fs/libfs.c

   1 /*
   2  *      fs/libfs.c
   3  *      Library for filesystems writers.
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/mount.h>
   9 #include <linux/vfs.h>
  10
  11 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
  12                    struct kstat *stat)
  13 {
  14         struct inode *inode = dentry->d_inode;
  15         generic_fillattr(inode, stat);
  16         stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
  17         return 0;
  18 }
  19
  20 int simple_statfs(struct super_block *sb, struct kstatfs *buf)
  21 {
  22         buf->f_type = sb->s_magic;
  23         buf->f_bsize = PAGE_CACHE_SIZE;
  24         buf->f_namelen = NAME_MAX;
  25         return 0;
  26 }
  27
  28 /*
  29  * Lookup the data. This is trivial - if the dentry didn't already
  30  * exist, we know it is negative.
  31  */
  32
  33 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
  34 {
  35         if (dentry->d_name.len > NAME_MAX)
  36                 return ERR_PTR(-ENAMETOOLONG);
  37         d_add(dentry, NULL);
  38         return NULL;
  39 }
  40
  41 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
  42 {
  43         return 0;
  44 }
  45
  46 int dcache_dir_open(struct inode *inode, struct file *file)
  47 {
  48         static struct qstr cursor_name = {.len = 1, .name = "."};
  49
  50         file->private_data = d_alloc(file->f_dentry, &cursor_name);
  51
  52         return file->private_data ? 0 : -ENOMEM;
  53 }
  54
  55 int dcache_dir_close(struct inode *inode, struct file *file)
  56 {
  57         dput(file->private_data);
  58         return 0;
  59 }
  60
  61 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
  62 {
  63         down(&file->f_dentry->d_inode->i_sem);
  64         switch (origin) {
  65                 case 1:
  66                         offset += file->f_pos;
  67                 case 0:
  68                         if (offset >= 0)
  69                                 break;
  70                 default:
  71                         up(&file->f_dentry->d_inode->i_sem);
  72                         return -EINVAL;
  73         }
  74         if (offset != file->f_pos) {
  75                 file->f_pos = offset;
  76                 if (file->f_pos >= 2) {
  77                         struct list_head *p;
  78                         struct dentry *cursor = file->private_data;
  79                         loff_t n = file->f_pos - 2;
  80
  81                         spin_lock(&dcache_lock);
  82                         list_del(&cursor->d_child);
  83                         p = file->f_dentry->d_subdirs.next;
  84                         while (n && p != &file->f_dentry->d_subdirs) {
  85                                 struct dentry *next;
  86                                 next = list_entry(p, struct dentry, d_child);
  87                                 if (!d_unhashed(next) && next->d_inode)
  88                                         n--;
  89                                 p = p->next;
  90                         }
  91                         list_add_tail(&cursor->d_child, p);
  92                         spin_unlock(&dcache_lock);
  93                 }
  94         }
  95         up(&file->f_dentry->d_inode->i_sem);
  96         return offset;
  97 }
  98
  99 /* Relationship between i_mode and the DT_xxx types */
 100 static inline unsigned char dt_type(struct inode *inode)
 101 {
 102         return (inode->i_mode >> 12) & 15;
 103 }
 104
 105 /*
 106  * Directory is locked and all positive dentries in it are safe, since
 107  * for ramfs-type trees they can't go away without unlink() or rmdir(),
 108  * both impossible due to the lock on directory.
 109  */
 110
 111 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
 112 {
 113         struct dentry *dentry = filp->f_dentry;
 114         struct dentry *cursor = filp->private_data;
 115         struct list_head *p, *q = &cursor->d_child;
 116         ino_t ino;
 117         int i = filp->f_pos;
 118
 119         switch (i) {
 120                 case 0:
 121                         ino = dentry->d_inode->i_ino;
 122                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 123                                 break;
 124                         filp->f_pos++;
 125                         i++;
 126                         /* fallthrough */
 127                 case 1:
 128                         ino = parent_ino(dentry);
 129                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 130                                 break;
 131                         filp->f_pos++;
 132                         i++;
 133                         /* fallthrough */
 134                 default:
 135                         spin_lock(&dcache_lock);
 136                         if (filp->f_pos == 2) {
 137                                 list_del(q);
 138                                 list_add(q, &dentry->d_subdirs);
 139                         }
 140                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 141                                 struct dentry *next;
 142                                 next = list_entry(p, struct dentry, d_child);
 143                                 if (d_unhashed(next) || !next->d_inode)
 144                                         continue;
 145
 146                                 spin_unlock(&dcache_lock);
 147                                 if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
 148                                         return 0;
 149                                 spin_lock(&dcache_lock);
 150                                 /* next is still alive */
 151                                 list_del(q);
 152                                 list_add(q, p);
 153                                 p = q;
 154                                 filp->f_pos++;
 155                         }
 156                         spin_unlock(&dcache_lock);
 157         }
 158         return 0;
 159 }
 160
 161 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 162 {
 163         return -EISDIR;
 164 }
 165
 166 struct file_operations simple_dir_operations = {
 167         .open           = dcache_dir_open,
 168         .release        = dcache_dir_close,
 169         .llseek         = dcache_dir_lseek,
 170         .read           = generic_read_dir,
 171         .readdir        = dcache_readdir,
 172 };
 173
 174 struct inode_operations simple_dir_inode_operations = {
 175         .lookup         = simple_lookup,
 176 };
 177
 178 /*
 179  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 180  * will never be mountable)
 181  */
 182 struct super_block *
 183 get_sb_pseudo(struct file_system_type *fs_type, char *name,
 184         struct super_operations *ops, unsigned long magic)
 185 {
 186         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 187         static struct super_operations default_ops = {.statfs = simple_statfs};
 188         struct dentry *dentry;
 189         struct inode *root;
 190         struct qstr d_name = {.name = name, .len = strlen(name)};
 191
 192         if (IS_ERR(s))
 193                 return s;
 194
 195         s->s_flags = MS_NOUSER;
 196         s->s_maxbytes = ~0ULL;
 197         s->s_blocksize = 1024;
 198         s->s_blocksize_bits = 10;
 199         s->s_magic = magic;
 200         s->s_op = ops ? ops : &default_ops;
 201         root = new_inode(s);
 202         if (!root)
 203                 goto Enomem;
 204         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 205         root->i_uid = root->i_gid = 0;
 206         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 207         dentry = d_alloc(NULL, &d_name);
 208         if (!dentry) {
 209                 iput(root);
 210                 goto Enomem;
 211         }
 212         dentry->d_sb = s;
 213         dentry->d_parent = dentry;
 214         d_instantiate(dentry, root);
 215         s->s_root = dentry;
 216         s->s_flags |= MS_ACTIVE;
 217         return s;
 218
 219 Enomem:
 220         up_write(&s->s_umount);
 221         deactivate_super(s);
 222         return ERR_PTR(-ENOMEM);
 223 }
 224
 225 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 226 {
 227         struct inode *inode = old_dentry->d_inode;
 228
 229         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 230         inode->i_nlink++;
 231         atomic_inc(&inode->i_count);
 232         dget(dentry);
 233         d_instantiate(dentry, inode);
 234         return 0;
 235 }
 236
 237 static inline int simple_positive(struct dentry *dentry)
 238 {
 239         return dentry->d_inode && !d_unhashed(dentry);
 240 }
 241
 242 int simple_empty(struct dentry *dentry)
 243 {
 244         struct dentry *child;
 245         int ret = 0;
 246
 247         spin_lock(&dcache_lock);
 248         list_for_each_entry(child, &dentry->d_subdirs, d_child)
 249                 if (simple_positive(child))
 250                         goto out;
 251         ret = 1;
 252 out:
 253         spin_unlock(&dcache_lock);
 254         return ret;
 255 }
 256
 257 int simple_unlink(struct inode *dir, struct dentry *dentry)
 258 {
 259         struct inode *inode = dentry->d_inode;
 260
 261         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 262         inode->i_nlink--;
 263         dput(dentry);
 264         return 0;
 265 }
 266
 267 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 268 {
 269         if (!simple_empty(dentry))
 270                 return -ENOTEMPTY;
 271
 272         dentry->d_inode->i_nlink--;
 273         simple_unlink(dir, dentry);
 274         dir->i_nlink--;
 275         return 0;
 276 }
 277
 278 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 279                 struct inode *new_dir, struct dentry *new_dentry)
 280 {
 281         struct inode *inode = old_dentry->d_inode;
 282         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 283
 284         if (!simple_empty(new_dentry))
 285                 return -ENOTEMPTY;
 286
 287         if (new_dentry->d_inode) {
 288                 simple_unlink(new_dir, new_dentry);
 289                 if (they_are_dirs)
 290                         old_dir->i_nlink--;
 291         } else if (they_are_dirs) {
 292                 old_dir->i_nlink--;
 293                 new_dir->i_nlink++;
 294         }
 295
 296         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 297                 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 298
 299         return 0;
 300 }
 301
 302 int simple_readpage(struct file *file, struct page *page)
 303 {
 304         void *kaddr;
 305
 306         if (PageUptodate(page))
 307                 goto out;
 308
 309         kaddr = kmap_atomic(page, KM_USER0);
 310         memset(kaddr, 0, PAGE_CACHE_SIZE);
 311         kunmap_atomic(kaddr, KM_USER0);
 312         flush_dcache_page(page);
 313         SetPageUptodate(page);
 314 out:
 315         unlock_page(page);
 316         return 0;
 317 }
 318
 319 int simple_prepare_write(struct file *file, struct page *page,
 320                         unsigned from, unsigned to)
 321 {
 322         if (!PageUptodate(page)) {
 323                 if (to - from != PAGE_CACHE_SIZE) {
 324                         void *kaddr = kmap_atomic(page, KM_USER0);
 325                         memset(kaddr, 0, from);
 326                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 327                         flush_dcache_page(page);
 328                         kunmap_atomic(kaddr, KM_USER0);
 329                 }
 330                 SetPageUptodate(page);
 331         }
 332         return 0;
 333 }
 334
 335 int simple_commit_write(struct file *file, struct page *page,
 336                         unsigned offset, unsigned to)
 337 {
 338         struct inode *inode = page->mapping->host;
 339         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 340
 341         /*
 342          * No need to use i_size_read() here, the i_size
 343          * cannot change under us because we hold the i_sem.
 344          */
 345         if (pos > inode->i_size)
 346                 i_size_write(inode, pos);
 347         set_page_dirty(page);
 348         return 0;
 349 }
 350
 351 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 352 {
 353         static struct super_operations s_ops = {.statfs = simple_statfs};
 354         struct inode *inode;
 355         struct dentry *root;
 356         struct dentry *dentry;
 357         int i;
 358
 359         s->s_blocksize = PAGE_CACHE_SIZE;
 360         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 361         s->s_magic = magic;
 362         s->s_op = &s_ops;
 363
 364         inode = new_inode(s);
 365         if (!inode)
 366                 return -ENOMEM;
 367         inode->i_mode = S_IFDIR | 0755;
 368         inode->i_uid = inode->i_gid = 0;
 369         inode->i_blksize = PAGE_CACHE_SIZE;
 370         inode->i_blocks = 0;
 371         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 372         inode->i_op = &simple_dir_inode_operations;
 373         inode->i_fop = &simple_dir_operations;
 374         root = d_alloc_root(inode);
 375         if (!root) {
 376                 iput(inode);
 377                 return -ENOMEM;
 378         }
 379         for (i = 0; !files->name || files->name[0]; i++, files++) {
 380                 struct qstr name;
 381                 if (!files->name)
 382                         continue;
 383                 name.name = files->name;
 384                 name.len = strlen(name.name);
 385                 name.hash = full_name_hash(name.name, name.len);
 386                 dentry = d_alloc(root, &name);
 387                 if (!dentry)
 388                         goto out;
 389                 inode = new_inode(s);
 390                 if (!inode)
 391                         goto out;
 392                 inode->i_mode = S_IFREG | files->mode;
 393                 inode->i_uid = inode->i_gid = 0;
 394                 inode->i_blksize = PAGE_CACHE_SIZE;
 395                 inode->i_blocks = 0;
 396                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 397                 inode->i_fop = files->ops;
 398                 inode->i_ino = i;
 399                 d_add(dentry, inode);
 400         }
 401         s->s_root = root;
 402         return 0;
 403 out:
 404         d_genocide(root);
 405         dput(root);
 406         return -ENOMEM;
 407 }
 408
 409 static spinlock_t pin_fs_lock = SPIN_LOCK_UNLOCKED;
 410
 411 int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
 412 {
 413         struct vfsmount *mnt = NULL;
 414         spin_lock(&pin_fs_lock);
 415         if (unlikely(!*mount)) {
 416                 spin_unlock(&pin_fs_lock);
 417                 mnt = do_kern_mount(name, 0, name, NULL);
 418                 if (IS_ERR(mnt))
 419                         return PTR_ERR(mnt);
 420                 spin_lock(&pin_fs_lock);
 421                 if (!*mount)
 422                         *mount = mnt;
 423         }
 424         mntget(*mount);
 425         ++*count;
 426         spin_unlock(&pin_fs_lock);
 427         mntput(mnt);
 428         return 0;
 429 }
 430
 431 void simple_release_fs(struct vfsmount **mount, int *count)
 432 {
 433         struct vfsmount *mnt;
 434         spin_lock(&pin_fs_lock);
 435         mnt = *mount;
 436         if (!--*count)
 437                 *mount = NULL;
 438         spin_unlock(&pin_fs_lock);
 439         mntput(mnt);
 440 }
 441
 442 EXPORT_SYMBOL(dcache_dir_close);
 443 EXPORT_SYMBOL(dcache_dir_lseek);
 444 EXPORT_SYMBOL(dcache_dir_open);
 445 EXPORT_SYMBOL(dcache_readdir);
 446 EXPORT_SYMBOL(generic_read_dir);
 447 EXPORT_SYMBOL(simple_commit_write);
 448 EXPORT_SYMBOL(simple_dir_inode_operations);
 449 EXPORT_SYMBOL(simple_dir_operations);
 450 EXPORT_SYMBOL(simple_empty);
 451 EXPORT_SYMBOL(simple_fill_super);
 452 EXPORT_SYMBOL(simple_getattr);
 453 EXPORT_SYMBOL(simple_link);
 454 EXPORT_SYMBOL(simple_lookup);
 455 EXPORT_SYMBOL(simple_pin_fs);
 456 EXPORT_SYMBOL(simple_prepare_write);
 457 EXPORT_SYMBOL(simple_readpage);
 458 EXPORT_SYMBOL(simple_release_fs);
 459 EXPORT_SYMBOL(simple_rename);
 460 EXPORT_SYMBOL(simple_rmdir);
 461 EXPORT_SYMBOL(simple_statfs);
 462 EXPORT_SYMBOL(simple_sync_file);
 463 EXPORT_SYMBOL(simple_unlink);