1 /* 2 * fs/f2fs/gc.c 3 * 4 * Copyright (c) 2012 Samsung Electronics Co., Ltd. 5 * http://www.samsung.com/ 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 #include <linux/fs.h> 12 #include <linux/module.h> 13 #include <linux/backing-dev.h> 14 #include <linux/init.h> 15 #include <linux/f2fs_fs.h> 16 #include <linux/kthread.h> 17 #include <linux/delay.h> 18 #include <linux/freezer.h> 19 #include <linux/blkdev.h> 20 21 #include "f2fs.h" 22 #include "node.h" 23 #include "segment.h" 24 #include "gc.h" 25 #include <trace/events/f2fs.h> 26 27 static struct kmem_cache *winode_slab; 28 29 static int gc_thread_func(void *data) 30 { 31 struct f2fs_sb_info *sbi = data; 32 wait_queue_head_t *wq = &sbi->gc_thread->gc_wait_queue_head; 33 long wait_ms; 34 35 wait_ms = GC_THREAD_MIN_SLEEP_TIME; 36 37 do { 38 if (try_to_freeze()) 39 continue; 40 else 41 wait_event_interruptible_timeout(*wq, 42 kthread_should_stop(), 43 msecs_to_jiffies(wait_ms)); 44 if (kthread_should_stop()) 45 break; 46 47 if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) { 48 wait_ms = GC_THREAD_MAX_SLEEP_TIME; 49 continue; 50 } 51 52 /* 53 * [GC triggering condition] 54 * 0. GC is not conducted currently. 55 * 1. There are enough dirty segments. 56 * 2. IO subsystem is idle by checking the # of writeback pages. 57 * 3. IO subsystem is idle by checking the # of requests in 58 * bdev's request list. 59 * 60 * Note) We have to avoid triggering GCs too much frequently. 61 * Because it is possible that some segments can be 62 * invalidated soon after by user update or deletion. 63 * So, I'd like to wait some time to collect dirty segments. 64 */ 65 if (!mutex_trylock(&sbi->gc_mutex)) 66 continue; 67 68 if (!is_idle(sbi)) { 69 wait_ms = increase_sleep_time(wait_ms); 70 mutex_unlock(&sbi->gc_mutex); 71 continue; 72 } 73 74 if (has_enough_invalid_blocks(sbi)) 75 wait_ms = decrease_sleep_time(wait_ms); 76 else 77 wait_ms = increase_sleep_time(wait_ms); 78 79 sbi->bg_gc++; 80 81 /* if return value is not zero, no victim was selected */ 82 if (f2fs_gc(sbi)) 83 wait_ms = GC_THREAD_NOGC_SLEEP_TIME; 84 } while (!kthread_should_stop()); 85 return 0; 86 } 87 88 int start_gc_thread(struct f2fs_sb_info *sbi) 89 { 90 struct f2fs_gc_kthread *gc_th; 91 dev_t dev = sbi->sb->s_bdev->bd_dev; 92 93 if (!test_opt(sbi, BG_GC)) 94 return 0; 95 gc_th = kmalloc(sizeof(struct f2fs_gc_kthread), GFP_KERNEL); 96 if (!gc_th) 97 return -ENOMEM; 98 99 sbi->gc_thread = gc_th; 100 init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head); 101 sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi, 102 "f2fs_gc-%u:%u", MAJOR(dev), MINOR(dev)); 103 if (IS_ERR(gc_th->f2fs_gc_task)) { 104 kfree(gc_th); 105 sbi->gc_thread = NULL; 106 return -ENOMEM; 107 } 108 return 0; 109 } 110 111 void stop_gc_thread(struct f2fs_sb_info *sbi) 112 { 113 struct f2fs_gc_kthread *gc_th = sbi->gc_thread; 114 if (!gc_th) 115 return; 116 kthread_stop(gc_th->f2fs_gc_task); 117 kfree(gc_th); 118 sbi->gc_thread = NULL; 119 } 120 121 static int select_gc_type(int gc_type) 122 { 123 return (gc_type == BG_GC) ? GC_CB : GC_GREEDY; 124 } 125 126 static void select_policy(struct f2fs_sb_info *sbi, int gc_type, 127 int type, struct victim_sel_policy *p) 128 { 129 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 130 131 if (p->alloc_mode == SSR) { 132 p->gc_mode = GC_GREEDY; 133 p->dirty_segmap = dirty_i->dirty_segmap[type]; 134 p->ofs_unit = 1; 135 } else { 136 p->gc_mode = select_gc_type(gc_type); 137 p->dirty_segmap = dirty_i->dirty_segmap[DIRTY]; 138 p->ofs_unit = sbi->segs_per_sec; 139 } 140 p->offset = sbi->last_victim[p->gc_mode]; 141 } 142 143 static unsigned int get_max_cost(struct f2fs_sb_info *sbi, 144 struct victim_sel_policy *p) 145 { 146 /* SSR allocates in a segment unit */ 147 if (p->alloc_mode == SSR) 148 return 1 << sbi->log_blocks_per_seg; 149 if (p->gc_mode == GC_GREEDY) 150 return (1 << sbi->log_blocks_per_seg) * p->ofs_unit; 151 else if (p->gc_mode == GC_CB) 152 return UINT_MAX; 153 else /* No other gc_mode */ 154 return 0; 155 } 156 157 static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) 158 { 159 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 160 unsigned int hint = 0; 161 unsigned int secno; 162 163 /* 164 * If the gc_type is FG_GC, we can select victim segments 165 * selected by background GC before. 166 * Those segments guarantee they have small valid blocks. 167 */ 168 next: 169 secno = find_next_bit(dirty_i->victim_secmap, TOTAL_SECS(sbi), hint++); 170 if (secno < TOTAL_SECS(sbi)) { 171 if (sec_usage_check(sbi, secno)) 172 goto next; 173 clear_bit(secno, dirty_i->victim_secmap); 174 return secno * sbi->segs_per_sec; 175 } 176 return NULL_SEGNO; 177 } 178 179 static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno) 180 { 181 struct sit_info *sit_i = SIT_I(sbi); 182 unsigned int secno = GET_SECNO(sbi, segno); 183 unsigned int start = secno * sbi->segs_per_sec; 184 unsigned long long mtime = 0; 185 unsigned int vblocks; 186 unsigned char age = 0; 187 unsigned char u; 188 unsigned int i; 189 190 for (i = 0; i < sbi->segs_per_sec; i++) 191 mtime += get_seg_entry(sbi, start + i)->mtime; 192 vblocks = get_valid_blocks(sbi, segno, sbi->segs_per_sec); 193 194 mtime = div_u64(mtime, sbi->segs_per_sec); 195 vblocks = div_u64(vblocks, sbi->segs_per_sec); 196 197 u = (vblocks * 100) >> sbi->log_blocks_per_seg; 198 199 /* Handle if the system time is changed by user */ 200 if (mtime < sit_i->min_mtime) 201 sit_i->min_mtime = mtime; 202 if (mtime > sit_i->max_mtime) 203 sit_i->max_mtime = mtime; 204 if (sit_i->max_mtime != sit_i->min_mtime) 205 age = 100 - div64_u64(100 * (mtime - sit_i->min_mtime), 206 sit_i->max_mtime - sit_i->min_mtime); 207 208 return UINT_MAX - ((100 * (100 - u) * age) / (100 + u)); 209 } 210 211 static unsigned int get_gc_cost(struct f2fs_sb_info *sbi, unsigned int segno, 212 struct victim_sel_policy *p) 213 { 214 if (p->alloc_mode == SSR) 215 return get_seg_entry(sbi, segno)->ckpt_valid_blocks; 216 217 /* alloc_mode == LFS */ 218 if (p->gc_mode == GC_GREEDY) 219 return get_valid_blocks(sbi, segno, sbi->segs_per_sec); 220 else 221 return get_cb_cost(sbi, segno); 222 } 223 224 /* 225 * This function is called from two paths. 226 * One is garbage collection and the other is SSR segment selection. 227 * When it is called during GC, it just gets a victim segment 228 * and it does not remove it from dirty seglist. 229 * When it is called from SSR segment selection, it finds a segment 230 * which has minimum valid blocks and removes it from dirty seglist. 231 */ 232 static int get_victim_by_default(struct f2fs_sb_info *sbi, 233 unsigned int *result, int gc_type, int type, char alloc_mode) 234 { 235 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 236 struct victim_sel_policy p; 237 unsigned int secno; 238 int nsearched = 0; 239 240 p.alloc_mode = alloc_mode; 241 select_policy(sbi, gc_type, type, &p); 242 243 p.min_segno = NULL_SEGNO; 244 p.min_cost = get_max_cost(sbi, &p); 245 246 mutex_lock(&dirty_i->seglist_lock); 247 248 if (p.alloc_mode == LFS && gc_type == FG_GC) { 249 p.min_segno = check_bg_victims(sbi); 250 if (p.min_segno != NULL_SEGNO) 251 goto got_it; 252 } 253 254 while (1) { 255 unsigned long cost; 256 unsigned int segno; 257 258 segno = find_next_bit(p.dirty_segmap, 259 TOTAL_SEGS(sbi), p.offset); 260 if (segno >= TOTAL_SEGS(sbi)) { 261 if (sbi->last_victim[p.gc_mode]) { 262 sbi->last_victim[p.gc_mode] = 0; 263 p.offset = 0; 264 continue; 265 } 266 break; 267 } 268 p.offset = ((segno / p.ofs_unit) * p.ofs_unit) + p.ofs_unit; 269 secno = GET_SECNO(sbi, segno); 270 271 if (sec_usage_check(sbi, secno)) 272 continue; 273 if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap)) 274 continue; 275 276 cost = get_gc_cost(sbi, segno, &p); 277 278 if (p.min_cost > cost) { 279 p.min_segno = segno; 280 p.min_cost = cost; 281 } 282 283 if (cost == get_max_cost(sbi, &p)) 284 continue; 285 286 if (nsearched++ >= MAX_VICTIM_SEARCH) { 287 sbi->last_victim[p.gc_mode] = segno; 288 break; 289 } 290 } 291 got_it: 292 if (p.min_segno != NULL_SEGNO) { 293 if (p.alloc_mode == LFS) { 294 secno = GET_SECNO(sbi, p.min_segno); 295 if (gc_type == FG_GC) 296 sbi->cur_victim_sec = secno; 297 else 298 set_bit(secno, dirty_i->victim_secmap); 299 } 300 *result = (p.min_segno / p.ofs_unit) * p.ofs_unit; 301 302 trace_f2fs_get_victim(sbi->sb, type, gc_type, &p, 303 sbi->cur_victim_sec, 304 prefree_segments(sbi), free_segments(sbi)); 305 } 306 mutex_unlock(&dirty_i->seglist_lock); 307 308 return (p.min_segno == NULL_SEGNO) ? 0 : 1; 309 } 310 311 static const struct victim_selection default_v_ops = { 312 .get_victim = get_victim_by_default, 313 }; 314 315 static struct inode *find_gc_inode(nid_t ino, struct list_head *ilist) 316 { 317 struct list_head *this; 318 struct inode_entry *ie; 319 320 list_for_each(this, ilist) { 321 ie = list_entry(this, struct inode_entry, list); 322 if (ie->inode->i_ino == ino) 323 return ie->inode; 324 } 325 return NULL; 326 } 327 328 static void add_gc_inode(struct inode *inode, struct list_head *ilist) 329 { 330 struct list_head *this; 331 struct inode_entry *new_ie, *ie; 332 333 list_for_each(this, ilist) { 334 ie = list_entry(this, struct inode_entry, list); 335 if (ie->inode == inode) { 336 iput(inode); 337 return; 338 } 339 } 340 repeat: 341 new_ie = kmem_cache_alloc(winode_slab, GFP_NOFS); 342 if (!new_ie) { 343 cond_resched(); 344 goto repeat; 345 } 346 new_ie->inode = inode; 347 list_add_tail(&new_ie->list, ilist); 348 } 349 350 static void put_gc_inode(struct list_head *ilist) 351 { 352 struct inode_entry *ie, *next_ie; 353 list_for_each_entry_safe(ie, next_ie, ilist, list) { 354 iput(ie->inode); 355 list_del(&ie->list); 356 kmem_cache_free(winode_slab, ie); 357 } 358 } 359 360 static int check_valid_map(struct f2fs_sb_info *sbi, 361 unsigned int segno, int offset) 362 { 363 struct sit_info *sit_i = SIT_I(sbi); 364 struct seg_entry *sentry; 365 int ret; 366 367 mutex_lock(&sit_i->sentry_lock); 368 sentry = get_seg_entry(sbi, segno); 369 ret = f2fs_test_bit(offset, sentry->cur_valid_map); 370 mutex_unlock(&sit_i->sentry_lock); 371 return ret; 372 } 373 374 /* 375 * This function compares node address got in summary with that in NAT. 376 * On validity, copy that node with cold status, otherwise (invalid node) 377 * ignore that. 378 */ 379 static void gc_node_segment(struct f2fs_sb_info *sbi, 380 struct f2fs_summary *sum, unsigned int segno, int gc_type) 381 { 382 bool initial = true; 383 struct f2fs_summary *entry; 384 int off; 385 386 next_step: 387 entry = sum; 388 389 for (off = 0; off < sbi->blocks_per_seg; off++, entry++) { 390 nid_t nid = le32_to_cpu(entry->nid); 391 struct page *node_page; 392 393 /* stop BG_GC if there is not enough free sections. */ 394 if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0)) 395 return; 396 397 if (check_valid_map(sbi, segno, off) == 0) 398 continue; 399 400 if (initial) { 401 ra_node_page(sbi, nid); 402 continue; 403 } 404 node_page = get_node_page(sbi, nid); 405 if (IS_ERR(node_page)) 406 continue; 407 408 /* set page dirty and write it */ 409 if (gc_type == FG_GC) { 410 f2fs_submit_bio(sbi, NODE, true); 411 wait_on_page_writeback(node_page); 412 set_page_dirty(node_page); 413 } else { 414 if (!PageWriteback(node_page)) 415 set_page_dirty(node_page); 416 } 417 f2fs_put_page(node_page, 1); 418 stat_inc_node_blk_count(sbi, 1); 419 } 420 421 if (initial) { 422 initial = false; 423 goto next_step; 424 } 425 426 if (gc_type == FG_GC) { 427 struct writeback_control wbc = { 428 .sync_mode = WB_SYNC_ALL, 429 .nr_to_write = LONG_MAX, 430 .for_reclaim = 0, 431 }; 432 sync_node_pages(sbi, 0, &wbc); 433 434 /* 435 * In the case of FG_GC, it'd be better to reclaim this victim 436 * completely. 437 */ 438 if (get_valid_blocks(sbi, segno, 1) != 0) 439 goto next_step; 440 } 441 } 442 443 /* 444 * Calculate start block index indicating the given node offset. 445 * Be careful, caller should give this node offset only indicating direct node 446 * blocks. If any node offsets, which point the other types of node blocks such 447 * as indirect or double indirect node blocks, are given, it must be a caller's 448 * bug. 449 */ 450 block_t start_bidx_of_node(unsigned int node_ofs) 451 { 452 unsigned int indirect_blks = 2 * NIDS_PER_BLOCK + 4; 453 unsigned int bidx; 454 455 if (node_ofs == 0) 456 return 0; 457 458 if (node_ofs <= 2) { 459 bidx = node_ofs - 1; 460 } else if (node_ofs <= indirect_blks) { 461 int dec = (node_ofs - 4) / (NIDS_PER_BLOCK + 1); 462 bidx = node_ofs - 2 - dec; 463 } else { 464 int dec = (node_ofs - indirect_blks - 3) / (NIDS_PER_BLOCK + 1); 465 bidx = node_ofs - 5 - dec; 466 } 467 return bidx * ADDRS_PER_BLOCK + ADDRS_PER_INODE; 468 } 469 470 static int check_dnode(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, 471 struct node_info *dni, block_t blkaddr, unsigned int *nofs) 472 { 473 struct page *node_page; 474 nid_t nid; 475 unsigned int ofs_in_node; 476 block_t source_blkaddr; 477 478 nid = le32_to_cpu(sum->nid); 479 ofs_in_node = le16_to_cpu(sum->ofs_in_node); 480 481 node_page = get_node_page(sbi, nid); 482 if (IS_ERR(node_page)) 483 return 0; 484 485 get_node_info(sbi, nid, dni); 486 487 if (sum->version != dni->version) { 488 f2fs_put_page(node_page, 1); 489 return 0; 490 } 491 492 *nofs = ofs_of_node(node_page); 493 source_blkaddr = datablock_addr(node_page, ofs_in_node); 494 f2fs_put_page(node_page, 1); 495 496 if (source_blkaddr != blkaddr) 497 return 0; 498 return 1; 499 } 500 501 static void move_data_page(struct inode *inode, struct page *page, int gc_type) 502 { 503 if (gc_type == BG_GC) { 504 if (PageWriteback(page)) 505 goto out; 506 set_page_dirty(page); 507 set_cold_data(page); 508 } else { 509 struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb); 510 511 if (PageWriteback(page)) { 512 f2fs_submit_bio(sbi, DATA, true); 513 wait_on_page_writeback(page); 514 } 515 516 if (clear_page_dirty_for_io(page) && 517 S_ISDIR(inode->i_mode)) { 518 dec_page_count(sbi, F2FS_DIRTY_DENTS); 519 inode_dec_dirty_dents(inode); 520 } 521 set_cold_data(page); 522 do_write_data_page(page); 523 clear_cold_data(page); 524 } 525 out: 526 f2fs_put_page(page, 1); 527 } 528 529 /* 530 * This function tries to get parent node of victim data block, and identifies 531 * data block validity. If the block is valid, copy that with cold status and 532 * modify parent node. 533 * If the parent node is not valid or the data block address is different, 534 * the victim data block is ignored. 535 */ 536 static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, 537 struct list_head *ilist, unsigned int segno, int gc_type) 538 { 539 struct super_block *sb = sbi->sb; 540 struct f2fs_summary *entry; 541 block_t start_addr; 542 int off; 543 int phase = 0; 544 545 start_addr = START_BLOCK(sbi, segno); 546 547 next_step: 548 entry = sum; 549 550 for (off = 0; off < sbi->blocks_per_seg; off++, entry++) { 551 struct page *data_page; 552 struct inode *inode; 553 struct node_info dni; /* dnode info for the data */ 554 unsigned int ofs_in_node, nofs; 555 block_t start_bidx; 556 557 /* stop BG_GC if there is not enough free sections. */ 558 if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0)) 559 return; 560 561 if (check_valid_map(sbi, segno, off) == 0) 562 continue; 563 564 if (phase == 0) { 565 ra_node_page(sbi, le32_to_cpu(entry->nid)); 566 continue; 567 } 568 569 /* Get an inode by ino with checking validity */ 570 if (check_dnode(sbi, entry, &dni, start_addr + off, &nofs) == 0) 571 continue; 572 573 if (phase == 1) { 574 ra_node_page(sbi, dni.ino); 575 continue; 576 } 577 578 start_bidx = start_bidx_of_node(nofs); 579 ofs_in_node = le16_to_cpu(entry->ofs_in_node); 580 581 if (phase == 2) { 582 inode = f2fs_iget(sb, dni.ino); 583 if (IS_ERR(inode)) 584 continue; 585 586 data_page = find_data_page(inode, 587 start_bidx + ofs_in_node, false); 588 if (IS_ERR(data_page)) 589 goto next_iput; 590 591 f2fs_put_page(data_page, 0); 592 add_gc_inode(inode, ilist); 593 } else { 594 inode = find_gc_inode(dni.ino, ilist); 595 if (inode) { 596 data_page = get_lock_data_page(inode, 597 start_bidx + ofs_in_node); 598 if (IS_ERR(data_page)) 599 continue; 600 move_data_page(inode, data_page, gc_type); 601 stat_inc_data_blk_count(sbi, 1); 602 } 603 } 604 continue; 605 next_iput: 606 iput(inode); 607 } 608 609 if (++phase < 4) 610 goto next_step; 611 612 if (gc_type == FG_GC) { 613 f2fs_submit_bio(sbi, DATA, true); 614 615 /* 616 * In the case of FG_GC, it'd be better to reclaim this victim 617 * completely. 618 */ 619 if (get_valid_blocks(sbi, segno, 1) != 0) { 620 phase = 2; 621 goto next_step; 622 } 623 } 624 } 625 626 static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim, 627 int gc_type, int type) 628 { 629 struct sit_info *sit_i = SIT_I(sbi); 630 int ret; 631 mutex_lock(&sit_i->sentry_lock); 632 ret = DIRTY_I(sbi)->v_ops->get_victim(sbi, victim, gc_type, type, LFS); 633 mutex_unlock(&sit_i->sentry_lock); 634 return ret; 635 } 636 637 static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno, 638 struct list_head *ilist, int gc_type) 639 { 640 struct page *sum_page; 641 struct f2fs_summary_block *sum; 642 struct blk_plug plug; 643 644 /* read segment summary of victim */ 645 sum_page = get_sum_page(sbi, segno); 646 if (IS_ERR(sum_page)) 647 return; 648 649 blk_start_plug(&plug); 650 651 sum = page_address(sum_page); 652 653 switch (GET_SUM_TYPE((&sum->footer))) { 654 case SUM_TYPE_NODE: 655 gc_node_segment(sbi, sum->entries, segno, gc_type); 656 break; 657 case SUM_TYPE_DATA: 658 gc_data_segment(sbi, sum->entries, ilist, segno, gc_type); 659 break; 660 } 661 blk_finish_plug(&plug); 662 663 stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer))); 664 stat_inc_call_count(sbi->stat_info); 665 666 f2fs_put_page(sum_page, 1); 667 } 668 669 int f2fs_gc(struct f2fs_sb_info *sbi) 670 { 671 struct list_head ilist; 672 unsigned int segno, i; 673 int gc_type = BG_GC; 674 int nfree = 0; 675 int ret = -1; 676 677 INIT_LIST_HEAD(&ilist); 678 gc_more: 679 if (!(sbi->sb->s_flags & MS_ACTIVE)) 680 goto stop; 681 682 if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) { 683 gc_type = FG_GC; 684 write_checkpoint(sbi, false); 685 } 686 687 if (!__get_victim(sbi, &segno, gc_type, NO_CHECK_TYPE)) 688 goto stop; 689 ret = 0; 690 691 for (i = 0; i < sbi->segs_per_sec; i++) 692 do_garbage_collect(sbi, segno + i, &ilist, gc_type); 693 694 if (gc_type == FG_GC) { 695 sbi->cur_victim_sec = NULL_SEGNO; 696 nfree++; 697 WARN_ON(get_valid_blocks(sbi, segno, sbi->segs_per_sec)); 698 } 699 700 if (has_not_enough_free_secs(sbi, nfree)) 701 goto gc_more; 702 703 if (gc_type == FG_GC) 704 write_checkpoint(sbi, false); 705 stop: 706 mutex_unlock(&sbi->gc_mutex); 707 708 put_gc_inode(&ilist); 709 return ret; 710 } 711 712 void build_gc_manager(struct f2fs_sb_info *sbi) 713 { 714 DIRTY_I(sbi)->v_ops = &default_v_ops; 715 } 716 717 int __init create_gc_caches(void) 718 { 719 winode_slab = f2fs_kmem_cache_create("f2fs_gc_inodes", 720 sizeof(struct inode_entry), NULL); 721 if (!winode_slab) 722 return -ENOMEM; 723 return 0; 724 } 725 726 void destroy_gc_caches(void) 727 { 728 kmem_cache_destroy(winode_slab); 729 } 730