1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 */
24
25 #include <sys/zfs_context.h>
26 #include <sys/txg_impl.h>
27 #include <sys/dmu_impl.h>
28 #include <sys/dmu_tx.h>
29 #include <sys/dsl_pool.h>
30 #include <sys/dsl_scan.h>
31 #include <sys/callb.h>
32
33 /*
34 * Pool-wide transaction groups.
35 */
36
37 static void txg_sync_thread(dsl_pool_t *dp);
38 static void txg_quiesce_thread(dsl_pool_t *dp);
39
40 int zfs_txg_timeout = 5; /* max seconds worth of delta per txg */
41
42 /*
43 * Prepare the txg subsystem.
44 */
45 void
46 txg_init(dsl_pool_t *dp, uint64_t txg)
47 {
48 tx_state_t *tx = &dp->dp_tx;
49 int c;
50 bzero(tx, sizeof (tx_state_t));
51
52 tx->tx_cpu = kmem_zalloc(max_ncpus * sizeof (tx_cpu_t), KM_SLEEP);
53
54 for (c = 0; c < max_ncpus; c++) {
55 int i;
56
57 mutex_init(&tx->tx_cpu[c].tc_lock, NULL, MUTEX_DEFAULT, NULL);
58 for (i = 0; i < TXG_SIZE; i++) {
59 cv_init(&tx->tx_cpu[c].tc_cv[i], NULL, CV_DEFAULT,
60 NULL);
61 list_create(&tx->tx_cpu[c].tc_callbacks[i],
62 sizeof (dmu_tx_callback_t),
63 offsetof(dmu_tx_callback_t, dcb_node));
64 }
65 }
66
67 mutex_init(&tx->tx_sync_lock, NULL, MUTEX_DEFAULT, NULL);
68
69 cv_init(&tx->tx_sync_more_cv, NULL, CV_DEFAULT, NULL);
70 cv_init(&tx->tx_sync_done_cv, NULL, CV_DEFAULT, NULL);
71 cv_init(&tx->tx_quiesce_more_cv, NULL, CV_DEFAULT, NULL);
72 cv_init(&tx->tx_quiesce_done_cv, NULL, CV_DEFAULT, NULL);
73 cv_init(&tx->tx_exit_cv, NULL, CV_DEFAULT, NULL);
74
75 tx->tx_open_txg = txg;
76 }
77
78 /*
79 * Close down the txg subsystem.
80 */
81 void
82 txg_fini(dsl_pool_t *dp)
83 {
84 tx_state_t *tx = &dp->dp_tx;
85 int c;
86
87 ASSERT(tx->tx_threads == 0);
88
89 mutex_destroy(&tx->tx_sync_lock);
90
91 cv_destroy(&tx->tx_sync_more_cv);
92 cv_destroy(&tx->tx_sync_done_cv);
93 cv_destroy(&tx->tx_quiesce_more_cv);
94 cv_destroy(&tx->tx_quiesce_done_cv);
95 cv_destroy(&tx->tx_exit_cv);
96
97 for (c = 0; c < max_ncpus; c++) {
98 int i;
99
100 mutex_destroy(&tx->tx_cpu[c].tc_lock);
101 for (i = 0; i < TXG_SIZE; i++) {
102 cv_destroy(&tx->tx_cpu[c].tc_cv[i]);
103 list_destroy(&tx->tx_cpu[c].tc_callbacks[i]);
104 }
105 }
106
107 if (tx->tx_commit_cb_taskq != NULL)
108 taskq_destroy(tx->tx_commit_cb_taskq);
109
110 kmem_free(tx->tx_cpu, max_ncpus * sizeof (tx_cpu_t));
111
112 bzero(tx, sizeof (tx_state_t));
113 }
114
115 /*
116 * Start syncing transaction groups.
117 */
118 void
119 txg_sync_start(dsl_pool_t *dp)
120 {
121 tx_state_t *tx = &dp->dp_tx;
122
123 mutex_enter(&tx->tx_sync_lock);
124
125 dprintf("pool %p\n", dp);
126
127 ASSERT(tx->tx_threads == 0);
128
129 tx->tx_threads = 2;
130
131 tx->tx_quiesce_thread = thread_create(NULL, 0, txg_quiesce_thread,
132 dp, 0, &p0, TS_RUN, minclsyspri);
133
134 /*
135 * The sync thread can need a larger-than-default stack size on
136 * 32-bit x86. This is due in part to nested pools and
137 * scrub_visitbp() recursion.
138 */
139 tx->tx_sync_thread = thread_create(NULL, 32<<10, txg_sync_thread,
140 dp, 0, &p0, TS_RUN, minclsyspri);
141
142 mutex_exit(&tx->tx_sync_lock);
143 }
144
145 static void
146 txg_thread_enter(tx_state_t *tx, callb_cpr_t *cpr)
147 {
148 CALLB_CPR_INIT(cpr, &tx->tx_sync_lock, callb_generic_cpr, FTAG);
149 mutex_enter(&tx->tx_sync_lock);
150 }
151
152 static void
153 txg_thread_exit(tx_state_t *tx, callb_cpr_t *cpr, kthread_t **tpp)
154 {
155 ASSERT(*tpp != NULL);
156 *tpp = NULL;
157 tx->tx_threads--;
158 cv_broadcast(&tx->tx_exit_cv);
159 CALLB_CPR_EXIT(cpr); /* drops &tx->tx_sync_lock */
160 thread_exit();
161 }
162
163 static void
164 txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, uint64_t time)
165 {
166 CALLB_CPR_SAFE_BEGIN(cpr);
167
168 if (time)
169 (void) cv_timedwait(cv, &tx->tx_sync_lock,
170 ddi_get_lbolt() + time);
171 else
172 cv_wait(cv, &tx->tx_sync_lock);
173
174 CALLB_CPR_SAFE_END(cpr, &tx->tx_sync_lock);
175 }
176
177 /*
178 * Stop syncing transaction groups.
179 */
180 void
181 txg_sync_stop(dsl_pool_t *dp)
182 {
183 tx_state_t *tx = &dp->dp_tx;
184
185 dprintf("pool %p\n", dp);
186 /*
187 * Finish off any work in progress.
188 */
189 ASSERT(tx->tx_threads == 2);
190
191 /*
192 * We need to ensure that we've vacated the deferred space_maps.
193 */
194 txg_wait_synced(dp, tx->tx_open_txg + TXG_DEFER_SIZE);
195
196 /*
197 * Wake all sync threads and wait for them to die.
198 */
199 mutex_enter(&tx->tx_sync_lock);
200
201 ASSERT(tx->tx_threads == 2);
202
203 tx->tx_exiting = 1;
204
205 cv_broadcast(&tx->tx_quiesce_more_cv);
206 cv_broadcast(&tx->tx_quiesce_done_cv);
207 cv_broadcast(&tx->tx_sync_more_cv);
208
209 while (tx->tx_threads != 0)
210 cv_wait(&tx->tx_exit_cv, &tx->tx_sync_lock);
211
212 tx->tx_exiting = 0;
213
214 mutex_exit(&tx->tx_sync_lock);
215 }
216
217 uint64_t
218 txg_hold_open(dsl_pool_t *dp, txg_handle_t *th)
219 {
220 tx_state_t *tx = &dp->dp_tx;
221 tx_cpu_t *tc = &tx->tx_cpu[CPU_SEQID];
222 uint64_t txg;
223
224 mutex_enter(&tc->tc_lock);
225
226 txg = tx->tx_open_txg;
227 tc->tc_count[txg & TXG_MASK]++;
228
229 th->th_cpu = tc;
230 th->th_txg = txg;
231
232 return (txg);
233 }
234
235 void
236 txg_rele_to_quiesce(txg_handle_t *th)
237 {
238 tx_cpu_t *tc = th->th_cpu;
239
240 mutex_exit(&tc->tc_lock);
241 }
242
243 void
244 txg_register_callbacks(txg_handle_t *th, list_t *tx_callbacks)
245 {
246 tx_cpu_t *tc = th->th_cpu;
247 int g = th->th_txg & TXG_MASK;
248
249 mutex_enter(&tc->tc_lock);
250 list_move_tail(&tc->tc_callbacks[g], tx_callbacks);
251 mutex_exit(&tc->tc_lock);
252 }
253
254 void
255 txg_rele_to_sync(txg_handle_t *th)
256 {
257 tx_cpu_t *tc = th->th_cpu;
258 int g = th->th_txg & TXG_MASK;
259
260 mutex_enter(&tc->tc_lock);
261 ASSERT(tc->tc_count[g] != 0);
262 if (--tc->tc_count[g] == 0)
263 cv_broadcast(&tc->tc_cv[g]);
264 mutex_exit(&tc->tc_lock);
265
266 th->th_cpu = NULL; /* defensive */
267 }
268
269 static void
270 txg_quiesce(dsl_pool_t *dp, uint64_t txg)
271 {
272 tx_state_t *tx = &dp->dp_tx;
273 int g = txg & TXG_MASK;
274 int c;
275
276 /*
277 * Grab all tx_cpu locks so nobody else can get into this txg.
278 */
279 for (c = 0; c < max_ncpus; c++)
280 mutex_enter(&tx->tx_cpu[c].tc_lock);
281
282 ASSERT(txg == tx->tx_open_txg);
283 tx->tx_open_txg++;
284
285 /*
286 * Now that we've incremented tx_open_txg, we can let threads
287 * enter the next transaction group.
288 */
289 for (c = 0; c < max_ncpus; c++)
290 mutex_exit(&tx->tx_cpu[c].tc_lock);
291
292 /*
293 * Quiesce the transaction group by waiting for everyone to txg_exit().
294 */
295 for (c = 0; c < max_ncpus; c++) {
296 tx_cpu_t *tc = &tx->tx_cpu[c];
297 mutex_enter(&tc->tc_lock);
298 while (tc->tc_count[g] != 0)
299 cv_wait(&tc->tc_cv[g], &tc->tc_lock);
300 mutex_exit(&tc->tc_lock);
301 }
302 }
303
304 static void
305 txg_do_callbacks(list_t *cb_list)
306 {
307 dmu_tx_do_callbacks(cb_list, 0);
308
309 list_destroy(cb_list);
310
311 kmem_free(cb_list, sizeof (list_t));
312 }
313
314 /*
315 * Dispatch the commit callbacks registered on this txg to worker threads.
316 */
317 static void
318 txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg)
319 {
320 int c;
321 tx_state_t *tx = &dp->dp_tx;
322 list_t *cb_list;
323
324 for (c = 0; c < max_ncpus; c++) {
325 tx_cpu_t *tc = &tx->tx_cpu[c];
326 /* No need to lock tx_cpu_t at this point */
327
328 int g = txg & TXG_MASK;
329
330 if (list_is_empty(&tc->tc_callbacks[g]))
331 continue;
332
333 if (tx->tx_commit_cb_taskq == NULL) {
334 /*
335 * Commit callback taskq hasn't been created yet.
336 */
337 tx->tx_commit_cb_taskq = taskq_create("tx_commit_cb",
338 max_ncpus, minclsyspri, max_ncpus, max_ncpus * 2,
339 TASKQ_PREPOPULATE);
340 }
341
342 cb_list = kmem_alloc(sizeof (list_t), KM_SLEEP);
343 list_create(cb_list, sizeof (dmu_tx_callback_t),
344 offsetof(dmu_tx_callback_t, dcb_node));
345
346 list_move_tail(&tc->tc_callbacks[g], cb_list);
347
348 (void) taskq_dispatch(tx->tx_commit_cb_taskq, (task_func_t *)
349 txg_do_callbacks, cb_list, TQ_SLEEP);
350 }
351 }
352
353 static void
354 txg_sync_thread(dsl_pool_t *dp)
355 {
356 spa_t *spa = dp->dp_spa;
357 tx_state_t *tx = &dp->dp_tx;
358 callb_cpr_t cpr;
359 uint64_t start, delta;
360
361 txg_thread_enter(tx, &cpr);
362
363 start = delta = 0;
364 for (;;) {
365 uint64_t timer, timeout = zfs_txg_timeout * hz;
366 uint64_t txg;
367
368 /*
369 * We sync when we're scanning, there's someone waiting
370 * on us, or the quiesce thread has handed off a txg to
371 * us, or we have reached our timeout.
372 */
373 timer = (delta >= timeout ? 0 : timeout - delta);
374 while (!dsl_scan_active(dp->dp_scan) &&
375 !tx->tx_exiting && timer > 0 &&
376 tx->tx_synced_txg >= tx->tx_sync_txg_waiting &&
377 tx->tx_quiesced_txg == 0) {
378 dprintf("waiting; tx_synced=%llu waiting=%llu dp=%p\n",
379 tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
380 txg_thread_wait(tx, &cpr, &tx->tx_sync_more_cv, timer);
381 delta = ddi_get_lbolt() - start;
382 timer = (delta > timeout ? 0 : timeout - delta);
383 }
384
385 /*
386 * Wait until the quiesce thread hands off a txg to us,
387 * prompting it to do so if necessary.
388 */
389 while (!tx->tx_exiting && tx->tx_quiesced_txg == 0) {
390 if (tx->tx_quiesce_txg_waiting < tx->tx_open_txg+1)
391 tx->tx_quiesce_txg_waiting = tx->tx_open_txg+1;
392 cv_broadcast(&tx->tx_quiesce_more_cv);
393 txg_thread_wait(tx, &cpr, &tx->tx_quiesce_done_cv, 0);
394 }
395
396 if (tx->tx_exiting)
397 txg_thread_exit(tx, &cpr, &tx->tx_sync_thread);
398
399 /*
400 * Consume the quiesced txg which has been handed off to
401 * us. This may cause the quiescing thread to now be
402 * able to quiesce another txg, so we must signal it.
403 */
404 txg = tx->tx_quiesced_txg;
405 tx->tx_quiesced_txg = 0;
406 tx->tx_syncing_txg = txg;
407 cv_broadcast(&tx->tx_quiesce_more_cv);
408
409 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
410 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
411 mutex_exit(&tx->tx_sync_lock);
412
413 start = ddi_get_lbolt();
414 spa_sync(spa, txg);
415 delta = ddi_get_lbolt() - start;
416
417 mutex_enter(&tx->tx_sync_lock);
418 tx->tx_synced_txg = txg;
419 tx->tx_syncing_txg = 0;
420 cv_broadcast(&tx->tx_sync_done_cv);
421
422 /*
423 * Dispatch commit callbacks to worker threads.
424 */
425 txg_dispatch_callbacks(dp, txg);
426 }
427 }
428
429 static void
430 txg_quiesce_thread(dsl_pool_t *dp)
431 {
432 tx_state_t *tx = &dp->dp_tx;
433 callb_cpr_t cpr;
434
435 txg_thread_enter(tx, &cpr);
436
437 for (;;) {
438 uint64_t txg;
439
440 /*
441 * We quiesce when there's someone waiting on us.
442 * However, we can only have one txg in "quiescing" or
443 * "quiesced, waiting to sync" state. So we wait until
444 * the "quiesced, waiting to sync" txg has been consumed
445 * by the sync thread.
446 */
447 while (!tx->tx_exiting &&
448 (tx->tx_open_txg >= tx->tx_quiesce_txg_waiting ||
449 tx->tx_quiesced_txg != 0))
450 txg_thread_wait(tx, &cpr, &tx->tx_quiesce_more_cv, 0);
451
452 if (tx->tx_exiting)
453 txg_thread_exit(tx, &cpr, &tx->tx_quiesce_thread);
454
455 txg = tx->tx_open_txg;
456 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
457 txg, tx->tx_quiesce_txg_waiting,
458 tx->tx_sync_txg_waiting);
459 mutex_exit(&tx->tx_sync_lock);
460 txg_quiesce(dp, txg);
461 mutex_enter(&tx->tx_sync_lock);
462
463 /*
464 * Hand this txg off to the sync thread.
465 */
466 dprintf("quiesce done, handing off txg %llu\n", txg);
467 tx->tx_quiesced_txg = txg;
468 cv_broadcast(&tx->tx_sync_more_cv);
469 cv_broadcast(&tx->tx_quiesce_done_cv);
470 }
471 }
472
473 /*
474 * Delay this thread by 'ticks' if we are still in the open transaction
475 * group and there is already a waiting txg quiesing or quiesced. Abort
476 * the delay if this txg stalls or enters the quiesing state.
477 */
478 void
479 txg_delay(dsl_pool_t *dp, uint64_t txg, int ticks)
480 {
481 tx_state_t *tx = &dp->dp_tx;
482 int timeout = ddi_get_lbolt() + ticks;
483
484 /* don't delay if this txg could transition to quiesing immediately */
485 if (tx->tx_open_txg > txg ||
486 tx->tx_syncing_txg == txg-1 || tx->tx_synced_txg == txg-1)
487 return;
488
489 mutex_enter(&tx->tx_sync_lock);
490 if (tx->tx_open_txg > txg || tx->tx_synced_txg == txg-1) {
491 mutex_exit(&tx->tx_sync_lock);
492 return;
493 }
494
495 while (ddi_get_lbolt() < timeout &&
496 tx->tx_syncing_txg < txg-1 && !txg_stalled(dp))
497 (void) cv_timedwait(&tx->tx_quiesce_more_cv, &tx->tx_sync_lock,
498 timeout);
499
500 mutex_exit(&tx->tx_sync_lock);
501 }
502
503 void
504 txg_wait_synced(dsl_pool_t *dp, uint64_t txg)
505 {
506 tx_state_t *tx = &dp->dp_tx;
507
508 mutex_enter(&tx->tx_sync_lock);
509 ASSERT(tx->tx_threads == 2);
510 if (txg == 0)
511 txg = tx->tx_open_txg + TXG_DEFER_SIZE;
512 if (tx->tx_sync_txg_waiting < txg)
513 tx->tx_sync_txg_waiting = txg;
514 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
515 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
516 while (tx->tx_synced_txg < txg) {
517 dprintf("broadcasting sync more "
518 "tx_synced=%llu waiting=%llu dp=%p\n",
519 tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
520 cv_broadcast(&tx->tx_sync_more_cv);
521 cv_wait(&tx->tx_sync_done_cv, &tx->tx_sync_lock);
522 }
523 mutex_exit(&tx->tx_sync_lock);
524 }
525
526 void
527 txg_wait_open(dsl_pool_t *dp, uint64_t txg)
528 {
529 tx_state_t *tx = &dp->dp_tx;
530
531 mutex_enter(&tx->tx_sync_lock);
532 ASSERT(tx->tx_threads == 2);
533 if (txg == 0)
534 txg = tx->tx_open_txg + 1;
535 if (tx->tx_quiesce_txg_waiting < txg)
536 tx->tx_quiesce_txg_waiting = txg;
537 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
538 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
539 while (tx->tx_open_txg < txg) {
540 cv_broadcast(&tx->tx_quiesce_more_cv);
541 cv_wait(&tx->tx_quiesce_done_cv, &tx->tx_sync_lock);
542 }
543 mutex_exit(&tx->tx_sync_lock);
544 }
545
546 boolean_t
547 txg_stalled(dsl_pool_t *dp)
548 {
549 tx_state_t *tx = &dp->dp_tx;
550 return (tx->tx_quiesce_txg_waiting > tx->tx_open_txg);
551 }
552
553 boolean_t
554 txg_sync_waiting(dsl_pool_t *dp)
555 {
556 tx_state_t *tx = &dp->dp_tx;
557
558 return (tx->tx_syncing_txg <= tx->tx_sync_txg_waiting ||
559 tx->tx_quiesced_txg != 0);
560 }
561
562 /*
563 * Per-txg object lists.
564 */
565 void
566 txg_list_create(txg_list_t *tl, size_t offset)
567 {
568 int t;
569
570 mutex_init(&tl->tl_lock, NULL, MUTEX_DEFAULT, NULL);
571
572 tl->tl_offset = offset;
573
574 for (t = 0; t < TXG_SIZE; t++)
575 tl->tl_head[t] = NULL;
576 }
577
578 void
579 txg_list_destroy(txg_list_t *tl)
580 {
581 int t;
582
583 for (t = 0; t < TXG_SIZE; t++)
584 ASSERT(txg_list_empty(tl, t));
585
586 mutex_destroy(&tl->tl_lock);
587 }
588
589 int
590 txg_list_empty(txg_list_t *tl, uint64_t txg)
591 {
592 return (tl->tl_head[txg & TXG_MASK] == NULL);
593 }
594
595 /*
596 * Add an entry to the list.
597 * Returns 0 if it's a new entry, 1 if it's already there.
598 */
599 int
600 txg_list_add(txg_list_t *tl, void *p, uint64_t txg)
601 {
602 int t = txg & TXG_MASK;
603 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
604 int already_on_list;
605
606 mutex_enter(&tl->tl_lock);
607 already_on_list = tn->tn_member[t];
608 if (!already_on_list) {
609 tn->tn_member[t] = 1;
610 tn->tn_next[t] = tl->tl_head[t];
611 tl->tl_head[t] = tn;
612 }
613 mutex_exit(&tl->tl_lock);
614
615 return (already_on_list);
616 }
617
618 /*
619 * Add an entry to the end of the list (walks list to find end).
620 * Returns 0 if it's a new entry, 1 if it's already there.
621 */
622 int
623 txg_list_add_tail(txg_list_t *tl, void *p, uint64_t txg)
624 {
625 int t = txg & TXG_MASK;
626 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
627 int already_on_list;
628
629 mutex_enter(&tl->tl_lock);
630 already_on_list = tn->tn_member[t];
631 if (!already_on_list) {
632 txg_node_t **tp;
633
634 for (tp = &tl->tl_head[t]; *tp != NULL; tp = &(*tp)->tn_next[t])
635 continue;
636
637 tn->tn_member[t] = 1;
638 tn->tn_next[t] = NULL;
639 *tp = tn;
640 }
641 mutex_exit(&tl->tl_lock);
642
643 return (already_on_list);
644 }
645
646 /*
647 * Remove the head of the list and return it.
648 */
649 void *
650 txg_list_remove(txg_list_t *tl, uint64_t txg)
651 {
652 int t = txg & TXG_MASK;
653 txg_node_t *tn;
654 void *p = NULL;
655
656 mutex_enter(&tl->tl_lock);
657 if ((tn = tl->tl_head[t]) != NULL) {
658 p = (char *)tn - tl->tl_offset;
659 tl->tl_head[t] = tn->tn_next[t];
660 tn->tn_next[t] = NULL;
661 tn->tn_member[t] = 0;
662 }
663 mutex_exit(&tl->tl_lock);
664
665 return (p);
666 }
667
668 /*
669 * Remove a specific item from the list and return it.
670 */
671 void *
672 txg_list_remove_this(txg_list_t *tl, void *p, uint64_t txg)
673 {
674 int t = txg & TXG_MASK;
675 txg_node_t *tn, **tp;
676
677 mutex_enter(&tl->tl_lock);
678
679 for (tp = &tl->tl_head[t]; (tn = *tp) != NULL; tp = &tn->tn_next[t]) {
680 if ((char *)tn - tl->tl_offset == p) {
681 *tp = tn->tn_next[t];
682 tn->tn_next[t] = NULL;
683 tn->tn_member[t] = 0;
684 mutex_exit(&tl->tl_lock);
685 return (p);
686 }
687 }
688
689 mutex_exit(&tl->tl_lock);
690
691 return (NULL);
692 }
693
694 int
695 txg_list_member(txg_list_t *tl, void *p, uint64_t txg)
696 {
697 int t = txg & TXG_MASK;
698 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
699
700 return (tn->tn_member[t]);
701 }
702
703 /*
704 * Walk a txg list -- only safe if you know it's not changing.
705 */
706 void *
707 txg_list_head(txg_list_t *tl, uint64_t txg)
708 {
709 int t = txg & TXG_MASK;
710 txg_node_t *tn = tl->tl_head[t];
711
712 return (tn == NULL ? NULL : (char *)tn - tl->tl_offset);
713 }
714
715 void *
716 txg_list_next(txg_list_t *tl, void *p, uint64_t txg)
717 {
718 int t = txg & TXG_MASK;
719 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
720
721 tn = tn->tn_next[t];
722
723 return (tn == NULL ? NULL : (char *)tn - tl->tl_offset);
724 }