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