| 1 | /* |
| 2 | * fs/libfs.c |
| 3 | * Library for filesystems writers. |
| 4 | */ |
| 5 | |
| 6 | #include <linux/blkdev.h> |
| 7 | #include <linux/export.h> |
| 8 | #include <linux/pagemap.h> |
| 9 | #include <linux/slab.h> |
| 10 | #include <linux/cred.h> |
| 11 | #include <linux/mount.h> |
| 12 | #include <linux/vfs.h> |
| 13 | #include <linux/quotaops.h> |
| 14 | #include <linux/mutex.h> |
| 15 | #include <linux/namei.h> |
| 16 | #include <linux/exportfs.h> |
| 17 | #include <linux/writeback.h> |
| 18 | #include <linux/buffer_head.h> /* sync_mapping_buffers */ |
| 19 | |
| 20 | #include <linux/uaccess.h> |
| 21 | |
| 22 | #include "internal.h" |
| 23 | |
| 24 | int simple_getattr(const struct path *path, struct kstat *stat, |
| 25 | u32 request_mask, unsigned int query_flags) |
| 26 | { |
| 27 | struct inode *inode = d_inode(path->dentry); |
| 28 | generic_fillattr(inode, stat); |
| 29 | stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9); |
| 30 | return 0; |
| 31 | } |
| 32 | EXPORT_SYMBOL(simple_getattr); |
| 33 | |
| 34 | int simple_statfs(struct dentry *dentry, struct kstatfs *buf) |
| 35 | { |
| 36 | buf->f_type = dentry->d_sb->s_magic; |
| 37 | buf->f_bsize = PAGE_SIZE; |
| 38 | buf->f_namelen = NAME_MAX; |
| 39 | return 0; |
| 40 | } |
| 41 | EXPORT_SYMBOL(simple_statfs); |
| 42 | |
| 43 | /* |
| 44 | * Retaining negative dentries for an in-memory filesystem just wastes |
| 45 | * memory and lookup time: arrange for them to be deleted immediately. |
| 46 | */ |
| 47 | int always_delete_dentry(const struct dentry *dentry) |
| 48 | { |
| 49 | return 1; |
| 50 | } |
| 51 | EXPORT_SYMBOL(always_delete_dentry); |
| 52 | |
| 53 | const struct dentry_operations simple_dentry_operations = { |
| 54 | .d_delete = always_delete_dentry, |
| 55 | }; |
| 56 | EXPORT_SYMBOL(simple_dentry_operations); |
| 57 | |
| 58 | /* |
| 59 | * Lookup the data. This is trivial - if the dentry didn't already |
| 60 | * exist, we know it is negative. Set d_op to delete negative dentries. |
| 61 | */ |
| 62 | struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) |
| 63 | { |
| 64 | if (dentry->d_name.len > NAME_MAX) |
| 65 | return ERR_PTR(-ENAMETOOLONG); |
| 66 | if (!dentry->d_sb->s_d_op) |
| 67 | d_set_d_op(dentry, &simple_dentry_operations); |
| 68 | d_add(dentry, NULL); |
| 69 | return NULL; |
| 70 | } |
| 71 | EXPORT_SYMBOL(simple_lookup); |
| 72 | |
| 73 | int dcache_dir_open(struct inode *inode, struct file *file) |
| 74 | { |
| 75 | file->private_data = d_alloc_cursor(file->f_path.dentry); |
| 76 | |
| 77 | return file->private_data ? 0 : -ENOMEM; |
| 78 | } |
| 79 | EXPORT_SYMBOL(dcache_dir_open); |
| 80 | |
| 81 | int dcache_dir_close(struct inode *inode, struct file *file) |
| 82 | { |
| 83 | dput(file->private_data); |
| 84 | return 0; |
| 85 | } |
| 86 | EXPORT_SYMBOL(dcache_dir_close); |
| 87 | |
| 88 | /* parent is locked at least shared */ |
| 89 | static struct dentry *next_positive(struct dentry *parent, |
| 90 | struct list_head *from, |
| 91 | int count) |
| 92 | { |
| 93 | unsigned *seq = &parent->d_inode->i_dir_seq, n; |
| 94 | struct dentry *res; |
| 95 | struct list_head *p; |
| 96 | bool skipped; |
| 97 | int i; |
| 98 | |
| 99 | retry: |
| 100 | i = count; |
| 101 | skipped = false; |
| 102 | n = smp_load_acquire(seq) & ~1; |
| 103 | res = NULL; |
| 104 | rcu_read_lock(); |
| 105 | for (p = from->next; p != &parent->d_subdirs; p = p->next) { |
| 106 | struct dentry *d = list_entry(p, struct dentry, d_child); |
| 107 | if (!simple_positive(d)) { |
| 108 | skipped = true; |
| 109 | } else if (!--i) { |
| 110 | res = d; |
| 111 | break; |
| 112 | } |
| 113 | } |
| 114 | rcu_read_unlock(); |
| 115 | if (skipped) { |
| 116 | smp_rmb(); |
| 117 | if (unlikely(*seq != n)) |
| 118 | goto retry; |
| 119 | } |
| 120 | return res; |
| 121 | } |
| 122 | |
| 123 | static void move_cursor(struct dentry *cursor, struct list_head *after) |
| 124 | { |
| 125 | struct dentry *parent = cursor->d_parent; |
| 126 | unsigned n, *seq = &parent->d_inode->i_dir_seq; |
| 127 | spin_lock(&parent->d_lock); |
| 128 | for (;;) { |
| 129 | n = *seq; |
| 130 | if (!(n & 1) && cmpxchg(seq, n, n + 1) == n) |
| 131 | break; |
| 132 | cpu_relax(); |
| 133 | } |
| 134 | __list_del(cursor->d_child.prev, cursor->d_child.next); |
| 135 | if (after) |
| 136 | list_add(&cursor->d_child, after); |
| 137 | else |
| 138 | list_add_tail(&cursor->d_child, &parent->d_subdirs); |
| 139 | smp_store_release(seq, n + 2); |
| 140 | spin_unlock(&parent->d_lock); |
| 141 | } |
| 142 | |
| 143 | loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence) |
| 144 | { |
| 145 | struct dentry *dentry = file->f_path.dentry; |
| 146 | switch (whence) { |
| 147 | case 1: |
| 148 | offset += file->f_pos; |
| 149 | case 0: |
| 150 | if (offset >= 0) |
| 151 | break; |
| 152 | default: |
| 153 | return -EINVAL; |
| 154 | } |
| 155 | if (offset != file->f_pos) { |
| 156 | file->f_pos = offset; |
| 157 | if (file->f_pos >= 2) { |
| 158 | struct dentry *cursor = file->private_data; |
| 159 | struct dentry *to; |
| 160 | loff_t n = file->f_pos - 2; |
| 161 | |
| 162 | inode_lock_shared(dentry->d_inode); |
| 163 | to = next_positive(dentry, &dentry->d_subdirs, n); |
| 164 | move_cursor(cursor, to ? &to->d_child : NULL); |
| 165 | inode_unlock_shared(dentry->d_inode); |
| 166 | } |
| 167 | } |
| 168 | return offset; |
| 169 | } |
| 170 | EXPORT_SYMBOL(dcache_dir_lseek); |
| 171 | |
| 172 | /* Relationship between i_mode and the DT_xxx types */ |
| 173 | static inline unsigned char dt_type(struct inode *inode) |
| 174 | { |
| 175 | return (inode->i_mode >> 12) & 15; |
| 176 | } |
| 177 | |
| 178 | /* |
| 179 | * Directory is locked and all positive dentries in it are safe, since |
| 180 | * for ramfs-type trees they can't go away without unlink() or rmdir(), |
| 181 | * both impossible due to the lock on directory. |
| 182 | */ |
| 183 | |
| 184 | int dcache_readdir(struct file *file, struct dir_context *ctx) |
| 185 | { |
| 186 | struct dentry *dentry = file->f_path.dentry; |
| 187 | struct dentry *cursor = file->private_data; |
| 188 | struct list_head *p = &cursor->d_child; |
| 189 | struct dentry *next; |
| 190 | bool moved = false; |
| 191 | |
| 192 | if (!dir_emit_dots(file, ctx)) |
| 193 | return 0; |
| 194 | |
| 195 | if (ctx->pos == 2) |
| 196 | p = &dentry->d_subdirs; |
| 197 | while ((next = next_positive(dentry, p, 1)) != NULL) { |
| 198 | if (!dir_emit(ctx, next->d_name.name, next->d_name.len, |
| 199 | d_inode(next)->i_ino, dt_type(d_inode(next)))) |
| 200 | break; |
| 201 | moved = true; |
| 202 | p = &next->d_child; |
| 203 | ctx->pos++; |
| 204 | } |
| 205 | if (moved) |
| 206 | move_cursor(cursor, p); |
| 207 | return 0; |
| 208 | } |
| 209 | EXPORT_SYMBOL(dcache_readdir); |
| 210 | |
| 211 | ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos) |
| 212 | { |
| 213 | return -EISDIR; |
| 214 | } |
| 215 | EXPORT_SYMBOL(generic_read_dir); |
| 216 | |
| 217 | const struct file_operations simple_dir_operations = { |
| 218 | .open = dcache_dir_open, |
| 219 | .release = dcache_dir_close, |
| 220 | .llseek = dcache_dir_lseek, |
| 221 | .read = generic_read_dir, |
| 222 | .iterate_shared = dcache_readdir, |
| 223 | .fsync = noop_fsync, |
| 224 | }; |
| 225 | EXPORT_SYMBOL(simple_dir_operations); |
| 226 | |
| 227 | const struct inode_operations simple_dir_inode_operations = { |
| 228 | .lookup = simple_lookup, |
| 229 | }; |
| 230 | EXPORT_SYMBOL(simple_dir_inode_operations); |
| 231 | |
| 232 | static const struct super_operations simple_super_operations = { |
| 233 | .statfs = simple_statfs, |
| 234 | }; |
| 235 | |
| 236 | /* |
| 237 | * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that |
| 238 | * will never be mountable) |
| 239 | */ |
| 240 | struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name, |
| 241 | const struct super_operations *ops, const struct xattr_handler **xattr, |
| 242 | const struct dentry_operations *dops, unsigned long magic) |
| 243 | { |
| 244 | struct super_block *s; |
| 245 | struct dentry *dentry; |
| 246 | struct inode *root; |
| 247 | struct qstr d_name = QSTR_INIT(name, strlen(name)); |
| 248 | |
| 249 | s = sget_userns(fs_type, NULL, set_anon_super, MS_KERNMOUNT|MS_NOUSER, |
| 250 | &init_user_ns, NULL); |
| 251 | if (IS_ERR(s)) |
| 252 | return ERR_CAST(s); |
| 253 | |
| 254 | s->s_maxbytes = MAX_LFS_FILESIZE; |
| 255 | s->s_blocksize = PAGE_SIZE; |
| 256 | s->s_blocksize_bits = PAGE_SHIFT; |
| 257 | s->s_magic = magic; |
| 258 | s->s_op = ops ? ops : &simple_super_operations; |
| 259 | s->s_xattr = xattr; |
| 260 | s->s_time_gran = 1; |
| 261 | root = new_inode(s); |
| 262 | if (!root) |
| 263 | goto Enomem; |
| 264 | /* |
| 265 | * since this is the first inode, make it number 1. New inodes created |
| 266 | * after this must take care not to collide with it (by passing |
| 267 | * max_reserved of 1 to iunique). |
| 268 | */ |
| 269 | root->i_ino = 1; |
| 270 | root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; |
| 271 | root->i_atime = root->i_mtime = root->i_ctime = current_time(root); |
| 272 | dentry = __d_alloc(s, &d_name); |
| 273 | if (!dentry) { |
| 274 | iput(root); |
| 275 | goto Enomem; |
| 276 | } |
| 277 | d_instantiate(dentry, root); |
| 278 | s->s_root = dentry; |
| 279 | s->s_d_op = dops; |
| 280 | s->s_flags |= MS_ACTIVE; |
| 281 | return dget(s->s_root); |
| 282 | |
| 283 | Enomem: |
| 284 | deactivate_locked_super(s); |
| 285 | return ERR_PTR(-ENOMEM); |
| 286 | } |
| 287 | EXPORT_SYMBOL(mount_pseudo_xattr); |
| 288 | |
| 289 | int simple_open(struct inode *inode, struct file *file) |
| 290 | { |
| 291 | if (inode->i_private) |
| 292 | file->private_data = inode->i_private; |
| 293 | return 0; |
| 294 | } |
| 295 | EXPORT_SYMBOL(simple_open); |
| 296 | |
| 297 | int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) |
| 298 | { |
| 299 | struct inode *inode = d_inode(old_dentry); |
| 300 | |
| 301 | inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode); |
| 302 | inc_nlink(inode); |
| 303 | ihold(inode); |
| 304 | dget(dentry); |
| 305 | d_instantiate(dentry, inode); |
| 306 | return 0; |
| 307 | } |
| 308 | EXPORT_SYMBOL(simple_link); |
| 309 | |
| 310 | int simple_empty(struct dentry *dentry) |
| 311 | { |
| 312 | struct dentry *child; |
| 313 | int ret = 0; |
| 314 | |
| 315 | spin_lock(&dentry->d_lock); |
| 316 | list_for_each_entry(child, &dentry->d_subdirs, d_child) { |
| 317 | spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); |
| 318 | if (simple_positive(child)) { |
| 319 | spin_unlock(&child->d_lock); |
| 320 | goto out; |
| 321 | } |
| 322 | spin_unlock(&child->d_lock); |
| 323 | } |
| 324 | ret = 1; |
| 325 | out: |
| 326 | spin_unlock(&dentry->d_lock); |
| 327 | return ret; |
| 328 | } |
| 329 | EXPORT_SYMBOL(simple_empty); |
| 330 | |
| 331 | int simple_unlink(struct inode *dir, struct dentry *dentry) |
| 332 | { |
| 333 | struct inode *inode = d_inode(dentry); |
| 334 | |
| 335 | inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode); |
| 336 | drop_nlink(inode); |
| 337 | dput(dentry); |
| 338 | return 0; |
| 339 | } |
| 340 | EXPORT_SYMBOL(simple_unlink); |
| 341 | |
| 342 | int simple_rmdir(struct inode *dir, struct dentry *dentry) |
| 343 | { |
| 344 | if (!simple_empty(dentry)) |
| 345 | return -ENOTEMPTY; |
| 346 | |
| 347 | drop_nlink(d_inode(dentry)); |
| 348 | simple_unlink(dir, dentry); |
| 349 | drop_nlink(dir); |
| 350 | return 0; |
| 351 | } |
| 352 | EXPORT_SYMBOL(simple_rmdir); |
| 353 | |
| 354 | int simple_rename(struct inode *old_dir, struct dentry *old_dentry, |
| 355 | struct inode *new_dir, struct dentry *new_dentry, |
| 356 | unsigned int flags) |
| 357 | { |
| 358 | struct inode *inode = d_inode(old_dentry); |
| 359 | int they_are_dirs = d_is_dir(old_dentry); |
| 360 | |
| 361 | if (flags & ~RENAME_NOREPLACE) |
| 362 | return -EINVAL; |
| 363 | |
| 364 | if (!simple_empty(new_dentry)) |
| 365 | return -ENOTEMPTY; |
| 366 | |
| 367 | if (d_really_is_positive(new_dentry)) { |
| 368 | simple_unlink(new_dir, new_dentry); |
| 369 | if (they_are_dirs) { |
| 370 | drop_nlink(d_inode(new_dentry)); |
| 371 | drop_nlink(old_dir); |
| 372 | } |
| 373 | } else if (they_are_dirs) { |
| 374 | drop_nlink(old_dir); |
| 375 | inc_nlink(new_dir); |
| 376 | } |
| 377 | |
| 378 | old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime = |
| 379 | new_dir->i_mtime = inode->i_ctime = current_time(old_dir); |
| 380 | |
| 381 | return 0; |
| 382 | } |
| 383 | EXPORT_SYMBOL(simple_rename); |
| 384 | |
| 385 | /** |
| 386 | * simple_setattr - setattr for simple filesystem |
| 387 | * @dentry: dentry |
| 388 | * @iattr: iattr structure |
| 389 | * |
| 390 | * Returns 0 on success, -error on failure. |
| 391 | * |
| 392 | * simple_setattr is a simple ->setattr implementation without a proper |
| 393 | * implementation of size changes. |
| 394 | * |
| 395 | * It can either be used for in-memory filesystems or special files |
| 396 | * on simple regular filesystems. Anything that needs to change on-disk |
| 397 | * or wire state on size changes needs its own setattr method. |
| 398 | */ |
| 399 | int simple_setattr(struct dentry *dentry, struct iattr *iattr) |
| 400 | { |
| 401 | struct inode *inode = d_inode(dentry); |
| 402 | int error; |
| 403 | |
| 404 | error = setattr_prepare(dentry, iattr); |
| 405 | if (error) |
| 406 | return error; |
| 407 | |
| 408 | if (iattr->ia_valid & ATTR_SIZE) |
| 409 | truncate_setsize(inode, iattr->ia_size); |
| 410 | setattr_copy(inode, iattr); |
| 411 | mark_inode_dirty(inode); |
| 412 | return 0; |
| 413 | } |
| 414 | EXPORT_SYMBOL(simple_setattr); |
| 415 | |
| 416 | int simple_readpage(struct file *file, struct page *page) |
| 417 | { |
| 418 | clear_highpage(page); |
| 419 | flush_dcache_page(page); |
| 420 | SetPageUptodate(page); |
| 421 | unlock_page(page); |
| 422 | return 0; |
| 423 | } |
| 424 | EXPORT_SYMBOL(simple_readpage); |
| 425 | |
| 426 | int simple_write_begin(struct file *file, struct address_space *mapping, |
| 427 | loff_t pos, unsigned len, unsigned flags, |
| 428 | struct page **pagep, void **fsdata) |
| 429 | { |
| 430 | struct page *page; |
| 431 | pgoff_t index; |
| 432 | |
| 433 | index = pos >> PAGE_SHIFT; |
| 434 | |
| 435 | page = grab_cache_page_write_begin(mapping, index, flags); |
| 436 | if (!page) |
| 437 | return -ENOMEM; |
| 438 | |
| 439 | *pagep = page; |
| 440 | |
| 441 | if (!PageUptodate(page) && (len != PAGE_SIZE)) { |
| 442 | unsigned from = pos & (PAGE_SIZE - 1); |
| 443 | |
| 444 | zero_user_segments(page, 0, from, from + len, PAGE_SIZE); |
| 445 | } |
| 446 | return 0; |
| 447 | } |
| 448 | EXPORT_SYMBOL(simple_write_begin); |
| 449 | |
| 450 | /** |
| 451 | * simple_write_end - .write_end helper for non-block-device FSes |
| 452 | * @available: See .write_end of address_space_operations |
| 453 | * @file: " |
| 454 | * @mapping: " |
| 455 | * @pos: " |
| 456 | * @len: " |
| 457 | * @copied: " |
| 458 | * @page: " |
| 459 | * @fsdata: " |
| 460 | * |
| 461 | * simple_write_end does the minimum needed for updating a page after writing is |
| 462 | * done. It has the same API signature as the .write_end of |
| 463 | * address_space_operations vector. So it can just be set onto .write_end for |
| 464 | * FSes that don't need any other processing. i_mutex is assumed to be held. |
| 465 | * Block based filesystems should use generic_write_end(). |
| 466 | * NOTE: Even though i_size might get updated by this function, mark_inode_dirty |
| 467 | * is not called, so a filesystem that actually does store data in .write_inode |
| 468 | * should extend on what's done here with a call to mark_inode_dirty() in the |
| 469 | * case that i_size has changed. |
| 470 | * |
| 471 | * Use *ONLY* with simple_readpage() |
| 472 | */ |
| 473 | int simple_write_end(struct file *file, struct address_space *mapping, |
| 474 | loff_t pos, unsigned len, unsigned copied, |
| 475 | struct page *page, void *fsdata) |
| 476 | { |
| 477 | struct inode *inode = page->mapping->host; |
| 478 | loff_t last_pos = pos + copied; |
| 479 | |
| 480 | /* zero the stale part of the page if we did a short copy */ |
| 481 | if (!PageUptodate(page)) { |
| 482 | if (copied < len) { |
| 483 | unsigned from = pos & (PAGE_SIZE - 1); |
| 484 | |
| 485 | zero_user(page, from + copied, len - copied); |
| 486 | } |
| 487 | SetPageUptodate(page); |
| 488 | } |
| 489 | /* |
| 490 | * No need to use i_size_read() here, the i_size |
| 491 | * cannot change under us because we hold the i_mutex. |
| 492 | */ |
| 493 | if (last_pos > inode->i_size) |
| 494 | i_size_write(inode, last_pos); |
| 495 | |
| 496 | set_page_dirty(page); |
| 497 | unlock_page(page); |
| 498 | put_page(page); |
| 499 | |
| 500 | return copied; |
| 501 | } |
| 502 | EXPORT_SYMBOL(simple_write_end); |
| 503 | |
| 504 | /* |
| 505 | * the inodes created here are not hashed. If you use iunique to generate |
| 506 | * unique inode values later for this filesystem, then you must take care |
| 507 | * to pass it an appropriate max_reserved value to avoid collisions. |
| 508 | */ |
| 509 | int simple_fill_super(struct super_block *s, unsigned long magic, |
| 510 | const struct tree_descr *files) |
| 511 | { |
| 512 | struct inode *inode; |
| 513 | struct dentry *root; |
| 514 | struct dentry *dentry; |
| 515 | int i; |
| 516 | |
| 517 | s->s_blocksize = PAGE_SIZE; |
| 518 | s->s_blocksize_bits = PAGE_SHIFT; |
| 519 | s->s_magic = magic; |
| 520 | s->s_op = &simple_super_operations; |
| 521 | s->s_time_gran = 1; |
| 522 | |
| 523 | inode = new_inode(s); |
| 524 | if (!inode) |
| 525 | return -ENOMEM; |
| 526 | /* |
| 527 | * because the root inode is 1, the files array must not contain an |
| 528 | * entry at index 1 |
| 529 | */ |
| 530 | inode->i_ino = 1; |
| 531 | inode->i_mode = S_IFDIR | 0755; |
| 532 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
| 533 | inode->i_op = &simple_dir_inode_operations; |
| 534 | inode->i_fop = &simple_dir_operations; |
| 535 | set_nlink(inode, 2); |
| 536 | root = d_make_root(inode); |
| 537 | if (!root) |
| 538 | return -ENOMEM; |
| 539 | for (i = 0; !files->name || files->name[0]; i++, files++) { |
| 540 | if (!files->name) |
| 541 | continue; |
| 542 | |
| 543 | /* warn if it tries to conflict with the root inode */ |
| 544 | if (unlikely(i == 1)) |
| 545 | printk(KERN_WARNING "%s: %s passed in a files array" |
| 546 | "with an index of 1!\n", __func__, |
| 547 | s->s_type->name); |
| 548 | |
| 549 | dentry = d_alloc_name(root, files->name); |
| 550 | if (!dentry) |
| 551 | goto out; |
| 552 | inode = new_inode(s); |
| 553 | if (!inode) { |
| 554 | dput(dentry); |
| 555 | goto out; |
| 556 | } |
| 557 | inode->i_mode = S_IFREG | files->mode; |
| 558 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
| 559 | inode->i_fop = files->ops; |
| 560 | inode->i_ino = i; |
| 561 | d_add(dentry, inode); |
| 562 | } |
| 563 | s->s_root = root; |
| 564 | return 0; |
| 565 | out: |
| 566 | d_genocide(root); |
| 567 | shrink_dcache_parent(root); |
| 568 | dput(root); |
| 569 | return -ENOMEM; |
| 570 | } |
| 571 | EXPORT_SYMBOL(simple_fill_super); |
| 572 | |
| 573 | static DEFINE_SPINLOCK(pin_fs_lock); |
| 574 | |
| 575 | int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count) |
| 576 | { |
| 577 | struct vfsmount *mnt = NULL; |
| 578 | spin_lock(&pin_fs_lock); |
| 579 | if (unlikely(!*mount)) { |
| 580 | spin_unlock(&pin_fs_lock); |
| 581 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, NULL); |
| 582 | if (IS_ERR(mnt)) |
| 583 | return PTR_ERR(mnt); |
| 584 | spin_lock(&pin_fs_lock); |
| 585 | if (!*mount) |
| 586 | *mount = mnt; |
| 587 | } |
| 588 | mntget(*mount); |
| 589 | ++*count; |
| 590 | spin_unlock(&pin_fs_lock); |
| 591 | mntput(mnt); |
| 592 | return 0; |
| 593 | } |
| 594 | EXPORT_SYMBOL(simple_pin_fs); |
| 595 | |
| 596 | void simple_release_fs(struct vfsmount **mount, int *count) |
| 597 | { |
| 598 | struct vfsmount *mnt; |
| 599 | spin_lock(&pin_fs_lock); |
| 600 | mnt = *mount; |
| 601 | if (!--*count) |
| 602 | *mount = NULL; |
| 603 | spin_unlock(&pin_fs_lock); |
| 604 | mntput(mnt); |
| 605 | } |
| 606 | EXPORT_SYMBOL(simple_release_fs); |
| 607 | |
| 608 | /** |
| 609 | * simple_read_from_buffer - copy data from the buffer to user space |
| 610 | * @to: the user space buffer to read to |
| 611 | * @count: the maximum number of bytes to read |
| 612 | * @ppos: the current position in the buffer |
| 613 | * @from: the buffer to read from |
| 614 | * @available: the size of the buffer |
| 615 | * |
| 616 | * The simple_read_from_buffer() function reads up to @count bytes from the |
| 617 | * buffer @from at offset @ppos into the user space address starting at @to. |
| 618 | * |
| 619 | * On success, the number of bytes read is returned and the offset @ppos is |
| 620 | * advanced by this number, or negative value is returned on error. |
| 621 | **/ |
| 622 | ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, |
| 623 | const void *from, size_t available) |
| 624 | { |
| 625 | loff_t pos = *ppos; |
| 626 | size_t ret; |
| 627 | |
| 628 | if (pos < 0) |
| 629 | return -EINVAL; |
| 630 | if (pos >= available || !count) |
| 631 | return 0; |
| 632 | if (count > available - pos) |
| 633 | count = available - pos; |
| 634 | ret = copy_to_user(to, from + pos, count); |
| 635 | if (ret == count) |
| 636 | return -EFAULT; |
| 637 | count -= ret; |
| 638 | *ppos = pos + count; |
| 639 | return count; |
| 640 | } |
| 641 | EXPORT_SYMBOL(simple_read_from_buffer); |
| 642 | |
| 643 | /** |
| 644 | * simple_write_to_buffer - copy data from user space to the buffer |
| 645 | * @to: the buffer to write to |
| 646 | * @available: the size of the buffer |
| 647 | * @ppos: the current position in the buffer |
| 648 | * @from: the user space buffer to read from |
| 649 | * @count: the maximum number of bytes to read |
| 650 | * |
| 651 | * The simple_write_to_buffer() function reads up to @count bytes from the user |
| 652 | * space address starting at @from into the buffer @to at offset @ppos. |
| 653 | * |
| 654 | * On success, the number of bytes written is returned and the offset @ppos is |
| 655 | * advanced by this number, or negative value is returned on error. |
| 656 | **/ |
| 657 | ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos, |
| 658 | const void __user *from, size_t count) |
| 659 | { |
| 660 | loff_t pos = *ppos; |
| 661 | size_t res; |
| 662 | |
| 663 | if (pos < 0) |
| 664 | return -EINVAL; |
| 665 | if (pos >= available || !count) |
| 666 | return 0; |
| 667 | if (count > available - pos) |
| 668 | count = available - pos; |
| 669 | res = copy_from_user(to + pos, from, count); |
| 670 | if (res == count) |
| 671 | return -EFAULT; |
| 672 | count -= res; |
| 673 | *ppos = pos + count; |
| 674 | return count; |
| 675 | } |
| 676 | EXPORT_SYMBOL(simple_write_to_buffer); |
| 677 | |
| 678 | /** |
| 679 | * memory_read_from_buffer - copy data from the buffer |
| 680 | * @to: the kernel space buffer to read to |
| 681 | * @count: the maximum number of bytes to read |
| 682 | * @ppos: the current position in the buffer |
| 683 | * @from: the buffer to read from |
| 684 | * @available: the size of the buffer |
| 685 | * |
| 686 | * The memory_read_from_buffer() function reads up to @count bytes from the |
| 687 | * buffer @from at offset @ppos into the kernel space address starting at @to. |
| 688 | * |
| 689 | * On success, the number of bytes read is returned and the offset @ppos is |
| 690 | * advanced by this number, or negative value is returned on error. |
| 691 | **/ |
| 692 | ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos, |
| 693 | const void *from, size_t available) |
| 694 | { |
| 695 | loff_t pos = *ppos; |
| 696 | |
| 697 | if (pos < 0) |
| 698 | return -EINVAL; |
| 699 | if (pos >= available) |
| 700 | return 0; |
| 701 | if (count > available - pos) |
| 702 | count = available - pos; |
| 703 | memcpy(to, from + pos, count); |
| 704 | *ppos = pos + count; |
| 705 | |
| 706 | return count; |
| 707 | } |
| 708 | EXPORT_SYMBOL(memory_read_from_buffer); |
| 709 | |
| 710 | /* |
| 711 | * Transaction based IO. |
| 712 | * The file expects a single write which triggers the transaction, and then |
| 713 | * possibly a read which collects the result - which is stored in a |
| 714 | * file-local buffer. |
| 715 | */ |
| 716 | |
| 717 | void simple_transaction_set(struct file *file, size_t n) |
| 718 | { |
| 719 | struct simple_transaction_argresp *ar = file->private_data; |
| 720 | |
| 721 | BUG_ON(n > SIMPLE_TRANSACTION_LIMIT); |
| 722 | |
| 723 | /* |
| 724 | * The barrier ensures that ar->size will really remain zero until |
| 725 | * ar->data is ready for reading. |
| 726 | */ |
| 727 | smp_mb(); |
| 728 | ar->size = n; |
| 729 | } |
| 730 | EXPORT_SYMBOL(simple_transaction_set); |
| 731 | |
| 732 | char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) |
| 733 | { |
| 734 | struct simple_transaction_argresp *ar; |
| 735 | static DEFINE_SPINLOCK(simple_transaction_lock); |
| 736 | |
| 737 | if (size > SIMPLE_TRANSACTION_LIMIT - 1) |
| 738 | return ERR_PTR(-EFBIG); |
| 739 | |
| 740 | ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); |
| 741 | if (!ar) |
| 742 | return ERR_PTR(-ENOMEM); |
| 743 | |
| 744 | spin_lock(&simple_transaction_lock); |
| 745 | |
| 746 | /* only one write allowed per open */ |
| 747 | if (file->private_data) { |
| 748 | spin_unlock(&simple_transaction_lock); |
| 749 | free_page((unsigned long)ar); |
| 750 | return ERR_PTR(-EBUSY); |
| 751 | } |
| 752 | |
| 753 | file->private_data = ar; |
| 754 | |
| 755 | spin_unlock(&simple_transaction_lock); |
| 756 | |
| 757 | if (copy_from_user(ar->data, buf, size)) |
| 758 | return ERR_PTR(-EFAULT); |
| 759 | |
| 760 | return ar->data; |
| 761 | } |
| 762 | EXPORT_SYMBOL(simple_transaction_get); |
| 763 | |
| 764 | ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) |
| 765 | { |
| 766 | struct simple_transaction_argresp *ar = file->private_data; |
| 767 | |
| 768 | if (!ar) |
| 769 | return 0; |
| 770 | return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); |
| 771 | } |
| 772 | EXPORT_SYMBOL(simple_transaction_read); |
| 773 | |
| 774 | int simple_transaction_release(struct inode *inode, struct file *file) |
| 775 | { |
| 776 | free_page((unsigned long)file->private_data); |
| 777 | return 0; |
| 778 | } |
| 779 | EXPORT_SYMBOL(simple_transaction_release); |
| 780 | |
| 781 | /* Simple attribute files */ |
| 782 | |
| 783 | struct simple_attr { |
| 784 | int (*get)(void *, u64 *); |
| 785 | int (*set)(void *, u64); |
| 786 | char get_buf[24]; /* enough to store a u64 and "\n\0" */ |
| 787 | char set_buf[24]; |
| 788 | void *data; |
| 789 | const char *fmt; /* format for read operation */ |
| 790 | struct mutex mutex; /* protects access to these buffers */ |
| 791 | }; |
| 792 | |
| 793 | /* simple_attr_open is called by an actual attribute open file operation |
| 794 | * to set the attribute specific access operations. */ |
| 795 | int simple_attr_open(struct inode *inode, struct file *file, |
| 796 | int (*get)(void *, u64 *), int (*set)(void *, u64), |
| 797 | const char *fmt) |
| 798 | { |
| 799 | struct simple_attr *attr; |
| 800 | |
| 801 | attr = kmalloc(sizeof(*attr), GFP_KERNEL); |
| 802 | if (!attr) |
| 803 | return -ENOMEM; |
| 804 | |
| 805 | attr->get = get; |
| 806 | attr->set = set; |
| 807 | attr->data = inode->i_private; |
| 808 | attr->fmt = fmt; |
| 809 | mutex_init(&attr->mutex); |
| 810 | |
| 811 | file->private_data = attr; |
| 812 | |
| 813 | return nonseekable_open(inode, file); |
| 814 | } |
| 815 | EXPORT_SYMBOL_GPL(simple_attr_open); |
| 816 | |
| 817 | int simple_attr_release(struct inode *inode, struct file *file) |
| 818 | { |
| 819 | kfree(file->private_data); |
| 820 | return 0; |
| 821 | } |
| 822 | EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */ |
| 823 | |
| 824 | /* read from the buffer that is filled with the get function */ |
| 825 | ssize_t simple_attr_read(struct file *file, char __user *buf, |
| 826 | size_t len, loff_t *ppos) |
| 827 | { |
| 828 | struct simple_attr *attr; |
| 829 | size_t size; |
| 830 | ssize_t ret; |
| 831 | |
| 832 | attr = file->private_data; |
| 833 | |
| 834 | if (!attr->get) |
| 835 | return -EACCES; |
| 836 | |
| 837 | ret = mutex_lock_interruptible(&attr->mutex); |
| 838 | if (ret) |
| 839 | return ret; |
| 840 | |
| 841 | if (*ppos) { /* continued read */ |
| 842 | size = strlen(attr->get_buf); |
| 843 | } else { /* first read */ |
| 844 | u64 val; |
| 845 | ret = attr->get(attr->data, &val); |
| 846 | if (ret) |
| 847 | goto out; |
| 848 | |
| 849 | size = scnprintf(attr->get_buf, sizeof(attr->get_buf), |
| 850 | attr->fmt, (unsigned long long)val); |
| 851 | } |
| 852 | |
| 853 | ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); |
| 854 | out: |
| 855 | mutex_unlock(&attr->mutex); |
| 856 | return ret; |
| 857 | } |
| 858 | EXPORT_SYMBOL_GPL(simple_attr_read); |
| 859 | |
| 860 | /* interpret the buffer as a number to call the set function with */ |
| 861 | ssize_t simple_attr_write(struct file *file, const char __user *buf, |
| 862 | size_t len, loff_t *ppos) |
| 863 | { |
| 864 | struct simple_attr *attr; |
| 865 | u64 val; |
| 866 | size_t size; |
| 867 | ssize_t ret; |
| 868 | |
| 869 | attr = file->private_data; |
| 870 | if (!attr->set) |
| 871 | return -EACCES; |
| 872 | |
| 873 | ret = mutex_lock_interruptible(&attr->mutex); |
| 874 | if (ret) |
| 875 | return ret; |
| 876 | |
| 877 | ret = -EFAULT; |
| 878 | size = min(sizeof(attr->set_buf) - 1, len); |
| 879 | if (copy_from_user(attr->set_buf, buf, size)) |
| 880 | goto out; |
| 881 | |
| 882 | attr->set_buf[size] = '\0'; |
| 883 | val = simple_strtoll(attr->set_buf, NULL, 0); |
| 884 | ret = attr->set(attr->data, val); |
| 885 | if (ret == 0) |
| 886 | ret = len; /* on success, claim we got the whole input */ |
| 887 | out: |
| 888 | mutex_unlock(&attr->mutex); |
| 889 | return ret; |
| 890 | } |
| 891 | EXPORT_SYMBOL_GPL(simple_attr_write); |
| 892 | |
| 893 | /** |
| 894 | * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation |
| 895 | * @sb: filesystem to do the file handle conversion on |
| 896 | * @fid: file handle to convert |
| 897 | * @fh_len: length of the file handle in bytes |
| 898 | * @fh_type: type of file handle |
| 899 | * @get_inode: filesystem callback to retrieve inode |
| 900 | * |
| 901 | * This function decodes @fid as long as it has one of the well-known |
| 902 | * Linux filehandle types and calls @get_inode on it to retrieve the |
| 903 | * inode for the object specified in the file handle. |
| 904 | */ |
| 905 | struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid, |
| 906 | int fh_len, int fh_type, struct inode *(*get_inode) |
| 907 | (struct super_block *sb, u64 ino, u32 gen)) |
| 908 | { |
| 909 | struct inode *inode = NULL; |
| 910 | |
| 911 | if (fh_len < 2) |
| 912 | return NULL; |
| 913 | |
| 914 | switch (fh_type) { |
| 915 | case FILEID_INO32_GEN: |
| 916 | case FILEID_INO32_GEN_PARENT: |
| 917 | inode = get_inode(sb, fid->i32.ino, fid->i32.gen); |
| 918 | break; |
| 919 | } |
| 920 | |
| 921 | return d_obtain_alias(inode); |
| 922 | } |
| 923 | EXPORT_SYMBOL_GPL(generic_fh_to_dentry); |
| 924 | |
| 925 | /** |
| 926 | * generic_fh_to_parent - generic helper for the fh_to_parent export operation |
| 927 | * @sb: filesystem to do the file handle conversion on |
| 928 | * @fid: file handle to convert |
| 929 | * @fh_len: length of the file handle in bytes |
| 930 | * @fh_type: type of file handle |
| 931 | * @get_inode: filesystem callback to retrieve inode |
| 932 | * |
| 933 | * This function decodes @fid as long as it has one of the well-known |
| 934 | * Linux filehandle types and calls @get_inode on it to retrieve the |
| 935 | * inode for the _parent_ object specified in the file handle if it |
| 936 | * is specified in the file handle, or NULL otherwise. |
| 937 | */ |
| 938 | struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid, |
| 939 | int fh_len, int fh_type, struct inode *(*get_inode) |
| 940 | (struct super_block *sb, u64 ino, u32 gen)) |
| 941 | { |
| 942 | struct inode *inode = NULL; |
| 943 | |
| 944 | if (fh_len <= 2) |
| 945 | return NULL; |
| 946 | |
| 947 | switch (fh_type) { |
| 948 | case FILEID_INO32_GEN_PARENT: |
| 949 | inode = get_inode(sb, fid->i32.parent_ino, |
| 950 | (fh_len > 3 ? fid->i32.parent_gen : 0)); |
| 951 | break; |
| 952 | } |
| 953 | |
| 954 | return d_obtain_alias(inode); |
| 955 | } |
| 956 | EXPORT_SYMBOL_GPL(generic_fh_to_parent); |
| 957 | |
| 958 | /** |
| 959 | * __generic_file_fsync - generic fsync implementation for simple filesystems |
| 960 | * |
| 961 | * @file: file to synchronize |
| 962 | * @start: start offset in bytes |
| 963 | * @end: end offset in bytes (inclusive) |
| 964 | * @datasync: only synchronize essential metadata if true |
| 965 | * |
| 966 | * This is a generic implementation of the fsync method for simple |
| 967 | * filesystems which track all non-inode metadata in the buffers list |
| 968 | * hanging off the address_space structure. |
| 969 | */ |
| 970 | int __generic_file_fsync(struct file *file, loff_t start, loff_t end, |
| 971 | int datasync) |
| 972 | { |
| 973 | struct inode *inode = file->f_mapping->host; |
| 974 | int err; |
| 975 | int ret; |
| 976 | |
| 977 | err = file_write_and_wait_range(file, start, end); |
| 978 | if (err) |
| 979 | return err; |
| 980 | |
| 981 | inode_lock(inode); |
| 982 | ret = sync_mapping_buffers(inode->i_mapping); |
| 983 | if (!(inode->i_state & I_DIRTY_ALL)) |
| 984 | goto out; |
| 985 | if (datasync && !(inode->i_state & I_DIRTY_DATASYNC)) |
| 986 | goto out; |
| 987 | |
| 988 | err = sync_inode_metadata(inode, 1); |
| 989 | if (ret == 0) |
| 990 | ret = err; |
| 991 | |
| 992 | out: |
| 993 | inode_unlock(inode); |
| 994 | /* check and advance again to catch errors after syncing out buffers */ |
| 995 | err = file_check_and_advance_wb_err(file); |
| 996 | if (ret == 0) |
| 997 | ret = err; |
| 998 | return ret; |
| 999 | } |
| 1000 | EXPORT_SYMBOL(__generic_file_fsync); |
| 1001 | |
| 1002 | /** |
| 1003 | * generic_file_fsync - generic fsync implementation for simple filesystems |
| 1004 | * with flush |
| 1005 | * @file: file to synchronize |
| 1006 | * @start: start offset in bytes |
| 1007 | * @end: end offset in bytes (inclusive) |
| 1008 | * @datasync: only synchronize essential metadata if true |
| 1009 | * |
| 1010 | */ |
| 1011 | |
| 1012 | int generic_file_fsync(struct file *file, loff_t start, loff_t end, |
| 1013 | int datasync) |
| 1014 | { |
| 1015 | struct inode *inode = file->f_mapping->host; |
| 1016 | int err; |
| 1017 | |
| 1018 | err = __generic_file_fsync(file, start, end, datasync); |
| 1019 | if (err) |
| 1020 | return err; |
| 1021 | return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL); |
| 1022 | } |
| 1023 | EXPORT_SYMBOL(generic_file_fsync); |
| 1024 | |
| 1025 | /** |
| 1026 | * generic_check_addressable - Check addressability of file system |
| 1027 | * @blocksize_bits: log of file system block size |
| 1028 | * @num_blocks: number of blocks in file system |
| 1029 | * |
| 1030 | * Determine whether a file system with @num_blocks blocks (and a |
| 1031 | * block size of 2**@blocksize_bits) is addressable by the sector_t |
| 1032 | * and page cache of the system. Return 0 if so and -EFBIG otherwise. |
| 1033 | */ |
| 1034 | int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks) |
| 1035 | { |
| 1036 | u64 last_fs_block = num_blocks - 1; |
| 1037 | u64 last_fs_page = |
| 1038 | last_fs_block >> (PAGE_SHIFT - blocksize_bits); |
| 1039 | |
| 1040 | if (unlikely(num_blocks == 0)) |
| 1041 | return 0; |
| 1042 | |
| 1043 | if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT)) |
| 1044 | return -EINVAL; |
| 1045 | |
| 1046 | if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) || |
| 1047 | (last_fs_page > (pgoff_t)(~0ULL))) { |
| 1048 | return -EFBIG; |
| 1049 | } |
| 1050 | return 0; |
| 1051 | } |
| 1052 | EXPORT_SYMBOL(generic_check_addressable); |
| 1053 | |
| 1054 | /* |
| 1055 | * No-op implementation of ->fsync for in-memory filesystems. |
| 1056 | */ |
| 1057 | int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync) |
| 1058 | { |
| 1059 | return 0; |
| 1060 | } |
| 1061 | EXPORT_SYMBOL(noop_fsync); |
| 1062 | |
| 1063 | /* Because kfree isn't assignment-compatible with void(void*) ;-/ */ |
| 1064 | void kfree_link(void *p) |
| 1065 | { |
| 1066 | kfree(p); |
| 1067 | } |
| 1068 | EXPORT_SYMBOL(kfree_link); |
| 1069 | |
| 1070 | /* |
| 1071 | * nop .set_page_dirty method so that people can use .page_mkwrite on |
| 1072 | * anon inodes. |
| 1073 | */ |
| 1074 | static int anon_set_page_dirty(struct page *page) |
| 1075 | { |
| 1076 | return 0; |
| 1077 | }; |
| 1078 | |
| 1079 | /* |
| 1080 | * A single inode exists for all anon_inode files. Contrary to pipes, |
| 1081 | * anon_inode inodes have no associated per-instance data, so we need |
| 1082 | * only allocate one of them. |
| 1083 | */ |
| 1084 | struct inode *alloc_anon_inode(struct super_block *s) |
| 1085 | { |
| 1086 | static const struct address_space_operations anon_aops = { |
| 1087 | .set_page_dirty = anon_set_page_dirty, |
| 1088 | }; |
| 1089 | struct inode *inode = new_inode_pseudo(s); |
| 1090 | |
| 1091 | if (!inode) |
| 1092 | return ERR_PTR(-ENOMEM); |
| 1093 | |
| 1094 | inode->i_ino = get_next_ino(); |
| 1095 | inode->i_mapping->a_ops = &anon_aops; |
| 1096 | |
| 1097 | /* |
| 1098 | * Mark the inode dirty from the very beginning, |
| 1099 | * that way it will never be moved to the dirty |
| 1100 | * list because mark_inode_dirty() will think |
| 1101 | * that it already _is_ on the dirty list. |
| 1102 | */ |
| 1103 | inode->i_state = I_DIRTY; |
| 1104 | inode->i_mode = S_IRUSR | S_IWUSR; |
| 1105 | inode->i_uid = current_fsuid(); |
| 1106 | inode->i_gid = current_fsgid(); |
| 1107 | inode->i_flags |= S_PRIVATE; |
| 1108 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
| 1109 | return inode; |
| 1110 | } |
| 1111 | EXPORT_SYMBOL(alloc_anon_inode); |
| 1112 | |
| 1113 | /** |
| 1114 | * simple_nosetlease - generic helper for prohibiting leases |
| 1115 | * @filp: file pointer |
| 1116 | * @arg: type of lease to obtain |
| 1117 | * @flp: new lease supplied for insertion |
| 1118 | * @priv: private data for lm_setup operation |
| 1119 | * |
| 1120 | * Generic helper for filesystems that do not wish to allow leases to be set. |
| 1121 | * All arguments are ignored and it just returns -EINVAL. |
| 1122 | */ |
| 1123 | int |
| 1124 | simple_nosetlease(struct file *filp, long arg, struct file_lock **flp, |
| 1125 | void **priv) |
| 1126 | { |
| 1127 | return -EINVAL; |
| 1128 | } |
| 1129 | EXPORT_SYMBOL(simple_nosetlease); |
| 1130 | |
| 1131 | const char *simple_get_link(struct dentry *dentry, struct inode *inode, |
| 1132 | struct delayed_call *done) |
| 1133 | { |
| 1134 | return inode->i_link; |
| 1135 | } |
| 1136 | EXPORT_SYMBOL(simple_get_link); |
| 1137 | |
| 1138 | const struct inode_operations simple_symlink_inode_operations = { |
| 1139 | .get_link = simple_get_link, |
| 1140 | }; |
| 1141 | EXPORT_SYMBOL(simple_symlink_inode_operations); |
| 1142 | |
| 1143 | /* |
| 1144 | * Operations for a permanently empty directory. |
| 1145 | */ |
| 1146 | static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) |
| 1147 | { |
| 1148 | return ERR_PTR(-ENOENT); |
| 1149 | } |
| 1150 | |
| 1151 | static int empty_dir_getattr(const struct path *path, struct kstat *stat, |
| 1152 | u32 request_mask, unsigned int query_flags) |
| 1153 | { |
| 1154 | struct inode *inode = d_inode(path->dentry); |
| 1155 | generic_fillattr(inode, stat); |
| 1156 | return 0; |
| 1157 | } |
| 1158 | |
| 1159 | static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr) |
| 1160 | { |
| 1161 | return -EPERM; |
| 1162 | } |
| 1163 | |
| 1164 | static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size) |
| 1165 | { |
| 1166 | return -EOPNOTSUPP; |
| 1167 | } |
| 1168 | |
| 1169 | static const struct inode_operations empty_dir_inode_operations = { |
| 1170 | .lookup = empty_dir_lookup, |
| 1171 | .permission = generic_permission, |
| 1172 | .setattr = empty_dir_setattr, |
| 1173 | .getattr = empty_dir_getattr, |
| 1174 | .listxattr = empty_dir_listxattr, |
| 1175 | }; |
| 1176 | |
| 1177 | static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence) |
| 1178 | { |
| 1179 | /* An empty directory has two entries . and .. at offsets 0 and 1 */ |
| 1180 | return generic_file_llseek_size(file, offset, whence, 2, 2); |
| 1181 | } |
| 1182 | |
| 1183 | static int empty_dir_readdir(struct file *file, struct dir_context *ctx) |
| 1184 | { |
| 1185 | dir_emit_dots(file, ctx); |
| 1186 | return 0; |
| 1187 | } |
| 1188 | |
| 1189 | static const struct file_operations empty_dir_operations = { |
| 1190 | .llseek = empty_dir_llseek, |
| 1191 | .read = generic_read_dir, |
| 1192 | .iterate_shared = empty_dir_readdir, |
| 1193 | .fsync = noop_fsync, |
| 1194 | }; |
| 1195 | |
| 1196 | |
| 1197 | void make_empty_dir_inode(struct inode *inode) |
| 1198 | { |
| 1199 | set_nlink(inode, 2); |
| 1200 | inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO; |
| 1201 | inode->i_uid = GLOBAL_ROOT_UID; |
| 1202 | inode->i_gid = GLOBAL_ROOT_GID; |
| 1203 | inode->i_rdev = 0; |
| 1204 | inode->i_size = 0; |
| 1205 | inode->i_blkbits = PAGE_SHIFT; |
| 1206 | inode->i_blocks = 0; |
| 1207 | |
| 1208 | inode->i_op = &empty_dir_inode_operations; |
| 1209 | inode->i_opflags &= ~IOP_XATTR; |
| 1210 | inode->i_fop = &empty_dir_operations; |
| 1211 | } |
| 1212 | |
| 1213 | bool is_empty_dir_inode(struct inode *inode) |
| 1214 | { |
| 1215 | return (inode->i_fop == &empty_dir_operations) && |
| 1216 | (inode->i_op == &empty_dir_inode_operations); |
| 1217 | } |