/* * CDDL HEADER START * * This file and its contents are supplied under the terms of the * Common Development and Distribution License ("CDDL"), version 1.0. * You may only use this file in accordance with the terms of version * 1.0 of the CDDL. * * A full copy of the text of the CDDL should have accompanied this * source. A copy of the CDDL is also available via the Internet at * http://www.illumos.org/license/CDDL. * * CDDL HEADER END */ /* * Copyright (c) 2014, 2017 by Delphix. All rights reserved. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * An indirect vdev corresponds to a vdev that has been removed. Since * we cannot rewrite block pointers of snapshots, etc., we keep a * mapping from old location on the removed device to the new location * on another device in the pool and use this mapping whenever we need * to access the DVA. Unfortunately, this mapping did not respect * logical block boundaries when it was first created, and so a DVA on * this indirect vdev may be "split" into multiple sections that each * map to a different location. As a consequence, not all DVAs can be * translated to an equivalent new DVA. Instead we must provide a * "vdev_remap" operation that executes a callback on each contiguous * segment of the new location. This function is used in multiple ways: * * - i/os to this vdev use the callback to determine where the * data is now located, and issue child i/os for each segment's new * location. * * - frees and claims to this vdev use the callback to free or claim * each mapped segment. (Note that we don't actually need to claim * log blocks on indirect vdevs, because we don't allocate to * removing vdevs. However, zdb uses zio_claim() for its leak * detection.) */ /* * "Big theory statement" for how we mark blocks obsolete. * * When a block on an indirect vdev is freed or remapped, a section of * that vdev's mapping may no longer be referenced (aka "obsolete"). We * keep track of how much of each mapping entry is obsolete. When * an entry becomes completely obsolete, we can remove it, thus reducing * the memory used by the mapping. The complete picture of obsolescence * is given by the following data structures, described below: * - the entry-specific obsolete count * - the vdev-specific obsolete spacemap * - the pool-specific obsolete bpobj * * == On disk data structures used == * * We track the obsolete space for the pool using several objects. Each * of these objects is created on demand and freed when no longer * needed, and is assumed to be empty if it does not exist. * SPA_FEATURE_OBSOLETE_COUNTS includes the count of these objects. * * - Each vic_mapping_object (associated with an indirect vdev) can * have a vimp_counts_object. This is an array of uint32_t's * with the same number of entries as the vic_mapping_object. When * the mapping is condensed, entries from the vic_obsolete_sm_object * (see below) are folded into the counts. Therefore, each * obsolete_counts entry tells us the number of bytes in the * corresponding mapping entry that were not referenced when the * mapping was last condensed. * * - Each indirect or removing vdev can have a vic_obsolete_sm_object. * This is a space map containing an alloc entry for every DVA that * has been obsoleted since the last time this indirect vdev was * condensed. We use this object in order to improve performance * when marking a DVA as obsolete. Instead of modifying an arbitrary * offset of the vimp_counts_object, we only need to append an entry * to the end of this object. When a DVA becomes obsolete, it is * added to the obsolete space map. This happens when the DVA is * freed, remapped and not referenced by a snapshot, or the last * snapshot referencing it is destroyed. * * - Each dataset can have a ds_remap_deadlist object. This is a * deadlist object containing all blocks that were remapped in this * dataset but referenced in a previous snapshot. Blocks can *only* * appear on this list if they were remapped (dsl_dataset_block_remapped); * blocks that were killed in a head dataset are put on the normal * ds_deadlist and marked obsolete when they are freed. * * - The pool can have a dp_obsolete_bpobj. This is a list of blocks * in the pool that need to be marked obsolete. When a snapshot is * destroyed, we move some of the ds_remap_deadlist to the obsolete * bpobj (see dsl_destroy_snapshot_handle_remaps()). We then * asynchronously process the obsolete bpobj, moving its entries to * the specific vdevs' obsolete space maps. * * == Summary of how we mark blocks as obsolete == * * - When freeing a block: if any DVA is on an indirect vdev, append to * vic_obsolete_sm_object. * - When remapping a block, add dva to ds_remap_deadlist (if prev snap * references; otherwise append to vic_obsolete_sm_object). * - When freeing a snapshot: move parts of ds_remap_deadlist to * dp_obsolete_bpobj (same algorithm as ds_deadlist). * - When syncing the spa: process dp_obsolete_bpobj, moving ranges to * individual vdev's vic_obsolete_sm_object. */ /* * "Big theory statement" for how we condense indirect vdevs. * * Condensing an indirect vdev's mapping is the process of determining * the precise counts of obsolete space for each mapping entry (by * integrating the obsolete spacemap into the obsolete counts) and * writing out a new mapping that contains only referenced entries. * * We condense a vdev when we expect the mapping to shrink (see * vdev_indirect_should_condense()), but only perform one condense at a * time to limit the memory usage. In addition, we use a separate * open-context thread (spa_condense_indirect_thread) to incrementally * create the new mapping object in a way that minimizes the impact on * the rest of the system. * * == Generating a new mapping == * * To generate a new mapping, we follow these steps: * * 1. Save the old obsolete space map and create a new mapping object * (see spa_condense_indirect_start_sync()). This initializes the * spa_condensing_indirect_phys with the "previous obsolete space map", * which is now read only. Newly obsolete DVAs will be added to a * new (initially empty) obsolete space map, and will not be * considered as part of this condense operation. * * 2. Construct in memory the precise counts of obsolete space for each * mapping entry, by incorporating the obsolete space map into the * counts. (See vdev_indirect_mapping_load_obsolete_{counts,spacemap}().) * * 3. Iterate through each mapping entry, writing to the new mapping any * entries that are not completely obsolete (i.e. which don't have * obsolete count == mapping length). (See * spa_condense_indirect_generate_new_mapping().) * * 4. Destroy the old mapping object and switch over to the new one * (spa_condense_indirect_complete_sync). * * == Restarting from failure == * * To restart the condense when we import/open the pool, we must start * at the 2nd step above: reconstruct the precise counts in memory, * based on the space map + counts. Then in the 3rd step, we start * iterating where we left off: at vimp_max_offset of the new mapping * object. */ boolean_t zfs_condense_indirect_vdevs_enable = B_TRUE; /* * Condense if at least this percent of the bytes in the mapping is * obsolete. With the default of 25%, the amount of space mapped * will be reduced to 1% of its original size after at most 16 * condenses. Higher values will condense less often (causing less * i/o); lower values will reduce the mapping size more quickly. */ int zfs_indirect_condense_obsolete_pct = 25; /* * Condense if the obsolete space map takes up more than this amount of * space on disk (logically). This limits the amount of disk space * consumed by the obsolete space map; the default of 1GB is small enough * that we typically don't mind "wasting" it. */ uint64_t zfs_condense_max_obsolete_bytes = 1024 * 1024 * 1024; /* * Don't bother condensing if the mapping uses less than this amount of * memory. The default of 128KB is considered a "trivial" amount of * memory and not worth reducing. */ unsigned long zfs_condense_min_mapping_bytes = 128 * 1024; /* * This is used by the test suite so that it can ensure that certain * actions happen while in the middle of a condense (which might otherwise * complete too quickly). If used to reduce the performance impact of * condensing in production, a maximum value of 1 should be sufficient. */ int zfs_condense_indirect_commit_entry_delay_ms = 0; /* * If an indirect split block contains more than this many possible unique * combinations when being reconstructed, consider it too computationally * expensive to check them all. Instead, try at most 100 randomly-selected * combinations each time the block is accessed. This allows all segment * copies to participate fairly in the reconstruction when all combinations * cannot be checked and prevents repeated use of one bad copy. */ int zfs_reconstruct_indirect_combinations_max = 100; /* * The indirect_child_t represents the vdev that we will read from, when we * need to read all copies of the data (e.g. for scrub or reconstruction). * For plain (non-mirror) top-level vdevs (i.e. is_vdev is not a mirror), * ic_vdev is the same as is_vdev. However, for mirror top-level vdevs, * ic_vdev is a child of the mirror. */ typedef struct indirect_child { abd_t *ic_data; vdev_t *ic_vdev; /* * ic_duplicate is -1 when the ic_data contents are unique, when it * is determined to be a duplicate it refers to the primary child. */ int ic_duplicate; } indirect_child_t; /* * The indirect_split_t represents one mapped segment of an i/o to the * indirect vdev. For non-split (contiguously-mapped) blocks, there will be * only one indirect_split_t, with is_split_offset==0 and is_size==io_size. * For split blocks, there will be several of these. */ typedef struct indirect_split { list_node_t is_node; /* link on iv_splits */ /* * is_split_offset is the offset into the i/o. * This is the sum of the previous splits' is_size's. */ uint64_t is_split_offset; vdev_t *is_vdev; /* top-level vdev */ uint64_t is_target_offset; /* offset on is_vdev */ uint64_t is_size; int is_children; /* number of entries in is_child[] */ /* * is_good_child is the child that we are currently using to * attempt reconstruction. */ int is_good_child; indirect_child_t is_child[1]; /* variable-length */ } indirect_split_t; /* * The indirect_vsd_t is associated with each i/o to the indirect vdev. * It is the "Vdev-Specific Data" in the zio_t's io_vsd. */ typedef struct indirect_vsd { boolean_t iv_split_block; boolean_t iv_reconstruct; list_t iv_splits; /* list of indirect_split_t's */ } indirect_vsd_t; static void vdev_indirect_map_free(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; indirect_split_t *is; while ((is = list_head(&iv->iv_splits)) != NULL) { for (int c = 0; c < is->is_children; c++) { indirect_child_t *ic = &is->is_child[c]; if (ic->ic_data != NULL) abd_free(ic->ic_data); } list_remove(&iv->iv_splits, is); kmem_free(is, offsetof(indirect_split_t, is_child[is->is_children])); } kmem_free(iv, sizeof (*iv)); } static const zio_vsd_ops_t vdev_indirect_vsd_ops = { vdev_indirect_map_free, zio_vsd_default_cksum_report }; /* * Mark the given offset and size as being obsolete in the given txg. */ void vdev_indirect_mark_obsolete(vdev_t *vd, uint64_t offset, uint64_t size, uint64_t txg) { spa_t *spa = vd->vdev_spa; ASSERT3U(spa_syncing_txg(spa), ==, txg); ASSERT3U(vd->vdev_indirect_config.vic_mapping_object, !=, 0); ASSERT(vd->vdev_removing || vd->vdev_ops == &vdev_indirect_ops); ASSERT(size > 0); VERIFY(vdev_indirect_mapping_entry_for_offset( vd->vdev_indirect_mapping, offset) != NULL); if (spa_feature_is_enabled(spa, SPA_FEATURE_OBSOLETE_COUNTS)) { mutex_enter(&vd->vdev_obsolete_lock); range_tree_add(vd->vdev_obsolete_segments, offset, size); mutex_exit(&vd->vdev_obsolete_lock); vdev_dirty(vd, 0, NULL, txg); } } /* * Mark the DVA vdev_id:offset:size as being obsolete in the given tx. This * wrapper is provided because the DMU does not know about vdev_t's and * cannot directly call vdev_indirect_mark_obsolete. */ void spa_vdev_indirect_mark_obsolete(spa_t *spa, uint64_t vdev_id, uint64_t offset, uint64_t size, dmu_tx_t *tx) { vdev_t *vd = vdev_lookup_top(spa, vdev_id); ASSERT(dmu_tx_is_syncing(tx)); /* The DMU can only remap indirect vdevs. */ ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops); vdev_indirect_mark_obsolete(vd, offset, size, dmu_tx_get_txg(tx)); } static spa_condensing_indirect_t * spa_condensing_indirect_create(spa_t *spa) { spa_condensing_indirect_phys_t *scip = &spa->spa_condensing_indirect_phys; spa_condensing_indirect_t *sci = kmem_zalloc(sizeof (*sci), KM_SLEEP); objset_t *mos = spa->spa_meta_objset; for (int i = 0; i < TXG_SIZE; i++) { list_create(&sci->sci_new_mapping_entries[i], sizeof (vdev_indirect_mapping_entry_t), offsetof(vdev_indirect_mapping_entry_t, vime_node)); } sci->sci_new_mapping = vdev_indirect_mapping_open(mos, scip->scip_next_mapping_object); return (sci); } static void spa_condensing_indirect_destroy(spa_condensing_indirect_t *sci) { for (int i = 0; i < TXG_SIZE; i++) list_destroy(&sci->sci_new_mapping_entries[i]); if (sci->sci_new_mapping != NULL) vdev_indirect_mapping_close(sci->sci_new_mapping); kmem_free(sci, sizeof (*sci)); } boolean_t vdev_indirect_should_condense(vdev_t *vd) { vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping; spa_t *spa = vd->vdev_spa; ASSERT(dsl_pool_sync_context(spa->spa_dsl_pool)); if (!zfs_condense_indirect_vdevs_enable) return (B_FALSE); /* * We can only condense one indirect vdev at a time. */ if (spa->spa_condensing_indirect != NULL) return (B_FALSE); if (spa_shutting_down(spa)) return (B_FALSE); /* * The mapping object size must not change while we are * condensing, so we can only condense indirect vdevs * (not vdevs that are still in the middle of being removed). */ if (vd->vdev_ops != &vdev_indirect_ops) return (B_FALSE); /* * If nothing new has been marked obsolete, there is no * point in condensing. */ if (vd->vdev_obsolete_sm == NULL) { ASSERT0(vdev_obsolete_sm_object(vd)); return (B_FALSE); } ASSERT(vd->vdev_obsolete_sm != NULL); ASSERT3U(vdev_obsolete_sm_object(vd), ==, space_map_object(vd->vdev_obsolete_sm)); uint64_t bytes_mapped = vdev_indirect_mapping_bytes_mapped(vim); uint64_t bytes_obsolete = space_map_allocated(vd->vdev_obsolete_sm); uint64_t mapping_size = vdev_indirect_mapping_size(vim); uint64_t obsolete_sm_size = space_map_length(vd->vdev_obsolete_sm); ASSERT3U(bytes_obsolete, <=, bytes_mapped); /* * If a high percentage of the bytes that are mapped have become * obsolete, condense (unless the mapping is already small enough). * This has a good chance of reducing the amount of memory used * by the mapping. */ if (bytes_obsolete * 100 / bytes_mapped >= zfs_indirect_condense_obsolete_pct && mapping_size > zfs_condense_min_mapping_bytes) { zfs_dbgmsg("should condense vdev %llu because obsolete " "spacemap covers %d%% of %lluMB mapping", (u_longlong_t)vd->vdev_id, (int)(bytes_obsolete * 100 / bytes_mapped), (u_longlong_t)bytes_mapped / 1024 / 1024); return (B_TRUE); } /* * If the obsolete space map takes up too much space on disk, * condense in order to free up this disk space. */ if (obsolete_sm_size >= zfs_condense_max_obsolete_bytes) { zfs_dbgmsg("should condense vdev %llu because obsolete sm " "length %lluMB >= max size %lluMB", (u_longlong_t)vd->vdev_id, (u_longlong_t)obsolete_sm_size / 1024 / 1024, (u_longlong_t)zfs_condense_max_obsolete_bytes / 1024 / 1024); return (B_TRUE); } return (B_FALSE); } /* * This sync task completes (finishes) a condense, deleting the old * mapping and replacing it with the new one. */ static void spa_condense_indirect_complete_sync(void *arg, dmu_tx_t *tx) { spa_condensing_indirect_t *sci = arg; spa_t *spa = dmu_tx_pool(tx)->dp_spa; spa_condensing_indirect_phys_t *scip = &spa->spa_condensing_indirect_phys; vdev_t *vd = vdev_lookup_top(spa, scip->scip_vdev); vdev_indirect_config_t *vic = &vd->vdev_indirect_config; objset_t *mos = spa->spa_meta_objset; vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping; uint64_t old_count = vdev_indirect_mapping_num_entries(old_mapping); uint64_t new_count = vdev_indirect_mapping_num_entries(sci->sci_new_mapping); ASSERT(dmu_tx_is_syncing(tx)); ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops); ASSERT3P(sci, ==, spa->spa_condensing_indirect); for (int i = 0; i < TXG_SIZE; i++) { ASSERT(list_is_empty(&sci->sci_new_mapping_entries[i])); } ASSERT(vic->vic_mapping_object != 0); ASSERT3U(vd->vdev_id, ==, scip->scip_vdev); ASSERT(scip->scip_next_mapping_object != 0); ASSERT(scip->scip_prev_obsolete_sm_object != 0); /* * Reset vdev_indirect_mapping to refer to the new object. */ rw_enter(&vd->vdev_indirect_rwlock, RW_WRITER); vdev_indirect_mapping_close(vd->vdev_indirect_mapping); vd->vdev_indirect_mapping = sci->sci_new_mapping; rw_exit(&vd->vdev_indirect_rwlock); sci->sci_new_mapping = NULL; vdev_indirect_mapping_free(mos, vic->vic_mapping_object, tx); vic->vic_mapping_object = scip->scip_next_mapping_object; scip->scip_next_mapping_object = 0; space_map_free_obj(mos, scip->scip_prev_obsolete_sm_object, tx); spa_feature_decr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx); scip->scip_prev_obsolete_sm_object = 0; scip->scip_vdev = 0; VERIFY0(zap_remove(mos, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONDENSING_INDIRECT, tx)); spa_condensing_indirect_destroy(spa->spa_condensing_indirect); spa->spa_condensing_indirect = NULL; zfs_dbgmsg("finished condense of vdev %llu in txg %llu: " "new mapping object %llu has %llu entries " "(was %llu entries)", vd->vdev_id, dmu_tx_get_txg(tx), vic->vic_mapping_object, new_count, old_count); vdev_config_dirty(spa->spa_root_vdev); } /* * This sync task appends entries to the new mapping object. */ static void spa_condense_indirect_commit_sync(void *arg, dmu_tx_t *tx) { spa_condensing_indirect_t *sci = arg; uint64_t txg = dmu_tx_get_txg(tx); ASSERTV(spa_t *spa = dmu_tx_pool(tx)->dp_spa); ASSERT(dmu_tx_is_syncing(tx)); ASSERT3P(sci, ==, spa->spa_condensing_indirect); vdev_indirect_mapping_add_entries(sci->sci_new_mapping, &sci->sci_new_mapping_entries[txg & TXG_MASK], tx); ASSERT(list_is_empty(&sci->sci_new_mapping_entries[txg & TXG_MASK])); } /* * Open-context function to add one entry to the new mapping. The new * entry will be remembered and written from syncing context. */ static void spa_condense_indirect_commit_entry(spa_t *spa, vdev_indirect_mapping_entry_phys_t *vimep, uint32_t count) { spa_condensing_indirect_t *sci = spa->spa_condensing_indirect; ASSERT3U(count, <, DVA_GET_ASIZE(&vimep->vimep_dst)); dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir); dmu_tx_hold_space(tx, sizeof (*vimep) + sizeof (count)); VERIFY0(dmu_tx_assign(tx, TXG_WAIT)); int txgoff = dmu_tx_get_txg(tx) & TXG_MASK; /* * If we are the first entry committed this txg, kick off the sync * task to write to the MOS on our behalf. */ if (list_is_empty(&sci->sci_new_mapping_entries[txgoff])) { dsl_sync_task_nowait(dmu_tx_pool(tx), spa_condense_indirect_commit_sync, sci, 0, ZFS_SPACE_CHECK_NONE, tx); } vdev_indirect_mapping_entry_t *vime = kmem_alloc(sizeof (*vime), KM_SLEEP); vime->vime_mapping = *vimep; vime->vime_obsolete_count = count; list_insert_tail(&sci->sci_new_mapping_entries[txgoff], vime); dmu_tx_commit(tx); } static void spa_condense_indirect_generate_new_mapping(vdev_t *vd, uint32_t *obsolete_counts, uint64_t start_index, zthr_t *zthr) { spa_t *spa = vd->vdev_spa; uint64_t mapi = start_index; vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping; uint64_t old_num_entries = vdev_indirect_mapping_num_entries(old_mapping); ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops); ASSERT3U(vd->vdev_id, ==, spa->spa_condensing_indirect_phys.scip_vdev); zfs_dbgmsg("starting condense of vdev %llu from index %llu", (u_longlong_t)vd->vdev_id, (u_longlong_t)mapi); while (mapi < old_num_entries) { if (zthr_iscancelled(zthr)) { zfs_dbgmsg("pausing condense of vdev %llu " "at index %llu", (u_longlong_t)vd->vdev_id, (u_longlong_t)mapi); break; } vdev_indirect_mapping_entry_phys_t *entry = &old_mapping->vim_entries[mapi]; uint64_t entry_size = DVA_GET_ASIZE(&entry->vimep_dst); ASSERT3U(obsolete_counts[mapi], <=, entry_size); if (obsolete_counts[mapi] < entry_size) { spa_condense_indirect_commit_entry(spa, entry, obsolete_counts[mapi]); /* * This delay may be requested for testing, debugging, * or performance reasons. */ hrtime_t now = gethrtime(); hrtime_t sleep_until = now + MSEC2NSEC( zfs_condense_indirect_commit_entry_delay_ms); zfs_sleep_until(sleep_until); } mapi++; } } /* ARGSUSED */ static boolean_t spa_condense_indirect_thread_check(void *arg, zthr_t *zthr) { spa_t *spa = arg; return (spa->spa_condensing_indirect != NULL); } /* ARGSUSED */ static int spa_condense_indirect_thread(void *arg, zthr_t *zthr) { spa_t *spa = arg; vdev_t *vd; ASSERT3P(spa->spa_condensing_indirect, !=, NULL); spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER); vd = vdev_lookup_top(spa, spa->spa_condensing_indirect_phys.scip_vdev); ASSERT3P(vd, !=, NULL); spa_config_exit(spa, SCL_VDEV, FTAG); spa_condensing_indirect_t *sci = spa->spa_condensing_indirect; spa_condensing_indirect_phys_t *scip = &spa->spa_condensing_indirect_phys; uint32_t *counts; uint64_t start_index; vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping; space_map_t *prev_obsolete_sm = NULL; ASSERT3U(vd->vdev_id, ==, scip->scip_vdev); ASSERT(scip->scip_next_mapping_object != 0); ASSERT(scip->scip_prev_obsolete_sm_object != 0); ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops); for (int i = 0; i < TXG_SIZE; i++) { /* * The list must start out empty in order for the * _commit_sync() sync task to be properly registered * on the first call to _commit_entry(); so it's wise * to double check and ensure we actually are starting * with empty lists. */ ASSERT(list_is_empty(&sci->sci_new_mapping_entries[i])); } VERIFY0(space_map_open(&prev_obsolete_sm, spa->spa_meta_objset, scip->scip_prev_obsolete_sm_object, 0, vd->vdev_asize, 0)); space_map_update(prev_obsolete_sm); counts = vdev_indirect_mapping_load_obsolete_counts(old_mapping); if (prev_obsolete_sm != NULL) { vdev_indirect_mapping_load_obsolete_spacemap(old_mapping, counts, prev_obsolete_sm); } space_map_close(prev_obsolete_sm); /* * Generate new mapping. Determine what index to continue from * based on the max offset that we've already written in the * new mapping. */ uint64_t max_offset = vdev_indirect_mapping_max_offset(sci->sci_new_mapping); if (max_offset == 0) { /* We haven't written anything to the new mapping yet. */ start_index = 0; } else { /* * Pick up from where we left off. _entry_for_offset() * returns a pointer into the vim_entries array. If * max_offset is greater than any of the mappings * contained in the table NULL will be returned and * that indicates we've exhausted our iteration of the * old_mapping. */ vdev_indirect_mapping_entry_phys_t *entry = vdev_indirect_mapping_entry_for_offset_or_next(old_mapping, max_offset); if (entry == NULL) { /* * We've already written the whole new mapping. * This special value will cause us to skip the * generate_new_mapping step and just do the sync * task to complete the condense. */ start_index = UINT64_MAX; } else { start_index = entry - old_mapping->vim_entries; ASSERT3U(start_index, <, vdev_indirect_mapping_num_entries(old_mapping)); } } spa_condense_indirect_generate_new_mapping(vd, counts, start_index, zthr); vdev_indirect_mapping_free_obsolete_counts(old_mapping, counts); /* * If the zthr has received a cancellation signal while running * in generate_new_mapping() or at any point after that, then bail * early. We don't want to complete the condense if the spa is * shutting down. */ if (zthr_iscancelled(zthr)) return (0); VERIFY0(dsl_sync_task(spa_name(spa), NULL, spa_condense_indirect_complete_sync, sci, 0, ZFS_SPACE_CHECK_NONE)); return (0); } /* * Sync task to begin the condensing process. */ void spa_condense_indirect_start_sync(vdev_t *vd, dmu_tx_t *tx) { spa_t *spa = vd->vdev_spa; spa_condensing_indirect_phys_t *scip = &spa->spa_condensing_indirect_phys; ASSERT0(scip->scip_next_mapping_object); ASSERT0(scip->scip_prev_obsolete_sm_object); ASSERT0(scip->scip_vdev); ASSERT(dmu_tx_is_syncing(tx)); ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops); ASSERT(spa_feature_is_active(spa, SPA_FEATURE_OBSOLETE_COUNTS)); ASSERT(vdev_indirect_mapping_num_entries(vd->vdev_indirect_mapping)); uint64_t obsolete_sm_obj = vdev_obsolete_sm_object(vd); ASSERT(obsolete_sm_obj != 0); scip->scip_vdev = vd->vdev_id; scip->scip_next_mapping_object = vdev_indirect_mapping_alloc(spa->spa_meta_objset, tx); scip->scip_prev_obsolete_sm_object = obsolete_sm_obj; /* * We don't need to allocate a new space map object, since * vdev_indirect_sync_obsolete will allocate one when needed. */ space_map_close(vd->vdev_obsolete_sm); vd->vdev_obsolete_sm = NULL; VERIFY0(zap_remove(spa->spa_meta_objset, vd->vdev_top_zap, VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM, tx)); VERIFY0(zap_add(spa->spa_dsl_pool->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONDENSING_INDIRECT, sizeof (uint64_t), sizeof (*scip) / sizeof (uint64_t), scip, tx)); ASSERT3P(spa->spa_condensing_indirect, ==, NULL); spa->spa_condensing_indirect = spa_condensing_indirect_create(spa); zfs_dbgmsg("starting condense of vdev %llu in txg %llu: " "posm=%llu nm=%llu", vd->vdev_id, dmu_tx_get_txg(tx), (u_longlong_t)scip->scip_prev_obsolete_sm_object, (u_longlong_t)scip->scip_next_mapping_object); zthr_wakeup(spa->spa_condense_zthr); } /* * Sync to the given vdev's obsolete space map any segments that are no longer * referenced as of the given txg. * * If the obsolete space map doesn't exist yet, create and open it. */ void vdev_indirect_sync_obsolete(vdev_t *vd, dmu_tx_t *tx) { spa_t *spa = vd->vdev_spa; ASSERTV(vdev_indirect_config_t *vic = &vd->vdev_indirect_config); ASSERT3U(vic->vic_mapping_object, !=, 0); ASSERT(range_tree_space(vd->vdev_obsolete_segments) > 0); ASSERT(vd->vdev_removing || vd->vdev_ops == &vdev_indirect_ops); ASSERT(spa_feature_is_enabled(spa, SPA_FEATURE_OBSOLETE_COUNTS)); if (vdev_obsolete_sm_object(vd) == 0) { uint64_t obsolete_sm_object = space_map_alloc(spa->spa_meta_objset, tx); ASSERT(vd->vdev_top_zap != 0); VERIFY0(zap_add(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap, VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM, sizeof (obsolete_sm_object), 1, &obsolete_sm_object, tx)); ASSERT3U(vdev_obsolete_sm_object(vd), !=, 0); spa_feature_incr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx); VERIFY0(space_map_open(&vd->vdev_obsolete_sm, spa->spa_meta_objset, obsolete_sm_object, 0, vd->vdev_asize, 0)); space_map_update(vd->vdev_obsolete_sm); } ASSERT(vd->vdev_obsolete_sm != NULL); ASSERT3U(vdev_obsolete_sm_object(vd), ==, space_map_object(vd->vdev_obsolete_sm)); space_map_write(vd->vdev_obsolete_sm, vd->vdev_obsolete_segments, SM_ALLOC, tx); space_map_update(vd->vdev_obsolete_sm); range_tree_vacate(vd->vdev_obsolete_segments, NULL, NULL); } int spa_condense_init(spa_t *spa) { int error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONDENSING_INDIRECT, sizeof (uint64_t), sizeof (spa->spa_condensing_indirect_phys) / sizeof (uint64_t), &spa->spa_condensing_indirect_phys); if (error == 0) { if (spa_writeable(spa)) { spa->spa_condensing_indirect = spa_condensing_indirect_create(spa); } return (0); } else if (error == ENOENT) { return (0); } else { return (error); } } void spa_condense_fini(spa_t *spa) { if (spa->spa_condensing_indirect != NULL) { spa_condensing_indirect_destroy(spa->spa_condensing_indirect); spa->spa_condensing_indirect = NULL; } } void spa_start_indirect_condensing_thread(spa_t *spa) { ASSERT3P(spa->spa_condense_zthr, ==, NULL); spa->spa_condense_zthr = zthr_create(spa_condense_indirect_thread_check, spa_condense_indirect_thread, spa); } /* * Gets the obsolete spacemap object from the vdev's ZAP. * Returns the spacemap object, or 0 if it wasn't in the ZAP or the ZAP doesn't * exist yet. */ int vdev_obsolete_sm_object(vdev_t *vd) { ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER)); if (vd->vdev_top_zap == 0) { return (0); } uint64_t sm_obj = 0; int err; err = zap_lookup(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap, VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM, sizeof (sm_obj), 1, &sm_obj); ASSERT(err == 0 || err == ENOENT); return (sm_obj); } boolean_t vdev_obsolete_counts_are_precise(vdev_t *vd) { ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER)); if (vd->vdev_top_zap == 0) { return (B_FALSE); } uint64_t val = 0; int err; err = zap_lookup(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap, VDEV_TOP_ZAP_OBSOLETE_COUNTS_ARE_PRECISE, sizeof (val), 1, &val); ASSERT(err == 0 || err == ENOENT); return (val != 0); } /* ARGSUSED */ static void vdev_indirect_close(vdev_t *vd) { } /* ARGSUSED */ static int vdev_indirect_open(vdev_t *vd, uint64_t *psize, uint64_t *max_psize, uint64_t *ashift) { *psize = *max_psize = vd->vdev_asize + VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE; *ashift = vd->vdev_ashift; return (0); } typedef struct remap_segment { vdev_t *rs_vd; uint64_t rs_offset; uint64_t rs_asize; uint64_t rs_split_offset; list_node_t rs_node; } remap_segment_t; remap_segment_t * rs_alloc(vdev_t *vd, uint64_t offset, uint64_t asize, uint64_t split_offset) { remap_segment_t *rs = kmem_alloc(sizeof (remap_segment_t), KM_SLEEP); rs->rs_vd = vd; rs->rs_offset = offset; rs->rs_asize = asize; rs->rs_split_offset = split_offset; return (rs); } /* * Given an indirect vdev and an extent on that vdev, it duplicates the * physical entries of the indirect mapping that correspond to the extent * to a new array and returns a pointer to it. In addition, copied_entries * is populated with the number of mapping entries that were duplicated. * * Note that the function assumes that the caller holds vdev_indirect_rwlock. * This ensures that the mapping won't change due to condensing as we * copy over its contents. * * Finally, since we are doing an allocation, it is up to the caller to * free the array allocated in this function. */ vdev_indirect_mapping_entry_phys_t * vdev_indirect_mapping_duplicate_adjacent_entries(vdev_t *vd, uint64_t offset, uint64_t asize, uint64_t *copied_entries) { vdev_indirect_mapping_entry_phys_t *duplicate_mappings = NULL; vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping; uint64_t entries = 0; ASSERT(RW_READ_HELD(&vd->vdev_indirect_rwlock)); vdev_indirect_mapping_entry_phys_t *first_mapping = vdev_indirect_mapping_entry_for_offset(vim, offset); ASSERT3P(first_mapping, !=, NULL); vdev_indirect_mapping_entry_phys_t *m = first_mapping; while (asize > 0) { uint64_t size = DVA_GET_ASIZE(&m->vimep_dst); ASSERT3U(offset, >=, DVA_MAPPING_GET_SRC_OFFSET(m)); ASSERT3U(offset, <, DVA_MAPPING_GET_SRC_OFFSET(m) + size); uint64_t inner_offset = offset - DVA_MAPPING_GET_SRC_OFFSET(m); uint64_t inner_size = MIN(asize, size - inner_offset); offset += inner_size; asize -= inner_size; entries++; m++; } size_t copy_length = entries * sizeof (*first_mapping); duplicate_mappings = kmem_alloc(copy_length, KM_SLEEP); bcopy(first_mapping, duplicate_mappings, copy_length); *copied_entries = entries; return (duplicate_mappings); } /* * Goes through the relevant indirect mappings until it hits a concrete vdev * and issues the callback. On the way to the concrete vdev, if any other * indirect vdevs are encountered, then the callback will also be called on * each of those indirect vdevs. For example, if the segment is mapped to * segment A on indirect vdev 1, and then segment A on indirect vdev 1 is * mapped to segment B on concrete vdev 2, then the callback will be called on * both vdev 1 and vdev 2. * * While the callback passed to vdev_indirect_remap() is called on every vdev * the function encounters, certain callbacks only care about concrete vdevs. * These types of callbacks should return immediately and explicitly when they * are called on an indirect vdev. * * Because there is a possibility that a DVA section in the indirect device * has been split into multiple sections in our mapping, we keep track * of the relevant contiguous segments of the new location (remap_segment_t) * in a stack. This way we can call the callback for each of the new sections * created by a single section of the indirect device. Note though, that in * this scenario the callbacks in each split block won't occur in-order in * terms of offset, so callers should not make any assumptions about that. * * For callbacks that don't handle split blocks and immediately return when * they encounter them (as is the case for remap_blkptr_cb), the caller can * assume that its callback will be applied from the first indirect vdev * encountered to the last one and then the concrete vdev, in that order. */ static void vdev_indirect_remap(vdev_t *vd, uint64_t offset, uint64_t asize, void (*func)(uint64_t, vdev_t *, uint64_t, uint64_t, void *), void *arg) { list_t stack; spa_t *spa = vd->vdev_spa; list_create(&stack, sizeof (remap_segment_t), offsetof(remap_segment_t, rs_node)); for (remap_segment_t *rs = rs_alloc(vd, offset, asize, 0); rs != NULL; rs = list_remove_head(&stack)) { vdev_t *v = rs->rs_vd; uint64_t num_entries = 0; ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0); ASSERT(rs->rs_asize > 0); /* * Note: As this function can be called from open context * (e.g. zio_read()), we need the following rwlock to * prevent the mapping from being changed by condensing. * * So we grab the lock and we make a copy of the entries * that are relevant to the extent that we are working on. * Once that is done, we drop the lock and iterate over * our copy of the mapping. Once we are done with the with * the remap segment and we free it, we also free our copy * of the indirect mapping entries that are relevant to it. * * This way we don't need to wait until the function is * finished with a segment, to condense it. In addition, we * don't need a recursive rwlock for the case that a call to * vdev_indirect_remap() needs to call itself (through the * codepath of its callback) for the same vdev in the middle * of its execution. */ rw_enter(&v->vdev_indirect_rwlock, RW_READER); ASSERT3P(v->vdev_indirect_mapping, !=, NULL); vdev_indirect_mapping_entry_phys_t *mapping = vdev_indirect_mapping_duplicate_adjacent_entries(v, rs->rs_offset, rs->rs_asize, &num_entries); ASSERT3P(mapping, !=, NULL); ASSERT3U(num_entries, >, 0); rw_exit(&v->vdev_indirect_rwlock); for (uint64_t i = 0; i < num_entries; i++) { /* * Note: the vdev_indirect_mapping can not change * while we are running. It only changes while the * removal is in progress, and then only from syncing * context. While a removal is in progress, this * function is only called for frees, which also only * happen from syncing context. */ vdev_indirect_mapping_entry_phys_t *m = &mapping[i]; ASSERT3P(m, !=, NULL); ASSERT3U(rs->rs_asize, >, 0); uint64_t size = DVA_GET_ASIZE(&m->vimep_dst); uint64_t dst_offset = DVA_GET_OFFSET(&m->vimep_dst); uint64_t dst_vdev = DVA_GET_VDEV(&m->vimep_dst); ASSERT3U(rs->rs_offset, >=, DVA_MAPPING_GET_SRC_OFFSET(m)); ASSERT3U(rs->rs_offset, <, DVA_MAPPING_GET_SRC_OFFSET(m) + size); ASSERT3U(dst_vdev, !=, v->vdev_id); uint64_t inner_offset = rs->rs_offset - DVA_MAPPING_GET_SRC_OFFSET(m); uint64_t inner_size = MIN(rs->rs_asize, size - inner_offset); vdev_t *dst_v = vdev_lookup_top(spa, dst_vdev); ASSERT3P(dst_v, !=, NULL); if (dst_v->vdev_ops == &vdev_indirect_ops) { list_insert_head(&stack, rs_alloc(dst_v, dst_offset + inner_offset, inner_size, rs->rs_split_offset)); } if ((zfs_flags & ZFS_DEBUG_INDIRECT_REMAP) && IS_P2ALIGNED(inner_size, 2 * SPA_MINBLOCKSIZE)) { /* * Note: This clause exists only solely for * testing purposes. We use it to ensure that * split blocks work and that the callbacks * using them yield the same result if issued * in reverse order. */ uint64_t inner_half = inner_size / 2; func(rs->rs_split_offset + inner_half, dst_v, dst_offset + inner_offset + inner_half, inner_half, arg); func(rs->rs_split_offset, dst_v, dst_offset + inner_offset, inner_half, arg); } else { func(rs->rs_split_offset, dst_v, dst_offset + inner_offset, inner_size, arg); } rs->rs_offset += inner_size; rs->rs_asize -= inner_size; rs->rs_split_offset += inner_size; } VERIFY0(rs->rs_asize); kmem_free(mapping, num_entries * sizeof (*mapping)); kmem_free(rs, sizeof (remap_segment_t)); } list_destroy(&stack); } static void vdev_indirect_child_io_done(zio_t *zio) { zio_t *pio = zio->io_private; mutex_enter(&pio->io_lock); pio->io_error = zio_worst_error(pio->io_error, zio->io_error); mutex_exit(&pio->io_lock); abd_put(zio->io_abd); } /* * This is a callback for vdev_indirect_remap() which allocates an * indirect_split_t for each split segment and adds it to iv_splits. */ static void vdev_indirect_gather_splits(uint64_t split_offset, vdev_t *vd, uint64_t offset, uint64_t size, void *arg) { zio_t *zio = arg; indirect_vsd_t *iv = zio->io_vsd; ASSERT3P(vd, !=, NULL); if (vd->vdev_ops == &vdev_indirect_ops) return; int n = 1; if (vd->vdev_ops == &vdev_mirror_ops) n = vd->vdev_children; indirect_split_t *is = kmem_zalloc(offsetof(indirect_split_t, is_child[n]), KM_SLEEP); is->is_children = n; is->is_size = size; is->is_split_offset = split_offset; is->is_target_offset = offset; is->is_vdev = vd; /* * Note that we only consider multiple copies of the data for * *mirror* vdevs. We don't for "replacing" or "spare" vdevs, even * though they use the same ops as mirror, because there's only one * "good" copy under the replacing/spare. */ if (vd->vdev_ops == &vdev_mirror_ops) { for (int i = 0; i < n; i++) { is->is_child[i].ic_vdev = vd->vdev_child[i]; } } else { is->is_child[0].ic_vdev = vd; } list_insert_tail(&iv->iv_splits, is); } static void vdev_indirect_read_split_done(zio_t *zio) { indirect_child_t *ic = zio->io_private; if (zio->io_error != 0) { /* * Clear ic_data to indicate that we do not have data for this * child. */ abd_free(ic->ic_data); ic->ic_data = NULL; } } /* * Issue reads for all copies (mirror children) of all splits. */ static void vdev_indirect_read_all(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { for (int i = 0; i < is->is_children; i++) { indirect_child_t *ic = &is->is_child[i]; if (!vdev_readable(ic->ic_vdev)) continue; /* * Note, we may read from a child whose DTL * indicates that the data may not be present here. * While this might result in a few i/os that will * likely return incorrect data, it simplifies the * code since we can treat scrub and resilver * identically. (The incorrect data will be * detected and ignored when we verify the * checksum.) */ ic->ic_data = abd_alloc_sametype(zio->io_abd, is->is_size); ic->ic_duplicate = -1; zio_nowait(zio_vdev_child_io(zio, NULL, ic->ic_vdev, is->is_target_offset, ic->ic_data, is->is_size, zio->io_type, zio->io_priority, 0, vdev_indirect_read_split_done, ic)); } } iv->iv_reconstruct = B_TRUE; } static void vdev_indirect_io_start(zio_t *zio) { ASSERTV(spa_t *spa = zio->io_spa); indirect_vsd_t *iv = kmem_zalloc(sizeof (*iv), KM_SLEEP); list_create(&iv->iv_splits, sizeof (indirect_split_t), offsetof(indirect_split_t, is_node)); zio->io_vsd = iv; zio->io_vsd_ops = &vdev_indirect_vsd_ops; ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0); if (zio->io_type != ZIO_TYPE_READ) { ASSERT3U(zio->io_type, ==, ZIO_TYPE_WRITE); /* * Note: this code can handle other kinds of writes, * but we don't expect them. */ ASSERT((zio->io_flags & (ZIO_FLAG_SELF_HEAL | ZIO_FLAG_RESILVER | ZIO_FLAG_INDUCE_DAMAGE)) != 0); } vdev_indirect_remap(zio->io_vd, zio->io_offset, zio->io_size, vdev_indirect_gather_splits, zio); indirect_split_t *first = list_head(&iv->iv_splits); if (first->is_size == zio->io_size) { /* * This is not a split block; we are pointing to the entire * data, which will checksum the same as the original data. * Pass the BP down so that the child i/o can verify the * checksum, and try a different location if available * (e.g. on a mirror). * * While this special case could be handled the same as the * general (split block) case, doing it this way ensures * that the vast majority of blocks on indirect vdevs * (which are not split) are handled identically to blocks * on non-indirect vdevs. This allows us to be less strict * about performance in the general (but rare) case. */ ASSERT0(first->is_split_offset); ASSERT3P(list_next(&iv->iv_splits, first), ==, NULL); zio_nowait(zio_vdev_child_io(zio, zio->io_bp, first->is_vdev, first->is_target_offset, abd_get_offset(zio->io_abd, 0), zio->io_size, zio->io_type, zio->io_priority, 0, vdev_indirect_child_io_done, zio)); } else { iv->iv_split_block = B_TRUE; if (zio->io_flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER)) { /* * Read all copies. Note that for simplicity, * we don't bother consulting the DTL in the * resilver case. */ vdev_indirect_read_all(zio); } else { /* * Read one copy of each split segment, from the * top-level vdev. Since we don't know the * checksum of each split individually, the child * zio can't ensure that we get the right data. * E.g. if it's a mirror, it will just read from a * random (healthy) leaf vdev. We have to verify * the checksum in vdev_indirect_io_done(). */ for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { zio_nowait(zio_vdev_child_io(zio, NULL, is->is_vdev, is->is_target_offset, abd_get_offset(zio->io_abd, is->is_split_offset), is->is_size, zio->io_type, zio->io_priority, 0, vdev_indirect_child_io_done, zio)); } } } zio_execute(zio); } /* * Report a checksum error for a child. */ static void vdev_indirect_checksum_error(zio_t *zio, indirect_split_t *is, indirect_child_t *ic) { vdev_t *vd = ic->ic_vdev; if (zio->io_flags & ZIO_FLAG_SPECULATIVE) return; mutex_enter(&vd->vdev_stat_lock); vd->vdev_stat.vs_checksum_errors++; mutex_exit(&vd->vdev_stat_lock); zio_bad_cksum_t zbc = {{{ 0 }}}; abd_t *bad_abd = ic->ic_data; abd_t *good_abd = is->is_child[is->is_good_child].ic_data; zfs_ereport_post_checksum(zio->io_spa, vd, NULL, zio, is->is_target_offset, is->is_size, good_abd, bad_abd, &zbc); } /* * Issue repair i/os for any incorrect copies. We do this by comparing * each split segment's correct data (is_good_child's ic_data) with each * other copy of the data. If they differ, then we overwrite the bad data * with the good copy. Note that we do this without regard for the DTL's, * which simplifies this code and also issues the optimal number of writes * (based on which copies actually read bad data, as opposed to which we * think might be wrong). For the same reason, we always use * ZIO_FLAG_SELF_HEAL, to bypass the DTL check in zio_vdev_io_start(). */ static void vdev_indirect_repair(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; enum zio_flag flags = ZIO_FLAG_IO_REPAIR; if (!(zio->io_flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER))) flags |= ZIO_FLAG_SELF_HEAL; if (!spa_writeable(zio->io_spa)) return; for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { indirect_child_t *good_child = &is->is_child[is->is_good_child]; for (int c = 0; c < is->is_children; c++) { indirect_child_t *ic = &is->is_child[c]; if (ic == good_child) continue; if (ic->ic_data == NULL) continue; if (ic->ic_duplicate == is->is_good_child) continue; zio_nowait(zio_vdev_child_io(zio, NULL, ic->ic_vdev, is->is_target_offset, good_child->ic_data, is->is_size, ZIO_TYPE_WRITE, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_IO_REPAIR | ZIO_FLAG_SELF_HEAL, NULL, NULL)); vdev_indirect_checksum_error(zio, is, ic); } } } /* * Report checksum errors on all children that we read from. */ static void vdev_indirect_all_checksum_errors(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; if (zio->io_flags & ZIO_FLAG_SPECULATIVE) return; for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { for (int c = 0; c < is->is_children; c++) { indirect_child_t *ic = &is->is_child[c]; if (ic->ic_data == NULL) continue; vdev_t *vd = ic->ic_vdev; mutex_enter(&vd->vdev_stat_lock); vd->vdev_stat.vs_checksum_errors++; mutex_exit(&vd->vdev_stat_lock); zfs_ereport_post_checksum(zio->io_spa, vd, NULL, zio, is->is_target_offset, is->is_size, NULL, NULL, NULL); } } } /* * This function is called when we have read all copies of the data and need * to try to find a combination of copies that gives us the right checksum. * * If we pointed to any mirror vdevs, this effectively does the job of the * mirror. The mirror vdev code can't do its own job because we don't know * the checksum of each split segment individually. * * We have to try every unique combination of copies of split segments, until * we find one that checksums correctly. Duplicate segment copies are first * discarded as an optimization to reduce the search space. After pruning * there will exist at most one valid combination. * * When the total number of combinations is small they can all be checked. * For example, if we have 3 segments in the split, and each points to a * 2-way mirror with unique copies, we will have the following pieces of data: * * | mirror child * split | [0] [1] * ======|===================== * A | data_A_0 data_A_1 * B | data_B_0 data_B_1 * C | data_C_0 data_C_1 * * We will try the following (mirror children)^(number of splits) (2^3=8) * combinations, which is similar to bitwise-little-endian counting in * binary. In general each "digit" corresponds to a split segment, and the * base of each digit is is_children, which can be different for each * digit. * * "low bit" "high bit" * v v * data_A_0 data_B_0 data_C_0 * data_A_1 data_B_0 data_C_0 * data_A_0 data_B_1 data_C_0 * data_A_1 data_B_1 data_C_0 * data_A_0 data_B_0 data_C_1 * data_A_1 data_B_0 data_C_1 * data_A_0 data_B_1 data_C_1 * data_A_1 data_B_1 data_C_1 * * Note that the split segments may be on the same or different top-level * vdevs. In either case, we try lots of combinations (see * zfs_reconstruct_indirect_segments_max). This ensures that if a mirror has * small silent errors on all of its children, we can still reconstruct the * correct data, as long as those errors are at sufficiently-separated * offsets (specifically, separated by the largest block size - default of * 128KB, but up to 16MB). */ static void vdev_indirect_reconstruct_io_done(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; uint64_t attempts = 0; uint64_t attempts_max = UINT64_MAX; uint64_t combinations = 1; if (zfs_reconstruct_indirect_combinations_max > 0) attempts_max = zfs_reconstruct_indirect_combinations_max; /* * Discard duplicate copies of split segments to minimize the * number of unique combinations when attempting reconstruction. */ for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { uint64_t is_copies = 0; for (int i = 0; i < is->is_children; i++) { if (is->is_child[i].ic_data == NULL) continue; for (int j = i + 1; j < is->is_children; j++) { if (is->is_child[j].ic_data == NULL) continue; if (is->is_child[j].ic_duplicate == -1 && abd_cmp(is->is_child[i].ic_data, is->is_child[j].ic_data) == 0) { is->is_child[j].ic_duplicate = i; } } is_copies++; } /* Reconstruction is impossible, no valid is->is_child[] */ if (is_copies == 0) { zio->io_error = EIO; vdev_indirect_all_checksum_errors(zio); zio_checksum_verified(zio); return; } combinations *= is_copies; } for (;;) { /* copy data from splits to main zio */ int ret; for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { /* * If this child failed, its ic_data will be NULL. * Skip this combination. */ if (is->is_child[is->is_good_child].ic_data == NULL) { ret = EIO; goto next; } /* * If this child is a duplicate, its is_duplicate will * refer to the primary copy. Skip this combination. */ if (is->is_child[is->is_good_child].ic_duplicate >= 0) { ret = ECKSUM; goto next; } abd_copy_off(zio->io_abd, is->is_child[is->is_good_child].ic_data, is->is_split_offset, 0, is->is_size); } /* See if this checksum matches. */ zio_bad_cksum_t zbc; ret = zio_checksum_error(zio, &zbc); if (ret == 0) { /* Found a matching checksum. Issue repair i/os. */ vdev_indirect_repair(zio); zio_checksum_verified(zio); return; } /* * Checksum failed; try a different combination of split * children. */ boolean_t more; next: more = B_FALSE; if (combinations <= attempts_max) { /* * There are relatively few possible combinations, so * deterministically check them all. We do this by * adding one to the first split's good_child. If it * overflows, then "carry over" to the next split * (like counting in base is_children, but each * digit can have a different base). */ for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { is->is_good_child++; if (is->is_good_child < is->is_children) { more = B_TRUE; break; } is->is_good_child = 0; } } else if (++attempts < attempts_max) { /* * There are too many combinations to try all of them * in a reasonable amount of time, so try a fixed * number of random combinations, after which we'll * consider the block unrecoverable. */ for (indirect_split_t *is = list_head(&iv->iv_splits); is != NULL; is = list_next(&iv->iv_splits, is)) { int c = spa_get_random(is->is_children); while (is->is_child[c].ic_duplicate >= 0) c = (c + 1) % is->is_children; is->is_good_child = c; } more = B_TRUE; } if (!more) { /* All combinations failed. */ zio->io_error = ret; vdev_indirect_all_checksum_errors(zio); zio_checksum_verified(zio); return; } } } static void vdev_indirect_io_done(zio_t *zio) { indirect_vsd_t *iv = zio->io_vsd; if (iv->iv_reconstruct) { /* * We have read all copies of the data (e.g. from mirrors), * either because this was a scrub/resilver, or because the * one-copy read didn't checksum correctly. */ vdev_indirect_reconstruct_io_done(zio); return; } if (!iv->iv_split_block) { /* * This was not a split block, so we passed the BP down, * and the checksum was handled by the (one) child zio. */ return; } zio_bad_cksum_t zbc; int ret = zio_checksum_error(zio, &zbc); if (ret == 0) { zio_checksum_verified(zio); return; } /* * The checksum didn't match. Read all copies of all splits, and * then we will try to reconstruct. The next time * vdev_indirect_io_done() is called, iv_reconstruct will be set. */ vdev_indirect_read_all(zio); zio_vdev_io_redone(zio); } vdev_ops_t vdev_indirect_ops = { vdev_indirect_open, vdev_indirect_close, vdev_default_asize, vdev_indirect_io_start, vdev_indirect_io_done, NULL, NULL, NULL, NULL, vdev_indirect_remap, VDEV_TYPE_INDIRECT, /* name of this vdev type */ B_FALSE /* leaf vdev */ }; #if defined(_KERNEL) && defined(HAVE_SPL) EXPORT_SYMBOL(rs_alloc); EXPORT_SYMBOL(spa_condense_fini); EXPORT_SYMBOL(spa_start_indirect_condensing_thread); EXPORT_SYMBOL(spa_condense_indirect_start_sync); EXPORT_SYMBOL(spa_condense_init); EXPORT_SYMBOL(spa_vdev_indirect_mark_obsolete); EXPORT_SYMBOL(vdev_indirect_mark_obsolete); EXPORT_SYMBOL(vdev_indirect_should_condense); EXPORT_SYMBOL(vdev_indirect_sync_obsolete); EXPORT_SYMBOL(vdev_obsolete_counts_are_precise); EXPORT_SYMBOL(vdev_obsolete_sm_object); /* CSTYLED */ module_param(zfs_condense_min_mapping_bytes, ulong, 0644); MODULE_PARM_DESC(zfs_condense_min_mapping_bytes, "Minimum size of vdev mapping to condense"); module_param(zfs_condense_indirect_commit_entry_delay_ms, int, 0644); MODULE_PARM_DESC(zfs_condense_indirect_commit_entry_delay_ms, "Delay while condensing vdev mapping"); module_param(zfs_reconstruct_indirect_combinations_max, int, 0644); MODULE_PARM_DESC(zfs_reconstruct_indirect_combinations_max, "Maximum number of combinations when reconstructing split segments"); #endif