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 "sysv.h"
  20
  21 static int sysv_readdir(struct file *, void *, filldir_t);
  22
  23 const struct file_operations sysv_dir_operations = {
  24         .read           = generic_read_dir,
  25         .readdir        = sysv_readdir,
  26         .fsync          = sysv_sync_file,
  27 };
  28
  29 static inline void dir_put_page(struct page *page)
  30 {
  31         kunmap(page);
  32         page_cache_release(page);
  33 }
  34
  35 static inline unsigned long dir_pages(struct inode *inode)
  36 {
  37         return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  38 }
  39
  40 static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)
  41 {
  42         struct inode *dir = (struct inode *)page->mapping->host;
  43         int err = 0;
  44
  45         page->mapping->a_ops->commit_write(NULL, page, from, to);
  46         if (IS_DIRSYNC(dir))
  47                 err = write_one_page(page, 1);
  48         else
  49                 unlock_page(page);
  50         return err;
  51 }
  52
  53 static struct page * dir_get_page(struct inode *dir, unsigned long n)
  54 {
  55         struct address_space *mapping = dir->i_mapping;
  56         struct page *page = read_mapping_page(mapping, n, NULL);
  57         if (!IS_ERR(page)) {
  58                 wait_on_page_locked(page);
  59                 kmap(page);
  60                 if (!PageUptodate(page))
  61                         goto fail;
  62         }
  63         return page;
  64
  65 fail:
  66         dir_put_page(page);
  67         return ERR_PTR(-EIO);
  68 }
  69
  70 static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
  71 {
  72         unsigned long pos = filp->f_pos;
  73         struct inode *inode = filp->f_path.dentry->d_inode;
  74         struct super_block *sb = inode->i_sb;
  75         unsigned offset = pos & ~PAGE_CACHE_MASK;
  76         unsigned long n = pos >> PAGE_CACHE_SHIFT;
  77         unsigned long npages = dir_pages(inode);
  78
  79         lock_kernel();
  80
  81         pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
  82         if (pos >= inode->i_size)
  83                 goto done;
  84
  85         for ( ; n < npages; n++, offset = 0) {
  86                 char *kaddr, *limit;
  87                 struct sysv_dir_entry *de;
  88                 struct page *page = dir_get_page(inode, n);
  89
  90                 if (IS_ERR(page))
  91                         continue;
  92                 kaddr = (char *)page_address(page);
  93                 de = (struct sysv_dir_entry *)(kaddr+offset);
  94                 limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
  95                 for ( ;(char*)de <= limit; de++) {
  96                         char *name = de->name;
  97                         int over;
  98
  99                         if (!de->inode)
 100                                 continue;
 101
 102                         offset = (char *)de - kaddr;
 103
 104                         over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
 105                                         ((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
 106                                         fs16_to_cpu(SYSV_SB(sb), de->inode),
 107                                         DT_UNKNOWN);
 108                         if (over) {
 109                                 dir_put_page(page);
 110                                 goto done;
 111                         }
 112                 }
 113                 dir_put_page(page);
 114         }
 115
 116 done:
 117         filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
 118         unlock_kernel();
 119         return 0;
 120 }
 121
 122 /* compare strings: name[0..len-1] (not zero-terminated) and
 123  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 124  */
 125 static inline int namecompare(int len, int maxlen,
 126         const char * name, const char * buffer)
 127 {
 128         if (len < maxlen && buffer[len])
 129                 return 0;
 130         return !memcmp(name, buffer, len);
 131 }
 132
 133 /*
 134  *      sysv_find_entry()
 135  *
 136  * finds an entry in the specified directory with the wanted name. It
 137  * returns the cache buffer in which the entry was found, and the entry
 138  * itself (as a parameter - res_dir). It does NOT read the inode of the
 139  * entry - you'll have to do that yourself if you want to.
 140  */
 141 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
 142 {
 143         const char * name = dentry->d_name.name;
 144         int namelen = dentry->d_name.len;
 145         struct inode * dir = dentry->d_parent->d_inode;
 146         unsigned long start, n;
 147         unsigned long npages = dir_pages(dir);
 148         struct page *page = NULL;
 149         struct sysv_dir_entry *de;
 150
 151         *res_page = NULL;
 152
 153         start = SYSV_I(dir)->i_dir_start_lookup;
 154         if (start >= npages)
 155                 start = 0;
 156         n = start;
 157
 158         do {
 159                 char *kaddr;
 160                 page = dir_get_page(dir, n);
 161                 if (!IS_ERR(page)) {
 162                         kaddr = (char*)page_address(page);
 163                         de = (struct sysv_dir_entry *) kaddr;
 164                         kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 165                         for ( ; (char *) de <= kaddr ; de++) {
 166                                 if (!de->inode)
 167                                         continue;
 168                                 if (namecompare(namelen, SYSV_NAMELEN,
 169                                                         name, de->name))
 170                                         goto found;
 171                         }
 172                 }
 173                 dir_put_page(page);
 174
 175                 if (++n >= npages)
 176                         n = 0;
 177         } while (n != start);
 178
 179         return NULL;
 180
 181 found:
 182         SYSV_I(dir)->i_dir_start_lookup = n;
 183         *res_page = page;
 184         return de;
 185 }
 186
 187 int sysv_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 page *page = NULL;
 193         struct sysv_dir_entry * de;
 194         unsigned long npages = dir_pages(dir);
 195         unsigned long n;
 196         char *kaddr;
 197         unsigned from, to;
 198         int err;
 199
 200         /* We take care of directory expansion in the same loop */
 201         for (n = 0; n <= npages; n++) {
 202                 page = dir_get_page(dir, n);
 203                 err = PTR_ERR(page);
 204                 if (IS_ERR(page))
 205                         goto out;
 206                 kaddr = (char*)page_address(page);
 207                 de = (struct sysv_dir_entry *)kaddr;
 208                 kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 209                 while ((char *)de <= kaddr) {
 210                         if (!de->inode)
 211                                 goto got_it;
 212                         err = -EEXIST;
 213                         if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
 214                                 goto out_page;
 215                         de++;
 216                 }
 217                 dir_put_page(page);
 218         }
 219         BUG();
 220         return -EINVAL;
 221
 222 got_it:
 223         from = (char*)de - (char*)page_address(page);
 224         to = from + SYSV_DIRSIZE;
 225         lock_page(page);
 226         err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
 227         if (err)
 228                 goto out_unlock;
 229         memcpy (de->name, name, namelen);
 230         memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
 231         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 232         err = dir_commit_chunk(page, from, to);
 233         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 234         mark_inode_dirty(dir);
 235 out_page:
 236         dir_put_page(page);
 237 out:
 238         return err;
 239 out_unlock:
 240         unlock_page(page);
 241         goto out_page;
 242 }
 243
 244 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
 245 {
 246         struct address_space *mapping = page->mapping;
 247         struct inode *inode = (struct inode*)mapping->host;
 248         char *kaddr = (char*)page_address(page);
 249         unsigned from = (char*)de - kaddr;
 250         unsigned to = from + SYSV_DIRSIZE;
 251         int err;
 252
 253         lock_page(page);
 254         err = mapping->a_ops->prepare_write(NULL, page, from, to);
 255         BUG_ON(err);
 256         de->inode = 0;
 257         err = dir_commit_chunk(page, from, to);
 258         dir_put_page(page);
 259         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 260         mark_inode_dirty(inode);
 261         return err;
 262 }
 263
 264 int sysv_make_empty(struct inode *inode, struct inode *dir)
 265 {
 266         struct address_space *mapping = inode->i_mapping;
 267         struct page *page = grab_cache_page(mapping, 0);
 268         struct sysv_dir_entry * de;
 269         char *base;
 270         int err;
 271
 272         if (!page)
 273                 return -ENOMEM;
 274         kmap(page);
 275         err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
 276         if (err) {
 277                 unlock_page(page);
 278                 goto fail;
 279         }
 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         err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
 292 fail:
 293         kunmap(page);
 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 inode *dir = (struct inode*)page->mapping->host;
 348         unsigned from = (char *)de-(char*)page_address(page);
 349         unsigned to = from + SYSV_DIRSIZE;
 350         int err;
 351
 352         lock_page(page);
 353         err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
 354         BUG_ON(err);
 355         de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 356         err = dir_commit_chunk(page, from, to);
 357         dir_put_page(page);
 358         dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 359         mark_inode_dirty(dir);
 360 }
 361
 362 struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
 363 {
 364         struct page *page = dir_get_page(dir, 0);
 365         struct sysv_dir_entry *de = NULL;
 366
 367         if (!IS_ERR(page)) {
 368                 de = (struct sysv_dir_entry*) page_address(page) + 1;
 369                 *p = page;
 370         }
 371         return de;
 372 }
 373
 374 ino_t sysv_inode_by_name(struct dentry *dentry)
 375 {
 376         struct page *page;
 377         struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
 378         ino_t res = 0;
 379
 380         if (de) {
 381                 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
 382                 dir_put_page(page);
 383         }
 384         return res;
 385 }