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 #ifdef CONFIG_F2FS_STAT_FS 80 sbi->bg_gc++; 81 #endif 82 83 /* if return value is not zero, no victim was selected */ 84 if (f2fs_gc(sbi)) 85 wait_ms = GC_THREAD_NOGC_SLEEP_TIME; 86 } while (!kthread_should_stop()); 87 return 0; 88 } 89 90 int start_gc_thread(struct f2fs_sb_info *sbi) 91 { 92 struct f2fs_gc_kthread *gc_th; 93 dev_t dev = sbi->sb->s_bdev->bd_dev; 94 int err = 0; 95 96 if (!test_opt(sbi, BG_GC)) 97 goto out; 98 gc_th = kmalloc(sizeof(struct f2fs_gc_kthread), GFP_KERNEL); 99 if (!gc_th) { 100 err = -ENOMEM; 101 goto out; 102 } 103 104 sbi->gc_thread = gc_th; 105 init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head); 106 sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi, 107 "f2fs_gc-%u:%u", MAJOR(dev), MINOR(dev)); 108 if (IS_ERR(gc_th->f2fs_gc_task)) { 109 err = PTR_ERR(gc_th->f2fs_gc_task); 110 kfree(gc_th); 111 sbi->gc_thread = NULL; 112 } 113 114 out: 115 return err; 116 } 117 118 void stop_gc_thread(struct f2fs_sb_info *sbi) 119 { 120 struct f2fs_gc_kthread *gc_th = sbi->gc_thread; 121 if (!gc_th) 122 return; 123 kthread_stop(gc_th->f2fs_gc_task); 124 kfree(gc_th); 125 sbi->gc_thread = NULL; 126 } 127 128 static int select_gc_type(int gc_type) 129 { 130 return (gc_type == BG_GC) ? GC_CB : GC_GREEDY; 131 } 132 133 static void select_policy(struct f2fs_sb_info *sbi, int gc_type, 134 int type, struct victim_sel_policy *p) 135 { 136 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 137 138 if (p->alloc_mode == SSR) { 139 p->gc_mode = GC_GREEDY; 140 p->dirty_segmap = dirty_i->dirty_segmap[type]; 141 p->ofs_unit = 1; 142 } else { 143 p->gc_mode = select_gc_type(gc_type); 144 p->dirty_segmap = dirty_i->dirty_segmap[DIRTY]; 145 p->ofs_unit = sbi->segs_per_sec; 146 } 147 p->offset = sbi->last_victim[p->gc_mode]; 148 } 149 150 static unsigned int get_max_cost(struct f2fs_sb_info *sbi, 151 struct victim_sel_policy *p) 152 { 153 /* SSR allocates in a segment unit */ 154 if (p->alloc_mode == SSR) 155 return 1 << sbi->log_blocks_per_seg; 156 if (p->gc_mode == GC_GREEDY) 157 return (1 << sbi->log_blocks_per_seg) * p->ofs_unit; 158 else if (p->gc_mode == GC_CB) 159 return UINT_MAX; 160 else /* No other gc_mode */ 161 return 0; 162 } 163 164 static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) 165 { 166 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 167 unsigned int hint = 0; 168 unsigned int secno; 169 170 /* 171 * If the gc_type is FG_GC, we can select victim segments 172 * selected by background GC before. 173 * Those segments guarantee they have small valid blocks. 174 */ 175 next: 176 secno = find_next_bit(dirty_i->victim_secmap, TOTAL_SECS(sbi), hint++); 177 if (secno < TOTAL_SECS(sbi)) { 178 if (sec_usage_check(sbi, secno)) 179 goto next; 180 clear_bit(secno, dirty_i->victim_secmap); 181 return secno * sbi->segs_per_sec; 182 } 183 return NULL_SEGNO; 184 } 185 186 static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno) 187 { 188 struct sit_info *sit_i = SIT_I(sbi); 189 unsigned int secno = GET_SECNO(sbi, segno); 190 unsigned int start = secno * sbi->segs_per_sec; 191 unsigned long long mtime = 0; 192 unsigned int vblocks; 193 unsigned char age = 0; 194 unsigned char u; 195 unsigned int i; 196 197 for (i = 0; i < sbi->segs_per_sec; i++) 198 mtime += get_seg_entry(sbi, start + i)->mtime; 199 vblocks = get_valid_blocks(sbi, segno, sbi->segs_per_sec); 200 201 mtime = div_u64(mtime, sbi->segs_per_sec); 202 vblocks = div_u64(vblocks, sbi->segs_per_sec); 203 204 u = (vblocks * 100) >> sbi->log_blocks_per_seg; 205 206 /* Handle if the system time is changed by user */ 207 if (mtime < sit_i->min_mtime) 208 sit_i->min_mtime = mtime; 209 if (mtime > sit_i->max_mtime) 210 sit_i->max_mtime = mtime; 211 if (sit_i->max_mtime != sit_i->min_mtime) 212 age = 100 - div64_u64(100 * (mtime - sit_i->min_mtime), 213 sit_i->max_mtime - sit_i->min_mtime); 214 215 return UINT_MAX - ((100 * (100 - u) * age) / (100 + u)); 216 } 217 218 static unsigned int get_gc_cost(struct f2fs_sb_info *sbi, unsigned int segno, 219 struct victim_sel_policy *p) 220 { 221 if (p->alloc_mode == SSR) 222 return get_seg_entry(sbi, segno)->ckpt_valid_blocks; 223 224 /* alloc_mode == LFS */ 225 if (p->gc_mode == GC_GREEDY) 226 return get_valid_blocks(sbi, segno, sbi->segs_per_sec); 227 else 228 return get_cb_cost(sbi, segno); 229 } 230 231 /* 232 * This function is called from two paths. 233 * One is garbage collection and the other is SSR segment selection. 234 * When it is called during GC, it just gets a victim segment 235 * and it does not remove it from dirty seglist. 236 * When it is called from SSR segment selection, it finds a segment 237 * which has minimum valid blocks and removes it from dirty seglist. 238 */ 239 static int get_victim_by_default(struct f2fs_sb_info *sbi, 240 unsigned int *result, int gc_type, int type, char alloc_mode) 241 { 242 struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); 243 struct victim_sel_policy p; 244 unsigned int secno, max_cost; 245 int nsearched = 0; 246 247 p.alloc_mode = alloc_mode; 248 select_policy(sbi, gc_type, type, &p); 249 250 p.min_segno = NULL_SEGNO; 251 p.min_cost = max_cost = get_max_cost(sbi, &p); 252 253 mutex_lock(&dirty_i->seglist_lock); 254 255 if (p.alloc_mode == LFS && gc_type == FG_GC) { 256 p.min_segno = check_bg_victims(sbi); 257 if (p.min_segno != NULL_SEGNO) 258 goto got_it; 259 } 260 261 while (1) { 262 unsigned long cost; 263 unsigned int segno; 264 265 segno = find_next_bit(p.dirty_segmap, 266 TOTAL_SEGS(sbi), p.offset); 267 if (segno >= TOTAL_SEGS(sbi)) { 268 if (sbi->last_victim[p.gc_mode]) { 269 sbi->last_victim[p.gc_mode] = 0; 270 p.offset = 0; 271 continue; 272 } 273 break; 274 } 275 p.offset = ((segno / p.ofs_unit) * p.ofs_unit) + p.ofs_unit; 276 secno = GET_SECNO(sbi, segno); 277 278 if (sec_usage_check(sbi, secno)) 279 continue; 280 if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap)) 281 continue; 282 283 cost = get_gc_cost(sbi, segno, &p); 284 285 if (p.min_cost > cost) { 286 p.min_segno = segno; 287 p.min_cost = cost; 288 } 289 290 if (cost == max_cost) 291 continue; 292 293 if (nsearched++ >= MAX_VICTIM_SEARCH) { 294 sbi->last_victim[p.gc_mode] = segno; 295 break; 296 } 297 } 298 if (p.min_segno != NULL_SEGNO) { 299 got_it: 300 if (p.alloc_mode == LFS) { 301 secno = GET_SECNO(sbi, p.min_segno); 302 if (gc_type == FG_GC) 303 sbi->cur_victim_sec = secno; 304 else 305 set_bit(secno, dirty_i->victim_secmap); 306 } 307 *result = (p.min_segno / p.ofs_unit) * p.ofs_unit; 308 309 trace_f2fs_get_victim(sbi->sb, type, gc_type, &p, 310 sbi->cur_victim_sec, 311 prefree_segments(sbi), free_segments(sbi)); 312 } 313 mutex_unlock(&dirty_i->seglist_lock); 314 315 return (p.min_segno == NULL_SEGNO) ? 0 : 1; 316 } 317 318 static const struct victim_selection default_v_ops = { 319 .get_victim = get_victim_by_default, 320 }; 321 322 static struct inode *find_gc_inode(nid_t ino, struct list_head *ilist) 323 { 324 struct inode_entry *ie; 325 326 list_for_each_entry(ie, ilist, list) 327 if (ie->inode->i_ino == ino) 328 return ie->inode; 329 return NULL; 330 } 331 332 static void add_gc_inode(struct inode *inode, struct list_head *ilist) 333 { 334 struct inode_entry *new_ie; 335 336 if (inode == find_gc_inode(inode->i_ino, ilist)) { 337 iput(inode); 338 return; 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