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 <asm/uaccess.h> 11 12 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry, 13 struct kstat *stat) 14 { 15 struct inode *inode = dentry->d_inode; 16 generic_fillattr(inode, stat); 17 stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9); 18 return 0; 19 } 20 21 int simple_statfs(struct super_block *sb, struct kstatfs *buf) 22 { 23 buf->f_type = sb->s_magic; 24 buf->f_bsize = PAGE_CACHE_SIZE; 25 buf->f_namelen = NAME_MAX; 26 return 0; 27 } 28 29 /* 30 * Retaining negative dentries for an in-memory filesystem just wastes 31 * memory and lookup time: arrange for them to be deleted immediately. 32 */ 33 static int simple_delete_dentry(struct dentry *dentry) 34 { 35 return 1; 36 } 37 38 /* 39 * Lookup the data. This is trivial - if the dentry didn't already 40 * exist, we know it is negative. Set d_op to delete negative dentries. 41 */ 42 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 43 { 44 static struct dentry_operations simple_dentry_operations = { 45 .d_delete = simple_delete_dentry, 46 }; 47 48 if (dentry->d_name.len > NAME_MAX) 49 return ERR_PTR(-ENAMETOOLONG); 50 dentry->d_op = &simple_dentry_operations; 51 d_add(dentry, NULL); 52 return NULL; 53 } 54 55 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync) 56 { 57 return 0; 58 } 59 60 int dcache_dir_open(struct inode *inode, struct file *file) 61 { 62 static struct qstr cursor_name = {.len = 1, .name = "."}; 63 64 file->private_data = d_alloc(file->f_dentry, &cursor_name); 65 66 return file->private_data ? 0 : -ENOMEM; 67 } 68 69 int dcache_dir_close(struct inode *inode, struct file *file) 70 { 71 dput(file->private_data); 72 return 0; 73 } 74 75 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin) 76 { 77 down(&file->f_dentry->d_inode->i_sem); 78 switch (origin) { 79 case 1: 80 offset += file->f_pos; 81 case 0: 82 if (offset >= 0) 83 break; 84 default: 85 up(&file->f_dentry->d_inode->i_sem); 86 return -EINVAL; 87 } 88 if (offset != file->f_pos) { 89 file->f_pos = offset; 90 if (file->f_pos >= 2) { 91 struct list_head *p; 92 struct dentry *cursor = file->private_data; 93 loff_t n = file->f_pos - 2; 94 95 spin_lock(&dcache_lock); 96 list_del(&cursor->d_child); 97 p = file->f_dentry->d_subdirs.next; 98 while (n && p != &file->f_dentry->d_subdirs) { 99 struct dentry *next; 100 next = list_entry(p, struct dentry, d_child); 101 if (!d_unhashed(next) && next->d_inode) 102 n--; 103 p = p->next; 104 } 105 list_add_tail(&cursor->d_child, p); 106 spin_unlock(&dcache_lock); 107 } 108 } 109 up(&file->f_dentry->d_inode->i_sem); 110 return offset; 111 } 112 113 /* Relationship between i_mode and the DT_xxx types */ 114 static inline unsigned char dt_type(struct inode *inode) 115 { 116 return (inode->i_mode >> 12) & 15; 117 } 118 119 /* 120 * Directory is locked and all positive dentries in it are safe, since 121 * for ramfs-type trees they can't go away without unlink() or rmdir(), 122 * both impossible due to the lock on directory. 123 */ 124 125 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir) 126 { 127 struct dentry *dentry = filp->f_dentry; 128 struct dentry *cursor = filp->private_data; 129 struct list_head *p, *q = &cursor->d_child; 130 ino_t ino; 131 int i = filp->f_pos; 132 133 switch (i) { 134 case 0: 135 ino = dentry->d_inode->i_ino; 136 if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0) 137 break; 138 filp->f_pos++; 139 i++; 140 /* fallthrough */ 141 case 1: 142 ino = parent_ino(dentry); 143 if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0) 144 break; 145 filp->f_pos++; 146 i++; 147 /* fallthrough */ 148 default: 149 spin_lock(&dcache_lock); 150 if (filp->f_pos == 2) { 151 list_del(q); 152 list_add(q, &dentry->d_subdirs); 153 } 154 for (p=q->next; p != &dentry->d_subdirs; p=p->next) { 155 struct dentry *next; 156 next = list_entry(p, struct dentry, d_child); 157 if (d_unhashed(next) || !next->d_inode) 158 continue; 159 160 spin_unlock(&dcache_lock); 161 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) 162 return 0; 163 spin_lock(&dcache_lock); 164 /* next is still alive */ 165 list_del(q); 166 list_add(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 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 struct super_block * 198 get_sb_pseudo(struct file_system_type *fs_type, char *name, 199 struct super_operations *ops, unsigned long magic) 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 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 s; 234 235 Enomem: 236 up_write(&s->s_umount); 237 deactivate_super(s); 238 return ERR_PTR(-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_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_sem. 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 root = d_alloc_root(inode); 392 if (!root) { 393 iput(inode); 394 return -ENOMEM; 395 } 396 for (i = 0; !files->name || files->name[0]; i++, files++) { 397 if (!files->name) 398 continue; 399 dentry = d_alloc_name(root, files->name); 400 if (!dentry) 401 goto out; 402 inode = new_inode(s); 403 if (!inode) 404 goto out; 405 inode->i_mode = S_IFREG | files->mode; 406 inode->i_uid = inode->i_gid = 0; 407 inode->i_blksize = PAGE_CACHE_SIZE; 408 inode->i_blocks = 0; 409 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 410 inode->i_fop = files->ops; 411 inode->i_ino = i; 412 d_add(dentry, inode); 413 } 414 s->s_root = root; 415 return 0; 416 out: 417 d_genocide(root); 418 dput(root); 419 return -ENOMEM; 420 } 421 422 static DEFINE_SPINLOCK(pin_fs_lock); 423 424 int simple_pin_fs(char *name, struct vfsmount **mount, int *count) 425 { 426 struct vfsmount *mnt = NULL; 427 spin_lock(&pin_fs_lock); 428 if (unlikely(!*mount)) { 429 spin_unlock(&pin_fs_lock); 430 mnt = do_kern_mount(name, 0, name, NULL); 431 if (IS_ERR(mnt)) 432 return PTR_ERR(mnt); 433 spin_lock(&pin_fs_lock); 434 if (!*mount) 435 *mount = mnt; 436 } 437 mntget(*mount); 438 ++*count; 439 spin_unlock(&pin_fs_lock); 440 mntput(mnt); 441 return 0; 442 } 443 444 void simple_release_fs(struct vfsmount **mount, int *count) 445 { 446 struct vfsmount *mnt; 447 spin_lock(&pin_fs_lock); 448 mnt = *mount; 449 if (!--*count) 450 *mount = NULL; 451 spin_unlock(&pin_fs_lock); 452 mntput(mnt); 453 } 454 455 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, 456 const void *from, size_t available) 457 { 458 loff_t pos = *ppos; 459 if (pos < 0) 460 return -EINVAL; 461 if (pos >= available) 462 return 0; 463 if (count > available - pos) 464 count = available - pos; 465 if (copy_to_user(to, from + pos, count)) 466 return -EFAULT; 467 *ppos = pos + count; 468 return count; 469 } 470 471 /* 472 * Transaction based IO. 473 * The file expects a single write which triggers the transaction, and then 474 * possibly a read which collects the result - which is stored in a 475 * file-local buffer. 476 */ 477 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) 478 { 479 struct simple_transaction_argresp *ar; 480 static DEFINE_SPINLOCK(simple_transaction_lock); 481 482 if (size > SIMPLE_TRANSACTION_LIMIT - 1) 483 return ERR_PTR(-EFBIG); 484 485 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); 486 if (!ar) 487 return ERR_PTR(-ENOMEM); 488 489 spin_lock(&simple_transaction_lock); 490 491 /* only one write allowed per open */ 492 if (file->private_data) { 493 spin_unlock(&simple_transaction_lock); 494 free_page((unsigned long)ar); 495 return ERR_PTR(-EBUSY); 496 } 497 498 file->private_data = ar; 499 500 spin_unlock(&simple_transaction_lock); 501 502 if (copy_from_user(ar->data, buf, size)) 503 return ERR_PTR(-EFAULT); 504 505 return ar->data; 506 } 507 508 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) 509 { 510 struct simple_transaction_argresp *ar = file->private_data; 511 512 if (!ar) 513 return 0; 514 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); 515 } 516 517 int simple_transaction_release(struct inode *inode, struct file *file) 518 { 519 free_page((unsigned long)file->private_data); 520 return 0; 521 } 522 523 /* Simple attribute files */ 524 525 struct simple_attr { 526 u64 (*get)(void *); 527 void (*set)(void *, u64); 528 char get_buf[24]; /* enough to store a u64 and "\n\0" */ 529 char set_buf[24]; 530 void *data; 531 const char *fmt; /* format for read operation */ 532 struct semaphore sem; /* protects access to these buffers */ 533 }; 534 535 /* simple_attr_open is called by an actual attribute open file operation 536 * to set the attribute specific access operations. */ 537 int simple_attr_open(struct inode *inode, struct file *file, 538 u64 (*get)(void *), void (*set)(void *, u64), 539 const char *fmt) 540 { 541 struct simple_attr *attr; 542 543 attr = kmalloc(sizeof(*attr), GFP_KERNEL); 544 if (!attr) 545 return -ENOMEM; 546 547 attr->get = get; 548 attr->set = set; 549 attr->data = inode->u.generic_ip; 550 attr->fmt = fmt; 551 init_MUTEX(&attr->sem); 552 553 file->private_data = attr; 554 555 return nonseekable_open(inode, file); 556 } 557 558 int simple_attr_close(struct inode *inode, struct file *file) 559 { 560 kfree(file->private_data); 561 return 0; 562 } 563 564 /* read from the buffer that is filled with the get function */ 565 ssize_t simple_attr_read(struct file *file, char __user *buf, 566 size_t len, loff_t *ppos) 567 { 568 struct simple_attr *attr; 569 size_t size; 570 ssize_t ret; 571 572 attr = file->private_data; 573 574 if (!attr->get) 575 return -EACCES; 576 577 down(&attr->sem); 578 if (*ppos) /* continued read */ 579 size = strlen(attr->get_buf); 580 else /* first read */ 581 size = scnprintf(attr->get_buf, sizeof(attr->get_buf), 582 attr->fmt, 583 (unsigned long long)attr->get(attr->data)); 584 585 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); 586 up(&attr->sem); 587 return ret; 588 } 589 590 /* interpret the buffer as a number to call the set function with */ 591 ssize_t simple_attr_write(struct file *file, const char __user *buf, 592 size_t len, loff_t *ppos) 593 { 594 struct simple_attr *attr; 595 u64 val; 596 size_t size; 597 ssize_t ret; 598 599 attr = file->private_data; 600 601 if (!attr->set) 602 return -EACCES; 603 604 down(&attr->sem); 605 ret = -EFAULT; 606 size = min(sizeof(attr->set_buf) - 1, len); 607 if (copy_from_user(attr->set_buf, buf, size)) 608 goto out; 609 610 ret = len; /* claim we got the whole input */ 611 attr->set_buf[size] = '\0'; 612 val = simple_strtol(attr->set_buf, NULL, 0); 613 attr->set(attr->data, val); 614 out: 615 up(&attr->sem); 616 return ret; 617 } 618 619 EXPORT_SYMBOL(dcache_dir_close); 620 EXPORT_SYMBOL(dcache_dir_lseek); 621 EXPORT_SYMBOL(dcache_dir_open); 622 EXPORT_SYMBOL(dcache_readdir); 623 EXPORT_SYMBOL(generic_read_dir); 624 EXPORT_SYMBOL(get_sb_pseudo); 625 EXPORT_SYMBOL(simple_commit_write); 626 EXPORT_SYMBOL(simple_dir_inode_operations); 627 EXPORT_SYMBOL(simple_dir_operations); 628 EXPORT_SYMBOL(simple_empty); 629 EXPORT_SYMBOL(d_alloc_name); 630 EXPORT_SYMBOL(simple_fill_super); 631 EXPORT_SYMBOL(simple_getattr); 632 EXPORT_SYMBOL(simple_link); 633 EXPORT_SYMBOL(simple_lookup); 634 EXPORT_SYMBOL(simple_pin_fs); 635 EXPORT_SYMBOL(simple_prepare_write); 636 EXPORT_SYMBOL(simple_readpage); 637 EXPORT_SYMBOL(simple_release_fs); 638 EXPORT_SYMBOL(simple_rename); 639 EXPORT_SYMBOL(simple_rmdir); 640 EXPORT_SYMBOL(simple_statfs); 641 EXPORT_SYMBOL(simple_sync_file); 642 EXPORT_SYMBOL(simple_unlink); 643 EXPORT_SYMBOL(simple_read_from_buffer); 644 EXPORT_SYMBOL(simple_transaction_get); 645 EXPORT_SYMBOL(simple_transaction_read); 646 EXPORT_SYMBOL(simple_transaction_release); 647 EXPORT_SYMBOL_GPL(simple_attr_open); 648 EXPORT_SYMBOL_GPL(simple_attr_close); 649 EXPORT_SYMBOL_GPL(simple_attr_read); 650 EXPORT_SYMBOL_GPL(simple_attr_write); 651