Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/fs/seq_file.c
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1 /* 2 * linux/fs/seq_file.c 3 * 4 * helper functions for making synthetic files from sequences of records. 5 * initial implementation -- AV, Oct 2001. 6 */ 7 8 #include <linux/fs.h> 9 #include <linux/export.h> 10 #include <linux/seq_file.h> 11 #include <linux/slab.h> 12 #include <linux/cred.h> 13 14 #include <asm/uaccess.h> 15 #include <asm/page.h> 16 17 18 /* 19 * seq_files have a buffer which can may overflow. When this happens a larger 20 * buffer is reallocated and all the data will be printed again. 21 * The overflow state is true when m->count == m->size. 22 */ 23 static bool seq_overflow(struct seq_file *m) 24 { 25 return m->count == m->size; 26 } 27 28 static void seq_set_overflow(struct seq_file *m) 29 { 30 m->count = m->size; 31 } 32 33 /** 34 * seq_open - initialize sequential file 35 * @file: file we initialize 36 * @op: method table describing the sequence 37 * 38 * seq_open() sets @file, associating it with a sequence described 39 * by @op. @op->start() sets the iterator up and returns the first 40 * element of sequence. @op->stop() shuts it down. @op->next() 41 * returns the next element of sequence. @op->show() prints element 42 * into the buffer. In case of error ->start() and ->next() return 43 * ERR_PTR(error). In the end of sequence they return %NULL. ->show() 44 * returns 0 in case of success and negative number in case of error. 45 * Returning SEQ_SKIP means "discard this element and move on". 46 */ 47 int seq_open(struct file *file, const struct seq_operations *op) 48 { 49 struct seq_file *p = file->private_data; 50 51 if (!p) { 52 p = kmalloc(sizeof(*p), GFP_KERNEL); 53 if (!p) 54 return -ENOMEM; 55 file->private_data = p; 56 } 57 memset(p, 0, sizeof(*p)); 58 mutex_init(&p->lock); 59 p->op = op; 60 #ifdef CONFIG_USER_NS 61 p->user_ns = file->f_cred->user_ns; 62 #endif 63 64 /* 65 * Wrappers around seq_open(e.g. swaps_open) need to be 66 * aware of this. If they set f_version themselves, they 67 * should call seq_open first and then set f_version. 68 */ 69 file->f_version = 0; 70 71 /* 72 * seq_files support lseek() and pread(). They do not implement 73 * write() at all, but we clear FMODE_PWRITE here for historical 74 * reasons. 75 * 76 * If a client of seq_files a) implements file.write() and b) wishes to 77 * support pwrite() then that client will need to implement its own 78 * file.open() which calls seq_open() and then sets FMODE_PWRITE. 79 */ 80 file->f_mode &= ~FMODE_PWRITE; 81 return 0; 82 } 83 EXPORT_SYMBOL(seq_open); 84 85 static int traverse(struct seq_file *m, loff_t offset) 86 { 87 loff_t pos = 0, index; 88 int error = 0; 89 void *p; 90 91 m->version = 0; 92 index = 0; 93 m->count = m->from = 0; 94 if (!offset) { 95 m->index = index; 96 return 0; 97 } 98 if (!m->buf) { 99 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 100 if (!m->buf) 101 return -ENOMEM; 102 } 103 p = m->op->start(m, &index); 104 while (p) { 105 error = PTR_ERR(p); 106 if (IS_ERR(p)) 107 break; 108 error = m->op->show(m, p); 109 if (error < 0) 110 break; 111 if (unlikely(error)) { 112 error = 0; 113 m->count = 0; 114 } 115 if (seq_overflow(m)) 116 goto Eoverflow; 117 if (pos + m->count > offset) { 118 m->from = offset - pos; 119 m->count -= m->from; 120 m->index = index; 121 break; 122 } 123 pos += m->count; 124 m->count = 0; 125 if (pos == offset) { 126 index++; 127 m->index = index; 128 break; 129 } 130 p = m->op->next(m, p, &index); 131 } 132 m->op->stop(m, p); 133 m->index = index; 134 return error; 135 136 Eoverflow: 137 m->op->stop(m, p); 138 kfree(m->buf); 139 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 140 return !m->buf ? -ENOMEM : -EAGAIN; 141 } 142 143 /** 144 * seq_read - ->read() method for sequential files. 145 * @file: the file to read from 146 * @buf: the buffer to read to 147 * @size: the maximum number of bytes to read 148 * @ppos: the current position in the file 149 * 150 * Ready-made ->f_op->read() 151 */ 152 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) 153 { 154 struct seq_file *m = file->private_data; 155 size_t copied = 0; 156 loff_t pos; 157 size_t n; 158 void *p; 159 int err = 0; 160 161 mutex_lock(&m->lock); 162 163 /* 164 * seq_file->op->..m_start/m_stop/m_next may do special actions 165 * or optimisations based on the file->f_version, so we want to 166 * pass the file->f_version to those methods. 167 * 168 * seq_file->version is just copy of f_version, and seq_file 169 * methods can treat it simply as file version. 170 * It is copied in first and copied out after all operations. 171 * It is convenient to have it as part of structure to avoid the 172 * need of passing another argument to all the seq_file methods. 173 */ 174 m->version = file->f_version; 175 176 /* Don't assume *ppos is where we left it */ 177 if (unlikely(*ppos != m->read_pos)) { 178 while ((err = traverse(m, *ppos)) == -EAGAIN) 179 ; 180 if (err) { 181 /* With prejudice... */ 182 m->read_pos = 0; 183 m->version = 0; 184 m->index = 0; 185 m->count = 0; 186 goto Done; 187 } else { 188 m->read_pos = *ppos; 189 } 190 } 191 192 /* grab buffer if we didn't have one */ 193 if (!m->buf) { 194 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 195 if (!m->buf) 196 goto Enomem; 197 } 198 /* if not empty - flush it first */ 199 if (m->count) { 200 n = min(m->count, size); 201 err = copy_to_user(buf, m->buf + m->from, n); 202 if (err) 203 goto Efault; 204 m->count -= n; 205 m->from += n; 206 size -= n; 207 buf += n; 208 copied += n; 209 if (!m->count) 210 m->index++; 211 if (!size) 212 goto Done; 213 } 214 /* we need at least one record in buffer */ 215 pos = m->index; 216 p = m->op->start(m, &pos); 217 while (1) { 218 err = PTR_ERR(p); 219 if (!p || IS_ERR(p)) 220 break; 221 err = m->op->show(m, p); 222 if (err < 0) 223 break; 224 if (unlikely(err)) 225 m->count = 0; 226 if (unlikely(!m->count)) { 227 p = m->op->next(m, p, &pos); 228 m->index = pos; 229 continue; 230 } 231 if (m->count < m->size) 232 goto Fill; 233 m->op->stop(m, p); 234 kfree(m->buf); 235 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 236 if (!m->buf) 237 goto Enomem; 238 m->count = 0; 239 m->version = 0; 240 pos = m->index; 241 p = m->op->start(m, &pos); 242 } 243 m->op->stop(m, p); 244 m->count = 0; 245 goto Done; 246 Fill: 247 /* they want more? let's try to get some more */ 248 while (m->count < size) { 249 size_t offs = m->count; 250 loff_t next = pos; 251 p = m->op->next(m, p, &next); 252 if (!p || IS_ERR(p)) { 253 err = PTR_ERR(p); 254 break; 255 } 256 err = m->op->show(m, p); 257 if (seq_overflow(m) || err) { 258 m->count = offs; 259 if (likely(err <= 0)) 260 break; 261 } 262 pos = next; 263 } 264 m->op->stop(m, p); 265 n = min(m->count, size); 266 err = copy_to_user(buf, m->buf, n); 267 if (err) 268 goto Efault; 269 copied += n; 270 m->count -= n; 271 if (m->count) 272 m->from = n; 273 else 274 pos++; 275 m->index = pos; 276 Done: 277 if (!copied) 278 copied = err; 279 else { 280 *ppos += copied; 281 m->read_pos += copied; 282 } 283 file->f_version = m->version; 284 mutex_unlock(&m->lock); 285 return copied; 286 Enomem: 287 err = -ENOMEM; 288 goto Done; 289 Efault: 290 err = -EFAULT; 291 goto Done; 292 } 293 EXPORT_SYMBOL(seq_read); 294 295 /** 296 * seq_lseek - ->llseek() method for sequential files. 297 * @file: the file in question 298 * @offset: new position 299 * @whence: 0 for absolute, 1 for relative position 300 * 301 * Ready-made ->f_op->llseek() 302 */ 303 loff_t seq_lseek(struct file *file, loff_t offset, int whence) 304 { 305 struct seq_file *m = file->private_data; 306 loff_t retval = -EINVAL; 307 308 mutex_lock(&m->lock); 309 m->version = file->f_version; 310 switch (whence) { 311 case 1: 312 offset += file->f_pos; 313 case 0: 314 if (offset < 0) 315 break; 316 retval = offset; 317 if (offset != m->read_pos) { 318 while ((retval=traverse(m, offset)) == -EAGAIN) 319 ; 320 if (retval) { 321 /* with extreme prejudice... */ 322 file->f_pos = 0; 323 m->read_pos = 0; 324 m->version = 0; 325 m->index = 0; 326 m->count = 0; 327 } else { 328 m->read_pos = offset; 329 retval = file->f_pos = offset; 330 } 331 } 332 } 333 file->f_version = m->version; 334 mutex_unlock(&m->lock); 335 return retval; 336 } 337 EXPORT_SYMBOL(seq_lseek); 338 339 /** 340 * seq_release - free the structures associated with sequential file. 341 * @file: file in question 342 * @inode: file->f_path.dentry->d_inode 343 * 344 * Frees the structures associated with sequential file; can be used 345 * as ->f_op->release() if you don't have private data to destroy. 346 */ 347 int seq_release(struct inode *inode, struct file *file) 348 { 349 struct seq_file *m = file->private_data; 350 kfree(m->buf); 351 kfree(m); 352 return 0; 353 } 354 EXPORT_SYMBOL(seq_release); 355 356 /** 357 * seq_escape - print string into buffer, escaping some characters 358 * @m: target buffer 359 * @s: string 360 * @esc: set of characters that need escaping 361 * 362 * Puts string into buffer, replacing each occurrence of character from 363 * @esc with usual octal escape. Returns 0 in case of success, -1 - in 364 * case of overflow. 365 */ 366 int seq_escape(struct seq_file *m, const char *s, const char *esc) 367 { 368 char *end = m->buf + m->size; 369 char *p; 370 char c; 371 372 for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) { 373 if (!strchr(esc, c)) { 374 *p++ = c; 375 continue; 376 } 377 if (p + 3 < end) { 378 *p++ = '\\'; 379 *p++ = '' + ((c & 0300) >> 6); 380 *p++ = '' + ((c & 070) >> 3); 381 *p++ = '' + (c & 07); 382 continue; 383 } 384 seq_set_overflow(m); 385 return -1; 386 } 387 m->count = p - m->buf; 388 return 0; 389 } 390 EXPORT_SYMBOL(seq_escape); 391 392 int seq_vprintf(struct seq_file *m, const char *f, va_list args) 393 { 394 int len; 395 396 if (m->count < m->size) { 397 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args); 398 if (m->count + len < m->size) { 399 m->count += len; 400 return 0; 401 } 402 } 403 seq_set_overflow(m); 404 return -1; 405 } 406 EXPORT_SYMBOL(seq_vprintf); 407 408 int seq_printf(struct seq_file *m, const char *f, ...) 409 { 410 int ret; 411 va_list args; 412 413 va_start(args, f); 414 ret = seq_vprintf(m, f, args); 415 va_end(args); 416 417 return ret; 418 } 419 EXPORT_SYMBOL(seq_printf); 420 421 /** 422 * mangle_path - mangle and copy path to buffer beginning 423 * @s: buffer start 424 * @p: beginning of path in above buffer 425 * @esc: set of characters that need escaping 426 * 427 * Copy the path from @p to @s, replacing each occurrence of character from 428 * @esc with usual octal escape. 429 * Returns pointer past last written character in @s, or NULL in case of 430 * failure. 431 */ 432 char *mangle_path(char *s, const char *p, const char *esc) 433 { 434 while (s <= p) { 435 char c = *p++; 436 if (!c) { 437 return s; 438 } else if (!strchr(esc, c)) { 439 *s++ = c; 440 } else if (s + 4 > p) { 441 break; 442 } else { 443 *s++ = '\\'; 444 *s++ = '' + ((c & 0300) >> 6); 445 *s++ = '' + ((c & 070) >> 3); 446 *s++ = '' + (c & 07); 447 } 448 } 449 return NULL; 450 } 451 EXPORT_SYMBOL(mangle_path); 452 453 /** 454 * seq_path - seq_file interface to print a pathname 455 * @m: the seq_file handle 456 * @path: the struct path to print 457 * @esc: set of characters to escape in the output 458 * 459 * return the absolute path of 'path', as represented by the 460 * dentry / mnt pair in the path parameter. 461 */ 462 int seq_path(struct seq_file *m, const struct path *path, const char *esc) 463 { 464 char *buf; 465 size_t size = seq_get_buf(m, &buf); 466 int res = -1; 467 468 if (size) { 469 char *p = d_path(path, buf, size); 470 if (!IS_ERR(p)) { 471 char *end = mangle_path(buf, p, esc); 472 if (end) 473 res = end - buf; 474 } 475 } 476 seq_commit(m, res); 477 478 return res; 479 } 480 EXPORT_SYMBOL(seq_path); 481 482 /* 483 * Same as seq_path, but relative to supplied root. 484 */ 485 int seq_path_root(struct seq_file *m, const struct path *path, 486 const struct path *root, const char *esc) 487 { 488 char *buf; 489 size_t size = seq_get_buf(m, &buf); 490 int res = -ENAMETOOLONG; 491 492 if (size) { 493 char *p; 494 495 p = __d_path(path, root, buf, size); 496 if (!p) 497 return SEQ_SKIP; 498 res = PTR_ERR(p); 499 if (!IS_ERR(p)) { 500 char *end = mangle_path(buf, p, esc); 501 if (end) 502 res = end - buf; 503 else 504 res = -ENAMETOOLONG; 505 } 506 } 507 seq_commit(m, res); 508 509 return res < 0 && res != -ENAMETOOLONG ? res : 0; 510 } 511 512 /* 513 * returns the path of the 'dentry' from the root of its filesystem. 514 */ 515 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc) 516 { 517 char *buf; 518 size_t size = seq_get_buf(m, &buf); 519 int res = -1; 520 521 if (size) { 522 char *p = dentry_path(dentry, buf, size); 523 if (!IS_ERR(p)) { 524 char *end = mangle_path(buf, p, esc); 525 if (end) 526 res = end - buf; 527 } 528 } 529 seq_commit(m, res); 530 531 return res; 532 } 533 534 int seq_bitmap(struct seq_file *m, const unsigned long *bits, 535 unsigned int nr_bits) 536 { 537 if (m->count < m->size) { 538 int len = bitmap_scnprintf(m->buf + m->count, 539 m->size - m->count, bits, nr_bits); 540 if (m->count + len < m->size) { 541 m->count += len; 542 return 0; 543 } 544 } 545 seq_set_overflow(m); 546 return -1; 547 } 548 EXPORT_SYMBOL(seq_bitmap); 549 550 int seq_bitmap_list(struct seq_file *m, const unsigned long *bits, 551 unsigned int nr_bits) 552 { 553 if (m->count < m->size) { 554 int len = bitmap_scnlistprintf(m->buf + m->count, 555 m->size - m->count, bits, nr_bits); 556 if (m->count + len < m->size) { 557 m->count += len; 558 return 0; 559 } 560 } 561 seq_set_overflow(m); 562 return -1; 563 } 564 EXPORT_SYMBOL(seq_bitmap_list); 565 566 static void *single_start(struct seq_file *p, loff_t *pos) 567 { 568 return NULL + (*pos == 0); 569 } 570 571 static void *single_next(struct seq_file *p, void *v, loff_t *pos) 572 { 573 ++*pos; 574 return NULL; 575 } 576 577 static void single_stop(struct seq_file *p, void *v) 578 { 579 } 580 581 int single_open(struct file *file, int (*show)(struct seq_file *, void *), 582 void *data) 583 { 584 struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL); 585 int res = -ENOMEM; 586 587 if (op) { 588 op->start = single_start; 589 op->next = single_next; 590 op->stop = single_stop; 591 op->show = show; 592 res = seq_open(file, op); 593 if (!res) 594 ((struct seq_file *)file->private_data)->private = data; 595 else 596 kfree(op); 597 } 598 return res; 599 } 600 EXPORT_SYMBOL(single_open); 601 602 int single_release(struct inode *inode, struct file *file) 603 { 604 const struct seq_operations *op = ((struct seq_file *)file->private_data)->op; 605 int res = seq_release(inode, file); 606 kfree(op); 607 return res; 608 } 609 EXPORT_SYMBOL(single_release); 610 611 int seq_release_private(struct inode *inode, struct file *file) 612 { 613 struct seq_file *seq = file->private_data; 614 615 kfree(seq->private); 616 seq->private = NULL; 617 return seq_release(inode, file); 618 } 619 EXPORT_SYMBOL(seq_release_private); 620 621 void *__seq_open_private(struct file *f, const struct seq_operations *ops, 622 int psize) 623 { 624 int rc; 625 void *private; 626 struct seq_file *seq; 627 628 private = kzalloc(psize, GFP_KERNEL); 629 if (private == NULL) 630 goto out; 631 632 rc = seq_open(f, ops); 633 if (rc < 0) 634 goto out_free; 635 636 seq = f->private_data; 637 seq->private = private; 638 return private; 639 640 out_free: 641 kfree(private); 642 out: 643 return NULL; 644 } 645 EXPORT_SYMBOL(__seq_open_private); 646 647 int seq_open_private(struct file *filp, const struct seq_operations *ops, 648 int psize) 649 { 650 return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM; 651 } 652 EXPORT_SYMBOL(seq_open_private); 653 654 int seq_putc(struct seq_file *m, char c) 655 { 656 if (m->count < m->size) { 657 m->buf[m->count++] = c; 658 return 0; 659 } 660 return -1; 661 } 662 EXPORT_SYMBOL(seq_putc); 663 664 int seq_puts(struct seq_file *m, const char *s) 665 { 666 int len = strlen(s); 667 if (m->count + len < m->size) { 668 memcpy(m->buf + m->count, s, len); 669 m->count += len; 670 return 0; 671 } 672 seq_set_overflow(m); 673 return -1; 674 } 675 EXPORT_SYMBOL(seq_puts); 676 677 /* 678 * A helper routine for putting decimal numbers without rich format of printf(). 679 * only 'unsigned long long' is supported. 680 * This routine will put one byte delimiter + number into seq_file. 681 * This routine is very quick when you show lots of numbers. 682 * In usual cases, it will be better to use seq_printf(). It's easier to read. 683 */ 684 int seq_put_decimal_ull(struct seq_file *m, char delimiter, 685 unsigned long long num) 686 { 687 int len; 688 689 if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */ 690 goto overflow; 691 692 if (delimiter) 693 m->buf[m->count++] = delimiter; 694 695 if (num < 10) { 696 m->buf[m->count++] = num + ''; 697 return 0; 698 } 699 700 len = num_to_str(m->buf + m->count, m->size - m->count, num); 701 if (!len) 702 goto overflow; 703 m->count += len; 704 return 0; 705 overflow: 706 seq_set_overflow(m); 707 return -1; 708 } 709 EXPORT_SYMBOL(seq_put_decimal_ull); 710 711 int seq_put_decimal_ll(struct seq_file *m, char delimiter, 712 long long num) 713 { 714 if (num < 0) { 715 if (m->count + 3 >= m->size) { 716 seq_set_overflow(m); 717 return -1; 718 } 719 if (delimiter) 720 m->buf[m->count++] = delimiter; 721 num = -num; 722 delimiter = '-'; 723 } 724 return seq_put_decimal_ull(m, delimiter, num); 725 726 } 727 EXPORT_SYMBOL(seq_put_decimal_ll); 728 729 /** 730 * seq_write - write arbitrary data to buffer 731 * @seq: seq_file identifying the buffer to which data should be written 732 * @data: data address 733 * @len: number of bytes 734 * 735 * Return 0 on success, non-zero otherwise. 736 */ 737 int seq_write(struct seq_file *seq, const void *data, size_t len) 738 { 739 if (seq->count + len < seq->size) { 740 memcpy(seq->buf + seq->count, data, len); 741 seq->count += len; 742 return 0; 743 } 744 seq_set_overflow(seq); 745 return -1; 746 } 747 EXPORT_SYMBOL(seq_write); 748 749 struct list_head *seq_list_start(struct list_head *head, loff_t pos) 750 { 751 struct list_head *lh; 752 753 list_for_each(lh, head) 754 if (pos-- == 0) 755 return lh; 756 757 return NULL; 758 } 759 EXPORT_SYMBOL(seq_list_start); 760 761 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos) 762 { 763 if (!pos) 764 return head; 765 766 return seq_list_start(head, pos - 1); 767 } 768 EXPORT_SYMBOL(seq_list_start_head); 769 770 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos) 771 { 772 struct list_head *lh; 773 774 lh = ((struct list_head *)v)->next; 775 ++*ppos; 776 return lh == head ? NULL : lh; 777 } 778 EXPORT_SYMBOL(seq_list_next); 779 780 /** 781 * seq_hlist_start - start an iteration of a hlist 782 * @head: the head of the hlist 783 * @pos: the start position of the sequence 784 * 785 * Called at seq_file->op->start(). 786 */ 787 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos) 788 { 789 struct hlist_node *node; 790 791 hlist_for_each(node, head) 792 if (pos-- == 0) 793 return node; 794 return NULL; 795 } 796 EXPORT_SYMBOL(seq_hlist_start); 797 798 /** 799 * seq_hlist_start_head - start an iteration of a hlist 800 * @head: the head of the hlist 801 * @pos: the start position of the sequence 802 * 803 * Called at seq_file->op->start(). Call this function if you want to 804 * print a header at the top of the output. 805 */ 806 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos) 807 { 808 if (!pos) 809 return SEQ_START_TOKEN; 810 811 return seq_hlist_start(head, pos - 1); 812 } 813 EXPORT_SYMBOL(seq_hlist_start_head); 814 815 /** 816 * seq_hlist_next - move to the next position of the hlist 817 * @v: the current iterator 818 * @head: the head of the hlist 819 * @ppos: the current position 820 * 821 * Called at seq_file->op->next(). 822 */ 823 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head, 824 loff_t *ppos) 825 { 826 struct hlist_node *node = v; 827 828 ++*ppos; 829 if (v == SEQ_START_TOKEN) 830 return head->first; 831 else 832 return node->next; 833 } 834 EXPORT_SYMBOL(seq_hlist_next); 835 836 /** 837 * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU 838 * @head: the head of the hlist 839 * @pos: the start position of the sequence 840 * 841 * Called at seq_file->op->start(). 842 * 843 * This list-traversal primitive may safely run concurrently with 844 * the _rcu list-mutation primitives such as hlist_add_head_rcu() 845 * as long as the traversal is guarded by rcu_read_lock(). 846 */ 847 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head, 848 loff_t pos) 849 { 850 struct hlist_node *node; 851 852 __hlist_for_each_rcu(node, head) 853 if (pos-- == 0) 854 return node; 855 return NULL; 856 } 857 EXPORT_SYMBOL(seq_hlist_start_rcu); 858 859 /** 860 * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU 861 * @head: the head of the hlist 862 * @pos: the start position of the sequence 863 * 864 * Called at seq_file->op->start(). Call this function if you want to 865 * print a header at the top of the output. 866 * 867 * This list-traversal primitive may safely run concurrently with 868 * the _rcu list-mutation primitives such as hlist_add_head_rcu() 869 * as long as the traversal is guarded by rcu_read_lock(). 870 */ 871 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head, 872 loff_t pos) 873 { 874 if (!pos) 875 return SEQ_START_TOKEN; 876 877 return seq_hlist_start_rcu(head, pos - 1); 878 } 879 EXPORT_SYMBOL(seq_hlist_start_head_rcu); 880 881 /** 882 * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU 883 * @v: the current iterator 884 * @head: the head of the hlist 885 * @ppos: the current position 886 * 887 * Called at seq_file->op->next(). 888 * 889 * This list-traversal primitive may safely run concurrently with 890 * the _rcu list-mutation primitives such as hlist_add_head_rcu() 891 * as long as the traversal is guarded by rcu_read_lock(). 892 */ 893 struct hlist_node *seq_hlist_next_rcu(void *v, 894 struct hlist_head *head, 895 loff_t *ppos) 896 { 897 struct hlist_node *node = v; 898 899 ++*ppos; 900 if (v == SEQ_START_TOKEN) 901 return rcu_dereference(head->first); 902 else 903 return rcu_dereference(node->next); 904 } 905 EXPORT_SYMBOL(seq_hlist_next_rcu);
Cache object: 7cbc1f9789c0ccf4dc162c820fb666d6
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