1 /*
2 * Copyright (c) 2007-2008 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 /*
36 * HAMMER B-Tree index - cursor support routines
37 */
38 #include "hammer.h"
39
40 static int hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive);
41
42 /*
43 * Initialize a fresh cursor using the B-Tree node cache. If the cache
44 * is not available initialize a fresh cursor at the root of the filesystem.
45 */
46 int
47 hammer_init_cursor(hammer_transaction_t trans, hammer_cursor_t cursor,
48 hammer_node_cache_t cache, hammer_inode_t ip)
49 {
50 hammer_volume_t volume;
51 hammer_node_t node;
52 hammer_mount_t hmp;
53 u_int tticks;
54 int error;
55
56 bzero(cursor, sizeof(*cursor));
57
58 cursor->trans = trans;
59 hmp = trans->hmp;
60
61 /*
62 * As the number of inodes queued to the flusher increases we use
63 * time-domain multiplexing to control read vs flush performance.
64 * We have to do it here, before acquiring any ip or node locks,
65 * to avoid deadlocking or excessively delaying the flusher.
66 *
67 * The full time period is hammer_tdmux_ticks, typically 1/5 of
68 * a second.
69 *
70 * inode allocation begins to get restrained at 2/4 the limit
71 * via the "hmrrcm" mechanism in hammer_inode. We want to begin
72 * limiting read activity before that to try to avoid processes
73 * stalling out in "hmrrcm".
74 */
75 tticks = hammer_tdmux_ticks;
76 if (trans->type != HAMMER_TRANS_FLS && tticks &&
77 hmp->count_reclaims > hammer_limit_reclaims / tticks &&
78 hmp->count_reclaims > hammer_autoflush * 2 &&
79 hammer_flusher_running(hmp)) {
80 u_int rticks;
81 u_int xticks;
82 u_int dummy;
83
84 /*
85 * 0 ... xticks ... tticks
86 *
87 * rticks is the calculated position, xticks is the demarc
88 * where values below xticks are reserved for the flusher
89 * and values >= to xticks may be used by the frontend.
90 *
91 * At least one tick is always made available for the
92 * frontend.
93 */
94 rticks = (u_int)ticks % tticks;
95 xticks = hmp->count_reclaims * tticks / hammer_limit_reclaims;
96
97 /*
98 * Ensure rticks and xticks are stable
99 */
100 cpu_ccfence();
101 if (rticks < xticks) {
102 if (hammer_debug_general & 0x0004)
103 kprintf("rt %3u, xt %3u, tt %3u\n",
104 rticks, xticks, tticks);
105 tsleep(&dummy, 0, "htdmux", xticks - rticks);
106 }
107 }
108
109 /*
110 * If the cursor operation is on behalf of an inode, lock
111 * the inode.
112 *
113 * When acquiring a shared lock on an inode on which the backend
114 * flusher deadlocked, wait up to hammer_tdmux_ticks (1 second)
115 * for the deadlock to clear.
116 */
117 if ((cursor->ip = ip) != NULL) {
118 ++ip->cursor_ip_refs;
119 if (trans->type == HAMMER_TRANS_FLS) {
120 hammer_lock_ex(&ip->lock);
121 } else {
122 #if 0
123 if (ip->cursor_exclreq_count) {
124 tsleep(&ip->cursor_exclreq_count, 0,
125 "hstag1", hammer_tdmux_ticks);
126 }
127 #endif
128 hammer_lock_sh(&ip->lock);
129 }
130 }
131
132 /*
133 * Step 1 - acquire a locked node from the cache if possible
134 */
135 if (cache && cache->node) {
136 node = hammer_ref_node_safe(trans, cache, &error);
137 if (error == 0) {
138 hammer_lock_sh(&node->lock);
139 if (node->flags & HAMMER_NODE_DELETED) {
140 hammer_unlock(&node->lock);
141 hammer_rel_node(node);
142 node = NULL;
143 }
144 }
145 if (node == NULL)
146 ++hammer_stats_btree_root_iterations;
147 } else {
148 node = NULL;
149 ++hammer_stats_btree_root_iterations;
150 }
151
152 /*
153 * Step 2 - If we couldn't get a node from the cache, get
154 * the one from the root of the filesystem.
155 */
156 while (node == NULL) {
157 volume = hammer_get_root_volume(hmp, &error);
158 if (error)
159 break;
160 node = hammer_get_node(trans, volume->ondisk->vol0_btree_root,
161 0, &error);
162 hammer_rel_volume(volume, 0);
163 if (error)
164 break;
165 /*
166 * When the frontend acquires the root b-tree node while the
167 * backend is deadlocked on it, wait up to hammer_tdmux_ticks
168 * (1 second) for the deadlock to clear.
169 */
170 #if 0
171 if (node->cursor_exclreq_count &&
172 cursor->trans->type != HAMMER_TRANS_FLS) {
173 tsleep(&node->cursor_exclreq_count, 0,
174 "hstag3", hammer_tdmux_ticks);
175 }
176 #endif
177 hammer_lock_sh(&node->lock);
178
179 /*
180 * If someone got in before we could lock the node, retry.
181 */
182 if (node->flags & HAMMER_NODE_DELETED) {
183 hammer_unlock(&node->lock);
184 hammer_rel_node(node);
185 node = NULL;
186 continue;
187 }
188 if (volume->ondisk->vol0_btree_root != node->node_offset) {
189 hammer_unlock(&node->lock);
190 hammer_rel_node(node);
191 node = NULL;
192 continue;
193 }
194 }
195
196 /*
197 * Step 3 - finish initializing the cursor by acquiring the parent
198 */
199 cursor->node = node;
200 if (error == 0)
201 error = hammer_load_cursor_parent(cursor, 0);
202 KKASSERT(error == 0);
203 /* if (error) hammer_done_cursor(cursor); */
204 return(error);
205 }
206
207 /*
208 * Normalize a cursor. Sometimes cursors can be left in a state
209 * where node is NULL. If the cursor is in this state, cursor up.
210 */
211 void
212 hammer_normalize_cursor(hammer_cursor_t cursor)
213 {
214 if (cursor->node == NULL) {
215 KKASSERT(cursor->parent != NULL);
216 hammer_cursor_up(cursor);
217 }
218 }
219
220
221 /*
222 * We are finished with a cursor. We NULL out various fields as sanity
223 * check, in case the structure is inappropriately used afterwords.
224 */
225 void
226 hammer_done_cursor(hammer_cursor_t cursor)
227 {
228 hammer_inode_t ip;
229
230 KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
231 if (cursor->parent) {
232 hammer_unlock(&cursor->parent->lock);
233 hammer_rel_node(cursor->parent);
234 cursor->parent = NULL;
235 }
236 if (cursor->node) {
237 hammer_unlock(&cursor->node->lock);
238 hammer_rel_node(cursor->node);
239 cursor->node = NULL;
240 }
241 if (cursor->data_buffer) {
242 hammer_rel_buffer(cursor->data_buffer, 0);
243 cursor->data_buffer = NULL;
244 }
245 if ((ip = cursor->ip) != NULL) {
246 KKASSERT(ip->cursor_ip_refs > 0);
247 --ip->cursor_ip_refs;
248 hammer_unlock(&ip->lock);
249 cursor->ip = NULL;
250 }
251 if (cursor->iprec) {
252 hammer_rel_mem_record(cursor->iprec);
253 cursor->iprec = NULL;
254 }
255
256 /*
257 * If we deadlocked this node will be referenced. Do a quick
258 * lock/unlock to wait for the deadlock condition to clear.
259 *
260 * Maintain exclreq_count / wakeup as necessary to notify new
261 * entrants into ip. We continue to hold the fs_token so our
262 * EDEADLK retry loop should get its chance before another thread
263 * steals the lock.
264 */
265 if (cursor->deadlk_node) {
266 #if 0
267 if (ip && cursor->trans->type == HAMMER_TRANS_FLS)
268 ++ip->cursor_exclreq_count;
269 ++cursor->deadlk_node->cursor_exclreq_count;
270 #endif
271 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
272 hammer_unlock(&cursor->deadlk_node->lock);
273 #if 0
274 if (--cursor->deadlk_node->cursor_exclreq_count == 0)
275 wakeup(&cursor->deadlk_node->cursor_exclreq_count);
276 if (ip && cursor->trans->type == HAMMER_TRANS_FLS) {
277 if (--ip->cursor_exclreq_count == 0)
278 wakeup(&ip->cursor_exclreq_count);
279 }
280 #endif
281 hammer_rel_node(cursor->deadlk_node);
282 cursor->deadlk_node = NULL;
283 }
284 if (cursor->deadlk_rec) {
285 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
286 hammer_rel_mem_record(cursor->deadlk_rec);
287 cursor->deadlk_rec = NULL;
288 }
289
290 cursor->data = NULL;
291 cursor->leaf = NULL;
292 cursor->left_bound = NULL;
293 cursor->right_bound = NULL;
294 cursor->trans = NULL;
295 }
296
297 /*
298 * Upgrade cursor->node and cursor->parent to exclusive locks. This
299 * function can return EDEADLK.
300 *
301 * The lock must already be either held shared or already held exclusively
302 * by us.
303 *
304 * We upgrade the parent first as it is the most likely to collide first
305 * with the downward traversal that the frontend typically does.
306 *
307 * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
308 * we add another reference to the node that failed and set
309 * cursor->deadlk_node so hammer_done_cursor() can block on it.
310 */
311 int
312 hammer_cursor_upgrade(hammer_cursor_t cursor)
313 {
314 int error;
315
316 if (cursor->parent) {
317 error = hammer_lock_upgrade(&cursor->parent->lock, 1);
318 if (error && cursor->deadlk_node == NULL) {
319 cursor->deadlk_node = cursor->parent;
320 hammer_ref_node(cursor->deadlk_node);
321 }
322 } else {
323 error = 0;
324 }
325 if (error == 0) {
326 error = hammer_lock_upgrade(&cursor->node->lock, 1);
327 if (error && cursor->deadlk_node == NULL) {
328 cursor->deadlk_node = cursor->node;
329 hammer_ref_node(cursor->deadlk_node);
330 }
331 }
332 #if 0
333 error = hammer_lock_upgrade(&cursor->node->lock, 1);
334 if (error && cursor->deadlk_node == NULL) {
335 cursor->deadlk_node = cursor->node;
336 hammer_ref_node(cursor->deadlk_node);
337 } else if (error == 0 && cursor->parent) {
338 error = hammer_lock_upgrade(&cursor->parent->lock, 1);
339 if (error && cursor->deadlk_node == NULL) {
340 cursor->deadlk_node = cursor->parent;
341 hammer_ref_node(cursor->deadlk_node);
342 }
343 }
344 #endif
345 return(error);
346 }
347
348 int
349 hammer_cursor_upgrade_node(hammer_cursor_t cursor)
350 {
351 int error;
352
353 error = hammer_lock_upgrade(&cursor->node->lock, 1);
354 if (error && cursor->deadlk_node == NULL) {
355 cursor->deadlk_node = cursor->node;
356 hammer_ref_node(cursor->deadlk_node);
357 }
358 return(error);
359 }
360
361 /*
362 * Downgrade cursor->node and cursor->parent to shared locks. This
363 * function can return EDEADLK.
364 */
365 void
366 hammer_cursor_downgrade(hammer_cursor_t cursor)
367 {
368 if (hammer_lock_excl_owned(&cursor->node->lock, curthread))
369 hammer_lock_downgrade(&cursor->node->lock, 1);
370 if (cursor->parent &&
371 hammer_lock_excl_owned(&cursor->parent->lock, curthread)) {
372 hammer_lock_downgrade(&cursor->parent->lock, 1);
373 }
374 }
375
376 /*
377 * Upgrade and downgrade pairs of cursors. This is used by the dedup
378 * code which must deal with two cursors. A special function is needed
379 * because some of the nodes may be shared between the two cursors,
380 * resulting in share counts > 1 which will normally cause an upgrade
381 * to fail.
382 */
383 static __noinline
384 int
385 collect_node(hammer_node_t *array, int *counts, int n, hammer_node_t node)
386 {
387 int i;
388
389 for (i = 0; i < n; ++i) {
390 if (array[i] == node)
391 break;
392 }
393 if (i == n) {
394 array[i] = node;
395 counts[i] = 1;
396 ++i;
397 } else {
398 ++counts[i];
399 }
400 return(i);
401 }
402
403 int
404 hammer_cursor_upgrade2(hammer_cursor_t cursor1, hammer_cursor_t cursor2)
405 {
406 hammer_node_t nodes[4];
407 int counts[4];
408 int error;
409 int i;
410 int n;
411
412 n = collect_node(nodes, counts, 0, cursor1->node);
413 if (cursor1->parent)
414 n = collect_node(nodes, counts, n, cursor1->parent);
415 n = collect_node(nodes, counts, n, cursor2->node);
416 if (cursor2->parent)
417 n = collect_node(nodes, counts, n, cursor2->parent);
418
419 error = 0;
420 for (i = 0; i < n; ++i) {
421 error = hammer_lock_upgrade(&nodes[i]->lock, counts[i]);
422 if (error)
423 break;
424 }
425 if (error) {
426 while (--i >= 0)
427 hammer_lock_downgrade(&nodes[i]->lock, counts[i]);
428 }
429 return (error);
430 }
431
432 void
433 hammer_cursor_downgrade2(hammer_cursor_t cursor1, hammer_cursor_t cursor2)
434 {
435 hammer_node_t nodes[4];
436 int counts[4];
437 int i;
438 int n;
439
440 n = collect_node(nodes, counts, 0, cursor1->node);
441 if (cursor1->parent)
442 n = collect_node(nodes, counts, n, cursor1->parent);
443 n = collect_node(nodes, counts, n, cursor2->node);
444 if (cursor2->parent)
445 n = collect_node(nodes, counts, n, cursor2->parent);
446
447 for (i = 0; i < n; ++i)
448 hammer_lock_downgrade(&nodes[i]->lock, counts[i]);
449 }
450
451 /*
452 * Seek the cursor to the specified node and index.
453 *
454 * The caller must ref the node prior to calling this routine and release
455 * it after it returns. If the seek succeeds the cursor will gain its own
456 * ref on the node.
457 */
458 int
459 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
460 {
461 int error;
462
463 hammer_cursor_downgrade(cursor);
464 error = 0;
465
466 if (cursor->node != node) {
467 hammer_unlock(&cursor->node->lock);
468 hammer_rel_node(cursor->node);
469 cursor->node = node;
470 hammer_ref_node(node);
471 hammer_lock_sh(&node->lock);
472 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
473
474 if (cursor->parent) {
475 hammer_unlock(&cursor->parent->lock);
476 hammer_rel_node(cursor->parent);
477 cursor->parent = NULL;
478 cursor->parent_index = 0;
479 }
480 error = hammer_load_cursor_parent(cursor, 0);
481 }
482 cursor->index = index;
483 return (error);
484 }
485
486 /*
487 * Load the parent of cursor->node into cursor->parent.
488 */
489 static
490 int
491 hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive)
492 {
493 hammer_mount_t hmp;
494 hammer_node_t parent;
495 hammer_node_t node;
496 hammer_btree_elm_t elm;
497 int error;
498 int parent_index;
499
500 hmp = cursor->trans->hmp;
501
502 if (cursor->node->ondisk->parent) {
503 node = cursor->node;
504 parent = hammer_btree_get_parent(cursor->trans, node,
505 &parent_index,
506 &error, try_exclusive);
507 if (error == 0) {
508 elm = &parent->ondisk->elms[parent_index];
509 cursor->parent = parent;
510 cursor->parent_index = parent_index;
511 cursor->left_bound = &elm[0].internal.base;
512 cursor->right_bound = &elm[1].internal.base;
513 }
514 } else {
515 cursor->parent = NULL;
516 cursor->parent_index = 0;
517 cursor->left_bound = &hmp->root_btree_beg;
518 cursor->right_bound = &hmp->root_btree_end;
519 error = 0;
520 }
521 return(error);
522 }
523
524 /*
525 * Cursor up to our parent node. Return ENOENT if we are at the root of
526 * the filesystem.
527 */
528 int
529 hammer_cursor_up(hammer_cursor_t cursor)
530 {
531 int error;
532
533 hammer_cursor_downgrade(cursor);
534
535 /*
536 * If the parent is NULL we are at the root of the B-Tree and
537 * return ENOENT.
538 */
539 if (cursor->parent == NULL)
540 return (ENOENT);
541
542 /*
543 * Set the node to its parent.
544 */
545 hammer_unlock(&cursor->node->lock);
546 hammer_rel_node(cursor->node);
547 cursor->node = cursor->parent;
548 cursor->index = cursor->parent_index;
549 cursor->parent = NULL;
550 cursor->parent_index = 0;
551
552 error = hammer_load_cursor_parent(cursor, 0);
553 return(error);
554 }
555
556 /*
557 * Special cursor up given a locked cursor. The orignal node is not
558 * unlocked or released and the cursor is not downgraded.
559 *
560 * This function can fail with EDEADLK.
561 *
562 * This function is only run when recursively deleting parent nodes
563 * to get rid of an empty leaf.
564 */
565 int
566 hammer_cursor_up_locked(hammer_cursor_t cursor)
567 {
568 hammer_node_t save;
569 int error;
570 int save_index;
571
572 /*
573 * If the parent is NULL we are at the root of the B-Tree and
574 * return ENOENT.
575 */
576 if (cursor->parent == NULL)
577 return (ENOENT);
578
579 save = cursor->node;
580 save_index = cursor->index;
581
582 /*
583 * Set the node to its parent.
584 */
585 cursor->node = cursor->parent;
586 cursor->index = cursor->parent_index;
587 cursor->parent = NULL;
588 cursor->parent_index = 0;
589
590 /*
591 * load the new parent, attempt to exclusively lock it. Note that
592 * we are still holding the old parent (now cursor->node) exclusively
593 * locked.
594 *
595 * This can return EDEADLK. Undo the operation on any error. These
596 * up sequences can occur during iterations so be sure to restore
597 * the index.
598 */
599 error = hammer_load_cursor_parent(cursor, 1);
600 if (error) {
601 cursor->parent = cursor->node;
602 cursor->parent_index = cursor->index;
603 cursor->node = save;
604 cursor->index = save_index;
605 }
606 return(error);
607 }
608
609
610 /*
611 * Cursor down through the current node, which must be an internal node.
612 *
613 * This routine adjusts the cursor and sets index to 0.
614 */
615 int
616 hammer_cursor_down(hammer_cursor_t cursor)
617 {
618 hammer_node_t node;
619 hammer_btree_elm_t elm;
620 int error;
621
622 /*
623 * The current node becomes the current parent
624 */
625 hammer_cursor_downgrade(cursor);
626 node = cursor->node;
627 KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
628 if (cursor->parent) {
629 hammer_unlock(&cursor->parent->lock);
630 hammer_rel_node(cursor->parent);
631 }
632 cursor->parent = node;
633 cursor->parent_index = cursor->index;
634 cursor->node = NULL;
635 cursor->index = 0;
636
637 /*
638 * Extract element to push into at (node,index), set bounds.
639 */
640 elm = &node->ondisk->elms[cursor->parent_index];
641
642 /*
643 * Ok, push down into elm. If elm specifies an internal or leaf
644 * node the current node must be an internal node. If elm specifies
645 * a spike then the current node must be a leaf node.
646 */
647 switch(elm->base.btype) {
648 case HAMMER_BTREE_TYPE_INTERNAL:
649 case HAMMER_BTREE_TYPE_LEAF:
650 KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
651 KKASSERT(elm->internal.subtree_offset != 0);
652 cursor->left_bound = &elm[0].internal.base;
653 cursor->right_bound = &elm[1].internal.base;
654 node = hammer_get_node(cursor->trans,
655 elm->internal.subtree_offset, 0, &error);
656 if (error == 0) {
657 KASSERT(elm->base.btype == node->ondisk->type, ("BTYPE MISMATCH %c %c NODE %p", elm->base.btype, node->ondisk->type, node));
658 if (node->ondisk->parent != cursor->parent->node_offset)
659 panic("node %p %016llx vs %016llx", node, (long long)node->ondisk->parent, (long long)cursor->parent->node_offset);
660 KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
661 }
662 break;
663 default:
664 panic("hammer_cursor_down: illegal btype %02x (%c)",
665 elm->base.btype,
666 (elm->base.btype ? elm->base.btype : '?'));
667 break;
668 }
669
670 /*
671 * If no error occured we can lock the new child node. If the
672 * node is deadlock flagged wait up to hammer_tdmux_ticks (1 second)
673 * for the deadlock to clear. Otherwise a large number of concurrent
674 * readers can continuously stall the flusher.
675 *
676 * We specifically do this in the cursor_down() code in order to
677 * deal with frontend top-down searches smashing against bottom-up
678 * flusher-based mirror updates. These collisions typically occur
679 * above the inode in the B-Tree and are not covered by the
680 * ip->cursor_exclreq_count logic.
681 */
682 if (error == 0) {
683 #if 0
684 if (node->cursor_exclreq_count &&
685 cursor->trans->type != HAMMER_TRANS_FLS) {
686 tsleep(&node->cursor_exclreq_count, 0,
687 "hstag2", hammer_tdmux_ticks);
688 }
689 #endif
690 hammer_lock_sh(&node->lock);
691 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
692 cursor->node = node;
693 cursor->index = 0;
694 }
695 return(error);
696 }
697
698 /************************************************************************
699 * DEADLOCK RECOVERY *
700 ************************************************************************
701 *
702 * These are the new deadlock recovery functions. Currently they are only
703 * used for the mirror propagation and physical node removal cases but
704 * ultimately the intention is to use them for all deadlock recovery
705 * operations.
706 *
707 * WARNING! The contents of the cursor may be modified while unlocked.
708 * passive modifications including adjusting the node, parent,
709 * indexes, and leaf pointer.
710 *
711 * An outright removal of the element the cursor was pointing at
712 * will cause the HAMMER_CURSOR_TRACKED_RIPOUT flag to be set,
713 * which chains to causing the HAMMER_CURSOR_RETEST to be set
714 * when the cursor is locked again.
715 */
716 void
717 hammer_unlock_cursor(hammer_cursor_t cursor)
718 {
719 hammer_node_t node;
720
721 KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
722 KKASSERT(cursor->node);
723
724 /*
725 * Release the cursor's locks and track B-Tree operations on node.
726 * While being tracked our cursor can be modified by other threads
727 * and the node may be replaced.
728 */
729 if (cursor->parent) {
730 hammer_unlock(&cursor->parent->lock);
731 hammer_rel_node(cursor->parent);
732 cursor->parent = NULL;
733 }
734 node = cursor->node;
735 cursor->flags |= HAMMER_CURSOR_TRACKED;
736 TAILQ_INSERT_TAIL(&node->cursor_list, cursor, deadlk_entry);
737 hammer_unlock(&node->lock);
738 }
739
740 /*
741 * Get the cursor heated up again. The cursor's node may have
742 * changed and we might have to locate the new parent.
743 *
744 * If the exact element we were on got deleted RIPOUT will be
745 * set and we must clear ATEDISK so an iteration does not skip
746 * the element after it.
747 */
748 int
749 hammer_lock_cursor(hammer_cursor_t cursor)
750 {
751 hammer_node_t node;
752 int error;
753
754 KKASSERT(cursor->flags & HAMMER_CURSOR_TRACKED);
755
756 /*
757 * Relock the node
758 */
759 for (;;) {
760 node = cursor->node;
761 hammer_ref_node(node);
762 hammer_lock_sh(&node->lock);
763 if (cursor->node == node) {
764 hammer_rel_node(node);
765 break;
766 }
767 hammer_unlock(&node->lock);
768 hammer_rel_node(node);
769 }
770
771 /*
772 * Untrack the cursor, clean up, and re-establish the parent node.
773 */
774 TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
775 cursor->flags &= ~HAMMER_CURSOR_TRACKED;
776
777 /*
778 * If a ripout has occured iterations must re-test the (new)
779 * current element. Clearing ATEDISK prevents the element from
780 * being skipped and RETEST causes it to be re-tested.
781 */
782 if (cursor->flags & HAMMER_CURSOR_TRACKED_RIPOUT) {
783 cursor->flags &= ~HAMMER_CURSOR_TRACKED_RIPOUT;
784 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
785 cursor->flags |= HAMMER_CURSOR_RETEST;
786 }
787 error = hammer_load_cursor_parent(cursor, 0);
788 return(error);
789 }
790
791 /*
792 * Recover from a deadlocked cursor, tracking any node removals or
793 * replacements. If the cursor's current node is removed by another
794 * thread (via btree_remove()) the cursor will be seeked upwards.
795 *
796 * The caller is working a modifying operation and must be holding the
797 * sync lock (shared). We do not release the sync lock because this
798 * would break atomicy.
799 */
800 int
801 hammer_recover_cursor(hammer_cursor_t cursor)
802 {
803 hammer_transaction_t trans __debugvar;
804 #if 0
805 hammer_inode_t ip;
806 #endif
807 int error;
808
809 hammer_unlock_cursor(cursor);
810
811 #if 0
812 ip = cursor->ip;
813 #endif
814 trans = cursor->trans;
815 KKASSERT(trans->sync_lock_refs > 0);
816
817 /*
818 * Wait for the deadlock to clear.
819 *
820 * Maintain exclreq_count / wakeup as necessary to notify new
821 * entrants into ip. We continue to hold the fs_token so our
822 * EDEADLK retry loop should get its chance before another thread
823 * steals the lock.
824 */
825 if (cursor->deadlk_node) {
826 #if 0
827 if (ip && trans->type == HAMMER_TRANS_FLS)
828 ++ip->cursor_exclreq_count;
829 ++cursor->deadlk_node->cursor_exclreq_count;
830 #endif
831 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
832 hammer_unlock(&cursor->deadlk_node->lock);
833 #if 0
834 if (--cursor->deadlk_node->cursor_exclreq_count == 0)
835 wakeup(&cursor->deadlk_node->cursor_exclreq_count);
836 if (ip && trans->type == HAMMER_TRANS_FLS) {
837 if (--ip->cursor_exclreq_count == 0)
838 wakeup(&ip->cursor_exclreq_count);
839 }
840 #endif
841 hammer_rel_node(cursor->deadlk_node);
842 cursor->deadlk_node = NULL;
843 }
844 if (cursor->deadlk_rec) {
845 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
846 hammer_rel_mem_record(cursor->deadlk_rec);
847 cursor->deadlk_rec = NULL;
848 }
849 error = hammer_lock_cursor(cursor);
850 return(error);
851 }
852
853 /*
854 * Dup ocursor to ncursor. ncursor inherits ocursor's locks and ocursor
855 * is effectively unlocked and becomes tracked. If ocursor was not locked
856 * then ncursor also inherits the tracking.
857 *
858 * After the caller finishes working with ncursor it must be cleaned up
859 * with hammer_done_cursor(), and the caller must re-lock ocursor.
860 */
861 hammer_cursor_t
862 hammer_push_cursor(hammer_cursor_t ocursor)
863 {
864 hammer_cursor_t ncursor;
865 hammer_inode_t ip;
866 hammer_node_t node;
867 hammer_mount_t hmp;
868
869 hmp = ocursor->trans->hmp;
870 ncursor = kmalloc(sizeof(*ncursor), hmp->m_misc, M_WAITOK | M_ZERO);
871 bcopy(ocursor, ncursor, sizeof(*ocursor));
872
873 node = ocursor->node;
874 hammer_ref_node(node);
875 if ((ocursor->flags & HAMMER_CURSOR_TRACKED) == 0) {
876 ocursor->flags |= HAMMER_CURSOR_TRACKED;
877 TAILQ_INSERT_TAIL(&node->cursor_list, ocursor, deadlk_entry);
878 }
879 if (ncursor->parent)
880 ocursor->parent = NULL;
881 ocursor->data_buffer = NULL;
882 ocursor->leaf = NULL;
883 ocursor->data = NULL;
884 if (ncursor->flags & HAMMER_CURSOR_TRACKED)
885 TAILQ_INSERT_TAIL(&node->cursor_list, ncursor, deadlk_entry);
886 if ((ip = ncursor->ip) != NULL) {
887 ++ip->cursor_ip_refs;
888 }
889 if (ncursor->iprec)
890 hammer_ref(&ncursor->iprec->lock);
891 return(ncursor);
892 }
893
894 /*
895 * Destroy ncursor and restore ocursor
896 *
897 * This is a temporary hack for the release. We can't afford to lose
898 * the IP lock until the IP object scan code is able to deal with it,
899 * so have ocursor inherit it back.
900 */
901 void
902 hammer_pop_cursor(hammer_cursor_t ocursor, hammer_cursor_t ncursor)
903 {
904 hammer_mount_t hmp;
905 hammer_inode_t ip;
906
907 hmp = ncursor->trans->hmp;
908 ip = ncursor->ip;
909 ncursor->ip = NULL;
910 if (ip)
911 --ip->cursor_ip_refs;
912 hammer_done_cursor(ncursor);
913 kfree(ncursor, hmp->m_misc);
914 KKASSERT(ocursor->ip == ip);
915 hammer_lock_cursor(ocursor);
916 }
917
918 /*
919 * onode is being replaced by nnode by the reblocking code.
920 */
921 void
922 hammer_cursor_replaced_node(hammer_node_t onode, hammer_node_t nnode)
923 {
924 hammer_cursor_t cursor;
925 hammer_node_ondisk_t ondisk;
926 hammer_node_ondisk_t nndisk;
927
928 ondisk = onode->ondisk;
929 nndisk = nnode->ondisk;
930
931 while ((cursor = TAILQ_FIRST(&onode->cursor_list)) != NULL) {
932 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
933 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
934 KKASSERT(cursor->node == onode);
935 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
936 cursor->leaf = &nndisk->elms[cursor->index].leaf;
937 cursor->node = nnode;
938 hammer_ref_node(nnode);
939 hammer_rel_node(onode);
940 }
941 }
942
943 /*
944 * We have removed <node> from the parent and collapsed the parent.
945 *
946 * Cursors in deadlock recovery are seeked upward to the parent so the
947 * btree_remove() recursion works properly even though we have marked
948 * the cursor as requiring a reseek.
949 *
950 * This is the only cursor function which sets HAMMER_CURSOR_ITERATE_CHECK,
951 * meaning the cursor is no longer definitively pointing at an element
952 * within its iteration (if the cursor is being used to iterate). The
953 * iteration code will take this into account instead of asserting if the
954 * cursor is outside the iteration range.
955 */
956 void
957 hammer_cursor_removed_node(hammer_node_t node, hammer_node_t parent, int index)
958 {
959 hammer_cursor_t cursor;
960 hammer_node_ondisk_t ondisk;
961
962 KKASSERT(parent != NULL);
963 ondisk = node->ondisk;
964
965 while ((cursor = TAILQ_FIRST(&node->cursor_list)) != NULL) {
966 KKASSERT(cursor->node == node);
967 KKASSERT(cursor->index == 0);
968 TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
969 TAILQ_INSERT_TAIL(&parent->cursor_list, cursor, deadlk_entry);
970 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
971 cursor->leaf = NULL;
972 cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
973 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
974 cursor->node = parent;
975 cursor->index = index;
976 hammer_ref_node(parent);
977 hammer_rel_node(node);
978 }
979 }
980
981 /*
982 * node was split at (onode, index) with elements >= index moved to nnode.
983 */
984 void
985 hammer_cursor_split_node(hammer_node_t onode, hammer_node_t nnode, int index)
986 {
987 hammer_cursor_t cursor;
988 hammer_node_ondisk_t ondisk;
989 hammer_node_ondisk_t nndisk;
990
991 ondisk = onode->ondisk;
992 nndisk = nnode->ondisk;
993
994 again:
995 TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
996 KKASSERT(cursor->node == onode);
997 if (cursor->index < index)
998 continue;
999 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
1000 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
1001 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
1002 cursor->leaf = &nndisk->elms[cursor->index - index].leaf;
1003 cursor->node = nnode;
1004 cursor->index -= index;
1005 hammer_ref_node(nnode);
1006 hammer_rel_node(onode);
1007 goto again;
1008 }
1009 }
1010
1011 /*
1012 * An element was moved from one node to another or within a node. The
1013 * index may also represent the end of the node (index == numelements).
1014 *
1015 * {oparent,pindex} is the parent node's pointer to onode/oindex.
1016 *
1017 * This is used by the rebalancing code. This is not an insertion or
1018 * deletion and any additional elements, including the degenerate case at
1019 * the end of the node, will be dealt with by additional distinct calls.
1020 */
1021 void
1022 hammer_cursor_moved_element(hammer_node_t oparent, int pindex,
1023 hammer_node_t onode, int oindex,
1024 hammer_node_t nnode, int nindex)
1025 {
1026 hammer_cursor_t cursor;
1027 hammer_node_ondisk_t ondisk;
1028 hammer_node_ondisk_t nndisk;
1029
1030 /*
1031 * Adjust any cursors pointing at the element
1032 */
1033 ondisk = onode->ondisk;
1034 nndisk = nnode->ondisk;
1035 again1:
1036 TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
1037 KKASSERT(cursor->node == onode);
1038 if (cursor->index != oindex)
1039 continue;
1040 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
1041 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
1042 if (cursor->leaf == &ondisk->elms[oindex].leaf)
1043 cursor->leaf = &nndisk->elms[nindex].leaf;
1044 cursor->node = nnode;
1045 cursor->index = nindex;
1046 hammer_ref_node(nnode);
1047 hammer_rel_node(onode);
1048 goto again1;
1049 }
1050
1051 /*
1052 * When moving the first element of onode to a different node any
1053 * cursor which is pointing at (oparent,pindex) must be repointed
1054 * to nnode and ATEDISK must be cleared.
1055 *
1056 * This prevents cursors from losing track due to insertions.
1057 * Insertions temporarily release the cursor in order to update
1058 * the mirror_tids. It primarily effects the mirror_write code.
1059 * The other code paths generally only do a single insertion and
1060 * then relookup or drop the cursor.
1061 */
1062 if (onode == nnode || oindex)
1063 return;
1064 ondisk = oparent->ondisk;
1065 again2:
1066 TAILQ_FOREACH(cursor, &oparent->cursor_list, deadlk_entry) {
1067 KKASSERT(cursor->node == oparent);
1068 if (cursor->index != pindex)
1069 continue;
1070 kprintf("HAMMER debug: shifted cursor pointing at parent\n"
1071 "parent %016jx:%d onode %016jx:%d nnode %016jx:%d\n",
1072 (intmax_t)oparent->node_offset, pindex,
1073 (intmax_t)onode->node_offset, oindex,
1074 (intmax_t)nnode->node_offset, nindex);
1075 TAILQ_REMOVE(&oparent->cursor_list, cursor, deadlk_entry);
1076 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
1077 if (cursor->leaf == &ondisk->elms[oindex].leaf)
1078 cursor->leaf = &nndisk->elms[nindex].leaf;
1079 cursor->node = nnode;
1080 cursor->index = nindex;
1081 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
1082 hammer_ref_node(nnode);
1083 hammer_rel_node(oparent);
1084 goto again2;
1085 }
1086 }
1087
1088 /*
1089 * The B-Tree element pointing to the specified node was moved from (oparent)
1090 * to (nparent, nindex). We must locate any tracked cursors pointing at
1091 * node and adjust their parent accordingly.
1092 *
1093 * This is used by the rebalancing code when packing elements causes an
1094 * element to shift from one node to another.
1095 */
1096 void
1097 hammer_cursor_parent_changed(hammer_node_t node, hammer_node_t oparent,
1098 hammer_node_t nparent, int nindex)
1099 {
1100 hammer_cursor_t cursor;
1101
1102 again:
1103 TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
1104 KKASSERT(cursor->node == node);
1105 if (cursor->parent == oparent) {
1106 cursor->parent = nparent;
1107 cursor->parent_index = nindex;
1108 hammer_ref_node(nparent);
1109 hammer_rel_node(oparent);
1110 goto again;
1111 }
1112 }
1113 }
1114
1115 /*
1116 * Deleted element at (node, index)
1117 *
1118 * Shift indexes >= index
1119 */
1120 void
1121 hammer_cursor_deleted_element(hammer_node_t node, int index)
1122 {
1123 hammer_cursor_t cursor;
1124 hammer_node_ondisk_t ondisk;
1125
1126 ondisk = node->ondisk;
1127
1128 TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
1129 KKASSERT(cursor->node == node);
1130 if (cursor->index == index) {
1131 cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
1132 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
1133 cursor->leaf = NULL;
1134 } else if (cursor->index > index) {
1135 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
1136 cursor->leaf = &ondisk->elms[cursor->index - 1].leaf;
1137 --cursor->index;
1138 }
1139 }
1140 }
1141
1142 /*
1143 * Inserted element at (node, index)
1144 *
1145 * Shift indexes >= index
1146 */
1147 void
1148 hammer_cursor_inserted_element(hammer_node_t node, int index)
1149 {
1150 hammer_cursor_t cursor;
1151 hammer_node_ondisk_t ondisk;
1152
1153 ondisk = node->ondisk;
1154
1155 TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
1156 KKASSERT(cursor->node == node);
1157 if (cursor->index >= index) {
1158 if (cursor->leaf == &ondisk->elms[cursor->index].leaf)
1159 cursor->leaf = &ondisk->elms[cursor->index + 1].leaf;
1160 ++cursor->index;
1161 }
1162 }
1163 }
1164
1165 /*
1166 * Invalidate the cached data buffer associated with a cursor.
1167 *
1168 * This needs to be done when the underlying block is being freed or
1169 * the referenced buffer can prevent the related buffer cache buffer
1170 * from being properly invalidated.
1171 */
1172 void
1173 hammer_cursor_invalidate_cache(hammer_cursor_t cursor)
1174 {
1175 if (cursor->data_buffer) {
1176 hammer_rel_buffer(cursor->data_buffer, 0);
1177 cursor->data_buffer = NULL;
1178 cursor->data = NULL;
1179 }
1180 }
1181
Cache object: 17fa8ced949985cd17a1aaf6c32aaba1
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