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_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_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_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_dentry->d_subdirs.next; 100 while (n && p != &file->f_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_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_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, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0) 163 return 0; 164 spin_lock(&dcache_lock); 165 /* next is still alive */ 166 list_move(q, p); 167 p = q; 168 filp->f_pos++; 169 } 170 spin_unlock(&dcache_lock); 171 } 172 return 0; 173 } 174 175 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos) 176 { 177 return -EISDIR; 178 } 179 180 const struct file_operations simple_dir_operations = { 181 .open = dcache_dir_open, 182 .release = dcache_dir_close, 183 .llseek = dcache_dir_lseek, 184 .read = generic_read_dir, 185 .readdir = dcache_readdir, 186 .fsync = simple_sync_file, 187 }; 188 189 struct inode_operations simple_dir_inode_operations = { 190 .lookup = simple_lookup, 191 }; 192 193 /* 194 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that 195 * will never be mountable) 196 */ 197 int get_sb_pseudo(struct file_system_type *fs_type, char *name, 198 struct super_operations *ops, unsigned long magic, 199 struct vfsmount *mnt) 200 { 201 struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); 202 static struct super_operations default_ops = {.statfs = simple_statfs}; 203 struct dentry *dentry; 204 struct inode *root; 205 struct qstr d_name = {.name = name, .len = strlen(name)}; 206 207 if (IS_ERR(s)) 208 return PTR_ERR(s); 209 210 s->s_flags = MS_NOUSER; 211 s->s_maxbytes = ~0ULL; 212 s->s_blocksize = 1024; 213 s->s_blocksize_bits = 10; 214 s->s_magic = magic; 215 s->s_op = ops ? ops : &default_ops; 216 s->s_time_gran = 1; 217 root = new_inode(s); 218 if (!root) 219 goto Enomem; 220 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; 221 root->i_uid = root->i_gid = 0; 222 root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME; 223 dentry = d_alloc(NULL, &d_name); 224 if (!dentry) { 225 iput(root); 226 goto Enomem; 227 } 228 dentry->d_sb = s; 229 dentry->d_parent = dentry; 230 d_instantiate(dentry, root); 231 s->s_root = dentry; 232 s->s_flags |= MS_ACTIVE; 233 return simple_set_mnt(mnt, s); 234 235 Enomem: 236 up_write(&s->s_umount); 237 deactivate_super(s); 238 return -ENOMEM; 239 } 240 241 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) 242 { 243 struct inode *inode = old_dentry->d_inode; 244 245 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 246 inode->i_nlink++; 247 atomic_inc(&inode->i_count); 248 dget(dentry); 249 d_instantiate(dentry, inode); 250 return 0; 251 } 252 253 static inline int simple_positive(struct dentry *dentry) 254 { 255 return dentry->d_inode && !d_unhashed(dentry); 256 } 257 258 int simple_empty(struct dentry *dentry) 259 { 260 struct dentry *child; 261 int ret = 0; 262 263 spin_lock(&dcache_lock); 264 list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) 265 if (simple_positive(child)) 266 goto out; 267 ret = 1; 268 out: 269 spin_unlock(&dcache_lock); 270 return ret; 271 } 272 273 int simple_unlink(struct inode *dir, struct dentry *dentry) 274 { 275 struct inode *inode = dentry->d_inode; 276 277 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 278 inode->i_nlink--; 279 dput(dentry); 280 return 0; 281 } 282 283 int simple_rmdir(struct inode *dir, struct dentry *dentry) 284 { 285 if (!simple_empty(dentry)) 286 return -ENOTEMPTY; 287 288 dentry->d_inode->i_nlink--; 289 simple_unlink(dir, dentry); 290 dir->i_nlink--; 291 return 0; 292 } 293 294 int simple_rename(struct inode *old_dir, struct dentry *old_dentry, 295 struct inode *new_dir, struct dentry *new_dentry) 296 { 297 struct inode *inode = old_dentry->d_inode; 298 int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode); 299 300 if (!simple_empty(new_dentry)) 301 return -ENOTEMPTY; 302 303 if (new_dentry->d_inode) { 304 simple_unlink(new_dir, new_dentry); 305 if (they_are_dirs) 306 old_dir->i_nlink--; 307 } else if (they_are_dirs) { 308 old_dir->i_nlink--; 309 new_dir->i_nlink++; 310 } 311 312 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime = 313 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME; 314 315 return 0; 316 } 317 318 int simple_readpage(struct file *file, struct page *page) 319 { 320 void *kaddr; 321 322 if (PageUptodate(page)) 323 goto out; 324 325 kaddr = kmap_atomic(page, KM_USER0); 326 memset(kaddr, 0, PAGE_CACHE_SIZE); 327 kunmap_atomic(kaddr, KM_USER0); 328 flush_dcache_page(page); 329 SetPageUptodate(page); 330 out: 331 unlock_page(page); 332 return 0; 333 } 334 335 int simple_prepare_write(struct file *file, struct page *page, 336 unsigned from, unsigned to) 337 { 338 if (!PageUptodate(page)) { 339 if (to - from != PAGE_CACHE_SIZE) { 340 void *kaddr = kmap_atomic(page, KM_USER0); 341 memset(kaddr, 0, from); 342 memset(kaddr + to, 0, PAGE_CACHE_SIZE - to); 343 flush_dcache_page(page); 344 kunmap_atomic(kaddr, KM_USER0); 345 } 346 SetPageUptodate(page); 347 } 348 return 0; 349 } 350 351 int simple_commit_write(struct file *file, struct page *page, 352 unsigned offset, unsigned to) 353 { 354 struct inode *inode = page->mapping->host; 355 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; 356 357 /* 358 * No need to use i_size_read() here, the i_size 359 * cannot change under us because we hold the i_mutex. 360 */ 361 if (pos > inode->i_size) 362 i_size_write(inode, pos); 363 set_page_dirty(page); 364 return 0; 365 } 366 367 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files) 368 { 369 static struct super_operations s_ops = {.statfs = simple_statfs}; 370 struct inode *inode; 371 struct dentry *root; 372 struct dentry *dentry; 373 int i; 374 375 s->s_blocksize = PAGE_CACHE_SIZE; 376 s->s_blocksize_bits = PAGE_CACHE_SHIFT; 377 s->s_magic = magic; 378 s->s_op = &s_ops; 379 s->s_time_gran = 1; 380 381 inode = new_inode(s); 382 if (!inode) 383 return -ENOMEM; 384 inode->i_mode = S_IFDIR | 0755; 385 inode->i_uid = inode->i_gid = 0; 386 inode->i_blksize = PAGE_CACHE_SIZE; 387 inode->i_blocks = 0; 388 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 389 inode->i_op = &simple_dir_inode_operations; 390 inode->i_fop = &simple_dir_operations; 391 inode->i_nlink = 2; 392 root = d_alloc_root(inode); 393 if (!root) { 394 iput(inode); 395 return -ENOMEM; 396 } 397 for (i = 0; !files->name || files->name[0]; i++, files++) { 398 if (!files->name) 399 continue; 400 dentry = d_alloc_name(root, files->name); 401 if (!dentry) 402 goto out; 403 inode = new_inode(s); 404 if (!inode) 405 goto out; 406 inode->i_mode = S_IFREG | files->mode; 407 inode->i_uid = inode->i_gid = 0; 408 inode->i_blksize = PAGE_CACHE_SIZE; 409 inode->i_blocks = 0; 410 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 411 inode->i_fop = files->ops; 412 inode->i_ino = i; 413 d_add(dentry, inode); 414 } 415 s->s_root = root; 416 return 0; 417 out: 418 d_genocide(root); 419 dput(root); 420 return -ENOMEM; 421 } 422 423 static DEFINE_SPINLOCK(pin_fs_lock); 424 425 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count) 426 { 427 struct vfsmount *mnt = NULL; 428 spin_lock(&pin_fs_lock); 429 if (unlikely(!*mount)) { 430 spin_unlock(&pin_fs_lock); 431 mnt = vfs_kern_mount(type, 0, type->name, NULL); 432 if (IS_ERR(mnt)) 433 return PTR_ERR(mnt); 434 spin_lock(&pin_fs_lock); 435 if (!*mount) 436 *mount = mnt; 437 } 438 mntget(*mount); 439 ++*count; 440 spin_unlock(&pin_fs_lock); 441 mntput(mnt); 442 return 0; 443 } 444 445 void simple_release_fs(struct vfsmount **mount, int *count) 446 { 447 struct vfsmount *mnt; 448 spin_lock(&pin_fs_lock); 449 mnt = *mount; 450 if (!--*count) 451 *mount = NULL; 452 spin_unlock(&pin_fs_lock); 453 mntput(mnt); 454 } 455 456 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, 457 const void *from, size_t available) 458 { 459 loff_t pos = *ppos; 460 if (pos < 0) 461 return -EINVAL; 462 if (pos >= available) 463 return 0; 464 if (count > available - pos) 465 count = available - pos; 466 if (copy_to_user(to, from + pos, count)) 467 return -EFAULT; 468 *ppos = pos + count; 469 return count; 470 } 471 472 /* 473 * Transaction based IO. 474 * The file expects a single write which triggers the transaction, and then 475 * possibly a read which collects the result - which is stored in a 476 * file-local buffer. 477 */ 478 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) 479 { 480 struct simple_transaction_argresp *ar; 481 static DEFINE_SPINLOCK(simple_transaction_lock); 482 483 if (size > SIMPLE_TRANSACTION_LIMIT - 1) 484 return ERR_PTR(-EFBIG); 485 486 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); 487 if (!ar) 488 return ERR_PTR(-ENOMEM); 489 490 spin_lock(&simple_transaction_lock); 491 492 /* only one write allowed per open */ 493 if (file->private_data) { 494 spin_unlock(&simple_transaction_lock); 495 free_page((unsigned long)ar); 496 return ERR_PTR(-EBUSY); 497 } 498 499 file->private_data = ar; 500 501 spin_unlock(&simple_transaction_lock); 502 503 if (copy_from_user(ar->data, buf, size)) 504 return ERR_PTR(-EFAULT); 505 506 return ar->data; 507 } 508 509 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) 510 { 511 struct simple_transaction_argresp *ar = file->private_data; 512 513 if (!ar) 514 return 0; 515 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); 516 } 517 518 int simple_transaction_release(struct inode *inode, struct file *file) 519 { 520 free_page((unsigned long)file->private_data); 521 return 0; 522 } 523 524 /* Simple attribute files */ 525 526 struct simple_attr { 527 u64 (*get)(void *); 528 void (*set)(void *, u64); 529 char get_buf[24]; /* enough to store a u64 and "\n\0" */ 530 char set_buf[24]; 531 void *data; 532 const char *fmt; /* format for read operation */ 533 struct mutex mutex; /* protects access to these buffers */ 534 }; 535 536 /* simple_attr_open is called by an actual attribute open file operation 537 * to set the attribute specific access operations. */ 538 int simple_attr_open(struct inode *inode, struct file *file, 539 u64 (*get)(void *), void (*set)(void *, u64), 540 const char *fmt) 541 { 542 struct simple_attr *attr; 543 544 attr = kmalloc(sizeof(*attr), GFP_KERNEL); 545 if (!attr) 546 return -ENOMEM; 547 548 attr->get = get; 549 attr->set = set; 550 attr->data = inode->u.generic_ip; 551 attr->fmt = fmt; 552 mutex_init(&attr->mutex); 553 554 file->private_data = attr; 555 556 return nonseekable_open(inode, file); 557 } 558 559 int simple_attr_close(struct inode *inode, struct file *file) 560 { 561 kfree(file->private_data); 562 return 0; 563 } 564 565 /* read from the buffer that is filled with the get function */ 566 ssize_t simple_attr_read(struct file *file, char __user *buf, 567 size_t len, loff_t *ppos) 568 { 569 struct simple_attr *attr; 570 size_t size; 571 ssize_t ret; 572 573 attr = file->private_data; 574 575 if (!attr->get) 576 return -EACCES; 577 578 mutex_lock(&attr->mutex); 579 if (*ppos) /* continued read */ 580 size = strlen(attr->get_buf); 581 else /* first read */ 582 size = scnprintf(attr->get_buf, sizeof(attr->get_buf), 583 attr->fmt, 584 (unsigned long long)attr->get(attr->data)); 585 586 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); 587 mutex_unlock(&attr->mutex); 588 return ret; 589 } 590 591 /* interpret the buffer as a number to call the set function with */ 592 ssize_t simple_attr_write(struct file *file, const char __user *buf, 593 size_t len, loff_t *ppos) 594 { 595 struct simple_attr *attr; 596 u64 val; 597 size_t size; 598 ssize_t ret; 599 600 attr = file->private_data; 601 602 if (!attr->set) 603 return -EACCES; 604 605 mutex_lock(&attr->mutex); 606 ret = -EFAULT; 607 size = min(sizeof(attr->set_buf) - 1, len); 608 if (copy_from_user(attr->set_buf, buf, size)) 609 goto out; 610 611 ret = len; /* claim we got the whole input */ 612 attr->set_buf[size] = '\0'; 613 val = simple_strtol(attr->set_buf, NULL, 0); 614 attr->set(attr->data, val); 615 out: 616 mutex_unlock(&attr->mutex); 617 return ret; 618 } 619 620 EXPORT_SYMBOL(dcache_dir_close); 621 EXPORT_SYMBOL(dcache_dir_lseek); 622 EXPORT_SYMBOL(dcache_dir_open); 623 EXPORT_SYMBOL(dcache_readdir); 624 EXPORT_SYMBOL(generic_read_dir); 625 EXPORT_SYMBOL(get_sb_pseudo); 626 EXPORT_SYMBOL(simple_commit_write); 627 EXPORT_SYMBOL(simple_dir_inode_operations); 628 EXPORT_SYMBOL(simple_dir_operations); 629 EXPORT_SYMBOL(simple_empty); 630 EXPORT_SYMBOL(d_alloc_name); 631 EXPORT_SYMBOL(simple_fill_super); 632 EXPORT_SYMBOL(simple_getattr); 633 EXPORT_SYMBOL(simple_link); 634 EXPORT_SYMBOL(simple_lookup); 635 EXPORT_SYMBOL(simple_pin_fs); 636 EXPORT_SYMBOL(simple_prepare_write); 637 EXPORT_SYMBOL(simple_readpage); 638 EXPORT_SYMBOL(simple_release_fs); 639 EXPORT_SYMBOL(simple_rename); 640 EXPORT_SYMBOL(simple_rmdir); 641 EXPORT_SYMBOL(simple_statfs); 642 EXPORT_SYMBOL(simple_sync_file); 643 EXPORT_SYMBOL(simple_unlink); 644 EXPORT_SYMBOL(simple_read_from_buffer); 645 EXPORT_SYMBOL(simple_transaction_get); 646 EXPORT_SYMBOL(simple_transaction_read); 647 EXPORT_SYMBOL(simple_transaction_release); 648 EXPORT_SYMBOL_GPL(simple_attr_open); 649 EXPORT_SYMBOL_GPL(simple_attr_close); 650 EXPORT_SYMBOL_GPL(simple_attr_read); 651 EXPORT_SYMBOL_GPL(simple_attr_write); 652