diff options
Diffstat (limited to 'module/zfs')
| -rw-r--r-- | module/zfs/dmu.c | 7 | ||||
| -rw-r--r-- | module/zfs/txg.c | 12 | ||||
| -rw-r--r-- | module/zfs/zfs_vnops.c | 12 | ||||
| -rw-r--r-- | module/zfs/zil.c | 1542 | ||||
| -rw-r--r-- | module/zfs/zio.c | 33 | ||||
| -rw-r--r-- | module/zfs/zvol.c | 11 |
6 files changed, 1331 insertions, 286 deletions
diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c index 108dfe157..56740ae37 100644 --- a/module/zfs/dmu.c +++ b/module/zfs/dmu.c @@ -1783,6 +1783,13 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd, return (SET_ERROR(EIO)); } + /* + * In order to prevent the zgd's lwb from being free'd prior to + * dmu_sync_late_arrival_done() being called, we have to ensure + * the lwb's "max txg" takes this tx's txg into account. + */ + zil_lwb_add_txg(zgd->zgd_lwb, dmu_tx_get_txg(tx)); + dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP); dsa->dsa_dr = NULL; dsa->dsa_done = done; diff --git a/module/zfs/txg.c b/module/zfs/txg.c index 078839a32..bf8544507 100644 --- a/module/zfs/txg.c +++ b/module/zfs/txg.c @@ -160,7 +160,7 @@ txg_fini(dsl_pool_t *dp) tx_state_t *tx = &dp->dp_tx; int c; - ASSERT(tx->tx_threads == 0); + ASSERT0(tx->tx_threads); mutex_destroy(&tx->tx_sync_lock); @@ -201,7 +201,7 @@ txg_sync_start(dsl_pool_t *dp) dprintf("pool %p\n", dp); - ASSERT(tx->tx_threads == 0); + ASSERT0(tx->tx_threads); tx->tx_threads = 2; @@ -263,7 +263,7 @@ txg_sync_stop(dsl_pool_t *dp) /* * Finish off any work in progress. */ - ASSERT(tx->tx_threads == 2); + ASSERT3U(tx->tx_threads, ==, 2); /* * We need to ensure that we've vacated the deferred space_maps. @@ -275,7 +275,7 @@ txg_sync_stop(dsl_pool_t *dp) */ mutex_enter(&tx->tx_sync_lock); - ASSERT(tx->tx_threads == 2); + ASSERT3U(tx->tx_threads, ==, 2); tx->tx_exiting = 1; @@ -648,7 +648,7 @@ txg_wait_synced(dsl_pool_t *dp, uint64_t txg) ASSERT(!dsl_pool_config_held(dp)); mutex_enter(&tx->tx_sync_lock); - ASSERT(tx->tx_threads == 2); + ASSERT3U(tx->tx_threads, ==, 2); if (txg == 0) txg = tx->tx_open_txg + TXG_DEFER_SIZE; if (tx->tx_sync_txg_waiting < txg) @@ -673,7 +673,7 @@ txg_wait_open(dsl_pool_t *dp, uint64_t txg) ASSERT(!dsl_pool_config_held(dp)); mutex_enter(&tx->tx_sync_lock); - ASSERT(tx->tx_threads == 2); + ASSERT3U(tx->tx_threads, ==, 2); if (txg == 0) txg = tx->tx_open_txg + 1; if (tx->tx_quiesce_txg_waiting < txg) diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c index a60cd6198..977035fd9 100644 --- a/module/zfs/zfs_vnops.c +++ b/module/zfs/zfs_vnops.c @@ -78,6 +78,7 @@ #include <sys/cred.h> #include <sys/attr.h> #include <sys/zpl.h> +#include <sys/zil.h> /* * Programming rules. @@ -983,7 +984,7 @@ zfs_get_done(zgd_t *zgd, int error) zfs_iput_async(ZTOI(zp)); if (error == 0 && zgd->zgd_bp) - zil_add_block(zgd->zgd_zilog, zgd->zgd_bp); + zil_lwb_add_block(zgd->zgd_lwb, zgd->zgd_bp); kmem_free(zgd, sizeof (zgd_t)); } @@ -996,7 +997,7 @@ static int zil_fault_io = 0; * Get data to generate a TX_WRITE intent log record. */ int -zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) +zfs_get_data(void *arg, lr_write_t *lr, char *buf, struct lwb *lwb, zio_t *zio) { zfsvfs_t *zfsvfs = arg; objset_t *os = zfsvfs->z_os; @@ -1008,8 +1009,9 @@ zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) zgd_t *zgd; int error = 0; - ASSERT(zio != NULL); - ASSERT(size != 0); + ASSERT3P(lwb, !=, NULL); + ASSERT3P(zio, !=, NULL); + ASSERT3U(size, !=, 0); /* * Nothing to do if the file has been removed @@ -1026,7 +1028,7 @@ zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) } zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_SLEEP); - zgd->zgd_zilog = zfsvfs->z_log; + zgd->zgd_lwb = lwb; zgd->zgd_private = zp; /* diff --git a/module/zfs/zil.c b/module/zfs/zil.c index 9f4312a5a..5300b3408 100644 --- a/module/zfs/zil.c +++ b/module/zfs/zil.c @@ -44,32 +44,53 @@ #include <sys/abd.h> /* - * The zfs intent log (ZIL) saves transaction records of system calls - * that change the file system in memory with enough information - * to be able to replay them. These are stored in memory until - * either the DMU transaction group (txg) commits them to the stable pool - * and they can be discarded, or they are flushed to the stable log - * (also in the pool) due to a fsync, O_DSYNC or other synchronous - * requirement. In the event of a panic or power fail then those log - * records (transactions) are replayed. + * The ZFS Intent Log (ZIL) saves "transaction records" (itxs) of system + * calls that change the file system. Each itx has enough information to + * be able to replay them after a system crash, power loss, or + * equivalent failure mode. These are stored in memory until either: * - * There is one ZIL per file system. Its on-disk (pool) format consists - * of 3 parts: + * 1. they are committed to the pool by the DMU transaction group + * (txg), at which point they can be discarded; or + * 2. they are committed to the on-disk ZIL for the dataset being + * modified (e.g. due to an fsync, O_DSYNC, or other synchronous + * requirement). * - * - ZIL header - * - ZIL blocks - * - ZIL records + * In the event of a crash or power loss, the itxs contained by each + * dataset's on-disk ZIL will be replayed when that dataset is first + * instantianted (e.g. if the dataset is a normal fileystem, when it is + * first mounted). * - * A log record holds a system call transaction. Log blocks can - * hold many log records and the blocks are chained together. - * Each ZIL block contains a block pointer (blkptr_t) to the next - * ZIL block in the chain. The ZIL header points to the first - * block in the chain. Note there is not a fixed place in the pool - * to hold blocks. They are dynamically allocated and freed as - * needed from the blocks available. Figure X shows the ZIL structure: + * As hinted at above, there is one ZIL per dataset (both the in-memory + * representation, and the on-disk representation). The on-disk format + * consists of 3 parts: + * + * - a single, per-dataset, ZIL header; which points to a chain of + * - zero or more ZIL blocks; each of which contains + * - zero or more ZIL records + * + * A ZIL record holds the information necessary to replay a single + * system call transaction. A ZIL block can hold many ZIL records, and + * the blocks are chained together, similarly to a singly linked list. + * + * Each ZIL block contains a block pointer (blkptr_t) to the next ZIL + * block in the chain, and the ZIL header points to the first block in + * the chain. + * + * Note, there is not a fixed place in the pool to hold these ZIL + * blocks; they are dynamically allocated and freed as needed from the + * blocks available on the pool, though they can be preferentially + * allocated from a dedicated "log" vdev. */ /* + * This controls the amount of time that a ZIL block (lwb) will remain + * "open" when it isn't "full", and it has a thread waiting for it to be + * committed to stable storage. Please refer to the zil_commit_waiter() + * function (and the comments within it) for more details. + */ +int zfs_commit_timeout_pct = 5; + +/* * See zil.h for more information about these fields. */ zil_stats_t zil_stats = { @@ -110,6 +131,7 @@ int zfs_nocacheflush = 0; unsigned long zil_slog_bulk = 768 * 1024; static kmem_cache_t *zil_lwb_cache; +static kmem_cache_t *zil_zcw_cache; static void zil_async_to_sync(zilog_t *zilog, uint64_t foid); @@ -476,6 +498,15 @@ zil_free_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t claim_txg) return (0); } +static int +zil_lwb_vdev_compare(const void *x1, const void *x2) +{ + const uint64_t v1 = ((zil_vdev_node_t *)x1)->zv_vdev; + const uint64_t v2 = ((zil_vdev_node_t *)x2)->zv_vdev; + + return (AVL_CMP(v1, v2)); +} + static lwb_t * zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, boolean_t slog, uint64_t txg, boolean_t fastwrite) @@ -487,10 +518,13 @@ zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, boolean_t slog, uint64_t txg, lwb->lwb_blk = *bp; lwb->lwb_fastwrite = fastwrite; lwb->lwb_slog = slog; + lwb->lwb_state = LWB_STATE_CLOSED; lwb->lwb_buf = zio_buf_alloc(BP_GET_LSIZE(bp)); lwb->lwb_max_txg = txg; - lwb->lwb_zio = NULL; + lwb->lwb_write_zio = NULL; + lwb->lwb_root_zio = NULL; lwb->lwb_tx = NULL; + lwb->lwb_issued_timestamp = 0; if (BP_GET_CHECKSUM(bp) == ZIO_CHECKSUM_ZILOG2) { lwb->lwb_nused = sizeof (zil_chain_t); lwb->lwb_sz = BP_GET_LSIZE(bp); @@ -503,9 +537,64 @@ zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, boolean_t slog, uint64_t txg, list_insert_tail(&zilog->zl_lwb_list, lwb); mutex_exit(&zilog->zl_lock); + ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock)); + ASSERT(avl_is_empty(&lwb->lwb_vdev_tree)); + ASSERT(list_is_empty(&lwb->lwb_waiters)); + ASSERT(list_is_empty(&lwb->lwb_itxs)); + return (lwb); } +static void +zil_free_lwb(zilog_t *zilog, lwb_t *lwb) +{ + ASSERT(MUTEX_HELD(&zilog->zl_lock)); + ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock)); + ASSERT(list_is_empty(&lwb->lwb_waiters)); + + if (lwb->lwb_state == LWB_STATE_OPENED) { + avl_tree_t *t = &lwb->lwb_vdev_tree; + void *cookie = NULL; + zil_vdev_node_t *zv; + itx_t *itx; + + while ((zv = avl_destroy_nodes(t, &cookie)) != NULL) + kmem_free(zv, sizeof (*zv)); + + while ((itx = list_head(&lwb->lwb_itxs)) != NULL) { + if (itx->itx_callback != NULL) + itx->itx_callback(itx->itx_callback_data); + list_remove(&lwb->lwb_itxs, itx); + zil_itx_destroy(itx); + } + + ASSERT3P(lwb->lwb_root_zio, !=, NULL); + ASSERT3P(lwb->lwb_write_zio, !=, NULL); + + zio_cancel(lwb->lwb_root_zio); + zio_cancel(lwb->lwb_write_zio); + + lwb->lwb_root_zio = NULL; + lwb->lwb_write_zio = NULL; + } else { + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED); + } + + ASSERT(avl_is_empty(&lwb->lwb_vdev_tree)); + ASSERT(list_is_empty(&lwb->lwb_itxs)); + ASSERT3P(lwb->lwb_write_zio, ==, NULL); + ASSERT3P(lwb->lwb_root_zio, ==, NULL); + + /* + * Clear the zilog's field to indicate this lwb is no longer + * valid, and prevent use-after-free errors. + */ + if (zilog->zl_last_lwb_opened == lwb) + zilog->zl_last_lwb_opened = NULL; + + kmem_cache_free(zil_lwb_cache, lwb); +} + /* * Called when we create in-memory log transactions so that we know * to cleanup the itxs at the end of spa_sync(). @@ -516,12 +605,16 @@ zilog_dirty(zilog_t *zilog, uint64_t txg) dsl_pool_t *dp = zilog->zl_dmu_pool; dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os); + ASSERT(spa_writeable(zilog->zl_spa)); + if (ds->ds_is_snapshot) panic("dirtying snapshot!"); if (txg_list_add(&dp->dp_dirty_zilogs, zilog, txg)) { /* up the hold count until we can be written out */ dmu_buf_add_ref(ds->ds_dbuf, zilog); + + zilog->zl_dirty_max_txg = MAX(txg, zilog->zl_dirty_max_txg); } } @@ -590,7 +683,7 @@ zil_create(zilog_t *zilog) */ if (BP_IS_HOLE(&blk) || BP_SHOULD_BYTESWAP(&blk)) { tx = dmu_tx_create(zilog->zl_os); - VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0); + VERIFY0(dmu_tx_assign(tx, TXG_WAIT)); dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx); txg = dmu_tx_get_txg(tx); @@ -608,7 +701,7 @@ zil_create(zilog_t *zilog) } /* - * Allocate a log write buffer (lwb) for the first log block. + * Allocate a log write block (lwb) for the first log block. */ if (error == 0) lwb = zil_alloc_lwb(zilog, &blk, slog, txg, fastwrite); @@ -629,13 +722,13 @@ zil_create(zilog_t *zilog) } /* - * In one tx, free all log blocks and clear the log header. - * If keep_first is set, then we're replaying a log with no content. - * We want to keep the first block, however, so that the first - * synchronous transaction doesn't require a txg_wait_synced() - * in zil_create(). We don't need to txg_wait_synced() here either - * when keep_first is set, because both zil_create() and zil_destroy() - * will wait for any in-progress destroys to complete. + * In one tx, free all log blocks and clear the log header. If keep_first + * is set, then we're replaying a log with no content. We want to keep the + * first block, however, so that the first synchronous transaction doesn't + * require a txg_wait_synced() in zil_create(). We don't need to + * txg_wait_synced() here either when keep_first is set, because both + * zil_create() and zil_destroy() will wait for any in-progress destroys + * to complete. */ void zil_destroy(zilog_t *zilog, boolean_t keep_first) @@ -656,7 +749,7 @@ zil_destroy(zilog_t *zilog, boolean_t keep_first) return; tx = dmu_tx_create(zilog->zl_os); - VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0); + VERIFY0(dmu_tx_assign(tx, TXG_WAIT)); dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx); txg = dmu_tx_get_txg(tx); @@ -670,15 +763,15 @@ zil_destroy(zilog_t *zilog, boolean_t keep_first) ASSERT(zh->zh_claim_txg == 0); VERIFY(!keep_first); while ((lwb = list_head(&zilog->zl_lwb_list)) != NULL) { - ASSERT(lwb->lwb_zio == NULL); if (lwb->lwb_fastwrite) metaslab_fastwrite_unmark(zilog->zl_spa, &lwb->lwb_blk); + list_remove(&zilog->zl_lwb_list, lwb); if (lwb->lwb_buf != NULL) zio_buf_free(lwb->lwb_buf, lwb->lwb_sz); - zio_free_zil(zilog->zl_spa, txg, &lwb->lwb_blk); - kmem_cache_free(zil_lwb_cache, lwb); + zio_free(zilog->zl_spa, txg, &lwb->lwb_blk); + zil_free_lwb(zilog, lwb); } } else if (!keep_first) { zil_destroy_sync(zilog, tx); @@ -820,19 +913,64 @@ zil_check_log_chain(dsl_pool_t *dp, dsl_dataset_t *ds, void *tx) return ((error == ECKSUM || error == ENOENT) ? 0 : error); } -static int -zil_vdev_compare(const void *x1, const void *x2) +/* + * When an itx is "skipped", this function is used to properly mark the + * waiter as "done, and signal any thread(s) waiting on it. An itx can + * be skipped (and not committed to an lwb) for a variety of reasons, + * one of them being that the itx was committed via spa_sync(), prior to + * it being committed to an lwb; this can happen if a thread calling + * zil_commit() is racing with spa_sync(). + */ +static void +zil_commit_waiter_skip(zil_commit_waiter_t *zcw) { - const uint64_t v1 = ((zil_vdev_node_t *)x1)->zv_vdev; - const uint64_t v2 = ((zil_vdev_node_t *)x2)->zv_vdev; + mutex_enter(&zcw->zcw_lock); + ASSERT3B(zcw->zcw_done, ==, B_FALSE); + zcw->zcw_done = B_TRUE; + cv_broadcast(&zcw->zcw_cv); + mutex_exit(&zcw->zcw_lock); +} - return (AVL_CMP(v1, v2)); +/* + * This function is used when the given waiter is to be linked into an + * lwb's "lwb_waiter" list; i.e. when the itx is committed to the lwb. + * At this point, the waiter will no longer be referenced by the itx, + * and instead, will be referenced by the lwb. + */ +static void +zil_commit_waiter_link_lwb(zil_commit_waiter_t *zcw, lwb_t *lwb) +{ + mutex_enter(&zcw->zcw_lock); + ASSERT(!list_link_active(&zcw->zcw_node)); + ASSERT3P(zcw->zcw_lwb, ==, NULL); + ASSERT3P(lwb, !=, NULL); + ASSERT(lwb->lwb_state == LWB_STATE_OPENED || + lwb->lwb_state == LWB_STATE_ISSUED); + + list_insert_tail(&lwb->lwb_waiters, zcw); + zcw->zcw_lwb = lwb; + mutex_exit(&zcw->zcw_lock); +} + +/* + * This function is used when zio_alloc_zil() fails to allocate a ZIL + * block, and the given waiter must be linked to the "nolwb waiters" + * list inside of zil_process_commit_list(). + */ +static void +zil_commit_waiter_link_nolwb(zil_commit_waiter_t *zcw, list_t *nolwb) +{ + mutex_enter(&zcw->zcw_lock); + ASSERT(!list_link_active(&zcw->zcw_node)); + ASSERT3P(zcw->zcw_lwb, ==, NULL); + list_insert_tail(nolwb, zcw); + mutex_exit(&zcw->zcw_lock); } void -zil_add_block(zilog_t *zilog, const blkptr_t *bp) +zil_lwb_add_block(lwb_t *lwb, const blkptr_t *bp) { - avl_tree_t *t = &zilog->zl_vdev_tree; + avl_tree_t *t = &lwb->lwb_vdev_tree; avl_index_t where; zil_vdev_node_t *zv, zvsearch; int ndvas = BP_GET_NDVAS(bp); @@ -841,14 +979,7 @@ zil_add_block(zilog_t *zilog, const blkptr_t *bp) if (zfs_nocacheflush) return; - ASSERT(zilog->zl_writer); - - /* - * Even though we're zl_writer, we still need a lock because the - * zl_get_data() callbacks may have dmu_sync() done callbacks - * that will run concurrently. - */ - mutex_enter(&zilog->zl_vdev_lock); + mutex_enter(&lwb->lwb_vdev_lock); for (i = 0; i < ndvas; i++) { zvsearch.zv_vdev = DVA_GET_VDEV(&bp->blk_dva[i]); if (avl_find(t, &zvsearch, &where) == NULL) { @@ -857,56 +988,122 @@ zil_add_block(zilog_t *zilog, const blkptr_t *bp) avl_insert(t, zv, where); } } - mutex_exit(&zilog->zl_vdev_lock); + mutex_exit(&lwb->lwb_vdev_lock); } +void +zil_lwb_add_txg(lwb_t *lwb, uint64_t txg) +{ + lwb->lwb_max_txg = MAX(lwb->lwb_max_txg, txg); +} + +/* + * This function is a called after all VDEVs associated with a given lwb + * write have completed their DKIOCFLUSHWRITECACHE command; or as soon + * as the lwb write completes, if "zfs_nocacheflush" is set. + * + * The intention is for this function to be called as soon as the + * contents of an lwb are considered "stable" on disk, and will survive + * any sudden loss of power. At this point, any threads waiting for the + * lwb to reach this state are signalled, and the "waiter" structures + * are marked "done". + */ static void -zil_flush_vdevs(zilog_t *zilog) +zil_lwb_flush_vdevs_done(zio_t *zio) { - spa_t *spa = zilog->zl_spa; - avl_tree_t *t = &zilog->zl_vdev_tree; - void *cookie = NULL; - zil_vdev_node_t *zv; - zio_t *zio; + lwb_t *lwb = zio->io_private; + zilog_t *zilog = lwb->lwb_zilog; + dmu_tx_t *tx = lwb->lwb_tx; + zil_commit_waiter_t *zcw; + itx_t *itx; + + spa_config_exit(zilog->zl_spa, SCL_STATE, lwb); + + zio_buf_free(lwb->lwb_buf, lwb->lwb_sz); - ASSERT(zilog->zl_writer); + mutex_enter(&zilog->zl_lock); /* - * We don't need zl_vdev_lock here because we're the zl_writer, - * and all zl_get_data() callbacks are done. + * Ensure the lwb buffer pointer is cleared before releasing the + * txg. If we have had an allocation failure and the txg is + * waiting to sync then we want zil_sync() to remove the lwb so + * that it's not picked up as the next new one in + * zil_process_commit_list(). zil_sync() will only remove the + * lwb if lwb_buf is null. */ - if (avl_numnodes(t) == 0) - return; + lwb->lwb_buf = NULL; + lwb->lwb_tx = NULL; - spa_config_enter(spa, SCL_STATE, FTAG, RW_READER); + ASSERT3U(lwb->lwb_issued_timestamp, >, 0); + zilog->zl_last_lwb_latency = gethrtime() - lwb->lwb_issued_timestamp; - zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL); + lwb->lwb_root_zio = NULL; + lwb->lwb_state = LWB_STATE_DONE; - while ((zv = avl_destroy_nodes(t, &cookie)) != NULL) { - vdev_t *vd = vdev_lookup_top(spa, zv->zv_vdev); - if (vd != NULL) - zio_flush(zio, vd); - kmem_free(zv, sizeof (*zv)); + if (zilog->zl_last_lwb_opened == lwb) { + /* + * Remember the highest committed log sequence number + * for ztest. We only update this value when all the log + * writes succeeded, because ztest wants to ASSERT that + * it got the whole log chain. + */ + zilog->zl_commit_lr_seq = zilog->zl_lr_seq; + } + + while ((itx = list_head(&lwb->lwb_itxs)) != NULL) { + list_remove(&lwb->lwb_itxs, itx); + zil_itx_destroy(itx); + } + + while ((zcw = list_head(&lwb->lwb_waiters)) != NULL) { + mutex_enter(&zcw->zcw_lock); + + ASSERT(list_link_active(&zcw->zcw_node)); + list_remove(&lwb->lwb_waiters, zcw); + + ASSERT3P(zcw->zcw_lwb, ==, lwb); + zcw->zcw_lwb = NULL; + + zcw->zcw_zio_error = zio->io_error; + + ASSERT3B(zcw->zcw_done, ==, B_FALSE); + zcw->zcw_done = B_TRUE; + cv_broadcast(&zcw->zcw_cv); + + mutex_exit(&zcw->zcw_lock); } + mutex_exit(&zilog->zl_lock); + /* - * Wait for all the flushes to complete. Not all devices actually - * support the DKIOCFLUSHWRITECACHE ioctl, so it's OK if it fails. + * Now that we've written this log block, we have a stable pointer + * to the next block in the chain, so it's OK to let the txg in + * which we allocated the next block sync. */ - (void) zio_wait(zio); - - spa_config_exit(spa, SCL_STATE, FTAG); + dmu_tx_commit(tx); } /* - * Function called when a log block write completes + * This is called when an lwb write completes. This means, this specific + * lwb was written to disk, and all dependent lwb have also been + * written to disk. + * + * At this point, a DKIOCFLUSHWRITECACHE command hasn't been issued to + * the VDEVs involved in writing out this specific lwb. The lwb will be + * "done" once zil_lwb_flush_vdevs_done() is called, which occurs in the + * zio completion callback for the lwb's root zio. */ static void zil_lwb_write_done(zio_t *zio) { lwb_t *lwb = zio->io_private; + spa_t *spa = zio->io_spa; zilog_t *zilog = lwb->lwb_zilog; - dmu_tx_t *tx = lwb->lwb_tx; + avl_tree_t *t = &lwb->lwb_vdev_tree; + void *cookie = NULL; + zil_vdev_node_t *zv; + + ASSERT3S(spa_config_held(spa, SCL_STATE, RW_READER), !=, 0); ASSERT(BP_GET_COMPRESS(zio->io_bp) == ZIO_COMPRESS_OFF); ASSERT(BP_GET_TYPE(zio->io_bp) == DMU_OT_INTENT_LOG); @@ -916,69 +1113,121 @@ zil_lwb_write_done(zio_t *zio) ASSERT(!BP_IS_HOLE(zio->io_bp)); ASSERT(BP_GET_FILL(zio->io_bp) == 0); - /* - * Ensure the lwb buffer pointer is cleared before releasing - * the txg. If we have had an allocation failure and - * the txg is waiting to sync then we want want zil_sync() - * to remove the lwb so that it's not picked up as the next new - * one in zil_commit_writer(). zil_sync() will only remove - * the lwb if lwb_buf is null. - */ abd_put(zio->io_abd); - zio_buf_free(lwb->lwb_buf, lwb->lwb_sz); + + ASSERT3S(lwb->lwb_state, ==, LWB_STATE_ISSUED); + mutex_enter(&zilog->zl_lock); - lwb->lwb_zio = NULL; + lwb->lwb_write_zio = NULL; lwb->lwb_fastwrite = FALSE; - lwb->lwb_buf = NULL; - lwb->lwb_tx = NULL; mutex_exit(&zilog->zl_lock); + if (avl_numnodes(t) == 0) + return; + /* - * Now that we've written this log block, we have a stable pointer - * to the next block in the chain, so it's OK to let the txg in - * which we allocated the next block sync. + * If there was an IO error, we're not going to call zio_flush() + * on these vdevs, so we simply empty the tree and free the + * nodes. We avoid calling zio_flush() since there isn't any + * good reason for doing so, after the lwb block failed to be + * written out. */ - dmu_tx_commit(tx); + if (zio->io_error != 0) { + while ((zv = avl_destroy_nodes(t, &cookie)) != NULL) + kmem_free(zv, sizeof (*zv)); + return; + } + + while ((zv = avl_destroy_nodes(t, &cookie)) != NULL) { + vdev_t *vd = vdev_lookup_top(spa, zv->zv_vdev); + if (vd != NULL) + zio_flush(lwb->lwb_root_zio, vd); + kmem_free(zv, sizeof (*zv)); + } } /* - * Initialize the io for a log block. + * This function's purpose is to "open" an lwb such that it is ready to + * accept new itxs being committed to it. To do this, the lwb's zio + * structures are created, and linked to the lwb. This function is + * idempotent; if the passed in lwb has already been opened, this + * function is essentially a no-op. */ static void -zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb) +zil_lwb_write_open(zilog_t *zilog, lwb_t *lwb) { zbookmark_phys_t zb; zio_priority_t prio; + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); + ASSERT3P(lwb, !=, NULL); + EQUIV(lwb->lwb_root_zio == NULL, lwb->lwb_state == LWB_STATE_CLOSED); + EQUIV(lwb->lwb_root_zio != NULL, lwb->lwb_state == LWB_STATE_OPENED); + SET_BOOKMARK(&zb, lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_OBJSET], ZB_ZIL_OBJECT, ZB_ZIL_LEVEL, lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_SEQ]); - if (zilog->zl_root_zio == NULL) { - zilog->zl_root_zio = zio_root(zilog->zl_spa, NULL, NULL, - ZIO_FLAG_CANFAIL); - } - /* Lock so zil_sync() doesn't fastwrite_unmark after zio is created */ mutex_enter(&zilog->zl_lock); - if (lwb->lwb_zio == NULL) { + if (lwb->lwb_root_zio == NULL) { abd_t *lwb_abd = abd_get_from_buf(lwb->lwb_buf, BP_GET_LSIZE(&lwb->lwb_blk)); + if (!lwb->lwb_fastwrite) { metaslab_fastwrite_mark(zilog->zl_spa, &lwb->lwb_blk); lwb->lwb_fastwrite = 1; } + if (!lwb->lwb_slog || zilog->zl_cur_used <= zil_slog_bulk) prio = ZIO_PRIORITY_SYNC_WRITE; else prio = ZIO_PRIORITY_ASYNC_WRITE; - lwb->lwb_zio = zio_rewrite(zilog->zl_root_zio, zilog->zl_spa, - 0, &lwb->lwb_blk, lwb_abd, BP_GET_LSIZE(&lwb->lwb_blk), - zil_lwb_write_done, lwb, prio, - ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | + + lwb->lwb_root_zio = zio_root(zilog->zl_spa, + zil_lwb_flush_vdevs_done, lwb, ZIO_FLAG_CANFAIL); + ASSERT3P(lwb->lwb_root_zio, !=, NULL); + + lwb->lwb_write_zio = zio_rewrite(lwb->lwb_root_zio, + zilog->zl_spa, 0, &lwb->lwb_blk, lwb_abd, + BP_GET_LSIZE(&lwb->lwb_blk), zil_lwb_write_done, lwb, + prio, ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_FASTWRITE, &zb); + ASSERT3P(lwb->lwb_write_zio, !=, NULL); + + lwb->lwb_state = LWB_STATE_OPENED; + + /* + * The zilog's "zl_last_lwb_opened" field is used to + * build the lwb/zio dependency chain, which is used to + * preserve the ordering of lwb completions that is + * required by the semantics of the ZIL. Each new lwb + * zio becomes a parent of the "previous" lwb zio, such + * that the new lwb's zio cannot complete until the + * "previous" lwb's zio completes. + * + * This is required by the semantics of zil_commit(); + * the commit waiters attached to the lwbs will be woken + * in the lwb zio's completion callback, so this zio + * dependency graph ensures the waiters are woken in the + * correct order (the same order the lwbs were created). + */ + lwb_t *last_lwb_opened = zilog->zl_last_lwb_opened; + if (last_lwb_opened != NULL && + last_lwb_opened->lwb_state != LWB_STATE_DONE) { + ASSERT(last_lwb_opened->lwb_state == LWB_STATE_OPENED || + last_lwb_opened->lwb_state == LWB_STATE_ISSUED); + ASSERT3P(last_lwb_opened->lwb_root_zio, !=, NULL); + zio_add_child(lwb->lwb_root_zio, + last_lwb_opened->lwb_root_zio); + } + zilog->zl_last_lwb_opened = lwb; } mutex_exit(&zilog->zl_lock); + + ASSERT3P(lwb->lwb_root_zio, !=, NULL); + ASSERT3P(lwb->lwb_write_zio, !=, NULL); + ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED); } /* @@ -1000,7 +1249,7 @@ uint64_t zil_block_buckets[] = { * Calls are serialized. */ static lwb_t * -zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) +zil_lwb_write_issue(zilog_t *zilog, lwb_t *lwb) { lwb_t *nlwb = NULL; zil_chain_t *zilc; @@ -1012,6 +1261,11 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) int i, error; boolean_t slog; + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); + ASSERT3P(lwb->lwb_root_zio, !=, NULL); + ASSERT3P(lwb->lwb_write_zio, !=, NULL); + ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED); + if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) { zilc = (zil_chain_t *)lwb->lwb_buf; bp = &zilc->zc_next_blk; @@ -1031,6 +1285,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) * We dirty the dataset to ensure that zil_sync() will be called * to clean up in the event of allocation failure or I/O failure. */ + tx = dmu_tx_create(zilog->zl_os); /* @@ -1046,7 +1301,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) */ error = dmu_tx_assign(tx, TXG_WAITED); if (error != 0) { - ASSERT3S(error, ==, EIO); + ASSERT(error == EIO || error == ERESTART); dmu_tx_abort(tx); return (NULL); } @@ -1097,19 +1352,16 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) bp->blk_cksum.zc_word[ZIL_ZC_SEQ]++; /* - * Allocate a new log write buffer (lwb). + * Allocate a new log write block (lwb). */ nlwb = zil_alloc_lwb(zilog, bp, slog, txg, TRUE); - - /* Record the block for later vdev flushing */ - zil_add_block(zilog, &lwb->lwb_blk); } if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) { /* For Slim ZIL only write what is used. */ wsz = P2ROUNDUP_TYPED(lwb->lwb_nused, ZIL_MIN_BLKSZ, uint64_t); ASSERT3U(wsz, <=, lwb->lwb_sz); - zio_shrink(lwb->lwb_zio, wsz); + zio_shrink(lwb->lwb_write_zio, wsz); } else { wsz = lwb->lwb_sz; @@ -1124,7 +1376,14 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb) */ bzero(lwb->lwb_buf + lwb->lwb_nused, wsz - lwb->lwb_nused); - zio_nowait(lwb->lwb_zio); /* Kick off the write for the old log block */ + spa_config_enter(zilog->zl_spa, SCL_STATE, lwb, RW_READER); + + zil_lwb_add_block(lwb, &lwb->lwb_blk); + lwb->lwb_issued_timestamp = gethrtime(); + lwb->lwb_state = LWB_STATE_ISSUED; + + zio_nowait(lwb->lwb_root_zio); + zio_nowait(lwb->lwb_write_zio); /* * If there was an allocation failure then nlwb will be null which @@ -1141,13 +1400,33 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb) char *lr_buf; uint64_t dlen, dnow, lwb_sp, reclen, txg; - if (lwb == NULL) - return (NULL); + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); + ASSERT3P(lwb, !=, NULL); + ASSERT3P(lwb->lwb_buf, !=, NULL); + + zil_lwb_write_open(zilog, lwb); - ASSERT(lwb->lwb_buf != NULL); + lrc = &itx->itx_lr; + lrw = (lr_write_t *)lrc; + + /* + * A commit itx doesn't represent any on-disk state; instead + * it's simply used as a place holder on the commit list, and + * provides a mechanism for attaching a "commit waiter" onto the + * correct lwb (such that the waiter can be signalled upon + * completion of that lwb). Thus, we don't process this itx's + * log record if it's a commit itx (these itx's don't have log + * records), and instead link the itx's waiter onto the lwb's + * list of waiters. + * + * For more details, see the comment above zil_commit(). + */ + if (lrc->lrc_txtype == TX_COMMIT) { + zil_commit_waiter_link_lwb(itx->itx_private, lwb); + itx->itx_private = NULL; + return (lwb); + } - lrc = &itx->itx_lr; /* Common log record inside itx. */ - lrw = (lr_write_t *)lrc; /* Write log record inside itx. */ if (lrc->lrc_txtype == TX_WRITE && itx->itx_wr_state == WR_NEED_COPY) { dlen = P2ROUNDUP_TYPED( lrw->lr_length, sizeof (uint64_t), uint64_t); @@ -1158,7 +1437,7 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb) zilog->zl_cur_used += (reclen + dlen); txg = lrc->lrc_txg; - zil_lwb_write_init(zilog, lwb); + ASSERT3U(zilog->zl_cur_used, <, UINT64_MAX - (reclen + dlen)); cont: /* @@ -1169,10 +1448,10 @@ cont: if (reclen > lwb_sp || (reclen + dlen > lwb_sp && lwb_sp < ZIL_MAX_WASTE_SPACE && (dlen % ZIL_MAX_LOG_DATA == 0 || lwb_sp < reclen + dlen % ZIL_MAX_LOG_DATA))) { - lwb = zil_lwb_write_start(zilog, lwb); + lwb = zil_lwb_write_issue(zilog, lwb); if (lwb == NULL) return (NULL); - zil_lwb_write_init(zilog, lwb); + zil_lwb_write_open(zilog, lwb); ASSERT(LWB_EMPTY(lwb)); lwb_sp = lwb->lwb_sz - lwb->lwb_nused; ASSERT3U(reclen + MIN(dlen, sizeof (uint64_t)), <=, lwb_sp); @@ -1210,14 +1489,31 @@ cont: ZIL_STAT_INCR(zil_itx_needcopy_bytes, lrw->lr_length); } else { - ASSERT(itx->itx_wr_state == WR_INDIRECT); + ASSERT3S(itx->itx_wr_state, ==, WR_INDIRECT); dbuf = NULL; ZIL_STAT_BUMP(zil_itx_indirect_count); ZIL_STAT_INCR(zil_itx_indirect_bytes, lrw->lr_length); } - error = zilog->zl_get_data( - itx->itx_private, lrwb, dbuf, lwb->lwb_zio); + + /* + * We pass in the "lwb_write_zio" rather than + * "lwb_root_zio" so that the "lwb_write_zio" + * becomes the parent of any zio's created by + * the "zl_get_data" callback. The vdevs are + * flushed after the "lwb_write_zio" completes, + * so we want to make sure that completion + * callback waits for these additional zio's, + * such that the vdevs used by those zio's will + * be included in the lwb's vdev tree, and those + * vdevs will be properly flushed. If we passed + * in "lwb_root_zio" here, then these additional + * vdevs may not be flushed; e.g. if these zio's + * completed after "lwb_write_zio" completed. + */ + error = zilog->zl_get_data(itx->itx_private, + lrwb, dbuf, lwb, lwb->lwb_write_zio); + if (error == EIO) { txg_wait_synced(zilog->zl_dmu_pool, txg); return (lwb); @@ -1236,9 +1532,11 @@ cont: * equal to the itx sequence number because not all transactions * are synchronous, and sometimes spa_sync() gets there first. */ - lrcb->lrc_seq = ++zilog->zl_lr_seq; /* we are single threaded */ + lrcb->lrc_seq = ++zilog->zl_lr_seq; lwb->lwb_nused += reclen + dnow; - lwb->lwb_max_txg = MAX(lwb->lwb_max_txg, txg); + + zil_lwb_add_txg(lwb, txg); + ASSERT3U(lwb->lwb_nused, <=, lwb->lwb_sz); ASSERT0(P2PHASE(lwb->lwb_nused, sizeof (uint64_t))); @@ -1275,6 +1573,12 @@ zil_itx_create(uint64_t txtype, size_t lrsize) void zil_itx_destroy(itx_t *itx) { + IMPLY(itx->itx_lr.lrc_txtype == TX_COMMIT, itx->itx_callback == NULL); + IMPLY(itx->itx_callback != NULL, itx->itx_lr.lrc_txtype != TX_COMMIT); + + if (itx->itx_callback != NULL) + itx->itx_callback(itx->itx_callback_data); + zio_data_buf_free(itx, itx->itx_size); } @@ -1293,8 +1597,28 @@ zil_itxg_clean(itxs_t *itxs) list = &itxs->i_sync_list; while ((itx = list_head(list)) != NULL) { - if (itx->itx_callback != NULL) - itx->itx_callback(itx->itx_callback_data); + /* + * In the general case, commit itxs will not be found + * here, as they'll be committed to an lwb via + * zil_lwb_commit(), and free'd in that function. Having + * said that, it is still possible for commit itxs to be + * found here, due to the following race: + * + * - a thread calls zil_commit() which assigns the + * commit itx to a per-txg i_sync_list + * - zil_itxg_clean() is called (e.g. via spa_sync()) + * while the waiter is still on the i_sync_list + * + * There's nothing to prevent syncing the txg while the + * waiter is on the i_sync_list. This normally doesn't + * happen because spa_sync() is slower than zil_commit(), + * but if zil_commit() calls txg_wait_synced() (e.g. + * because zil_create() or zil_commit_writer_stall() is + * called) we will hit this case. + */ + if (itx->itx_lr.lrc_txtype == TX_COMMIT) + zil_commit_waiter_skip(itx->itx_private); + list_remove(list, itx); zil_itx_destroy(itx); } @@ -1304,9 +1628,9 @@ zil_itxg_clean(itxs_t *itxs) while ((ian = avl_destroy_nodes(t, &cookie)) != NULL) { list = &ian->ia_list; while ((itx = list_head(list)) != NULL) { - if (itx->itx_callback != NULL) - itx->itx_callback(itx->itx_callback_data); list_remove(list, itx); + /* commit itxs should never be on the async lists. */ + ASSERT3U(itx->itx_lr.lrc_txtype, !=, TX_COMMIT); zil_itx_destroy(itx); } list_destroy(list); @@ -1366,9 +1690,9 @@ zil_remove_async(zilog_t *zilog, uint64_t oid) mutex_exit(&itxg->itxg_lock); } while ((itx = list_head(&clean_list)) != NULL) { - if (itx->itx_callback != NULL) - itx->itx_callback(itx->itx_callback_data); list_remove(&clean_list, itx); + /* commit itxs should never be on the async lists. */ + ASSERT3U(itx->itx_lr.lrc_txtype, !=, TX_COMMIT); zil_itx_destroy(itx); } list_destroy(&clean_list); @@ -1448,7 +1772,14 @@ zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx) } itx->itx_lr.lrc_txg = dmu_tx_get_txg(tx); - zilog_dirty(zilog, txg); + + /* + * We don't want to dirty the ZIL using ZILTEST_TXG, because + * zil_clean() will never be called using ZILTEST_TXG. Thus, we + * need to be careful to always dirty the ZIL using the "real" + * TXG (not itxg_txg) even when the SPA is frozen. + */ + zilog_dirty(zilog, dmu_tx_get_txg(tx)); mutex_exit(&itxg->itxg_lock); /* Release the old itxs now we've dropped the lock */ @@ -1469,6 +1800,8 @@ zil_clean(zilog_t *zilog, uint64_t synced_txg) itxg_t *itxg = &zilog->zl_itxg[synced_txg & TXG_MASK]; itxs_t *clean_me; + ASSERT3U(synced_txg, <, ZILTEST_TXG); + mutex_enter(&itxg->itxg_lock); if (itxg->itxg_itxs == NULL || itxg->itxg_txg == ZILTEST_TXG) { mutex_exit(&itxg->itxg_lock); @@ -1495,7 +1828,8 @@ zil_clean(zilog_t *zilog, uint64_t synced_txg) } /* - * Get the list of itxs to commit into zl_itx_commit_list. + * This function will traverse the queue of itxs that need to be + * committed, and move them onto the ZIL's zl_itx_commit_list. */ static void zil_get_commit_list(zilog_t *zilog) @@ -1503,6 +1837,8 @@ zil_get_commit_list(zilog_t *zilog) uint64_t otxg, txg; list_t *commit_list = &zilog->zl_itx_commit_list; + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); + if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */ otxg = ZILTEST_TXG; else @@ -1594,154 +1930,809 @@ zil_async_to_sync(zilog_t *zilog, uint64_t foid) } } +/* + * This function will prune commit itxs that are at the head of the + * commit list (it won't prune past the first non-commit itx), and + * either: a) attach them to the last lwb that's still pending + * completion, or b) skip them altogether. + * + * This is used as a performance optimization to prevent commit itxs + * from generating new lwbs when it's unnecessary to do so. + */ static void -zil_commit_writer(zilog_t *zilog) +zil_prune_commit_list(zilog_t *zilog) { - uint64_t txg; itx_t *itx; - lwb_t *lwb; - spa_t *spa = zilog->zl_spa; - int error = 0; - ASSERT(zilog->zl_root_zio == NULL); + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); - mutex_exit(&zilog->zl_lock); + while ((itx = list_head(&zilog->zl_itx_commit_list)) != NULL) { + lr_t *lrc = &itx->itx_lr; + if (lrc->lrc_txtype != TX_COMMIT) + break; - zil_get_commit_list(zilog); + mutex_enter(&zilog->zl_lock); + + lwb_t *last_lwb = zilog->zl_last_lwb_opened; + if (last_lwb == NULL || last_lwb->lwb_state == LWB_STATE_DONE) { + /* + * All of the itxs this waiter was waiting on + * must have already completed (or there were + * never any itx's for it to wait on), so it's + * safe to skip this waiter and mark it done. + */ + zil_commit_waiter_skip(itx->itx_private); + } else { + zil_commit_waiter_link_lwb(itx->itx_private, last_lwb); + itx->itx_private = NULL; + } + + mutex_exit(&zilog->zl_lock); + + list_remove(&zilog->zl_itx_commit_list, itx); + zil_itx_destroy(itx); + } + + IMPLY(itx != NULL, itx->itx_lr.lrc_txtype != TX_COMMIT); +} + +static void +zil_commit_writer_stall(zilog_t *zilog) +{ + /* + * When zio_alloc_zil() fails to allocate the next lwb block on + * disk, we must call txg_wait_synced() to ensure all of the + * lwbs in the zilog's zl_lwb_list are synced and then freed (in + * zil_sync()), such that any subsequent ZIL writer (i.e. a call + * to zil_process_commit_list()) will have to call zil_create(), + * and start a new ZIL chain. + * + * Since zil_alloc_zil() failed, the lwb that was previously + * issued does not have a pointer to the "next" lwb on disk. + * Thus, if another ZIL writer thread was to allocate the "next" + * on-disk lwb, that block could be leaked in the event of a + * crash (because the previous lwb on-disk would not point to + * it). + * + * We must hold the zilog's zl_writer_lock while we do this, to + * ensure no new threads enter zil_process_commit_list() until + * all lwb's in the zl_lwb_list have been synced and freed + * (which is achieved via the txg_wait_synced() call). + */ + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); + txg_wait_synced(zilog->zl_dmu_pool, 0); + ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL); +} + +/* + * This function will traverse the commit list, creating new lwbs as + * needed, and committing the itxs from the commit list to these newly + * created lwbs. Additionally, as a new lwb is created, the previous + * lwb will be issued to the zio layer to be written to disk. + */ +static void +zil_process_commit_list(zilog_t *zilog) +{ + spa_t *spa = zilog->zl_spa; + list_t nolwb_itxs; + list_t nolwb_waiters; + lwb_t *lwb; + itx_t *itx; + + ASSERT(MUTEX_HELD(&zilog->zl_writer_lock)); /* * Return if there's nothing to commit before we dirty the fs by * calling zil_create(). */ - if (list_head(&zilog->zl_itx_commit_list) == NULL) { - mutex_enter(&zilog->zl_lock); + if (list_head(&zilog->zl_itx_commit_list) == NULL) return; - } - if (zilog->zl_suspend) { - lwb = NULL; + list_create(&nolwb_itxs, sizeof (itx_t), offsetof(itx_t, itx_node)); + list_create(&nolwb_waiters, sizeof (zil_commit_waiter_t), + offsetof(zil_commit_waiter_t, zcw_node)); + + lwb = list_tail(&zilog->zl_lwb_list); + if (lwb == NULL) { + lwb = zil_create(zilog); } else { - lwb = list_tail(&zilog->zl_lwb_list); - if (lwb == NULL) - lwb = zil_create(zilog); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_DONE); } - DTRACE_PROBE1(zil__cw1, zilog_t *, zilog); - for (itx = list_head(&zilog->zl_itx_commit_list); itx != NULL; - itx = list_next(&zilog->zl_itx_commit_list, itx)) { - txg = itx->itx_lr.lrc_txg; + while ((itx = list_head(&zilog->zl_itx_commit_list)) != NULL) { + lr_t *lrc = &itx->itx_lr; + uint64_t txg = lrc->lrc_txg; + ASSERT3U(txg, !=, 0); + if (lrc->lrc_txtype == TX_COMMIT) { + DTRACE_PROBE2(zil__process__commit__itx, + zilog_t *, zilog, itx_t *, itx); + } else { + DTRACE_PROBE2(zil__process__normal__itx, + zilog_t *, zilog, itx_t *, itx); + } + + list_remove(&zilog->zl_itx_commit_list, itx); + /* * This is inherently racy and may result in us writing - * out a log block for a txg that was just synced. This is - * ok since we'll end cleaning up that log block the next - * time we call zil_sync(). + * out a log block for a txg that was just synced. This + * is ok since we'll end cleaning up that log block the + * next time we call zil_sync(). */ - if (txg > spa_last_synced_txg(spa) || txg > spa_freeze_txg(spa)) - lwb = zil_lwb_commit(zilog, itx, lwb); + boolean_t synced = txg <= spa_last_synced_txg(spa); + boolean_t frozen = txg > spa_freeze_txg(spa); + + if (!synced || frozen) { + if (lwb != NULL) { + lwb = zil_lwb_commit(zilog, itx, lwb); + + if (lwb == NULL) + list_insert_tail(&nolwb_itxs, itx); + else + list_insert_tail(&lwb->lwb_itxs, itx); + } else { + if (lrc->lrc_txtype == TX_COMMIT) { + zil_commit_waiter_link_nolwb( + itx->itx_private, &nolwb_waiters); + } + + list_insert_tail(&nolwb_itxs, itx); + } + } else { + /* + * If this is a commit itx, then there will be a + * thread that is either: already waiting for + * it, or soon will be waiting. + * + * This itx has already been committed to disk + * via spa_sync() so we don't bother committing + * it to an lwb. As a result, we cannot use the + * lwb zio callback to signal the waiter and + * mark it as done, so we must do that here. + */ + if (lrc->lrc_txtype == TX_COMMIT) + zil_commit_waiter_skip(itx->itx_private); + + zil_itx_destroy(itx); + } } - DTRACE_PROBE1(zil__cw2, zilog_t *, zilog); - /* write the last block out */ - if (lwb != NULL && lwb->lwb_zio != NULL) - lwb = zil_lwb_write_start(zilog, lwb); + if (lwb == NULL) { + /* + * This indicates zio_alloc_zil() failed to allocate the + * "next" lwb on-disk. When this happens, we must stall + * the ZIL write pipeline; see the comment within + * zil_commit_writer_stall() for more details. + */ + zil_commit_writer_stall(zilog); - zilog->zl_cur_used = 0; + /* + * Additionally, we have to signal and mark the "nolwb" + * waiters as "done" here, since without an lwb, we + * can't do this via zil_lwb_flush_vdevs_done() like + * normal. + */ + zil_commit_waiter_t *zcw; + while ((zcw = list_head(&nolwb_waiters)) != NULL) { + zil_commit_waiter_skip(zcw); + list_remove(&nolwb_waiters, zcw); + } + + /* + * And finally, we have to destroy the itx's that + * couldn't be committed to an lwb; this will also call + * the itx's callback if one exists for the itx. + */ + while ((itx = list_head(&nolwb_itxs)) != NULL) { + list_remove(&nolwb_itxs, itx); + zil_itx_destroy(itx); + } + } else { + ASSERT(list_is_empty(&nolwb_waiters)); + ASSERT3P(lwb, !=, NULL); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_DONE); + + /* + * At this point, the ZIL block pointed at by the "lwb" + * variable is in one of the following states: "closed" + * or "open". + * + * If its "closed", then no itxs have been committed to + * it, so there's no point in issueing its zio (i.e. + * it's "empty"). + * + * If its "open" state, then it contains one or more + * itxs that eventually need to be committed to stable + * storage. In this case we intentionally do not issue + * the lwb's zio to disk yet, and instead rely on one of + * the following two mechanisms for issuing the zio: + * + * 1. Ideally, there will be more ZIL activity occuring + * on the system, such that this function will be + * immeidately called again (not necessarily by the same + * thread) and this lwb's zio will be issued via + * zil_lwb_commit(). This way, the lwb is guaranteed to + * be "full" when it is issued to disk, and we'll make + * use of the lwb's size the best we can. + * + * 2. If there isn't sufficient ZIL activity occuring on + * the system, such that this lwb's zio isn't issued via + * zil_lwb_commit(), zil_commit_waiter() will issue the + * lwb's zio. If this occurs, the lwb is not guaranteed + * to be "full" by the time its zio is issued, and means + * the size of the lwb was "too large" given the amount + * of ZIL activity occuring on the system at that time. + * + * We do this for a couple of reasons: + * + * 1. To try and reduce the number of IOPs needed to + * write the same number of itxs. If an lwb has space + * available in it's buffer for more itxs, and more itxs + * will be committed relatively soon (relative to the + * latency of performing a write), then it's beneficial + * to wait for these "next" itxs. This way, more itxs + * can be committed to stable storage with fewer writes. + * + * 2. To try and use the largest lwb block size that the + * incoming rate of itxs can support. Again, this is to + * try and pack as many itxs into as few lwbs as + * possible, without significantly impacting the latency + * of each individual itx. + */ + } +} + +/* + * This function is responsible for ensuring the passed in commit waiter + * (and associated commit itx) is committed to an lwb. If the waiter is + * not already committed to an lwb, all itxs in the zilog's queue of + * itxs will be processed. The assumption is the passed in waiter's + * commit itx will found in the queue just like the other non-commit + * itxs, such that when the entire queue is processed, the waiter will + * have been commited to an lwb. + * + * The lwb associated with the passed in waiter is not guaranteed to + * have been issued by the time this function completes. If the lwb is + * not issued, we rely on future calls to zil_commit_writer() to issue + * the lwb, or the timeout mechanism found in zil_commit_waiter(). + */ +static void +zil_commit_writer(zilog_t *zilog, zil_commit_waiter_t *zcw) +{ + ASSERT(!MUTEX_HELD(&zilog->zl_lock)); + ASSERT(spa_writeable(zilog->zl_spa)); + ASSERT0(zilog->zl_suspend); + + mutex_enter(&zilog->zl_writer_lock); + + if (zcw->zcw_lwb != NULL || zcw->zcw_done) { + /* + * It's possible that, while we were waiting to acquire + * the "zl_writer_lock", another thread committed this + * waiter to an lwb. If that occurs, we bail out early, + * without processing any of the zilog's queue of itxs. + * + * On certain workloads and system configurations, the + * "zl_writer_lock" can become highly contended. In an + * attempt to reduce this contention, we immediately drop + * the lock if the waiter has already been processed. + * + * We've measured this optimization to reduce CPU spent + * contending on this lock by up to 5%, using a system + * with 32 CPUs, low latency storage (~50 usec writes), + * and 1024 threads performing sync writes. + */ + goto out; + } + + ZIL_STAT_BUMP(zil_commit_writer_count); + + zil_get_commit_list(zilog); + zil_prune_commit_list(zilog); + zil_process_commit_list(zilog); + +out: + mutex_exit(&zilog->zl_writer_lock); +} + +static void +zil_commit_waiter_timeout(zilog_t *zilog, zil_commit_waiter_t *zcw) +{ + ASSERT(!MUTEX_HELD(&zilog->zl_writer_lock)); + ASSERT(MUTEX_HELD(&zcw->zcw_lock)); + ASSERT3B(zcw->zcw_done, ==, B_FALSE); + + lwb_t *lwb = zcw->zcw_lwb; + ASSERT3P(lwb, !=, NULL); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_CLOSED); /* - * Wait if necessary for the log blocks to be on stable storage. + * If the lwb has already been issued by another thread, we can + * immediately return since there's no work to be done (the + * point of this function is to issue the lwb). Additionally, we + * do this prior to acquiring the zl_writer_lock, to avoid + * acquiring it when it's not necessary to do so. */ - if (zilog->zl_root_zio) { - error = zio_wait(zilog->zl_root_zio); - zilog->zl_root_zio = NULL; - zil_flush_vdevs(zilog); - } + if (lwb->lwb_state == LWB_STATE_ISSUED || + lwb->lwb_state == LWB_STATE_DONE) + return; - if (error || lwb == NULL) - txg_wait_synced(zilog->zl_dmu_pool, 0); + /* + * In order to call zil_lwb_write_issue() we must hold the + * zilog's "zl_writer_lock". We can't simply acquire that lock, + * since we're already holding the commit waiter's "zcw_lock", + * and those two locks are aquired in the opposite order + * elsewhere. + */ + mutex_exit(&zcw->zcw_lock); + mutex_enter(&zilog->zl_writer_lock); + mutex_enter(&zcw->zcw_lock); - while ((itx = list_head(&zilog->zl_itx_commit_list))) { - txg = itx->itx_lr.lrc_txg; - ASSERT(txg); + /* + * Since we just dropped and re-acquired the commit waiter's + * lock, we have to re-check to see if the waiter was marked + * "done" during that process. If the waiter was marked "done", + * the "lwb" pointer is no longer valid (it can be free'd after + * the waiter is marked "done"), so without this check we could + * wind up with a use-after-free error below. + */ + if (zcw->zcw_done) + goto out; - if (itx->itx_callback != NULL) - itx->itx_callback(itx->itx_callback_data); - list_remove(&zilog->zl_itx_commit_list, itx); - zil_itx_destroy(itx); + ASSERT3P(lwb, ==, zcw->zcw_lwb); + + /* + * We've already checked this above, but since we hadn't + * acquired the zilog's zl_writer_lock, we have to perform this + * check a second time while holding the lock. We can't call + * zil_lwb_write_issue() if the lwb had already been issued. + */ + if (lwb->lwb_state == LWB_STATE_ISSUED || + lwb->lwb_state == LWB_STATE_DONE) + goto out; + + ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED); + + /* + * As described in the comments above zil_commit_waiter() and + * zil_process_commit_list(), we need to issue this lwb's zio + * since we've reached the commit waiter's timeout and it still + * hasn't been issued. + */ + lwb_t *nlwb = zil_lwb_write_issue(zilog, lwb); + + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_OPENED); + + /* + * Since the lwb's zio hadn't been issued by the time this thread + * reached its timeout, we reset the zilog's "zl_cur_used" field + * to influence the zil block size selection algorithm. + * + * By having to issue the lwb's zio here, it means the size of the + * lwb was too large, given the incoming throughput of itxs. By + * setting "zl_cur_used" to zero, we communicate this fact to the + * block size selection algorithm, so it can take this informaiton + * into account, and potentially select a smaller size for the + * next lwb block that is allocated. + */ + zilog->zl_cur_used = 0; + + if (nlwb == NULL) { + /* + * When zil_lwb_write_issue() returns NULL, this + * indicates zio_alloc_zil() failed to allocate the + * "next" lwb on-disk. When this occurs, the ZIL write + * pipeline must be stalled; see the comment within the + * zil_commit_writer_stall() function for more details. + * + * We must drop the commit waiter's lock prior to + * calling zil_commit_writer_stall() or else we can wind + * up with the following deadlock: + * + * - This thread is waiting for the txg to sync while + * holding the waiter's lock; txg_wait_synced() is + * used within txg_commit_writer_stall(). + * + * - The txg can't sync because it is waiting for this + * lwb's zio callback to call dmu_tx_commit(). + * + * - The lwb's zio callback can't call dmu_tx_commit() + * because it's blocked trying to acquire the waiter's + * lock, which occurs prior to calling dmu_tx_commit() + */ + mutex_exit(&zcw->zcw_lock); + zil_commit_writer_stall(zilog); + mutex_enter(&zcw->zcw_lock); } - mutex_enter(&zilog->zl_lock); +out: + mutex_exit(&zilog->zl_writer_lock); + ASSERT(MUTEX_HELD(&zcw->zcw_lock)); +} + +/* + * This function is responsible for performing the following two tasks: + * + * 1. its primary responsibility is to block until the given "commit + * waiter" is considered "done". + * + * 2. its secondary responsibility is to issue the zio for the lwb that + * the given "commit waiter" is waiting on, if this function has + * waited "long enough" and the lwb is still in the "open" state. + * + * Given a sufficient amount of itxs being generated and written using + * the ZIL, the lwb's zio will be issued via the zil_lwb_commit() + * function. If this does not occur, this secondary responsibility will + * ensure the lwb is issued even if there is not other synchronous + * activity on the system. + * + * For more details, see zil_process_commit_list(); more specifically, + * the comment at the bottom of that function. + */ +static void +zil_commit_waiter(zilog_t *zilog, zil_commit_waiter_t *zcw) +{ + ASSERT(!MUTEX_HELD(&zilog->zl_lock)); + ASSERT(!MUTEX_HELD(&zilog->zl_writer_lock)); + ASSERT(spa_writeable(zilog->zl_spa)); + ASSERT0(zilog->zl_suspend); + + mutex_enter(&zcw->zcw_lock); /* - * Remember the highest committed log sequence number for ztest. - * We only update this value when all the log writes succeeded, - * because ztest wants to ASSERT that it got the whole log chain. + * The timeout is scaled based on the lwb latency to avoid + * significantly impacting the latency of each individual itx. + * For more details, see the comment at the bottom of the + * zil_process_commit_list() function. */ - if (error == 0 && lwb != NULL) - zilog->zl_commit_lr_seq = zilog->zl_lr_seq; + int pct = MAX(zfs_commit_timeout_pct, 1); + hrtime_t sleep = (zilog->zl_last_lwb_latency * pct) / 100; + hrtime_t wakeup = gethrtime() + sleep; + boolean_t timedout = B_FALSE; + + while (!zcw->zcw_done) { + ASSERT(MUTEX_HELD(&zcw->zcw_lock)); + + lwb_t *lwb = zcw->zcw_lwb; + + /* + * Usually, the waiter will have a non-NULL lwb field here, + * but it's possible for it to be NULL as a result of + * zil_commit() racing with spa_sync(). + * + * When zil_clean() is called, it's possible for the itxg + * list (which may be cleaned via a taskq) to contain + * commit itxs. When this occurs, the commit waiters linked + * off of these commit itxs will not be committed to an + * lwb. Additionally, these commit waiters will not be + * marked done until zil_commit_waiter_skip() is called via + * zil_itxg_clean(). + * + * Thus, it's possible for this commit waiter (i.e. the + * "zcw" variable) to be found in this "in between" state; + * where it's "zcw_lwb" field is NULL, and it hasn't yet + * been skipped, so it's "zcw_done" field is still B_FALSE. + */ + IMPLY(lwb != NULL, lwb->lwb_state != LWB_STATE_CLOSED); + + if (lwb != NULL && lwb->lwb_state == LWB_STATE_OPENED) { + ASSERT3B(timedout, ==, B_FALSE); + + /* + * If the lwb hasn't been issued yet, then we + * need to wait with a timeout, in case this + * function needs to issue the lwb after the + * timeout is reached; responsibility (2) from + * the comment above this function. + */ + clock_t timeleft = cv_timedwait_hires(&zcw->zcw_cv, + &zcw->zcw_lock, wakeup, USEC2NSEC(1), + CALLOUT_FLAG_ABSOLUTE); + + if (timeleft >= 0 || zcw->zcw_done) + continue; + + timedout = B_TRUE; + zil_commit_waiter_timeout(zilog, zcw); + + if (!zcw->zcw_done) { + /* + * If the commit waiter has already been + * marked "done", it's possible for the + * waiter's lwb structure to have already + * been freed. Thus, we can only reliably + * make these assertions if the waiter + * isn't done. + */ + ASSERT3P(lwb, ==, zcw->zcw_lwb); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_OPENED); + } + } else { + /* + * If the lwb isn't open, then it must have already + * been issued. In that case, there's no need to + * use a timeout when waiting for the lwb to + * complete. + * + * Additionally, if the lwb is NULL, the waiter + * will soon be signalled and marked done via + * zil_clean() and zil_itxg_clean(), so no timeout + * is required. + */ + + IMPLY(lwb != NULL, + lwb->lwb_state == LWB_STATE_ISSUED || + lwb->lwb_state == LWB_STATE_DONE); + cv_wait(&zcw->zcw_cv, &zcw->zcw_lock); + } + } + + mutex_exit(&zcw->zcw_lock); +} + +static zil_commit_waiter_t * +zil_alloc_commit_waiter(void) +{ + zil_commit_waiter_t *zcw = kmem_cache_alloc(zil_zcw_cache, KM_SLEEP); + + cv_init(&zcw->zcw_cv, NULL, CV_DEFAULT, NULL); + mutex_init(&zcw->zcw_lock, NULL, MUTEX_DEFAULT, NULL); + list_link_init(&zcw->zcw_node); + zcw->zcw_lwb = NULL; + zcw->zcw_done = B_FALSE; + zcw->zcw_zio_error = 0; + + return (zcw); +} + +static void +zil_free_commit_waiter(zil_commit_waiter_t *zcw) +{ + ASSERT(!list_link_active(&zcw->zcw_node)); + ASSERT3P(zcw->zcw_lwb, ==, NULL); + ASSERT3B(zcw->zcw_done, ==, B_TRUE); + mutex_destroy(&zcw->zcw_lock); + cv_destroy(&zcw->zcw_cv); + kmem_cache_free(zil_zcw_cache, zcw); } /* - * Commit zfs transactions to stable storage. - * If foid is 0 push out all transactions, otherwise push only those - * for that object or might reference that object. + * This function is used to create a TX_COMMIT itx and assign it. This + * way, it will be linked into the ZIL's list of synchronous itxs, and + * then later committed to an lwb (or skipped) when + * zil_process_commit_list() is called. + */ +static void +zil_commit_itx_assign(zilog_t *zilog, zil_commit_waiter_t *zcw) +{ + dmu_tx_t *tx = dmu_tx_create(zilog->zl_os); + VERIFY0(dmu_tx_assign(tx, TXG_WAIT)); + + itx_t *itx = zil_itx_create(TX_COMMIT, sizeof (lr_t)); + itx->itx_sync = B_TRUE; + itx->itx_private = zcw; + + zil_itx_assign(zilog, itx, tx); + + dmu_tx_commit(tx); +} + +/* + * Commit ZFS Intent Log transactions (itxs) to stable storage. + * + * When writing ZIL transactions to the on-disk representation of the + * ZIL, the itxs are committed to a Log Write Block (lwb). Multiple + * itxs can be committed to a single lwb. Once a lwb is written and + * committed to stable storage (i.e. the lwb is written, and vdevs have + * been flushed), each itx that was committed to that lwb is also + * considered to be committed to stable storage. + * + * When an itx is committed to an lwb, the log record (lr_t) contained + * by the itx is copied into the lwb's zio buffer, and once this buffer + * is written to disk, it becomes an on-disk ZIL block. + * + * As itxs are generated, they're inserted into the ZIL's queue of + * uncommitted itxs. The semantics of zil_commit() are such that it will + * block until all itxs that were in the queue when it was called, are + * committed to stable storage. + * + * If "foid" is zero, this means all "synchronous" and "asynchronous" + * itxs, for all objects in the dataset, will be committed to stable + * storage prior to zil_commit() returning. If "foid" is non-zero, all + * "synchronous" itxs for all objects, but only "asynchronous" itxs + * that correspond to the foid passed in, will be committed to stable + * storage prior to zil_commit() returning. + * + * Generally speaking, when zil_commit() is called, the consumer doesn't + * actually care about _all_ of the uncommitted itxs. Instead, they're + * simply trying to waiting for a specific itx to be committed to disk, + * but the interface(s) for interacting with the ZIL don't allow such + * fine-grained communication. A better interface would allow a consumer + * to create and assign an itx, and then pass a reference to this itx to + * zil_commit(); such that zil_commit() would return as soon as that + * specific itx was committed to disk (instead of waiting for _all_ + * itxs to be committed). + * + * When a thread calls zil_commit() a special "commit itx" will be + * generated, along with a corresponding "waiter" for this commit itx. + * zil_commit() will wait on this waiter's CV, such that when the waiter + * is marked done, and signalled, zil_commit() will return. + * + * This commit itx is inserted into the queue of uncommitted itxs. This + * provides an easy mechanism for determining which itxs were in the + * queue prior to zil_commit() having been called, and which itxs were + * added after zil_commit() was called. + * + * The commit it is special; it doesn't have any on-disk representation. + * When a commit itx is "committed" to an lwb, the waiter associated + * with it is linked onto the lwb's list of waiters. Then, when that lwb + * completes, each waiter on the lwb's list is marked done and signalled + * -- allowing the thread waiting on the waiter to return from zil_commit(). + * + * It's important to point out a few critical factors that allow us + * to make use of the commit itxs, commit waiters, per-lwb lists of + * commit waiters, and zio completion callbacks like we're doing: * - * itxs are committed in batches. In a heavily stressed zil there will be - * a commit writer thread who is writing out a bunch of itxs to the log - * for a set of committing threads (cthreads) in the same batch as the writer. - * Those cthreads are all waiting on the same cv for that batch. + * 1. The list of waiters for each lwb is traversed, and each commit + * waiter is marked "done" and signalled, in the zio completion + * callback of the lwb's zio[*]. * - * There will also be a different and growing batch of threads that are - * waiting to commit (qthreads). When the committing batch completes - * a transition occurs such that the cthreads exit and the qthreads become - * cthreads. One of the new cthreads becomes the writer thread for the - * batch. Any new threads arriving become new qthreads. + * * Actually, the waiters are signalled in the zio completion + * callback of the root zio for the DKIOCFLUSHWRITECACHE commands + * that are sent to the vdevs upon completion of the lwb zio. * - * Only 2 condition variables are needed and there's no transition - * between the two cvs needed. They just flip-flop between qthreads - * and cthreads. + * 2. When the itxs are inserted into the ZIL's queue of uncommitted + * itxs, the order in which they are inserted is preserved[*]; as + * itxs are added to the queue, they are added to the tail of + * in-memory linked lists. * - * Using this scheme we can efficiently wakeup up only those threads - * that have been committed. + * When committing the itxs to lwbs (to be written to disk), they + * are committed in the same order in which the itxs were added to + * the uncommitted queue's linked list(s); i.e. the linked list of + * itxs to commit is traversed from head to tail, and each itx is + * committed to an lwb in that order. + * + * * To clarify: + * + * - the order of "sync" itxs is preserved w.r.t. other + * "sync" itxs, regardless of the corresponding objects. + * - the order of "async" itxs is preserved w.r.t. other + * "async" itxs corresponding to the same object. + * - the order of "async" itxs is *not* preserved w.r.t. other + * "async" itxs corresponding to different objects. + * - the order of "sync" itxs w.r.t. "async" itxs (or vice + * versa) is *not* preserved, even for itxs that correspond + * to the same object. + * + * For more details, see: zil_itx_assign(), zil_async_to_sync(), + * zil_get_commit_list(), and zil_process_commit_list(). + * + * 3. The lwbs represent a linked list of blocks on disk. Thus, any + * lwb cannot be considered committed to stable storage, until its + * "previous" lwb is also committed to stable storage. This fact, + * coupled with the fact described above, means that itxs are + * committed in (roughly) the order in which they were generated. + * This is essential because itxs are dependent on prior itxs. + * Thus, we *must not* deem an itx as being committed to stable + * storage, until *all* prior itxs have also been committed to + * stable storage. + * + * To enforce this ordering of lwb zio's, while still leveraging as + * much of the underlying storage performance as possible, we rely + * on two fundamental concepts: + * + * 1. The creation and issuance of lwb zio's is protected by + * the zilog's "zl_writer_lock", which ensures only a single + * thread is creating and/or issuing lwb's at a time + * 2. The "previous" lwb is a child of the "current" lwb + * (leveraging the zio parent-child depenency graph) + * + * By relying on this parent-child zio relationship, we can have + * many lwb zio's concurrently issued to the underlying storage, + * but the order in which they complete will be the same order in + * which they were created. */ void zil_commit(zilog_t *zilog, uint64_t foid) { - uint64_t mybatch; + /* + * We should never attempt to call zil_commit on a snapshot for + * a couple of reasons: + * + * 1. A snapshot may never be modified, thus it cannot have any + * in-flight itxs that would have modified the dataset. + * + * 2. By design, when zil_commit() is called, a commit itx will + * be assigned to this zilog; as a result, the zilog will be + * dirtied. We must not dirty the zilog of a snapshot; there's + * checks in the code that enforce this invariant, and will + * cause a panic if it's not upheld. + */ + ASSERT3B(dmu_objset_is_snapshot(zilog->zl_os), ==, B_FALSE); if (zilog->zl_sync == ZFS_SYNC_DISABLED) return; + if (!spa_writeable(zilog->zl_spa)) { + /* + * If the SPA is not writable, there should never be any + * pending itxs waiting to be committed to disk. If that + * weren't true, we'd skip writing those itxs out, and + * would break the sematics of zil_commit(); thus, we're + * verifying that truth before we return to the caller. + */ + ASSERT(list_is_empty(&zilog->zl_lwb_list)); + ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL); + for (int i = 0; i < TXG_SIZE; i++) + ASSERT3P(zilog->zl_itxg[i].itxg_itxs, ==, NULL); + return; + } + + /* + * If the ZIL is suspended, we don't want to dirty it by calling + * zil_commit_itx_assign() below, nor can we write out + * lwbs like would be done in zil_commit_write(). Thus, we + * simply rely on txg_wait_synced() to maintain the necessary + * semantics, and avoid calling those functions altogether. + */ + if (zilog->zl_suspend > 0) { + txg_wait_synced(zilog->zl_dmu_pool, 0); + return; + } + ZIL_STAT_BUMP(zil_commit_count); - /* move the async itxs for the foid to the sync queues */ + /* + * Move the "async" itxs for the specified foid to the "sync" + * queues, such that they will be later committed (or skipped) + * to an lwb when zil_process_commit_list() is called. + * + * Since these "async" itxs must be committed prior to this + * call to zil_commit returning, we must perform this operation + * before we call zil_commit_itx_assign(). + */ zil_async_to_sync(zilog, foid); - mutex_enter(&zilog->zl_lock); - mybatch = zilog->zl_next_batch; - while (zilog->zl_writer) { - cv_wait(&zilog->zl_cv_batch[mybatch & 1], &zilog->zl_lock); - if (mybatch <= zilog->zl_com_batch) { - mutex_exit(&zilog->zl_lock); - return; - } - } - - zilog->zl_next_batch++; - zilog->zl_writer = B_TRUE; - ZIL_STAT_BUMP(zil_commit_writer_count); - zil_commit_writer(zilog); - zilog->zl_com_batch = mybatch; - zilog->zl_writer = B_FALSE; + /* + * We allocate a new "waiter" structure which will initially be + * linked to the commit itx using the itx's "itx_private" field. + * Since the commit itx doesn't represent any on-disk state, + * when it's committed to an lwb, rather than copying the its + * lr_t into the lwb's buffer, the commit itx's "waiter" will be + * added to the lwb's list of waiters. Then, when the lwb is + * committed to stable storage, each waiter in the lwb's list of + * waiters will be marked "done", and signalled. + * + * We must create the waiter and assign the commit itx prior to + * calling zil_commit_writer(), or else our specific commit itx + * is not guaranteed to be committed to an lwb prior to calling + * zil_commit_waiter(). + */ + zil_commit_waiter_t *zcw = zil_alloc_commit_waiter(); + zil_commit_itx_assign(zilog, zcw); - /* wake up one thread to become the next writer */ - cv_signal(&zilog->zl_cv_batch[(mybatch+1) & 1]); + zil_commit_writer(zilog, zcw); + zil_commit_waiter(zilog, zcw); - /* wake up all threads waiting for this batch to be committed */ - cv_broadcast(&zilog->zl_cv_batch[mybatch & 1]); + if (zcw->zcw_zio_error != 0) { + /* + * If there was an error writing out the ZIL blocks that + * this thread is waiting on, then we fallback to + * relying on spa_sync() to write out the data this + * thread is waiting on. Obviously this has performance + * implications, but the expectation is for this to be + * an exceptional case, and shouldn't occur often. + */ + DTRACE_PROBE2(zil__commit__io__error, + zilog_t *, zilog, zil_commit_waiter_t *, zcw); + txg_wait_synced(zilog->zl_dmu_pool, 0); + } - mutex_exit(&zilog->zl_lock); + zil_free_commit_waiter(zcw); } /* @@ -1799,12 +2790,9 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx) zh->zh_log = lwb->lwb_blk; if (lwb->lwb_buf != NULL || lwb->lwb_max_txg > txg) break; - - ASSERT(lwb->lwb_zio == NULL); - list_remove(&zilog->zl_lwb_list, lwb); - zio_free_zil(spa, txg, &lwb->lwb_blk); - kmem_cache_free(zil_lwb_cache, lwb); + zio_free(spa, txg, &lwb->lwb_blk); + zil_free_lwb(zilog, lwb); /* * If we don't have anything left in the lwb list then @@ -1822,7 +2810,7 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx) * unused, long-lived LWBs. */ for (; lwb != NULL; lwb = list_next(&zilog->zl_lwb_list, lwb)) { - if (lwb->lwb_fastwrite && !lwb->lwb_zio) { + if (lwb->lwb_fastwrite && !lwb->lwb_write_zio) { metaslab_fastwrite_unmark(zilog->zl_spa, &lwb->lwb_blk); lwb->lwb_fastwrite = 0; } @@ -1831,11 +2819,39 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx) mutex_exit(&zilog->zl_lock); } +/* ARGSUSED */ +static int +zil_lwb_cons(void *vbuf, void *unused, int kmflag) +{ + lwb_t *lwb = vbuf; + list_create(&lwb->lwb_itxs, sizeof (itx_t), offsetof(itx_t, itx_node)); + list_create(&lwb->lwb_waiters, sizeof (zil_commit_waiter_t), + offsetof(zil_commit_waiter_t, zcw_node)); + avl_create(&lwb->lwb_vdev_tree, zil_lwb_vdev_compare, + sizeof (zil_vdev_node_t), offsetof(zil_vdev_node_t, zv_node)); + mutex_init(&lwb->lwb_vdev_lock, NULL, MUTEX_DEFAULT, NULL); + return (0); +} + +/* ARGSUSED */ +static void +zil_lwb_dest(void *vbuf, void *unused) +{ + lwb_t *lwb = vbuf; + mutex_destroy(&lwb->lwb_vdev_lock); + avl_destroy(&lwb->lwb_vdev_tree); + list_destroy(&lwb->lwb_waiters); + list_destroy(&lwb->lwb_itxs); +} + void zil_init(void) { zil_lwb_cache = kmem_cache_create("zil_lwb_cache", - sizeof (struct lwb), 0, NULL, NULL, NULL, NULL, NULL, 0); + sizeof (lwb_t), 0, zil_lwb_cons, zil_lwb_dest, NULL, NULL, NULL, 0); + + zil_zcw_cache = kmem_cache_create("zil_zcw_cache", + sizeof (zil_commit_waiter_t), 0, NULL, NULL, NULL, NULL, NULL, 0); zil_ksp = kstat_create("zfs", 0, "zil", "misc", KSTAT_TYPE_NAMED, sizeof (zil_stats) / sizeof (kstat_named_t), @@ -1850,6 +2866,7 @@ zil_init(void) void zil_fini(void) { + kmem_cache_destroy(zil_zcw_cache); kmem_cache_destroy(zil_lwb_cache); if (zil_ksp != NULL) { @@ -1884,9 +2901,12 @@ zil_alloc(objset_t *os, zil_header_t *zh_phys) zilog->zl_destroy_txg = TXG_INITIAL - 1; zilog->zl_logbias = dmu_objset_logbias(os); zilog->zl_sync = dmu_objset_syncprop(os); - zilog->zl_next_batch = 1; + zilog->zl_dirty_max_txg = 0; + zilog->zl_last_lwb_opened = NULL; + zilog->zl_last_lwb_latency = 0; mutex_init(&zilog->zl_lock, NULL, MUTEX_DEFAULT, NULL); + mutex_init(&zilog->zl_writer_lock, NULL, MUTEX_DEFAULT, NULL); for (int i = 0; i < TXG_SIZE; i++) { mutex_init(&zilog->zl_itxg[i].itxg_lock, NULL, @@ -1899,15 +2919,7 @@ zil_alloc(objset_t *os, zil_header_t *zh_phys) list_create(&zilog->zl_itx_commit_list, sizeof (itx_t), offsetof(itx_t, itx_node)); - mutex_init(&zilog->zl_vdev_lock, NULL, MUTEX_DEFAULT, NULL); - - avl_create(&zilog->zl_vdev_tree, zil_vdev_compare, - sizeof (zil_vdev_node_t), offsetof(zil_vdev_node_t, zv_node)); - - cv_init(&zilog->zl_cv_writer, NULL, CV_DEFAULT, NULL); cv_init(&zilog->zl_cv_suspend, NULL, CV_DEFAULT, NULL); - cv_init(&zilog->zl_cv_batch[0], NULL, CV_DEFAULT, NULL); - cv_init(&zilog->zl_cv_batch[1], NULL, CV_DEFAULT, NULL); return (zilog); } @@ -1925,9 +2937,6 @@ zil_free(zilog_t *zilog) ASSERT(list_is_empty(&zilog->zl_lwb_list)); list_destroy(&zilog->zl_lwb_list); - avl_destroy(&zilog->zl_vdev_tree); - mutex_destroy(&zilog->zl_vdev_lock); - ASSERT(list_is_empty(&zilog->zl_itx_commit_list)); list_destroy(&zilog->zl_itx_commit_list); @@ -1944,12 +2953,10 @@ zil_free(zilog_t *zilog) mutex_destroy(&zilog->zl_itxg[i].itxg_lock); } + mutex_destroy(&zilog->zl_writer_lock); mutex_destroy(&zilog->zl_lock); - cv_destroy(&zilog->zl_cv_writer); cv_destroy(&zilog->zl_cv_suspend); - cv_destroy(&zilog->zl_cv_batch[0]); - cv_destroy(&zilog->zl_cv_batch[1]); kmem_free(zilog, sizeof (zilog_t)); } @@ -1962,7 +2969,8 @@ zil_open(objset_t *os, zil_get_data_t *get_data) { zilog_t *zilog = dmu_objset_zil(os); - ASSERT(zilog->zl_get_data == NULL); + ASSERT3P(zilog->zl_get_data, ==, NULL); + ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL); ASSERT(list_is_empty(&zilog->zl_lwb_list)); zilog->zl_get_data = get_data; @@ -1977,22 +2985,30 @@ void zil_close(zilog_t *zilog) { lwb_t *lwb; - uint64_t txg = 0; + uint64_t txg; - zil_commit(zilog, 0); /* commit all itx */ + if (!dmu_objset_is_snapshot(zilog->zl_os)) { + zil_commit(zilog, 0); + } else { + ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL); + ASSERT0(zilog->zl_dirty_max_txg); + ASSERT3B(zilog_is_dirty(zilog), ==, B_FALSE); + } - /* - * The lwb_max_txg for the stubby lwb will reflect the last activity - * for the zil. After a txg_wait_synced() on the txg we know all the - * callbacks have occurred that may clean the zil. Only then can we - * destroy the zl_clean_taskq. - */ mutex_enter(&zilog->zl_lock); lwb = list_tail(&zilog->zl_lwb_list); - if (lwb != NULL) - txg = lwb->lwb_max_txg; + if (lwb == NULL) + txg = zilog->zl_dirty_max_txg; + else + txg = MAX(zilog->zl_dirty_max_txg, lwb->lwb_max_txg); mutex_exit(&zilog->zl_lock); - if (txg) + + /* + * We need to use txg_wait_synced() to wait long enough for the + * ZIL to be clean, and to wait for all pending lwbs to be + * written out. + */ + if (txg != 0) txg_wait_synced(zilog->zl_dmu_pool, txg); if (zilog_is_dirty(zilog)) @@ -2003,18 +3019,20 @@ zil_close(zilog_t *zilog) zilog->zl_get_data = NULL; /* - * We should have only one LWB left on the list; remove it now. + * We should have only one lwb left on the list; remove it now. */ mutex_enter(&zilog->zl_lock); lwb = list_head(&zilog->zl_lwb_list); if (lwb != NULL) { - ASSERT(lwb == list_tail(&zilog->zl_lwb_list)); - ASSERT(lwb->lwb_zio == NULL); + ASSERT3P(lwb, ==, list_tail(&zilog->zl_lwb_list)); + ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED); + if (lwb->lwb_fastwrite) metaslab_fastwrite_unmark(zilog->zl_spa, &lwb->lwb_blk); + list_remove(&zilog->zl_lwb_list, lwb); zio_buf_free(lwb->lwb_buf, lwb->lwb_sz); - kmem_cache_free(zil_lwb_cache, lwb); + zil_free_lwb(zilog, lwb); } mutex_exit(&zilog->zl_lock); } @@ -2376,7 +3394,7 @@ EXPORT_SYMBOL(zil_sync); EXPORT_SYMBOL(zil_clean); EXPORT_SYMBOL(zil_suspend); EXPORT_SYMBOL(zil_resume); -EXPORT_SYMBOL(zil_add_block); +EXPORT_SYMBOL(zil_lwb_add_block); EXPORT_SYMBOL(zil_bp_tree_add); EXPORT_SYMBOL(zil_set_sync); EXPORT_SYMBOL(zil_set_logbias); diff --git a/module/zfs/zio.c b/module/zfs/zio.c index 311f79e23..92e5a8dd8 100644 --- a/module/zfs/zio.c +++ b/module/zfs/zio.c @@ -568,7 +568,7 @@ zio_add_child(zio_t *pio, zio_t *cio) * Vdev I/Os can only have vdev children. * The following ASSERT captures all of these constraints. */ - ASSERT(cio->io_child_type <= pio->io_child_type); + ASSERT3S(cio->io_child_type, <=, pio->io_child_type); zl->zl_parent = pio; zl->zl_child = cio; @@ -1281,9 +1281,9 @@ zio_flush(zio_t *zio, vdev_t *vd) void zio_shrink(zio_t *zio, uint64_t size) { - ASSERT(zio->io_executor == NULL); - ASSERT(zio->io_orig_size == zio->io_size); - ASSERT(size <= zio->io_size); + ASSERT3P(zio->io_executor, ==, NULL); + ASSERT3U(zio->io_orig_size, ==, zio->io_size); + ASSERT3U(size, <=, zio->io_size); /* * We don't shrink for raidz because of problems with the @@ -1877,8 +1877,8 @@ zio_wait(zio_t *zio) { int error; - ASSERT(zio->io_stage == ZIO_STAGE_OPEN); - ASSERT(zio->io_executor == NULL); + ASSERT3S(zio->io_stage, ==, ZIO_STAGE_OPEN); + ASSERT3P(zio->io_executor, ==, NULL); zio->io_waiter = curthread; ASSERT0(zio->io_queued_timestamp); @@ -1900,7 +1900,7 @@ zio_wait(zio_t *zio) void zio_nowait(zio_t *zio) { - ASSERT(zio->io_executor == NULL); + ASSERT3P(zio->io_executor, ==, NULL); if (zio->io_child_type == ZIO_CHILD_LOGICAL && zio_unique_parent(zio) == NULL) { @@ -1926,7 +1926,7 @@ zio_nowait(zio_t *zio) /* * ========================================================================== - * Reexecute or suspend/resume failed I/O + * Reexecute, cancel, or suspend/resume failed I/O * ========================================================================== */ @@ -1984,6 +1984,20 @@ zio_reexecute(zio_t *pio) } void +zio_cancel(zio_t *zio) +{ + /* + * Disallow cancellation of a zio that's already been issued. + */ + VERIFY3P(zio->io_executor, ==, NULL); + + zio->io_pipeline = ZIO_INTERLOCK_PIPELINE; + zio->io_done = NULL; + + zio_nowait(zio); +} + +void zio_suspend(spa_t *spa, zio_t *zio) { if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_PANIC) @@ -3276,6 +3290,9 @@ zio_alloc_zil(spa_t *spa, objset_t *os, uint64_t txg, blkptr_t *new_bp, zio_crypt_encode_params_bp(new_bp, salt, iv); } + } else { + zfs_dbgmsg("%s: zil block allocation failure: " + "size %llu, error %d", spa_name(spa), size, error); } return (error); diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c index 5cd190c09..6ea822467 100644 --- a/module/zfs/zvol.c +++ b/module/zfs/zvol.c @@ -1052,7 +1052,7 @@ zvol_get_done(zgd_t *zgd, int error) zfs_range_unlock(zgd->zgd_rl); if (error == 0 && zgd->zgd_bp) - zil_add_block(zgd->zgd_zilog, zgd->zgd_bp); + zil_lwb_add_block(zgd->zgd_lwb, zgd->zgd_bp); kmem_free(zgd, sizeof (zgd_t)); } @@ -1061,7 +1061,7 @@ zvol_get_done(zgd_t *zgd, int error) * Get data to generate a TX_WRITE intent log record. */ static int -zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) +zvol_get_data(void *arg, lr_write_t *lr, char *buf, struct lwb *lwb, zio_t *zio) { zvol_state_t *zv = arg; uint64_t offset = lr->lr_offset; @@ -1070,11 +1070,12 @@ zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio) zgd_t *zgd; int error; - ASSERT(zio != NULL); - ASSERT(size != 0); + ASSERT3P(lwb, !=, NULL); + ASSERT3P(zio, !=, NULL); + ASSERT3U(size, !=, 0); zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_SLEEP); - zgd->zgd_zilog = zv->zv_zilog; + zgd->zgd_lwb = lwb; /* * Write records come in two flavors: immediate and indirect. |