diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c index 9120fef93c74..17b971248283 100644 --- a/module/zfs/dsl_pool.c +++ b/module/zfs/dsl_pool.c @@ -1,1494 +1,1494 @@ /* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or https://opensource.org/licenses/CDDL-1.0. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2011, 2020 by Delphix. All rights reserved. * Copyright (c) 2013 Steven Hartland. All rights reserved. * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved. * Copyright 2016 Nexenta Systems, Inc. All rights reserved. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * ZFS Write Throttle * ------------------ * * ZFS must limit the rate of incoming writes to the rate at which it is able * to sync data modifications to the backend storage. Throttling by too much * creates an artificial limit; throttling by too little can only be sustained * for short periods and would lead to highly lumpy performance. On a per-pool * basis, ZFS tracks the amount of modified (dirty) data. As operations change * data, the amount of dirty data increases; as ZFS syncs out data, the amount * of dirty data decreases. When the amount of dirty data exceeds a * predetermined threshold further modifications are blocked until the amount * of dirty data decreases (as data is synced out). * * The limit on dirty data is tunable, and should be adjusted according to * both the IO capacity and available memory of the system. The larger the * window, the more ZFS is able to aggregate and amortize metadata (and data) * changes. However, memory is a limited resource, and allowing for more dirty * data comes at the cost of keeping other useful data in memory (for example * ZFS data cached by the ARC). * * Implementation * * As buffers are modified dsl_pool_willuse_space() increments both the per- * txg (dp_dirty_pertxg[]) and poolwide (dp_dirty_total) accounting of * dirty space used; dsl_pool_dirty_space() decrements those values as data * is synced out from dsl_pool_sync(). While only the poolwide value is * relevant, the per-txg value is useful for debugging. The tunable * zfs_dirty_data_max determines the dirty space limit. Once that value is * exceeded, new writes are halted until space frees up. * * The zfs_dirty_data_sync_percent tunable dictates the threshold at which we * ensure that there is a txg syncing (see the comment in txg.c for a full * description of transaction group stages). * * The IO scheduler uses both the dirty space limit and current amount of * dirty data as inputs. Those values affect the number of concurrent IOs ZFS * issues. See the comment in vdev_queue.c for details of the IO scheduler. * * The delay is also calculated based on the amount of dirty data. See the * comment above dmu_tx_delay() for details. */ /* * zfs_dirty_data_max will be set to zfs_dirty_data_max_percent% of all memory, * capped at zfs_dirty_data_max_max. It can also be overridden with a module * parameter. */ uint64_t zfs_dirty_data_max = 0; uint64_t zfs_dirty_data_max_max = 0; uint_t zfs_dirty_data_max_percent = 10; uint_t zfs_dirty_data_max_max_percent = 25; /* * The upper limit of TX_WRITE log data. Write operations are throttled * when approaching the limit until log data is cleared out after txg sync. * It only counts TX_WRITE log with WR_COPIED or WR_NEED_COPY. */ uint64_t zfs_wrlog_data_max = 0; /* * If there's at least this much dirty data (as a percentage of * zfs_dirty_data_max), push out a txg. This should be less than * zfs_vdev_async_write_active_min_dirty_percent. */ static uint_t zfs_dirty_data_sync_percent = 20; /* * Once there is this amount of dirty data, the dmu_tx_delay() will kick in * and delay each transaction. * This value should be >= zfs_vdev_async_write_active_max_dirty_percent. */ uint_t zfs_delay_min_dirty_percent = 60; /* * This controls how quickly the delay approaches infinity. * Larger values cause it to delay more for a given amount of dirty data. * Therefore larger values will cause there to be less dirty data for a * given throughput. * * For the smoothest delay, this value should be about 1 billion divided * by the maximum number of operations per second. This will smoothly * handle between 10x and 1/10th this number. * * Note: zfs_delay_scale * zfs_dirty_data_max must be < 2^64, due to the * multiply in dmu_tx_delay(). */ uint64_t zfs_delay_scale = 1000 * 1000 * 1000 / 2000; /* * This determines the number of threads used by the dp_sync_taskq. */ static int zfs_sync_taskq_batch_pct = 75; /* * These tunables determine the behavior of how zil_itxg_clean() is * called via zil_clean() in the context of spa_sync(). When an itxg * list needs to be cleaned, TQ_NOSLEEP will be used when dispatching. * If the dispatch fails, the call to zil_itxg_clean() will occur * synchronously in the context of spa_sync(), which can negatively * impact the performance of spa_sync() (e.g. in the case of the itxg * list having a large number of itxs that needs to be cleaned). * * Thus, these tunables can be used to manipulate the behavior of the * taskq used by zil_clean(); they determine the number of taskq entries * that are pre-populated when the taskq is first created (via the * "zfs_zil_clean_taskq_minalloc" tunable) and the maximum number of * taskq entries that are cached after an on-demand allocation (via the * "zfs_zil_clean_taskq_maxalloc"). * * The idea being, we want to try reasonably hard to ensure there will * already be a taskq entry pre-allocated by the time that it is needed * by zil_clean(). This way, we can avoid the possibility of an * on-demand allocation of a new taskq entry from failing, which would * result in zil_itxg_clean() being called synchronously from zil_clean() * (which can adversely affect performance of spa_sync()). * * Additionally, the number of threads used by the taskq can be * configured via the "zfs_zil_clean_taskq_nthr_pct" tunable. */ static int zfs_zil_clean_taskq_nthr_pct = 100; static int zfs_zil_clean_taskq_minalloc = 1024; static int zfs_zil_clean_taskq_maxalloc = 1024 * 1024; int dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp) { uint64_t obj; int err; err = zap_lookup(dp->dp_meta_objset, dsl_dir_phys(dp->dp_root_dir)->dd_child_dir_zapobj, name, sizeof (obj), 1, &obj); if (err) return (err); return (dsl_dir_hold_obj(dp, obj, name, dp, ddp)); } static dsl_pool_t * dsl_pool_open_impl(spa_t *spa, uint64_t txg) { dsl_pool_t *dp; blkptr_t *bp = spa_get_rootblkptr(spa); dp = kmem_zalloc(sizeof (dsl_pool_t), KM_SLEEP); dp->dp_spa = spa; dp->dp_meta_rootbp = *bp; rrw_init(&dp->dp_config_rwlock, B_TRUE); txg_init(dp, txg); mmp_init(spa); txg_list_create(&dp->dp_dirty_datasets, spa, offsetof(dsl_dataset_t, ds_dirty_link)); txg_list_create(&dp->dp_dirty_zilogs, spa, offsetof(zilog_t, zl_dirty_link)); txg_list_create(&dp->dp_dirty_dirs, spa, offsetof(dsl_dir_t, dd_dirty_link)); txg_list_create(&dp->dp_sync_tasks, spa, offsetof(dsl_sync_task_t, dst_node)); txg_list_create(&dp->dp_early_sync_tasks, spa, offsetof(dsl_sync_task_t, dst_node)); dp->dp_sync_taskq = taskq_create("dp_sync_taskq", zfs_sync_taskq_batch_pct, minclsyspri, 1, INT_MAX, TASKQ_THREADS_CPU_PCT); dp->dp_zil_clean_taskq = taskq_create("dp_zil_clean_taskq", zfs_zil_clean_taskq_nthr_pct, minclsyspri, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, TASKQ_PREPOPULATE | TASKQ_THREADS_CPU_PCT); mutex_init(&dp->dp_lock, NULL, MUTEX_DEFAULT, NULL); cv_init(&dp->dp_spaceavail_cv, NULL, CV_DEFAULT, NULL); aggsum_init(&dp->dp_wrlog_total, 0); for (int i = 0; i < TXG_SIZE; i++) { aggsum_init(&dp->dp_wrlog_pertxg[i], 0); } dp->dp_zrele_taskq = taskq_create("z_zrele", 100, defclsyspri, boot_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC | TASKQ_THREADS_CPU_PCT); dp->dp_unlinked_drain_taskq = taskq_create("z_unlinked_drain", 100, defclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC | TASKQ_THREADS_CPU_PCT); return (dp); } int dsl_pool_init(spa_t *spa, uint64_t txg, dsl_pool_t **dpp) { int err; dsl_pool_t *dp = dsl_pool_open_impl(spa, txg); /* * Initialize the caller's dsl_pool_t structure before we actually open * the meta objset. This is done because a self-healing write zio may * be issued as part of dmu_objset_open_impl() and the spa needs its * dsl_pool_t initialized in order to handle the write. */ *dpp = dp; err = dmu_objset_open_impl(spa, NULL, &dp->dp_meta_rootbp, &dp->dp_meta_objset); if (err != 0) { dsl_pool_close(dp); *dpp = NULL; } return (err); } int dsl_pool_open(dsl_pool_t *dp) { int err; dsl_dir_t *dd; dsl_dataset_t *ds; uint64_t obj; rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG); err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1, &dp->dp_root_dir_obj); if (err) goto out; err = dsl_dir_hold_obj(dp, dp->dp_root_dir_obj, NULL, dp, &dp->dp_root_dir); if (err) goto out; err = dsl_pool_open_special_dir(dp, MOS_DIR_NAME, &dp->dp_mos_dir); if (err) goto out; if (spa_version(dp->dp_spa) >= SPA_VERSION_ORIGIN) { err = dsl_pool_open_special_dir(dp, ORIGIN_DIR_NAME, &dd); if (err) goto out; err = dsl_dataset_hold_obj(dp, dsl_dir_phys(dd)->dd_head_dataset_obj, FTAG, &ds); if (err == 0) { err = dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj, dp, &dp->dp_origin_snap); dsl_dataset_rele(ds, FTAG); } dsl_dir_rele(dd, dp); if (err) goto out; } if (spa_version(dp->dp_spa) >= SPA_VERSION_DEADLISTS) { err = dsl_pool_open_special_dir(dp, FREE_DIR_NAME, &dp->dp_free_dir); if (err) goto out; err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj); if (err) goto out; VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj)); } if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS)) { err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj); if (err == 0) { VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj, dp->dp_meta_objset, obj)); } else if (err == ENOENT) { /* * We might not have created the remap bpobj yet. */ } else { goto out; } } /* * Note: errors ignored, because the these special dirs, used for * space accounting, are only created on demand. */ (void) dsl_pool_open_special_dir(dp, LEAK_DIR_NAME, &dp->dp_leak_dir); if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_ASYNC_DESTROY)) { err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_BPTREE_OBJ, sizeof (uint64_t), 1, &dp->dp_bptree_obj); if (err != 0) goto out; } if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_EMPTY_BPOBJ)) { err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1, &dp->dp_empty_bpobj); if (err != 0) goto out; } err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, sizeof (uint64_t), 1, &dp->dp_tmp_userrefs_obj); if (err == ENOENT) err = 0; if (err) goto out; err = dsl_scan_init(dp, dp->dp_tx.tx_open_txg); out: rrw_exit(&dp->dp_config_rwlock, FTAG); return (err); } void dsl_pool_close(dsl_pool_t *dp) { /* * Drop our references from dsl_pool_open(). * * Since we held the origin_snap from "syncing" context (which * includes pool-opening context), it actually only got a "ref" * and not a hold, so just drop that here. */ if (dp->dp_origin_snap != NULL) dsl_dataset_rele(dp->dp_origin_snap, dp); if (dp->dp_mos_dir != NULL) dsl_dir_rele(dp->dp_mos_dir, dp); if (dp->dp_free_dir != NULL) dsl_dir_rele(dp->dp_free_dir, dp); if (dp->dp_leak_dir != NULL) dsl_dir_rele(dp->dp_leak_dir, dp); if (dp->dp_root_dir != NULL) dsl_dir_rele(dp->dp_root_dir, dp); bpobj_close(&dp->dp_free_bpobj); bpobj_close(&dp->dp_obsolete_bpobj); /* undo the dmu_objset_open_impl(mos) from dsl_pool_open() */ if (dp->dp_meta_objset != NULL) dmu_objset_evict(dp->dp_meta_objset); txg_list_destroy(&dp->dp_dirty_datasets); txg_list_destroy(&dp->dp_dirty_zilogs); txg_list_destroy(&dp->dp_sync_tasks); txg_list_destroy(&dp->dp_early_sync_tasks); txg_list_destroy(&dp->dp_dirty_dirs); taskq_destroy(dp->dp_zil_clean_taskq); taskq_destroy(dp->dp_sync_taskq); /* * We can't set retry to TRUE since we're explicitly specifying * a spa to flush. This is good enough; any missed buffers for * this spa won't cause trouble, and they'll eventually fall * out of the ARC just like any other unused buffer. */ arc_flush(dp->dp_spa, FALSE); mmp_fini(dp->dp_spa); txg_fini(dp); dsl_scan_fini(dp); dmu_buf_user_evict_wait(); rrw_destroy(&dp->dp_config_rwlock); mutex_destroy(&dp->dp_lock); cv_destroy(&dp->dp_spaceavail_cv); ASSERT0(aggsum_value(&dp->dp_wrlog_total)); aggsum_fini(&dp->dp_wrlog_total); for (int i = 0; i < TXG_SIZE; i++) { ASSERT0(aggsum_value(&dp->dp_wrlog_pertxg[i])); aggsum_fini(&dp->dp_wrlog_pertxg[i]); } taskq_destroy(dp->dp_unlinked_drain_taskq); taskq_destroy(dp->dp_zrele_taskq); if (dp->dp_blkstats != NULL) vmem_free(dp->dp_blkstats, sizeof (zfs_all_blkstats_t)); kmem_free(dp, sizeof (dsl_pool_t)); } void dsl_pool_create_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx) { uint64_t obj; /* * Currently, we only create the obsolete_bpobj where there are * indirect vdevs with referenced mappings. */ ASSERT(spa_feature_is_active(dp->dp_spa, SPA_FEATURE_DEVICE_REMOVAL)); /* create and open the obsolete_bpobj */ obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx); VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj, dp->dp_meta_objset, obj)); VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj, tx)); spa_feature_incr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx); } void dsl_pool_destroy_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx) { spa_feature_decr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx); VERIFY0(zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_OBSOLETE_BPOBJ, tx)); bpobj_free(dp->dp_meta_objset, dp->dp_obsolete_bpobj.bpo_object, tx); bpobj_close(&dp->dp_obsolete_bpobj); } dsl_pool_t * dsl_pool_create(spa_t *spa, nvlist_t *zplprops __attribute__((unused)), dsl_crypto_params_t *dcp, uint64_t txg) { int err; dsl_pool_t *dp = dsl_pool_open_impl(spa, txg); dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg); #ifdef _KERNEL objset_t *os; #else objset_t *os __attribute__((unused)); #endif dsl_dataset_t *ds; uint64_t obj; rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG); /* create and open the MOS (meta-objset) */ dp->dp_meta_objset = dmu_objset_create_impl(spa, NULL, &dp->dp_meta_rootbp, DMU_OST_META, tx); spa->spa_meta_objset = dp->dp_meta_objset; /* create the pool directory */ err = zap_create_claim(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_OT_OBJECT_DIRECTORY, DMU_OT_NONE, 0, tx); ASSERT0(err); /* Initialize scan structures */ VERIFY0(dsl_scan_init(dp, txg)); /* create and open the root dir */ dp->dp_root_dir_obj = dsl_dir_create_sync(dp, NULL, NULL, tx); VERIFY0(dsl_dir_hold_obj(dp, dp->dp_root_dir_obj, NULL, dp, &dp->dp_root_dir)); /* create and open the meta-objset dir */ (void) dsl_dir_create_sync(dp, dp->dp_root_dir, MOS_DIR_NAME, tx); VERIFY0(dsl_pool_open_special_dir(dp, MOS_DIR_NAME, &dp->dp_mos_dir)); if (spa_version(spa) >= SPA_VERSION_DEADLISTS) { /* create and open the free dir */ (void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx); VERIFY0(dsl_pool_open_special_dir(dp, FREE_DIR_NAME, &dp->dp_free_dir)); /* create and open the free_bplist */ obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx); VERIFY(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx) == 0); VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj)); } if (spa_version(spa) >= SPA_VERSION_DSL_SCRUB) dsl_pool_create_origin(dp, tx); /* * Some features may be needed when creating the root dataset, so we * create the feature objects here. */ if (spa_version(spa) >= SPA_VERSION_FEATURES) spa_feature_create_zap_objects(spa, tx); if (dcp != NULL && dcp->cp_crypt != ZIO_CRYPT_OFF && dcp->cp_crypt != ZIO_CRYPT_INHERIT) spa_feature_enable(spa, SPA_FEATURE_ENCRYPTION, tx); /* create the root dataset */ obj = dsl_dataset_create_sync_dd(dp->dp_root_dir, NULL, dcp, 0, tx); /* create the root objset */ VERIFY0(dsl_dataset_hold_obj_flags(dp, obj, DS_HOLD_FLAG_DECRYPT, FTAG, &ds)); rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG); os = dmu_objset_create_impl(dp->dp_spa, ds, dsl_dataset_get_blkptr(ds), DMU_OST_ZFS, tx); rrw_exit(&ds->ds_bp_rwlock, FTAG); #ifdef _KERNEL zfs_create_fs(os, kcred, zplprops, tx); #endif dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG); dmu_tx_commit(tx); rrw_exit(&dp->dp_config_rwlock, FTAG); return (dp); } /* * Account for the meta-objset space in its placeholder dsl_dir. */ void dsl_pool_mos_diduse_space(dsl_pool_t *dp, int64_t used, int64_t comp, int64_t uncomp) { ASSERT3U(comp, ==, uncomp); /* it's all metadata */ mutex_enter(&dp->dp_lock); dp->dp_mos_used_delta += used; dp->dp_mos_compressed_delta += comp; dp->dp_mos_uncompressed_delta += uncomp; mutex_exit(&dp->dp_lock); } static void dsl_pool_sync_mos(dsl_pool_t *dp, dmu_tx_t *tx) { zio_t *zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED); dmu_objset_sync(dp->dp_meta_objset, zio, tx); VERIFY0(zio_wait(zio)); dmu_objset_sync_done(dp->dp_meta_objset, tx); taskq_wait(dp->dp_sync_taskq); multilist_destroy(&dp->dp_meta_objset->os_synced_dnodes); dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", ""); spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp); } static void dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta) { ASSERT(MUTEX_HELD(&dp->dp_lock)); if (delta < 0) ASSERT3U(-delta, <=, dp->dp_dirty_total); dp->dp_dirty_total += delta; /* * Note: we signal even when increasing dp_dirty_total. * This ensures forward progress -- each thread wakes the next waiter. */ if (dp->dp_dirty_total < zfs_dirty_data_max) cv_signal(&dp->dp_spaceavail_cv); } void dsl_pool_wrlog_count(dsl_pool_t *dp, int64_t size, uint64_t txg) { ASSERT3S(size, >=, 0); aggsum_add(&dp->dp_wrlog_pertxg[txg & TXG_MASK], size); aggsum_add(&dp->dp_wrlog_total, size); /* Choose a value slightly bigger than min dirty sync bytes */ uint64_t sync_min = zfs_wrlog_data_max * (zfs_dirty_data_sync_percent + 10) / 200; if (aggsum_compare(&dp->dp_wrlog_pertxg[txg & TXG_MASK], sync_min) > 0) txg_kick(dp, txg); } boolean_t dsl_pool_need_wrlog_delay(dsl_pool_t *dp) { uint64_t delay_min_bytes = zfs_wrlog_data_max * zfs_delay_min_dirty_percent / 100; return (aggsum_compare(&dp->dp_wrlog_total, delay_min_bytes) > 0); } static void dsl_pool_wrlog_clear(dsl_pool_t *dp, uint64_t txg) { int64_t delta; delta = -(int64_t)aggsum_value(&dp->dp_wrlog_pertxg[txg & TXG_MASK]); aggsum_add(&dp->dp_wrlog_pertxg[txg & TXG_MASK], delta); aggsum_add(&dp->dp_wrlog_total, delta); /* Compact per-CPU sums after the big change. */ (void) aggsum_value(&dp->dp_wrlog_pertxg[txg & TXG_MASK]); (void) aggsum_value(&dp->dp_wrlog_total); } #ifdef ZFS_DEBUG static boolean_t dsl_early_sync_task_verify(dsl_pool_t *dp, uint64_t txg) { spa_t *spa = dp->dp_spa; vdev_t *rvd = spa->spa_root_vdev; for (uint64_t c = 0; c < rvd->vdev_children; c++) { vdev_t *vd = rvd->vdev_child[c]; txg_list_t *tl = &vd->vdev_ms_list; metaslab_t *ms; for (ms = txg_list_head(tl, TXG_CLEAN(txg)); ms; ms = txg_list_next(tl, ms, TXG_CLEAN(txg))) { VERIFY(range_tree_is_empty(ms->ms_freeing)); VERIFY(range_tree_is_empty(ms->ms_checkpointing)); } } return (B_TRUE); } #else #define dsl_early_sync_task_verify(dp, txg) \ ((void) sizeof (dp), (void) sizeof (txg), B_TRUE) #endif void dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) { zio_t *zio; dmu_tx_t *tx; dsl_dir_t *dd; dsl_dataset_t *ds; objset_t *mos = dp->dp_meta_objset; list_t synced_datasets; list_create(&synced_datasets, sizeof (dsl_dataset_t), offsetof(dsl_dataset_t, ds_synced_link)); tx = dmu_tx_create_assigned(dp, txg); /* * Run all early sync tasks before writing out any dirty blocks. * For more info on early sync tasks see block comment in * dsl_early_sync_task(). */ if (!txg_list_empty(&dp->dp_early_sync_tasks, txg)) { dsl_sync_task_t *dst; ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1); while ((dst = txg_list_remove(&dp->dp_early_sync_tasks, txg)) != NULL) { ASSERT(dsl_early_sync_task_verify(dp, txg)); dsl_sync_task_sync(dst, tx); } ASSERT(dsl_early_sync_task_verify(dp, txg)); } /* * Write out all dirty blocks of dirty datasets. */ zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED); while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) { /* * We must not sync any non-MOS datasets twice, because * we may have taken a snapshot of them. However, we * may sync newly-created datasets on pass 2. */ ASSERT(!list_link_active(&ds->ds_synced_link)); list_insert_tail(&synced_datasets, ds); dsl_dataset_sync(ds, zio, tx); } VERIFY0(zio_wait(zio)); /* * Update the long range free counter after * we're done syncing user data */ mutex_enter(&dp->dp_lock); ASSERT(spa_sync_pass(dp->dp_spa) == 1 || dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] == 0); dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] = 0; mutex_exit(&dp->dp_lock); /* * After the data blocks have been written (ensured by the zio_wait() * above), update the user/group/project space accounting. This happens * in tasks dispatched to dp_sync_taskq, so wait for them before * continuing. */ for (ds = list_head(&synced_datasets); ds != NULL; ds = list_next(&synced_datasets, ds)) { dmu_objset_sync_done(ds->ds_objset, tx); } taskq_wait(dp->dp_sync_taskq); /* * Sync the datasets again to push out the changes due to * userspace updates. This must be done before we process the * sync tasks, so that any snapshots will have the correct * user accounting information (and we won't get confused * about which blocks are part of the snapshot). */ zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED); while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) { objset_t *os = ds->ds_objset; ASSERT(list_link_active(&ds->ds_synced_link)); dmu_buf_rele(ds->ds_dbuf, ds); dsl_dataset_sync(ds, zio, tx); /* * Release any key mappings created by calls to * dsl_dataset_dirty() from the userquota accounting * code paths. */ if (os->os_encrypted && !os->os_raw_receive && !os->os_next_write_raw[txg & TXG_MASK]) { ASSERT3P(ds->ds_key_mapping, !=, NULL); key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds); } } VERIFY0(zio_wait(zio)); /* * Now that the datasets have been completely synced, we can * clean up our in-memory structures accumulated while syncing: * * - move dead blocks from the pending deadlist and livelists * to the on-disk versions * - release hold from dsl_dataset_dirty() * - release key mapping hold from dsl_dataset_dirty() */ while ((ds = list_remove_head(&synced_datasets)) != NULL) { objset_t *os = ds->ds_objset; if (os->os_encrypted && !os->os_raw_receive && !os->os_next_write_raw[txg & TXG_MASK]) { ASSERT3P(ds->ds_key_mapping, !=, NULL); key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds); } dsl_dataset_sync_done(ds, tx); dmu_buf_rele(ds->ds_dbuf, ds); } while ((dd = txg_list_remove(&dp->dp_dirty_dirs, txg)) != NULL) { dsl_dir_sync(dd, tx); } /* * The MOS's space is accounted for in the pool/$MOS * (dp_mos_dir). We can't modify the mos while we're syncing * it, so we remember the deltas and apply them here. */ if (dp->dp_mos_used_delta != 0 || dp->dp_mos_compressed_delta != 0 || dp->dp_mos_uncompressed_delta != 0) { dsl_dir_diduse_space(dp->dp_mos_dir, DD_USED_HEAD, dp->dp_mos_used_delta, dp->dp_mos_compressed_delta, dp->dp_mos_uncompressed_delta, tx); dp->dp_mos_used_delta = 0; dp->dp_mos_compressed_delta = 0; dp->dp_mos_uncompressed_delta = 0; } if (dmu_objset_is_dirty(mos, txg)) { dsl_pool_sync_mos(dp, tx); } /* * We have written all of the accounted dirty data, so our * dp_space_towrite should now be zero. However, some seldom-used * code paths do not adhere to this (e.g. dbuf_undirty()). Shore up * the accounting of any dirtied space now. * * Note that, besides any dirty data from datasets, the amount of * dirty data in the MOS is also accounted by the pool. Therefore, * we want to do this cleanup after dsl_pool_sync_mos() so we don't * attempt to update the accounting for the same dirty data twice. * (i.e. at this point we only update the accounting for the space * that we know that we "leaked"). */ dsl_pool_undirty_space(dp, dp->dp_dirty_pertxg[txg & TXG_MASK], txg); /* * If we modify a dataset in the same txg that we want to destroy it, * its dsl_dir's dd_dbuf will be dirty, and thus have a hold on it. * dsl_dir_destroy_check() will fail if there are unexpected holds. * Therefore, we want to sync the MOS (thus syncing the dd_dbuf * and clearing the hold on it) before we process the sync_tasks. * The MOS data dirtied by the sync_tasks will be synced on the next * pass. */ if (!txg_list_empty(&dp->dp_sync_tasks, txg)) { dsl_sync_task_t *dst; /* * No more sync tasks should have been added while we * were syncing. */ ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1); while ((dst = txg_list_remove(&dp->dp_sync_tasks, txg)) != NULL) dsl_sync_task_sync(dst, tx); } dmu_tx_commit(tx); DTRACE_PROBE2(dsl_pool_sync__done, dsl_pool_t *dp, dp, uint64_t, txg); } void dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg) { zilog_t *zilog; while ((zilog = txg_list_head(&dp->dp_dirty_zilogs, txg))) { dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os); /* * We don't remove the zilog from the dp_dirty_zilogs * list until after we've cleaned it. This ensures that * callers of zilog_is_dirty() receive an accurate * answer when they are racing with the spa sync thread. */ zil_clean(zilog, txg); (void) txg_list_remove_this(&dp->dp_dirty_zilogs, zilog, txg); ASSERT(!dmu_objset_is_dirty(zilog->zl_os, txg)); dmu_buf_rele(ds->ds_dbuf, zilog); } dsl_pool_wrlog_clear(dp, txg); ASSERT(!dmu_objset_is_dirty(dp->dp_meta_objset, txg)); } /* * TRUE if the current thread is the tx_sync_thread or if we * are being called from SPA context during pool initialization. */ int dsl_pool_sync_context(dsl_pool_t *dp) { return (curthread == dp->dp_tx.tx_sync_thread || spa_is_initializing(dp->dp_spa) || taskq_member(dp->dp_sync_taskq, curthread)); } /* * This function returns the amount of allocatable space in the pool * minus whatever space is currently reserved by ZFS for specific * purposes. Specifically: * * 1] Any reserved SLOP space * 2] Any space used by the checkpoint * 3] Any space used for deferred frees * * The latter 2 are especially important because they are needed to * rectify the SPA's and DMU's different understanding of how much space * is used. Now the DMU is aware of that extra space tracked by the SPA * without having to maintain a separate special dir (e.g similar to * $MOS, $FREEING, and $LEAKED). * * Note: By deferred frees here, we mean the frees that were deferred * in spa_sync() after sync pass 1 (spa_deferred_bpobj), and not the * segments placed in ms_defer trees during metaslab_sync_done(). */ uint64_t dsl_pool_adjustedsize(dsl_pool_t *dp, zfs_space_check_t slop_policy) { spa_t *spa = dp->dp_spa; uint64_t space, resv, adjustedsize; uint64_t spa_deferred_frees = spa->spa_deferred_bpobj.bpo_phys->bpo_bytes; space = spa_get_dspace(spa) - spa_get_checkpoint_space(spa) - spa_deferred_frees; resv = spa_get_slop_space(spa); switch (slop_policy) { case ZFS_SPACE_CHECK_NORMAL: break; case ZFS_SPACE_CHECK_RESERVED: resv >>= 1; break; case ZFS_SPACE_CHECK_EXTRA_RESERVED: resv >>= 2; break; case ZFS_SPACE_CHECK_NONE: resv = 0; break; default: panic("invalid slop policy value: %d", slop_policy); break; } adjustedsize = (space >= resv) ? (space - resv) : 0; return (adjustedsize); } uint64_t dsl_pool_unreserved_space(dsl_pool_t *dp, zfs_space_check_t slop_policy) { uint64_t poolsize = dsl_pool_adjustedsize(dp, slop_policy); uint64_t deferred = metaslab_class_get_deferred(spa_normal_class(dp->dp_spa)); uint64_t quota = (poolsize >= deferred) ? (poolsize - deferred) : 0; return (quota); } uint64_t dsl_pool_deferred_space(dsl_pool_t *dp) { return (metaslab_class_get_deferred(spa_normal_class(dp->dp_spa))); } boolean_t dsl_pool_need_dirty_delay(dsl_pool_t *dp) { uint64_t delay_min_bytes = zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100; - mutex_enter(&dp->dp_lock); - uint64_t dirty = dp->dp_dirty_total; - mutex_exit(&dp->dp_lock); - - return (dirty > delay_min_bytes); + /* + * We are not taking the dp_lock here and few other places, since torn + * reads are unlikely: on 64-bit systems due to register size and on + * 32-bit due to memory constraints. Pool-wide locks in hot path may + * be too expensive, while we do not need a precise result here. + */ + return (dp->dp_dirty_total > delay_min_bytes); } static boolean_t dsl_pool_need_dirty_sync(dsl_pool_t *dp, uint64_t txg) { - ASSERT(MUTEX_HELD(&dp->dp_lock)); - uint64_t dirty_min_bytes = zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100; uint64_t dirty = dp->dp_dirty_pertxg[txg & TXG_MASK]; return (dirty > dirty_min_bytes); } void dsl_pool_dirty_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx) { if (space > 0) { mutex_enter(&dp->dp_lock); dp->dp_dirty_pertxg[tx->tx_txg & TXG_MASK] += space; dsl_pool_dirty_delta(dp, space); boolean_t needsync = !dmu_tx_is_syncing(tx) && dsl_pool_need_dirty_sync(dp, tx->tx_txg); mutex_exit(&dp->dp_lock); if (needsync) txg_kick(dp, tx->tx_txg); } } void dsl_pool_undirty_space(dsl_pool_t *dp, int64_t space, uint64_t txg) { ASSERT3S(space, >=, 0); if (space == 0) return; mutex_enter(&dp->dp_lock); if (dp->dp_dirty_pertxg[txg & TXG_MASK] < space) { /* XXX writing something we didn't dirty? */ space = dp->dp_dirty_pertxg[txg & TXG_MASK]; } ASSERT3U(dp->dp_dirty_pertxg[txg & TXG_MASK], >=, space); dp->dp_dirty_pertxg[txg & TXG_MASK] -= space; ASSERT3U(dp->dp_dirty_total, >=, space); dsl_pool_dirty_delta(dp, -space); mutex_exit(&dp->dp_lock); } static int upgrade_clones_cb(dsl_pool_t *dp, dsl_dataset_t *hds, void *arg) { dmu_tx_t *tx = arg; dsl_dataset_t *ds, *prev = NULL; int err; err = dsl_dataset_hold_obj(dp, hds->ds_object, FTAG, &ds); if (err) return (err); while (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) { err = dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj, FTAG, &prev); if (err) { dsl_dataset_rele(ds, FTAG); return (err); } if (dsl_dataset_phys(prev)->ds_next_snap_obj != ds->ds_object) break; dsl_dataset_rele(ds, FTAG); ds = prev; prev = NULL; } if (prev == NULL) { prev = dp->dp_origin_snap; /* * The $ORIGIN can't have any data, or the accounting * will be wrong. */ rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG); ASSERT0(dsl_dataset_phys(prev)->ds_bp.blk_birth); rrw_exit(&ds->ds_bp_rwlock, FTAG); /* The origin doesn't get attached to itself */ if (ds->ds_object == prev->ds_object) { dsl_dataset_rele(ds, FTAG); return (0); } dmu_buf_will_dirty(ds->ds_dbuf, tx); dsl_dataset_phys(ds)->ds_prev_snap_obj = prev->ds_object; dsl_dataset_phys(ds)->ds_prev_snap_txg = dsl_dataset_phys(prev)->ds_creation_txg; dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx); dsl_dir_phys(ds->ds_dir)->dd_origin_obj = prev->ds_object; dmu_buf_will_dirty(prev->ds_dbuf, tx); dsl_dataset_phys(prev)->ds_num_children++; if (dsl_dataset_phys(ds)->ds_next_snap_obj == 0) { ASSERT(ds->ds_prev == NULL); VERIFY0(dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj, ds, &ds->ds_prev)); } } ASSERT3U(dsl_dir_phys(ds->ds_dir)->dd_origin_obj, ==, prev->ds_object); ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_obj, ==, prev->ds_object); if (dsl_dataset_phys(prev)->ds_next_clones_obj == 0) { dmu_buf_will_dirty(prev->ds_dbuf, tx); dsl_dataset_phys(prev)->ds_next_clones_obj = zap_create(dp->dp_meta_objset, DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx); } VERIFY0(zap_add_int(dp->dp_meta_objset, dsl_dataset_phys(prev)->ds_next_clones_obj, ds->ds_object, tx)); dsl_dataset_rele(ds, FTAG); if (prev != dp->dp_origin_snap) dsl_dataset_rele(prev, FTAG); return (0); } void dsl_pool_upgrade_clones(dsl_pool_t *dp, dmu_tx_t *tx) { ASSERT(dmu_tx_is_syncing(tx)); ASSERT(dp->dp_origin_snap != NULL); VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj, upgrade_clones_cb, tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE)); } static int upgrade_dir_clones_cb(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg) { dmu_tx_t *tx = arg; objset_t *mos = dp->dp_meta_objset; if (dsl_dir_phys(ds->ds_dir)->dd_origin_obj != 0) { dsl_dataset_t *origin; VERIFY0(dsl_dataset_hold_obj(dp, dsl_dir_phys(ds->ds_dir)->dd_origin_obj, FTAG, &origin)); if (dsl_dir_phys(origin->ds_dir)->dd_clones == 0) { dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx); dsl_dir_phys(origin->ds_dir)->dd_clones = zap_create(mos, DMU_OT_DSL_CLONES, DMU_OT_NONE, 0, tx); } VERIFY0(zap_add_int(dp->dp_meta_objset, dsl_dir_phys(origin->ds_dir)->dd_clones, ds->ds_object, tx)); dsl_dataset_rele(origin, FTAG); } return (0); } void dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx) { uint64_t obj; ASSERT(dmu_tx_is_syncing(tx)); (void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx); VERIFY0(dsl_pool_open_special_dir(dp, FREE_DIR_NAME, &dp->dp_free_dir)); /* * We can't use bpobj_alloc(), because spa_version() still * returns the old version, and we need a new-version bpobj with * subobj support. So call dmu_object_alloc() directly. */ obj = dmu_object_alloc(dp->dp_meta_objset, DMU_OT_BPOBJ, SPA_OLD_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx); VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx)); VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj)); VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj, upgrade_dir_clones_cb, tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE)); } void dsl_pool_create_origin(dsl_pool_t *dp, dmu_tx_t *tx) { uint64_t dsobj; dsl_dataset_t *ds; ASSERT(dmu_tx_is_syncing(tx)); ASSERT(dp->dp_origin_snap == NULL); ASSERT(rrw_held(&dp->dp_config_rwlock, RW_WRITER)); /* create the origin dir, ds, & snap-ds */ dsobj = dsl_dataset_create_sync(dp->dp_root_dir, ORIGIN_DIR_NAME, NULL, 0, kcred, NULL, tx); VERIFY0(dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds)); dsl_dataset_snapshot_sync_impl(ds, ORIGIN_DIR_NAME, tx); VERIFY0(dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj, dp, &dp->dp_origin_snap)); dsl_dataset_rele(ds, FTAG); } taskq_t * dsl_pool_zrele_taskq(dsl_pool_t *dp) { return (dp->dp_zrele_taskq); } taskq_t * dsl_pool_unlinked_drain_taskq(dsl_pool_t *dp) { return (dp->dp_unlinked_drain_taskq); } /* * Walk through the pool-wide zap object of temporary snapshot user holds * and release them. */ void dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp) { zap_attribute_t za; zap_cursor_t zc; objset_t *mos = dp->dp_meta_objset; uint64_t zapobj = dp->dp_tmp_userrefs_obj; nvlist_t *holds; if (zapobj == 0) return; ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS); holds = fnvlist_alloc(); for (zap_cursor_init(&zc, mos, zapobj); zap_cursor_retrieve(&zc, &za) == 0; zap_cursor_advance(&zc)) { char *htag; nvlist_t *tags; htag = strchr(za.za_name, '-'); *htag = '\0'; ++htag; if (nvlist_lookup_nvlist(holds, za.za_name, &tags) != 0) { tags = fnvlist_alloc(); fnvlist_add_boolean(tags, htag); fnvlist_add_nvlist(holds, za.za_name, tags); fnvlist_free(tags); } else { fnvlist_add_boolean(tags, htag); } } dsl_dataset_user_release_tmp(dp, holds); fnvlist_free(holds); zap_cursor_fini(&zc); } /* * Create the pool-wide zap object for storing temporary snapshot holds. */ static void dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx) { objset_t *mos = dp->dp_meta_objset; ASSERT(dp->dp_tmp_userrefs_obj == 0); ASSERT(dmu_tx_is_syncing(tx)); dp->dp_tmp_userrefs_obj = zap_create_link(mos, DMU_OT_USERREFS, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, tx); } static int dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj, const char *tag, uint64_t now, dmu_tx_t *tx, boolean_t holding) { objset_t *mos = dp->dp_meta_objset; uint64_t zapobj = dp->dp_tmp_userrefs_obj; char *name; int error; ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS); ASSERT(dmu_tx_is_syncing(tx)); /* * If the pool was created prior to SPA_VERSION_USERREFS, the * zap object for temporary holds might not exist yet. */ if (zapobj == 0) { if (holding) { dsl_pool_user_hold_create_obj(dp, tx); zapobj = dp->dp_tmp_userrefs_obj; } else { return (SET_ERROR(ENOENT)); } } name = kmem_asprintf("%llx-%s", (u_longlong_t)dsobj, tag); if (holding) error = zap_add(mos, zapobj, name, 8, 1, &now, tx); else error = zap_remove(mos, zapobj, name, tx); kmem_strfree(name); return (error); } /* * Add a temporary hold for the given dataset object and tag. */ int dsl_pool_user_hold(dsl_pool_t *dp, uint64_t dsobj, const char *tag, uint64_t now, dmu_tx_t *tx) { return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, now, tx, B_TRUE)); } /* * Release a temporary hold for the given dataset object and tag. */ int dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj, const char *tag, dmu_tx_t *tx) { return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, 0, tx, B_FALSE)); } /* * DSL Pool Configuration Lock * * The dp_config_rwlock protects against changes to DSL state (e.g. dataset * creation / destruction / rename / property setting). It must be held for * read to hold a dataset or dsl_dir. I.e. you must call * dsl_pool_config_enter() or dsl_pool_hold() before calling * dsl_{dataset,dir}_hold{_obj}. In most circumstances, the dp_config_rwlock * must be held continuously until all datasets and dsl_dirs are released. * * The only exception to this rule is that if a "long hold" is placed on * a dataset, then the dp_config_rwlock may be dropped while the dataset * is still held. The long hold will prevent the dataset from being * destroyed -- the destroy will fail with EBUSY. A long hold can be * obtained by calling dsl_dataset_long_hold(), or by "owning" a dataset * (by calling dsl_{dataset,objset}_{try}own{_obj}). * * Legitimate long-holders (including owners) should be long-running, cancelable * tasks that should cause "zfs destroy" to fail. This includes DMU * consumers (i.e. a ZPL filesystem being mounted or ZVOL being open), * "zfs send", and "zfs diff". There are several other long-holders whose * uses are suboptimal (e.g. "zfs promote", and zil_suspend()). * * The usual formula for long-holding would be: * dsl_pool_hold() * dsl_dataset_hold() * ... perform checks ... * dsl_dataset_long_hold() * dsl_pool_rele() * ... perform long-running task ... * dsl_dataset_long_rele() * dsl_dataset_rele() * * Note that when the long hold is released, the dataset is still held but * the pool is not held. The dataset may change arbitrarily during this time * (e.g. it could be destroyed). Therefore you shouldn't do anything to the * dataset except release it. * * Operations generally fall somewhere into the following taxonomy: * * Read-Only Modifying * * Dataset Layer / MOS zfs get zfs destroy * * Individual Dataset read() write() * * * Dataset Layer Operations * * Modifying operations should generally use dsl_sync_task(). The synctask * infrastructure enforces proper locking strategy with respect to the * dp_config_rwlock. See the comment above dsl_sync_task() for details. * * Read-only operations will manually hold the pool, then the dataset, obtain * information from the dataset, then release the pool and dataset. * dmu_objset_{hold,rele}() are convenience routines that also do the pool * hold/rele. * * * Operations On Individual Datasets * * Objects _within_ an objset should only be modified by the current 'owner' * of the objset to prevent incorrect concurrent modification. Thus, use * {dmu_objset,dsl_dataset}_own to mark some entity as the current owner, * and fail with EBUSY if there is already an owner. The owner can then * implement its own locking strategy, independent of the dataset layer's * locking infrastructure. * (E.g., the ZPL has its own set of locks to control concurrency. A regular * vnop will not reach into the dataset layer). * * Ideally, objects would also only be read by the objset’s owner, so that we * don’t observe state mid-modification. * (E.g. the ZPL is creating a new object and linking it into a directory; if * you don’t coordinate with the ZPL to hold ZPL-level locks, you could see an * intermediate state. The ioctl level violates this but in pretty benign * ways, e.g. reading the zpl props object.) */ int dsl_pool_hold(const char *name, const void *tag, dsl_pool_t **dp) { spa_t *spa; int error; error = spa_open(name, &spa, tag); if (error == 0) { *dp = spa_get_dsl(spa); dsl_pool_config_enter(*dp, tag); } return (error); } void dsl_pool_rele(dsl_pool_t *dp, const void *tag) { dsl_pool_config_exit(dp, tag); spa_close(dp->dp_spa, tag); } void dsl_pool_config_enter(dsl_pool_t *dp, const void *tag) { /* * We use a "reentrant" reader-writer lock, but not reentrantly. * * The rrwlock can (with the track_all flag) track all reading threads, * which is very useful for debugging which code path failed to release * the lock, and for verifying that the *current* thread does hold * the lock. * * (Unlike a rwlock, which knows that N threads hold it for * read, but not *which* threads, so rw_held(RW_READER) returns TRUE * if any thread holds it for read, even if this thread doesn't). */ ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER)); rrw_enter(&dp->dp_config_rwlock, RW_READER, tag); } void dsl_pool_config_enter_prio(dsl_pool_t *dp, const void *tag) { ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER)); rrw_enter_read_prio(&dp->dp_config_rwlock, tag); } void dsl_pool_config_exit(dsl_pool_t *dp, const void *tag) { rrw_exit(&dp->dp_config_rwlock, tag); } boolean_t dsl_pool_config_held(dsl_pool_t *dp) { return (RRW_LOCK_HELD(&dp->dp_config_rwlock)); } boolean_t dsl_pool_config_held_writer(dsl_pool_t *dp) { return (RRW_WRITE_HELD(&dp->dp_config_rwlock)); } EXPORT_SYMBOL(dsl_pool_config_enter); EXPORT_SYMBOL(dsl_pool_config_exit); /* zfs_dirty_data_max_percent only applied at module load in arc_init(). */ ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_percent, UINT, ZMOD_RD, "Max percent of RAM allowed to be dirty"); /* zfs_dirty_data_max_max_percent only applied at module load in arc_init(). */ ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max_percent, UINT, ZMOD_RD, "zfs_dirty_data_max upper bound as % of RAM"); ZFS_MODULE_PARAM(zfs, zfs_, delay_min_dirty_percent, UINT, ZMOD_RW, "Transaction delay threshold"); ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max, U64, ZMOD_RW, "Determines the dirty space limit"); ZFS_MODULE_PARAM(zfs, zfs_, wrlog_data_max, U64, ZMOD_RW, "The size limit of write-transaction zil log data"); /* zfs_dirty_data_max_max only applied at module load in arc_init(). */ ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max, U64, ZMOD_RD, "zfs_dirty_data_max upper bound in bytes"); ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_sync_percent, UINT, ZMOD_RW, "Dirty data txg sync threshold as a percentage of zfs_dirty_data_max"); ZFS_MODULE_PARAM(zfs, zfs_, delay_scale, U64, ZMOD_RW, "How quickly delay approaches infinity"); ZFS_MODULE_PARAM(zfs, zfs_, sync_taskq_batch_pct, INT, ZMOD_RW, "Max percent of CPUs that are used to sync dirty data"); ZFS_MODULE_PARAM(zfs_zil, zfs_zil_, clean_taskq_nthr_pct, INT, ZMOD_RW, "Max percent of CPUs that are used per dp_sync_taskq"); ZFS_MODULE_PARAM(zfs_zil, zfs_zil_, clean_taskq_minalloc, INT, ZMOD_RW, "Number of taskq entries that are pre-populated"); ZFS_MODULE_PARAM(zfs_zil, zfs_zil_, clean_taskq_maxalloc, INT, ZMOD_RW, "Max number of taskq entries that are cached");