
 262
 263 int sysv_make_empty(struct inode *inode, struct inode *dir)
 264 {
 265         struct address_space *mapping = inode->i_mapping;
 266         struct page *page = grab_cache_page(mapping, 0);
 267         struct sysv_dir_entry * de;
 268         char *base;
 269         int err;
 270
 271         if (!page)
 272                 return -ENOMEM;
 273         err = __sysv_write_begin(NULL, mapping, 0, 2 * SYSV_DIRSIZE,
 274                                 AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 275         if (err) {
 276                 unlock_page(page);
 277                 goto fail;
 278         }
 279         kmap(page);
 280
 281         base = (char*)page_address(page);
 282         memset(base, 0, PAGE_CACHE_SIZE);
 283
 284         de = (struct sysv_dir_entry *) base;
 285         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 286         strcpy(de->name,".");
 287         de++;
 288         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
 289         strcpy(de->name,"..");
 290
 291         kunmap(page);
 292         err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
 293 fail:
 294         page_cache_release(page);
 295         return err;
 296 }
 297
 298 /*
 299  * routine to check that the specified directory is empty (for rmdir)
 300  */
 301 int sysv_empty_dir(struct inode * inode)
 302 {
 303         struct super_block *sb = inode->i_sb;
 304         struct page *page = NULL;
 305         unsigned long i, npages = dir_pages(inode);
 306
 307         for (i = 0; i < npages; i++) {
 308                 char *kaddr;
 309                 struct sysv_dir_entry * de;
 310                 page = dir_get_page(inode, i);
 311
 312                 if (IS_ERR(page))
 313                         continue;
 314
 315                 kaddr = (char *)page_address(page);
 316                 de = (struct sysv_dir_entry *)kaddr;
 317                 kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
 318
 319                 for ( ;(char *)de <= kaddr; de++) {
 320                         if (!de->inode)
 321                                 continue;
 322                         /* check for . and .. */
 323                         if (de->name[0] != '.')
 324                                 goto not_empty;
 325                         if (!de->name[1]) {
 326                                 if (de->inode == cpu_to_fs16(SYSV_SB(sb),
 327                                                         inode->i_ino))
 328                                         continue;
 329                                 goto not_empty;
 330                         }
 331                         if (de->name[1] != '.' || de->name[2])
 332                                 goto not_empty;
 333                 }
 334                 dir_put_page(page);
 335         }
 336         return 1;
 337
 338 not_empty:
 339         dir_put_page(page);
 340         return 0;
 341 }
 342
 343 /* Releases the page */
 344 void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
 345         struct inode *inode)
 346 {
 347         struct address_space *mapping = page->mapping;
 348         struct inode *dir = mapping->host;
 349         loff_t pos = page_offset(page) +
 350                         (char *)de-(char*)page_address(page);
 351         int err;
 352
 353         lock_page(page);
 354         err = __sysv_write_begin(NULL, mapping, pos, SYSV_DIRSIZE,
 355                                 AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 356         BUG_ON(err);
 357         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 358         err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 359         dir_put_page(page);
 360         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 361         mark_inode_dirty(dir);
 362 }
 363
 364 struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
 365 {
 366         struct page *page = dir_get_page(dir, 0);
 367         struct sysv_dir_entry *de = NULL;
 368
 369         if (!IS_ERR(page)) {
 370                 de = (struct sysv_dir_entry*) page_address(page) + 1;
 371                 *p = page;
 372         }
 373         return de;
 374 }
 375
 376 ino_t sysv_inode_by_name(struct dentry *dentry)
 377 {
 378         struct page *page;
 379         struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
 380         ino_t res = 0;
 381
 382         if (de) {
 383                 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
 384                 dir_put_page(page);
 385         }
 386         return res;
 387 }