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.
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.
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]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Portions Copyright 2011 Martin Matuska <mm@FreeBSD.org>
24 * Copyright (c) 2013 by Delphix. All rights reserved.
27 #include <sys/zfs_context.h>
28 #include <sys/txg_impl.h>
29 #include <sys/dmu_impl.h>
30 #include <sys/dmu_tx.h>
31 #include <sys/dsl_pool.h>
32 #include <sys/dsl_scan.h>
33 #include <sys/callb.h>
36 * ZFS Transaction Groups
37 * ----------------------
39 * ZFS transaction groups are, as the name implies, groups of transactions
40 * that act on persistent state. ZFS asserts consistency at the granularity of
41 * these transaction groups. Each successive transaction group (txg) is
42 * assigned a 64-bit consecutive identifier. There are three active
43 * transaction group states: open, quiescing, or syncing. At any given time,
44 * there may be an active txg associated with each state; each active txg may
45 * either be processing, or blocked waiting to enter the next state. There may
46 * be up to three active txgs, and there is always a txg in the open state
47 * (though it may be blocked waiting to enter the quiescing state). In broad
48 * strokes, transactions — operations that change in-memory structures — are
49 * accepted into the txg in the open state, and are completed while the txg is
50 * in the open or quiescing states. The accumulated changes are written to
51 * disk in the syncing state.
55 * When a new txg becomes active, it first enters the open state. New
56 * transactions — updates to in-memory structures — are assigned to the
57 * currently open txg. There is always a txg in the open state so that ZFS can
58 * accept new changes (though the txg may refuse new changes if it has hit
59 * some limit). ZFS advances the open txg to the next state for a variety of
60 * reasons such as it hitting a time or size threshold, or the execution of an
61 * administrative action that must be completed in the syncing state.
65 * After a txg exits the open state, it enters the quiescing state. The
66 * quiescing state is intended to provide a buffer between accepting new
67 * transactions in the open state and writing them out to stable storage in
68 * the syncing state. While quiescing, transactions can continue their
69 * operation without delaying either of the other states. Typically, a txg is
70 * in the quiescing state very briefly since the operations are bounded by
71 * software latencies rather than, say, slower I/O latencies. After all
72 * transactions complete, the txg is ready to enter the next state.
76 * In the syncing state, the in-memory state built up during the open and (to
77 * a lesser degree) the quiescing states is written to stable storage. The
78 * process of writing out modified data can, in turn modify more data. For
79 * example when we write new blocks, we need to allocate space for them; those
80 * allocations modify metadata (space maps)... which themselves must be
81 * written to stable storage. During the sync state, ZFS iterates, writing out
82 * data until it converges and all in-memory changes have been written out.
83 * The first such pass is the largest as it encompasses all the modified user
84 * data (as opposed to filesystem metadata). Subsequent passes typically have
85 * far less data to write as they consist exclusively of filesystem metadata.
87 * To ensure convergence, after a certain number of passes ZFS begins
88 * overwriting locations on stable storage that had been allocated earlier in
89 * the syncing state (and subsequently freed). ZFS usually allocates new
90 * blocks to optimize for large, continuous, writes. For the syncing state to
91 * converge however it must complete a pass where no new blocks are allocated
92 * since each allocation requires a modification of persistent metadata.
93 * Further, to hasten convergence, after a prescribed number of passes, ZFS
94 * also defers frees, and stops compressing.
96 * In addition to writing out user data, we must also execute synctasks during
97 * the syncing context. A synctask is the mechanism by which some
98 * administrative activities work such as creating and destroying snapshots or
99 * datasets. Note that when a synctask is initiated it enters the open txg,
100 * and ZFS then pushes that txg as quickly as possible to completion of the
101 * syncing state in order to reduce the latency of the administrative
102 * activity. To complete the syncing state, ZFS writes out a new uberblock,
103 * the root of the tree of blocks that comprise all state stored on the ZFS
104 * pool. Finally, if there is a quiesced txg waiting, we signal that it can
105 * now transition to the syncing state.
108 static void txg_sync_thread(void *arg);
109 static void txg_quiesce_thread(void *arg);
111 int zfs_txg_timeout = 5; /* max seconds worth of delta per txg */
113 SYSCTL_DECL(_vfs_zfs);
114 SYSCTL_NODE(_vfs_zfs, OID_AUTO, txg, CTLFLAG_RW, 0, "ZFS TXG");
115 TUNABLE_INT("vfs.zfs.txg.timeout", &zfs_txg_timeout);
116 SYSCTL_INT(_vfs_zfs_txg, OID_AUTO, timeout, CTLFLAG_RW, &zfs_txg_timeout, 0,
117 "Maximum seconds worth of delta per txg");
120 * Prepare the txg subsystem.
123 txg_init(dsl_pool_t *dp, uint64_t txg)
125 tx_state_t *tx = &dp->dp_tx;
127 bzero(tx, sizeof (tx_state_t));
129 tx->tx_cpu = kmem_zalloc(max_ncpus * sizeof (tx_cpu_t), KM_SLEEP);
131 for (c = 0; c < max_ncpus; c++) {
134 mutex_init(&tx->tx_cpu[c].tc_lock, NULL, MUTEX_DEFAULT, NULL);
135 mutex_init(&tx->tx_cpu[c].tc_open_lock, NULL, MUTEX_DEFAULT,
137 for (i = 0; i < TXG_SIZE; i++) {
138 cv_init(&tx->tx_cpu[c].tc_cv[i], NULL, CV_DEFAULT,
140 list_create(&tx->tx_cpu[c].tc_callbacks[i],
141 sizeof (dmu_tx_callback_t),
142 offsetof(dmu_tx_callback_t, dcb_node));
146 mutex_init(&tx->tx_sync_lock, NULL, MUTEX_DEFAULT, NULL);
148 cv_init(&tx->tx_sync_more_cv, NULL, CV_DEFAULT, NULL);
149 cv_init(&tx->tx_sync_done_cv, NULL, CV_DEFAULT, NULL);
150 cv_init(&tx->tx_quiesce_more_cv, NULL, CV_DEFAULT, NULL);
151 cv_init(&tx->tx_quiesce_done_cv, NULL, CV_DEFAULT, NULL);
152 cv_init(&tx->tx_exit_cv, NULL, CV_DEFAULT, NULL);
154 tx->tx_open_txg = txg;
158 * Close down the txg subsystem.
161 txg_fini(dsl_pool_t *dp)
163 tx_state_t *tx = &dp->dp_tx;
166 ASSERT(tx->tx_threads == 0);
168 mutex_destroy(&tx->tx_sync_lock);
170 cv_destroy(&tx->tx_sync_more_cv);
171 cv_destroy(&tx->tx_sync_done_cv);
172 cv_destroy(&tx->tx_quiesce_more_cv);
173 cv_destroy(&tx->tx_quiesce_done_cv);
174 cv_destroy(&tx->tx_exit_cv);
176 for (c = 0; c < max_ncpus; c++) {
179 mutex_destroy(&tx->tx_cpu[c].tc_open_lock);
180 mutex_destroy(&tx->tx_cpu[c].tc_lock);
181 for (i = 0; i < TXG_SIZE; i++) {
182 cv_destroy(&tx->tx_cpu[c].tc_cv[i]);
183 list_destroy(&tx->tx_cpu[c].tc_callbacks[i]);
187 if (tx->tx_commit_cb_taskq != NULL)
188 taskq_destroy(tx->tx_commit_cb_taskq);
190 kmem_free(tx->tx_cpu, max_ncpus * sizeof (tx_cpu_t));
192 bzero(tx, sizeof (tx_state_t));
196 * Start syncing transaction groups.
199 txg_sync_start(dsl_pool_t *dp)
201 tx_state_t *tx = &dp->dp_tx;
203 mutex_enter(&tx->tx_sync_lock);
205 dprintf("pool %p\n", dp);
207 ASSERT(tx->tx_threads == 0);
211 tx->tx_quiesce_thread = thread_create(NULL, 0, txg_quiesce_thread,
212 dp, 0, &p0, TS_RUN, minclsyspri);
215 * The sync thread can need a larger-than-default stack size on
216 * 32-bit x86. This is due in part to nested pools and
217 * scrub_visitbp() recursion.
219 tx->tx_sync_thread = thread_create(NULL, 32<<10, txg_sync_thread,
220 dp, 0, &p0, TS_RUN, minclsyspri);
222 mutex_exit(&tx->tx_sync_lock);
226 txg_thread_enter(tx_state_t *tx, callb_cpr_t *cpr)
228 CALLB_CPR_INIT(cpr, &tx->tx_sync_lock, callb_generic_cpr, FTAG);
229 mutex_enter(&tx->tx_sync_lock);
233 txg_thread_exit(tx_state_t *tx, callb_cpr_t *cpr, kthread_t **tpp)
235 ASSERT(*tpp != NULL);
238 cv_broadcast(&tx->tx_exit_cv);
239 CALLB_CPR_EXIT(cpr); /* drops &tx->tx_sync_lock */
244 txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, clock_t time)
246 CALLB_CPR_SAFE_BEGIN(cpr);
249 (void) cv_timedwait(cv, &tx->tx_sync_lock, time);
251 cv_wait(cv, &tx->tx_sync_lock);
253 CALLB_CPR_SAFE_END(cpr, &tx->tx_sync_lock);
257 * Stop syncing transaction groups.
260 txg_sync_stop(dsl_pool_t *dp)
262 tx_state_t *tx = &dp->dp_tx;
264 dprintf("pool %p\n", dp);
266 * Finish off any work in progress.
268 ASSERT(tx->tx_threads == 2);
271 * We need to ensure that we've vacated the deferred space_maps.
273 txg_wait_synced(dp, tx->tx_open_txg + TXG_DEFER_SIZE);
276 * Wake all sync threads and wait for them to die.
278 mutex_enter(&tx->tx_sync_lock);
280 ASSERT(tx->tx_threads == 2);
284 cv_broadcast(&tx->tx_quiesce_more_cv);
285 cv_broadcast(&tx->tx_quiesce_done_cv);
286 cv_broadcast(&tx->tx_sync_more_cv);
288 while (tx->tx_threads != 0)
289 cv_wait(&tx->tx_exit_cv, &tx->tx_sync_lock);
293 mutex_exit(&tx->tx_sync_lock);
297 txg_hold_open(dsl_pool_t *dp, txg_handle_t *th)
299 tx_state_t *tx = &dp->dp_tx;
300 tx_cpu_t *tc = &tx->tx_cpu[CPU_SEQID];
303 mutex_enter(&tc->tc_open_lock);
304 txg = tx->tx_open_txg;
306 mutex_enter(&tc->tc_lock);
307 tc->tc_count[txg & TXG_MASK]++;
308 mutex_exit(&tc->tc_lock);
317 txg_rele_to_quiesce(txg_handle_t *th)
319 tx_cpu_t *tc = th->th_cpu;
321 ASSERT(!MUTEX_HELD(&tc->tc_lock));
322 mutex_exit(&tc->tc_open_lock);
326 txg_register_callbacks(txg_handle_t *th, list_t *tx_callbacks)
328 tx_cpu_t *tc = th->th_cpu;
329 int g = th->th_txg & TXG_MASK;
331 mutex_enter(&tc->tc_lock);
332 list_move_tail(&tc->tc_callbacks[g], tx_callbacks);
333 mutex_exit(&tc->tc_lock);
337 txg_rele_to_sync(txg_handle_t *th)
339 tx_cpu_t *tc = th->th_cpu;
340 int g = th->th_txg & TXG_MASK;
342 mutex_enter(&tc->tc_lock);
343 ASSERT(tc->tc_count[g] != 0);
344 if (--tc->tc_count[g] == 0)
345 cv_broadcast(&tc->tc_cv[g]);
346 mutex_exit(&tc->tc_lock);
348 th->th_cpu = NULL; /* defensive */
352 * Blocks until all transactions in the group are committed.
354 * On return, the transaction group has reached a stable state in which it can
355 * then be passed off to the syncing context.
358 txg_quiesce(dsl_pool_t *dp, uint64_t txg)
360 tx_state_t *tx = &dp->dp_tx;
361 int g = txg & TXG_MASK;
365 * Grab all tc_open_locks so nobody else can get into this txg.
367 for (c = 0; c < max_ncpus; c++)
368 mutex_enter(&tx->tx_cpu[c].tc_open_lock);
370 ASSERT(txg == tx->tx_open_txg);
373 DTRACE_PROBE2(txg__quiescing, dsl_pool_t *, dp, uint64_t, txg);
374 DTRACE_PROBE2(txg__opened, dsl_pool_t *, dp, uint64_t, tx->tx_open_txg);
377 * Now that we've incremented tx_open_txg, we can let threads
378 * enter the next transaction group.
380 for (c = 0; c < max_ncpus; c++)
381 mutex_exit(&tx->tx_cpu[c].tc_open_lock);
384 * Quiesce the transaction group by waiting for everyone to txg_exit().
386 for (c = 0; c < max_ncpus; c++) {
387 tx_cpu_t *tc = &tx->tx_cpu[c];
388 mutex_enter(&tc->tc_lock);
389 while (tc->tc_count[g] != 0)
390 cv_wait(&tc->tc_cv[g], &tc->tc_lock);
391 mutex_exit(&tc->tc_lock);
396 txg_do_callbacks(void *arg)
398 list_t *cb_list = arg;
400 dmu_tx_do_callbacks(cb_list, 0);
402 list_destroy(cb_list);
404 kmem_free(cb_list, sizeof (list_t));
408 * Dispatch the commit callbacks registered on this txg to worker threads.
410 * If no callbacks are registered for a given TXG, nothing happens.
411 * This function creates a taskq for the associated pool, if needed.
414 txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg)
417 tx_state_t *tx = &dp->dp_tx;
420 for (c = 0; c < max_ncpus; c++) {
421 tx_cpu_t *tc = &tx->tx_cpu[c];
423 * No need to lock tx_cpu_t at this point, since this can
424 * only be called once a txg has been synced.
427 int g = txg & TXG_MASK;
429 if (list_is_empty(&tc->tc_callbacks[g]))
432 if (tx->tx_commit_cb_taskq == NULL) {
434 * Commit callback taskq hasn't been created yet.
436 tx->tx_commit_cb_taskq = taskq_create("tx_commit_cb",
437 max_ncpus, minclsyspri, max_ncpus, max_ncpus * 2,
441 cb_list = kmem_alloc(sizeof (list_t), KM_SLEEP);
442 list_create(cb_list, sizeof (dmu_tx_callback_t),
443 offsetof(dmu_tx_callback_t, dcb_node));
445 list_move_tail(cb_list, &tc->tc_callbacks[g]);
447 (void) taskq_dispatch(tx->tx_commit_cb_taskq, (task_func_t *)
448 txg_do_callbacks, cb_list, TQ_SLEEP);
453 txg_sync_thread(void *arg)
455 dsl_pool_t *dp = arg;
456 spa_t *spa = dp->dp_spa;
457 tx_state_t *tx = &dp->dp_tx;
459 uint64_t start, delta;
461 txg_thread_enter(tx, &cpr);
465 uint64_t timer, timeout = zfs_txg_timeout * hz;
469 * We sync when we're scanning, there's someone waiting
470 * on us, or the quiesce thread has handed off a txg to
471 * us, or we have reached our timeout.
473 timer = (delta >= timeout ? 0 : timeout - delta);
474 while (!dsl_scan_active(dp->dp_scan) &&
475 !tx->tx_exiting && timer > 0 &&
476 tx->tx_synced_txg >= tx->tx_sync_txg_waiting &&
477 tx->tx_quiesced_txg == 0) {
478 dprintf("waiting; tx_synced=%llu waiting=%llu dp=%p\n",
479 tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
480 txg_thread_wait(tx, &cpr, &tx->tx_sync_more_cv, timer);
481 delta = ddi_get_lbolt() - start;
482 timer = (delta > timeout ? 0 : timeout - delta);
486 * Wait until the quiesce thread hands off a txg to us,
487 * prompting it to do so if necessary.
489 while (!tx->tx_exiting && tx->tx_quiesced_txg == 0) {
490 if (tx->tx_quiesce_txg_waiting < tx->tx_open_txg+1)
491 tx->tx_quiesce_txg_waiting = tx->tx_open_txg+1;
492 cv_broadcast(&tx->tx_quiesce_more_cv);
493 txg_thread_wait(tx, &cpr, &tx->tx_quiesce_done_cv, 0);
497 txg_thread_exit(tx, &cpr, &tx->tx_sync_thread);
500 * Consume the quiesced txg which has been handed off to
501 * us. This may cause the quiescing thread to now be
502 * able to quiesce another txg, so we must signal it.
504 txg = tx->tx_quiesced_txg;
505 tx->tx_quiesced_txg = 0;
506 tx->tx_syncing_txg = txg;
507 DTRACE_PROBE2(txg__syncing, dsl_pool_t *, dp, uint64_t, txg);
508 cv_broadcast(&tx->tx_quiesce_more_cv);
510 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
511 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
512 mutex_exit(&tx->tx_sync_lock);
514 start = ddi_get_lbolt();
516 delta = ddi_get_lbolt() - start;
518 mutex_enter(&tx->tx_sync_lock);
519 tx->tx_synced_txg = txg;
520 tx->tx_syncing_txg = 0;
521 DTRACE_PROBE2(txg__synced, dsl_pool_t *, dp, uint64_t, txg);
522 cv_broadcast(&tx->tx_sync_done_cv);
525 * Dispatch commit callbacks to worker threads.
527 txg_dispatch_callbacks(dp, txg);
532 txg_quiesce_thread(void *arg)
534 dsl_pool_t *dp = arg;
535 tx_state_t *tx = &dp->dp_tx;
538 txg_thread_enter(tx, &cpr);
544 * We quiesce when there's someone waiting on us.
545 * However, we can only have one txg in "quiescing" or
546 * "quiesced, waiting to sync" state. So we wait until
547 * the "quiesced, waiting to sync" txg has been consumed
548 * by the sync thread.
550 while (!tx->tx_exiting &&
551 (tx->tx_open_txg >= tx->tx_quiesce_txg_waiting ||
552 tx->tx_quiesced_txg != 0))
553 txg_thread_wait(tx, &cpr, &tx->tx_quiesce_more_cv, 0);
556 txg_thread_exit(tx, &cpr, &tx->tx_quiesce_thread);
558 txg = tx->tx_open_txg;
559 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
560 txg, tx->tx_quiesce_txg_waiting,
561 tx->tx_sync_txg_waiting);
562 mutex_exit(&tx->tx_sync_lock);
563 txg_quiesce(dp, txg);
564 mutex_enter(&tx->tx_sync_lock);
567 * Hand this txg off to the sync thread.
569 dprintf("quiesce done, handing off txg %llu\n", txg);
570 tx->tx_quiesced_txg = txg;
571 DTRACE_PROBE2(txg__quiesced, dsl_pool_t *, dp, uint64_t, txg);
572 cv_broadcast(&tx->tx_sync_more_cv);
573 cv_broadcast(&tx->tx_quiesce_done_cv);
578 * Delay this thread by delay nanoseconds if we are still in the open
579 * transaction group and there is already a waiting txg quiesing or quiesced.
580 * Abort the delay if this txg stalls or enters the quiesing state.
583 txg_delay(dsl_pool_t *dp, uint64_t txg, hrtime_t delay, hrtime_t resolution)
585 tx_state_t *tx = &dp->dp_tx;
586 hrtime_t start = gethrtime();
588 /* don't delay if this txg could transition to quiescing immediately */
589 if (tx->tx_open_txg > txg ||
590 tx->tx_syncing_txg == txg-1 || tx->tx_synced_txg == txg-1)
593 mutex_enter(&tx->tx_sync_lock);
594 if (tx->tx_open_txg > txg || tx->tx_synced_txg == txg-1) {
595 mutex_exit(&tx->tx_sync_lock);
599 while (gethrtime() - start < delay &&
600 tx->tx_syncing_txg < txg-1 && !txg_stalled(dp)) {
601 (void) cv_timedwait_hires(&tx->tx_quiesce_more_cv,
602 &tx->tx_sync_lock, delay, resolution, 0);
605 mutex_exit(&tx->tx_sync_lock);
609 txg_wait_synced(dsl_pool_t *dp, uint64_t txg)
611 tx_state_t *tx = &dp->dp_tx;
613 ASSERT(!dsl_pool_config_held(dp));
615 mutex_enter(&tx->tx_sync_lock);
616 ASSERT(tx->tx_threads == 2);
618 txg = tx->tx_open_txg + TXG_DEFER_SIZE;
619 if (tx->tx_sync_txg_waiting < txg)
620 tx->tx_sync_txg_waiting = txg;
621 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
622 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
623 while (tx->tx_synced_txg < txg) {
624 dprintf("broadcasting sync more "
625 "tx_synced=%llu waiting=%llu dp=%p\n",
626 tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
627 cv_broadcast(&tx->tx_sync_more_cv);
628 cv_wait(&tx->tx_sync_done_cv, &tx->tx_sync_lock);
630 mutex_exit(&tx->tx_sync_lock);
634 txg_wait_open(dsl_pool_t *dp, uint64_t txg)
636 tx_state_t *tx = &dp->dp_tx;
638 ASSERT(!dsl_pool_config_held(dp));
640 mutex_enter(&tx->tx_sync_lock);
641 ASSERT(tx->tx_threads == 2);
643 txg = tx->tx_open_txg + 1;
644 if (tx->tx_quiesce_txg_waiting < txg)
645 tx->tx_quiesce_txg_waiting = txg;
646 dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
647 txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
648 while (tx->tx_open_txg < txg) {
649 cv_broadcast(&tx->tx_quiesce_more_cv);
650 cv_wait(&tx->tx_quiesce_done_cv, &tx->tx_sync_lock);
652 mutex_exit(&tx->tx_sync_lock);
656 txg_stalled(dsl_pool_t *dp)
658 tx_state_t *tx = &dp->dp_tx;
659 return (tx->tx_quiesce_txg_waiting > tx->tx_open_txg);
663 txg_sync_waiting(dsl_pool_t *dp)
665 tx_state_t *tx = &dp->dp_tx;
667 return (tx->tx_syncing_txg <= tx->tx_sync_txg_waiting ||
668 tx->tx_quiesced_txg != 0);
672 * Per-txg object lists.
675 txg_list_create(txg_list_t *tl, size_t offset)
679 mutex_init(&tl->tl_lock, NULL, MUTEX_DEFAULT, NULL);
681 tl->tl_offset = offset;
683 for (t = 0; t < TXG_SIZE; t++)
684 tl->tl_head[t] = NULL;
688 txg_list_destroy(txg_list_t *tl)
692 for (t = 0; t < TXG_SIZE; t++)
693 ASSERT(txg_list_empty(tl, t));
695 mutex_destroy(&tl->tl_lock);
699 txg_list_empty(txg_list_t *tl, uint64_t txg)
701 return (tl->tl_head[txg & TXG_MASK] == NULL);
705 * Add an entry to the list (unless it's already on the list).
706 * Returns B_TRUE if it was actually added.
709 txg_list_add(txg_list_t *tl, void *p, uint64_t txg)
711 int t = txg & TXG_MASK;
712 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
715 mutex_enter(&tl->tl_lock);
716 add = (tn->tn_member[t] == 0);
718 tn->tn_member[t] = 1;
719 tn->tn_next[t] = tl->tl_head[t];
722 mutex_exit(&tl->tl_lock);
728 * Add an entry to the end of the list, unless it's already on the list.
729 * (walks list to find end)
730 * Returns B_TRUE if it was actually added.
733 txg_list_add_tail(txg_list_t *tl, void *p, uint64_t txg)
735 int t = txg & TXG_MASK;
736 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
739 mutex_enter(&tl->tl_lock);
740 add = (tn->tn_member[t] == 0);
744 for (tp = &tl->tl_head[t]; *tp != NULL; tp = &(*tp)->tn_next[t])
747 tn->tn_member[t] = 1;
748 tn->tn_next[t] = NULL;
751 mutex_exit(&tl->tl_lock);
757 * Remove the head of the list and return it.
760 txg_list_remove(txg_list_t *tl, uint64_t txg)
762 int t = txg & TXG_MASK;
766 mutex_enter(&tl->tl_lock);
767 if ((tn = tl->tl_head[t]) != NULL) {
768 p = (char *)tn - tl->tl_offset;
769 tl->tl_head[t] = tn->tn_next[t];
770 tn->tn_next[t] = NULL;
771 tn->tn_member[t] = 0;
773 mutex_exit(&tl->tl_lock);
779 * Remove a specific item from the list and return it.
782 txg_list_remove_this(txg_list_t *tl, void *p, uint64_t txg)
784 int t = txg & TXG_MASK;
785 txg_node_t *tn, **tp;
787 mutex_enter(&tl->tl_lock);
789 for (tp = &tl->tl_head[t]; (tn = *tp) != NULL; tp = &tn->tn_next[t]) {
790 if ((char *)tn - tl->tl_offset == p) {
791 *tp = tn->tn_next[t];
792 tn->tn_next[t] = NULL;
793 tn->tn_member[t] = 0;
794 mutex_exit(&tl->tl_lock);
799 mutex_exit(&tl->tl_lock);
805 txg_list_member(txg_list_t *tl, void *p, uint64_t txg)
807 int t = txg & TXG_MASK;
808 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
810 return (tn->tn_member[t] != 0);
814 * Walk a txg list -- only safe if you know it's not changing.
817 txg_list_head(txg_list_t *tl, uint64_t txg)
819 int t = txg & TXG_MASK;
820 txg_node_t *tn = tl->tl_head[t];
822 return (tn == NULL ? NULL : (char *)tn - tl->tl_offset);
826 txg_list_next(txg_list_t *tl, void *p, uint64_t txg)
828 int t = txg & TXG_MASK;
829 txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
833 return (tn == NULL ? NULL : (char *)tn - tl->tl_offset);