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 #include <linux/mutex.h> 11 12 #include <asm/uaccess.h> 13 14 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry, 15 struct kstat *stat) 16 { 17 struct inode *inode = dentry->d_inode; 18 generic_fillattr(inode, stat); 19 stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9); 20 return 0; 21 } 22 23 int simple_statfs(struct dentry *dentry, struct kstatfs *buf) 24 { 25 buf->f_type = dentry->d_sb->s_magic; 26 buf->f_bsize = PAGE_CACHE_SIZE; 27 buf->f_namelen = NAME_MAX; 28 return 0; 29 } 30 31 /* 32 * Retaining negative dentries for an in-memory filesystem just wastes 33 * memory and lookup time: arrange for them to be deleted immediately. 34 */ 35 static int simple_delete_dentry(struct dentry *dentry) 36 { 37 return 1; 38 } 39 40 /* 41 * Lookup the data. This is trivial - if the dentry didn't already 42 * exist, we know it is negative. Set d_op to delete negative dentries. 43 */ 44 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 45 { 46 static struct dentry_operations simple_dentry_operations = { 47 .d_delete = simple_delete_dentry, 48 }; 49 50 if (dentry->d_name.len > NAME_MAX) 51 return ERR_PTR(-ENAMETOOLONG); 52 dentry->d_op = &simple_dentry_operations; 53 d_add(dentry, NULL); 54 return NULL; 55 } 56 57 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync) 58 { 59 return 0; 60 } 61 62 int dcache_dir_open(struct inode *inode, struct file *file) 63 { 64 static struct qstr cursor_name = {.len = 1, .name = "."}; 65 66 file->private_data = d_alloc(file->f_path.dentry, &cursor_name); 67 68 return file->private_data ? 0 : -ENOMEM; 69 } 70 71 int dcache_dir_close(struct inode *inode, struct file *file) 72 { 73 dput(file->private_data); 74 return 0; 75 } 76 77 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin) 78 { 79 mutex_lock(&file->f_path.dentry->d_inode->i_mutex); 80 switch (origin) { 81 case 1: 82 offset += file->f_pos; 83 case 0: 84 if (offset >= 0) 85 break; 86 default: 87 mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); 88 return -EINVAL; 89 } 90 if (offset != file->f_pos) { 91 file->f_pos = offset; 92 if (file->f_pos >= 2) { 93 struct list_head *p; 94 struct dentry *cursor = file->private_data; 95 loff_t n = file->f_pos - 2; 96 97 spin_lock(&dcache_lock); 98 list_del(&cursor->d_u.d_child); 99 p = file->f_path.dentry->d_subdirs.next; 100 while (n && p != &file->f_path.dentry->d_subdirs) { 101 struct dentry *next; 102 next = list_entry(p, struct dentry, d_u.d_child); 103 if (!d_unhashed(next) && next->d_inode) 104 n--; 105 p = p->next; 106 } 107 list_add_tail(&cursor->d_u.d_child, p); 108 spin_unlock(&dcache_lock); 109 } 110 } 111 mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); 112 return offset; 113 } 114 115 /* Relationship between i_mode and the DT_xxx types */ 116 static inline unsigned char dt_type(struct inode *inode) 117 { 118 return (inode->i_mode >> 12) & 15; 119 } 120 121 /* 122 * Directory is locked and all positive dentries in it are safe, since 123 * for ramfs-type trees they can't go away without unlink() or rmdir(), 124 * both impossible due to the lock on directory. 125 */ 126 127 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir) 128 { 129 struct dentry *dentry = filp->f_path.dentry; 130 struct dentry *cursor = filp->private_data; 131 struct list_head *p, *q = &cursor->d_u.d_child; 132 ino_t ino; 133 int i = filp->f_pos; 134 135 switch (i) { 136 case 0: 137 ino = dentry->d_inode->i_ino; 138 if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0) 139 break; 140 filp->f_pos++; 141 i++; 142 /* fallthrough */ 143 case 1: 144 ino = parent_ino(dentry); 145 if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0) 146 break; 147 filp->f_pos++; 148 i++; 149 /* fallthrough */ 150 default: 151 spin_lock(&dcache_lock); 152 if (filp->f_pos == 2) 153 list_move(q, &dentry->d_subdirs); 154 155 for (p=q->next; p != &dentry->d_subdirs; p=p->next) { 156 struct dentry *next; 157 next = list_entry(p, struct dentry, d_u.d_child); 158 if (d_unhashed(next) || !next->d_inode) 159 continue; 160 161 spin_unlock(&dcache_lock); 162 if (filldir(dirent, next->d_name.name, 163 next->d_name.len, filp->f_pos, 164 next->d_inode->i_ino, 165 dt_type(next->d_inode)) < 0) 166 return 0; 167 spin_lock(&dcache_lock); 168 /* next is still alive */ 169 list_move(q, p); 170 p = q; 171 filp->f_pos++; 172 } 173 spin_unlock(&dcache_lock); 174 } 175 return 0; 176 } 177 178 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos) 179 { 180 return -EISDIR; 181 } 182 183 const struct file_operations simple_dir_operations = { 184 .open = dcache_dir_open, 185 .release = dcache_dir_close, 186 .llseek = dcache_dir_lseek, 187 .read = generic_read_dir, 188 .readdir = dcache_readdir, 189 .fsync = simple_sync_file, 190 }; 191 192 const struct inode_operations simple_dir_inode_operations = { 193 .lookup = simple_lookup, 194 }; 195 196 static const struct super_operations simple_super_operations = { 197 .statfs = simple_statfs, 198 }; 199 200 /* 201 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that 202 * will never be mountable) 203 */ 204 int get_sb_pseudo(struct file_system_type *fs_type, char *name, 205 const struct super_operations *ops, unsigned long magic, 206 struct vfsmount *mnt) 207 { 208 struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); 209 struct dentry *dentry; 210 struct inode *root; 211 struct qstr d_name = {.name = name, .len = strlen(name)}; 212 213 if (IS_ERR(s)) 214 return PTR_ERR(s); 215 216 s->s_flags = MS_NOUSER; 217 s->s_maxbytes = ~0ULL; 218 s->s_blocksize = 1024; 219 s->s_blocksize_bits = 10; 220 s->s_magic = magic; 221 s->s_op = ops ? ops : &simple_super_operations; 222 s->s_time_gran = 1; 223 root = new_inode(s); 224 if (!root) 225 goto Enomem; 226 /* 227 * since this is the first inode, make it number 1. New inodes created 228 * after this must take care not to collide with it (by passing 229 * max_reserved of 1 to iunique). 230 */ 231 root->i_ino = 1; 232 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; 233 root->i_uid = root->i_gid = 0; 234 root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME; 235 dentry = d_alloc(NULL, &d_name); 236 if (!dentry) { 237 iput(root); 238 goto Enomem; 239 } 240 dentry->d_sb = s; 241 dentry->d_parent = dentry; 242 d_instantiate(dentry, root); 243 s->s_root = dentry; 244 s->s_flags |= MS_ACTIVE; 245 return simple_set_mnt(mnt, s); 246 247 Enomem: 248 up_write(&s->s_umount); 249 deactivate_super(s); 250 return -ENOMEM; 251 } 252 253 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) 254 { 255 struct inode *inode = old_dentry->d_inode; 256 257 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 258 inc_nlink(inode); 259 atomic_inc(&inode->i_count); 260 dget(dentry); 261 d_instantiate(dentry, inode); 262 return 0; 263 } 264 265 static inline int simple_positive(struct dentry *dentry) 266 { 267 return dentry->d_inode && !d_unhashed(dentry); 268 } 269 270 int simple_empty(struct dentry *dentry) 271 { 272 struct dentry *child; 273 int ret = 0; 274 275 spin_lock(&dcache_lock); 276 list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) 277 if (simple_positive(child)) 278 goto out; 279 ret = 1; 280 out: 281 spin_unlock(&dcache_lock); 282 return ret; 283 } 284 285 int simple_unlink(struct inode *dir, struct dentry *dentry) 286 { 287 struct inode *inode = dentry->d_inode; 288 289 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 290 drop_nlink(inode); 291 dput(dentry); 292 return 0; 293 } 294 295 int simple_rmdir(struct inode *dir, struct dentry *dentry) 296 { 297 if (!simple_empty(dentry)) 298 return -ENOTEMPTY; 299 300 drop_nlink(dentry->d_inode); 301 simple_unlink(dir, dentry); 302 drop_nlink(dir); 303 return 0; 304 } 305 306 int simple_rename(struct inode *old_dir, struct dentry *old_dentry, 307 struct inode *new_dir, struct dentry *new_dentry) 308 { 309 struct inode *inode = old_dentry->d_inode; 310 int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode); 311 312 if (!simple_empty(new_dentry)) 313 return -ENOTEMPTY; 314 315 if (new_dentry->d_inode) { 316 simple_unlink(new_dir, new_dentry); 317 if (they_are_dirs) 318 drop_nlink(old_dir); 319 } else if (they_are_dirs) { 320 drop_nlink(old_dir); 321 inc_nlink(new_dir); 322 } 323 324 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime = 325 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME; 326 327 return 0; 328 } 329 330 int simple_readpage(struct file *file, struct page *page) 331 { 332 clear_highpage(page); 333 flush_dcache_page(page); 334 SetPageUptodate(page); 335 unlock_page(page); 336 return 0; 337 } 338 339 int simple_prepare_write(struct file *file, struct page *page, 340 unsigned from, unsigned to) 341 { 342 if (!PageUptodate(page)) { 343 if (to - from != PAGE_CACHE_SIZE) { 344 void *kaddr = kmap_atomic(page, KM_USER0); 345 memset(kaddr, 0, from); 346 memset(kaddr + to, 0, PAGE_CACHE_SIZE - to); 347 flush_dcache_page(page); 348 kunmap_atomic(kaddr, KM_USER0); 349 } 350 } 351 return 0; 352 } 353 354 int simple_commit_write(struct file *file, struct page *page, 355 unsigned from, unsigned to) 356 { 357 struct inode *inode = page->mapping->host; 358 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; 359 360 if (!PageUptodate(page)) 361 SetPageUptodate(page); 362 /* 363 * No need to use i_size_read() here, the i_size 364 * cannot change under us because we hold the i_mutex. 365 */ 366 if (pos > inode->i_size) 367 i_size_write(inode, pos); 368 set_page_dirty(page); 369 return 0; 370 } 371 372 /* 373 * the inodes created here are not hashed. If you use iunique to generate 374 * unique inode values later for this filesystem, then you must take care 375 * to pass it an appropriate max_reserved value to avoid collisions. 376 */ 377 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files) 378 { 379 struct inode *inode; 380 struct dentry *root; 381 struct dentry *dentry; 382 int i; 383 384 s->s_blocksize = PAGE_CACHE_SIZE; 385 s->s_blocksize_bits = PAGE_CACHE_SHIFT; 386 s->s_magic = magic; 387 s->s_op = &simple_super_operations; 388 s->s_time_gran = 1; 389 390 inode = new_inode(s); 391 if (!inode) 392 return -ENOMEM; 393 /* 394 * because the root inode is 1, the files array must not contain an 395 * entry at index 1 396 */ 397 inode->i_ino = 1; 398 inode->i_mode = S_IFDIR | 0755; 399 inode->i_uid = inode->i_gid = 0; 400 inode->i_blocks = 0; 401 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 402 inode->i_op = &simple_dir_inode_operations; 403 inode->i_fop = &simple_dir_operations; 404 inode->i_nlink = 2; 405 root = d_alloc_root(inode); 406 if (!root) { 407 iput(inode); 408 return -ENOMEM; 409 } 410 for (i = 0; !files->name || files->name[0]; i++, files++) { 411 if (!files->name) 412 continue; 413 414 /* warn if it tries to conflict with the root inode */ 415 if (unlikely(i == 1)) 416 printk(KERN_WARNING "%s: %s passed in a files array" 417 "with an index of 1!\n", __func__, 418 s->s_type->name); 419 420 dentry = d_alloc_name(root, files->name); 421 if (!dentry) 422 goto out; 423 inode = new_inode(s); 424 if (!inode) 425 goto out; 426 inode->i_mode = S_IFREG | files->mode; 427 inode->i_uid = inode->i_gid = 0; 428 inode->i_blocks = 0; 429 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 430 inode->i_fop = files->ops; 431 inode->i_ino = i; 432 d_add(dentry, inode); 433 } 434 s->s_root = root; 435 return 0; 436 out: 437 d_genocide(root); 438 dput(root); 439 return -ENOMEM; 440 } 441 442 static DEFINE_SPINLOCK(pin_fs_lock); 443 444 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count) 445 { 446 struct vfsmount *mnt = NULL; 447 spin_lock(&pin_fs_lock); 448 if (unlikely(!*mount)) { 449 spin_unlock(&pin_fs_lock); 450 mnt = vfs_kern_mount(type, 0, type->name, NULL); 451 if (IS_ERR(mnt)) 452 return PTR_ERR(mnt); 453 spin_lock(&pin_fs_lock); 454 if (!*mount) 455 *mount = mnt; 456 } 457 mntget(*mount); 458 ++*count; 459 spin_unlock(&pin_fs_lock); 460 mntput(mnt); 461 return 0; 462 } 463 464 void simple_release_fs(struct vfsmount **mount, int *count) 465 { 466 struct vfsmount *mnt; 467 spin_lock(&pin_fs_lock); 468 mnt = *mount; 469 if (!--*count) 470 *mount = NULL; 471 spin_unlock(&pin_fs_lock); 472 mntput(mnt); 473 } 474 475 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, 476 const void *from, size_t available) 477 { 478 loff_t pos = *ppos; 479 if (pos < 0) 480 return -EINVAL; 481 if (pos >= available) 482 return 0; 483 if (count > available - pos) 484 count = available - pos; 485 if (copy_to_user(to, from + pos, count)) 486 return -EFAULT; 487 *ppos = pos + count; 488 return count; 489 } 490 491 /* 492 * Transaction based IO. 493 * The file expects a single write which triggers the transaction, and then 494 * possibly a read which collects the result - which is stored in a 495 * file-local buffer. 496 */ 497 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) 498 { 499 struct simple_transaction_argresp *ar; 500 static DEFINE_SPINLOCK(simple_transaction_lock); 501 502 if (size > SIMPLE_TRANSACTION_LIMIT - 1) 503 return ERR_PTR(-EFBIG); 504 505 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); 506 if (!ar) 507 return ERR_PTR(-ENOMEM); 508 509 spin_lock(&simple_transaction_lock); 510 511 /* only one write allowed per open */ 512 if (file->private_data) { 513 spin_unlock(&simple_transaction_lock); 514 free_page((unsigned long)ar); 515 return ERR_PTR(-EBUSY); 516 } 517 518 file->private_data = ar; 519 520 spin_unlock(&simple_transaction_lock); 521 522 if (copy_from_user(ar->data, buf, size)) 523 return ERR_PTR(-EFAULT); 524 525 return ar->data; 526 } 527 528 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) 529 { 530 struct simple_transaction_argresp *ar = file->private_data; 531 532 if (!ar) 533 return 0; 534 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); 535 } 536 537 int simple_transaction_release(struct inode *inode, struct file *file) 538 { 539 free_page((unsigned long)file->private_data); 540 return 0; 541 } 542 543 /* Simple attribute files */ 544 545 struct simple_attr { 546 u64 (*get)(void *); 547 void (*set)(void *, u64); 548 char get_buf[24]; /* enough to store a u64 and "\n\0" */ 549 char set_buf[24]; 550 void *data; 551 const char *fmt; /* format for read operation */ 552 struct mutex mutex; /* protects access to these buffers */ 553 }; 554 555 /* simple_attr_open is called by an actual attribute open file operation 556 * to set the attribute specific access operations. */ 557 int simple_attr_open(struct inode *inode, struct file *file, 558 u64 (*get)(void *), void (*set)(void *, u64), 559 const char *fmt) 560 { 561 struct simple_attr *attr; 562 563 attr = kmalloc(sizeof(*attr), GFP_KERNEL); 564 if (!attr) 565 return -ENOMEM; 566 567 attr->get = get; 568 attr->set = set; 569 attr->data = inode->i_private; 570 attr->fmt = fmt; 571 mutex_init(&attr->mutex); 572 573 file->private_data = attr; 574 575 return nonseekable_open(inode, file); 576 } 577 578 int simple_attr_close(struct inode *inode, struct file *file) 579 { 580 kfree(file->private_data); 581 return 0; 582 } 583 584 /* read from the buffer that is filled with the get function */ 585 ssize_t simple_attr_read(struct file *file, char __user *buf, 586 size_t len, loff_t *ppos) 587 { 588 struct simple_attr *attr; 589 size_t size; 590 ssize_t ret; 591 592 attr = file->private_data; 593 594 if (!attr->get) 595 return -EACCES; 596 597 mutex_lock(&attr->mutex); 598 if (*ppos) /* continued read */ 599 size = strlen(attr->get_buf); 600 else /* first read */ 601 size = scnprintf(attr->get_buf, sizeof(attr->get_buf), 602 attr->fmt, 603 (unsigned long long)attr->get(attr->data)); 604 605 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); 606 mutex_unlock(&attr->mutex); 607 return ret; 608 } 609 610 /* interpret the buffer as a number to call the set function with */ 611 ssize_t simple_attr_write(struct file *file, const char __user *buf, 612 size_t len, loff_t *ppos) 613 { 614 struct simple_attr *attr; 615 u64 val; 616 size_t size; 617 ssize_t ret; 618 619 attr = file->private_data; 620 621 if (!attr->set) 622 return -EACCES; 623 624 mutex_lock(&attr->mutex); 625 ret = -EFAULT; 626 size = min(sizeof(attr->set_buf) - 1, len); 627 if (copy_from_user(attr->set_buf, buf, size)) 628 goto out; 629 630 ret = len; /* claim we got the whole input */ 631 attr->set_buf[size] = '\0'; 632 val = simple_strtol(attr->set_buf, NULL, 0); 633 attr->set(attr->data, val); 634 out: 635 mutex_unlock(&attr->mutex); 636 return ret; 637 } 638 639 EXPORT_SYMBOL(dcache_dir_close); 640 EXPORT_SYMBOL(dcache_dir_lseek); 641 EXPORT_SYMBOL(dcache_dir_open); 642 EXPORT_SYMBOL(dcache_readdir); 643 EXPORT_SYMBOL(generic_read_dir); 644 EXPORT_SYMBOL(get_sb_pseudo); 645 EXPORT_SYMBOL(simple_commit_write); 646 EXPORT_SYMBOL(simple_dir_inode_operations); 647 EXPORT_SYMBOL(simple_dir_operations); 648 EXPORT_SYMBOL(simple_empty); 649 EXPORT_SYMBOL(d_alloc_name); 650 EXPORT_SYMBOL(simple_fill_super); 651 EXPORT_SYMBOL(simple_getattr); 652 EXPORT_SYMBOL(simple_link); 653 EXPORT_SYMBOL(simple_lookup); 654 EXPORT_SYMBOL(simple_pin_fs); 655 EXPORT_SYMBOL(simple_prepare_write); 656 EXPORT_SYMBOL(simple_readpage); 657 EXPORT_SYMBOL(simple_release_fs); 658 EXPORT_SYMBOL(simple_rename); 659 EXPORT_SYMBOL(simple_rmdir); 660 EXPORT_SYMBOL(simple_statfs); 661 EXPORT_SYMBOL(simple_sync_file); 662 EXPORT_SYMBOL(simple_unlink); 663 EXPORT_SYMBOL(simple_read_from_buffer); 664 EXPORT_SYMBOL(simple_transaction_get); 665 EXPORT_SYMBOL(simple_transaction_read); 666 EXPORT_SYMBOL(simple_transaction_release); 667 EXPORT_SYMBOL_GPL(simple_attr_open); 668 EXPORT_SYMBOL_GPL(simple_attr_close); 669 EXPORT_SYMBOL_GPL(simple_attr_read); 670 EXPORT_SYMBOL_GPL(simple_attr_write); 671