FreeBSD: Lock vnode in zfs_ioctl()

[zfs.git] / module / zfs / ddt_log.c

/*
 * 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) 2023, Klara Inc.
 */

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/ddt.h>
#include <sys/dmu_tx.h>
#include <sys/dmu.h>
#include <sys/ddt_impl.h>
#include <sys/dnode.h>
#include <sys/dbuf.h>
#include <sys/zap.h>
#include <sys/zio_checksum.h>

/*
 * No more than this many txgs before swapping logs.
 */
uint_t zfs_dedup_log_txg_max = 8;

/*
 * Max memory for the log AVL trees. If zfs_dedup_log_mem_max is zero at module
 * load, it will be set to zfs_dedup_log_mem_max_percent% of total memory.
 */
uint64_t zfs_dedup_log_mem_max = 0;
uint_t zfs_dedup_log_mem_max_percent = 1;


static kmem_cache_t *ddt_log_entry_flat_cache;
static kmem_cache_t *ddt_log_entry_trad_cache;

#define DDT_LOG_ENTRY_FLAT_SIZE \
        (sizeof (ddt_log_entry_t) + DDT_FLAT_PHYS_SIZE)
#define DDT_LOG_ENTRY_TRAD_SIZE \
        (sizeof (ddt_log_entry_t) + DDT_TRAD_PHYS_SIZE)

#define DDT_LOG_ENTRY_SIZE(ddt) \
        _DDT_PHYS_SWITCH(ddt, DDT_LOG_ENTRY_FLAT_SIZE, DDT_LOG_ENTRY_TRAD_SIZE)

void
ddt_log_init(void)
{
        ddt_log_entry_flat_cache = kmem_cache_create("ddt_log_entry_flat_cache",
            DDT_LOG_ENTRY_FLAT_SIZE, 0, NULL, NULL, NULL, NULL, NULL, 0);
        ddt_log_entry_trad_cache = kmem_cache_create("ddt_log_entry_trad_cache",
            DDT_LOG_ENTRY_TRAD_SIZE, 0, NULL, NULL, NULL, NULL, NULL, 0);

        /*
         * Max memory for log AVL entries. At least 1M, because we need
         * something (that's ~3800 entries per tree). They can say 100% if they
         * want; it just means they're at the mercy of the the txg flush limit.
         */
        if (zfs_dedup_log_mem_max == 0) {
                zfs_dedup_log_mem_max_percent =
                    MIN(zfs_dedup_log_mem_max_percent, 100);
                zfs_dedup_log_mem_max = (physmem * PAGESIZE) *
                    zfs_dedup_log_mem_max_percent / 100;
        }
        zfs_dedup_log_mem_max = MAX(zfs_dedup_log_mem_max, 1*1024*1024);
}

void
ddt_log_fini(void)
{
        kmem_cache_destroy(ddt_log_entry_trad_cache);
        kmem_cache_destroy(ddt_log_entry_flat_cache);
}

static void
ddt_log_name(ddt_t *ddt, char *name, uint_t n)
{
        snprintf(name, DDT_NAMELEN, DMU_POOL_DDT_LOG,
            zio_checksum_table[ddt->ddt_checksum].ci_name, n);
}

static void
ddt_log_update_header(ddt_t *ddt, ddt_log_t *ddl, dmu_tx_t *tx)
{
        dmu_buf_t *db;
        VERIFY0(dmu_bonus_hold(ddt->ddt_os, ddl->ddl_object, FTAG, &db));
        dmu_buf_will_dirty(db, tx);

        ddt_log_header_t *hdr = (ddt_log_header_t *)db->db_data;
        DLH_SET_VERSION(hdr, 1);
        DLH_SET_FLAGS(hdr, ddl->ddl_flags);
        hdr->dlh_length = ddl->ddl_length;
        hdr->dlh_first_txg = ddl->ddl_first_txg;
        hdr->dlh_checkpoint = ddl->ddl_checkpoint;

        dmu_buf_rele(db, FTAG);
}

static void
ddt_log_create_one(ddt_t *ddt, ddt_log_t *ddl, uint_t n, dmu_tx_t *tx)
{
        ASSERT3U(ddt->ddt_dir_object, >, 0);
        ASSERT3U(ddl->ddl_object, ==, 0);

        char name[DDT_NAMELEN];
        ddt_log_name(ddt, name, n);

        ddl->ddl_object = dmu_object_alloc(ddt->ddt_os,
            DMU_OTN_UINT64_METADATA, SPA_OLD_MAXBLOCKSIZE,
            DMU_OTN_UINT64_METADATA, sizeof (ddt_log_header_t), tx);
        VERIFY0(zap_add(ddt->ddt_os, ddt->ddt_dir_object, name,
            sizeof (uint64_t), 1, &ddl->ddl_object, tx));
        ddl->ddl_length = 0;
        ddl->ddl_first_txg = tx->tx_txg;
        ddt_log_update_header(ddt, ddl, tx);
}

static void
ddt_log_create(ddt_t *ddt, dmu_tx_t *tx)
{
        ddt_log_create_one(ddt, ddt->ddt_log_active, 0, tx);
        ddt_log_create_one(ddt, ddt->ddt_log_flushing, 1, tx);
}

static void
ddt_log_destroy_one(ddt_t *ddt, ddt_log_t *ddl, uint_t n, dmu_tx_t *tx)
{
        ASSERT3U(ddt->ddt_dir_object, >, 0);

        if (ddl->ddl_object == 0)
                return;

        ASSERT0(ddl->ddl_length);

        char name[DDT_NAMELEN];
        ddt_log_name(ddt, name, n);

        VERIFY0(zap_remove(ddt->ddt_os, ddt->ddt_dir_object, name, tx));
        VERIFY0(dmu_object_free(ddt->ddt_os, ddl->ddl_object, tx));

        ddl->ddl_object = 0;
}

void
ddt_log_destroy(ddt_t *ddt, dmu_tx_t *tx)
{
        ddt_log_destroy_one(ddt, ddt->ddt_log_active, 0, tx);
        ddt_log_destroy_one(ddt, ddt->ddt_log_flushing, 1, tx);
}

static void
ddt_log_update_stats(ddt_t *ddt)
{
        /*
         * Log object stats. We count the number of live entries in the log
         * tree, even if there are more than on disk, and even if the same
         * entry is on both append and flush trees, because that's more what
         * the user expects to see. This does mean the on-disk size is not
         * really correlated with the number of entries, but I don't think
         * that's reasonable to expect anyway.
         */
        dmu_object_info_t doi;
        uint64_t nblocks;
        dmu_object_info(ddt->ddt_os, ddt->ddt_log_active->ddl_object, &doi);
        nblocks = doi.doi_physical_blocks_512;
        dmu_object_info(ddt->ddt_os, ddt->ddt_log_flushing->ddl_object, &doi);
        nblocks += doi.doi_physical_blocks_512;

        ddt_object_t *ddo = &ddt->ddt_log_stats;
        ddo->ddo_count =
            avl_numnodes(&ddt->ddt_log_active->ddl_tree) +
            avl_numnodes(&ddt->ddt_log_flushing->ddl_tree);
        ddo->ddo_mspace = ddo->ddo_count * DDT_LOG_ENTRY_SIZE(ddt);
        ddo->ddo_dspace = nblocks << 9;
}

void
ddt_log_begin(ddt_t *ddt, size_t nentries, dmu_tx_t *tx, ddt_log_update_t *dlu)
{
        ASSERT3U(nentries, >, 0);
        ASSERT3P(dlu->dlu_dbp, ==, NULL);

        if (ddt->ddt_log_active->ddl_object == 0)
                ddt_log_create(ddt, tx);

        /*
         * We want to store as many entries as we can in a block, but never
         * split an entry across block boundaries.
         */
        size_t reclen = P2ALIGN_TYPED(
            sizeof (ddt_log_record_t) + sizeof (ddt_log_record_entry_t) +
            DDT_PHYS_SIZE(ddt), sizeof (uint64_t), size_t);
        ASSERT3U(reclen, <=, UINT16_MAX);
        dlu->dlu_reclen = reclen;

        VERIFY0(dnode_hold(ddt->ddt_os, ddt->ddt_log_active->ddl_object, FTAG,
            &dlu->dlu_dn));
        dnode_set_storage_type(dlu->dlu_dn, DMU_OT_DDT_ZAP);

        uint64_t nblocks = howmany(nentries,
            dlu->dlu_dn->dn_datablksz / dlu->dlu_reclen);
        uint64_t offset = ddt->ddt_log_active->ddl_length;
        uint64_t length = nblocks * dlu->dlu_dn->dn_datablksz;

        VERIFY0(dmu_buf_hold_array_by_dnode(dlu->dlu_dn, offset, length,
            B_FALSE, FTAG, &dlu->dlu_ndbp, &dlu->dlu_dbp,
            DMU_READ_NO_PREFETCH));

        dlu->dlu_tx = tx;
        dlu->dlu_block = dlu->dlu_offset = 0;
}

static ddt_log_entry_t *
ddt_log_alloc_entry(ddt_t *ddt)
{
        ddt_log_entry_t *ddle;

        if (ddt->ddt_flags & DDT_FLAG_FLAT) {
                ddle = kmem_cache_alloc(ddt_log_entry_flat_cache, KM_SLEEP);
                memset(ddle, 0, DDT_LOG_ENTRY_FLAT_SIZE);
        } else {
                ddle = kmem_cache_alloc(ddt_log_entry_trad_cache, KM_SLEEP);
                memset(ddle, 0, DDT_LOG_ENTRY_TRAD_SIZE);
        }

        return (ddle);
}

static void
ddt_log_update_entry(ddt_t *ddt, ddt_log_t *ddl, ddt_lightweight_entry_t *ddlwe)
{
        /* Create the log tree entry from a live or stored entry */
        avl_index_t where;
        ddt_log_entry_t *ddle =
            avl_find(&ddl->ddl_tree, &ddlwe->ddlwe_key, &where);
        if (ddle == NULL) {
                ddle = ddt_log_alloc_entry(ddt);
                ddle->ddle_key = ddlwe->ddlwe_key;
                avl_insert(&ddl->ddl_tree, ddle, where);
        }
        ddle->ddle_type = ddlwe->ddlwe_type;
        ddle->ddle_class = ddlwe->ddlwe_class;
        memcpy(ddle->ddle_phys, &ddlwe->ddlwe_phys, DDT_PHYS_SIZE(ddt));
}

void
ddt_log_entry(ddt_t *ddt, ddt_lightweight_entry_t *ddlwe, ddt_log_update_t *dlu)
{
        ASSERT3U(dlu->dlu_dbp, !=, NULL);

        ddt_log_update_entry(ddt, ddt->ddt_log_active, ddlwe);
        ddt_histogram_add_entry(ddt, &ddt->ddt_log_histogram, ddlwe);

        /* Get our block */
        ASSERT3U(dlu->dlu_block, <, dlu->dlu_ndbp);
        dmu_buf_t *db = dlu->dlu_dbp[dlu->dlu_block];

        /*
         * If this would take us past the end of the block, finish it and
         * move to the next one.
         */
        if (db->db_size < (dlu->dlu_offset + dlu->dlu_reclen)) {
                ASSERT3U(dlu->dlu_offset, >, 0);
                dmu_buf_fill_done(db, dlu->dlu_tx, B_FALSE);
                dlu->dlu_block++;
                dlu->dlu_offset = 0;
                ASSERT3U(dlu->dlu_block, <, dlu->dlu_ndbp);
                db = dlu->dlu_dbp[dlu->dlu_block];
        }

        /*
         * If this is the first time touching the block, inform the DMU that
         * we will fill it, and zero it out.
         */
        if (dlu->dlu_offset == 0) {
                dmu_buf_will_fill(db, dlu->dlu_tx, B_FALSE);
                memset(db->db_data, 0, db->db_size);
        }

        /* Create the log record directly in the buffer */
        ddt_log_record_t *dlr = (db->db_data + dlu->dlu_offset);
        DLR_SET_TYPE(dlr, DLR_ENTRY);
        DLR_SET_RECLEN(dlr, dlu->dlu_reclen);
        DLR_SET_ENTRY_TYPE(dlr, ddlwe->ddlwe_type);
        DLR_SET_ENTRY_CLASS(dlr, ddlwe->ddlwe_class);

        ddt_log_record_entry_t *dlre =
            (ddt_log_record_entry_t *)&dlr->dlr_payload;
        dlre->dlre_key = ddlwe->ddlwe_key;
        memcpy(dlre->dlre_phys, &ddlwe->ddlwe_phys, DDT_PHYS_SIZE(ddt));

        /* Advance offset for next record. */
        dlu->dlu_offset += dlu->dlu_reclen;
}

void
ddt_log_commit(ddt_t *ddt, ddt_log_update_t *dlu)
{
        ASSERT3U(dlu->dlu_dbp, !=, NULL);
        ASSERT3U(dlu->dlu_block+1, ==, dlu->dlu_ndbp);
        ASSERT3U(dlu->dlu_offset, >, 0);

        /*
         * Close out the last block. Whatever we haven't used will be zeroed,
         * which matches DLR_INVALID, so we can detect this during load.
         */
        dmu_buf_fill_done(dlu->dlu_dbp[dlu->dlu_block], dlu->dlu_tx, B_FALSE);

        dmu_buf_rele_array(dlu->dlu_dbp, dlu->dlu_ndbp, FTAG);

        ddt->ddt_log_active->ddl_length +=
            dlu->dlu_ndbp * (uint64_t)dlu->dlu_dn->dn_datablksz;
        dnode_rele(dlu->dlu_dn, FTAG);

        ddt_log_update_header(ddt, ddt->ddt_log_active, dlu->dlu_tx);

        memset(dlu, 0, sizeof (ddt_log_update_t));

        ddt_log_update_stats(ddt);
}

boolean_t
ddt_log_take_first(ddt_t *ddt, ddt_log_t *ddl, ddt_lightweight_entry_t *ddlwe)
{
        ddt_log_entry_t *ddle = avl_first(&ddl->ddl_tree);
        if (ddle == NULL)
                return (B_FALSE);

        DDT_LOG_ENTRY_TO_LIGHTWEIGHT(ddt, ddle, ddlwe);

        ddt_histogram_sub_entry(ddt, &ddt->ddt_log_histogram, ddlwe);

        avl_remove(&ddl->ddl_tree, ddle);
        kmem_cache_free(ddt->ddt_flags & DDT_FLAG_FLAT ?
            ddt_log_entry_flat_cache : ddt_log_entry_trad_cache, ddle);

        return (B_TRUE);
}

boolean_t
ddt_log_remove_key(ddt_t *ddt, ddt_log_t *ddl, const ddt_key_t *ddk)
{
        ddt_log_entry_t *ddle = avl_find(&ddl->ddl_tree, ddk, NULL);
        if (ddle == NULL)
                return (B_FALSE);

        ddt_lightweight_entry_t ddlwe;
        DDT_LOG_ENTRY_TO_LIGHTWEIGHT(ddt, ddle, &ddlwe);
        ddt_histogram_sub_entry(ddt, &ddt->ddt_log_histogram, &ddlwe);

        avl_remove(&ddl->ddl_tree, ddle);
        kmem_cache_free(ddt->ddt_flags & DDT_FLAG_FLAT ?
            ddt_log_entry_flat_cache : ddt_log_entry_trad_cache, ddle);

        return (B_TRUE);
}

boolean_t
ddt_log_find_key(ddt_t *ddt, const ddt_key_t *ddk,
    ddt_lightweight_entry_t *ddlwe)
{
        ddt_log_entry_t *ddle =
            avl_find(&ddt->ddt_log_active->ddl_tree, ddk, NULL);
        if (!ddle)
                ddle = avl_find(&ddt->ddt_log_flushing->ddl_tree, ddk, NULL);
        if (!ddle)
                return (B_FALSE);
        if (ddlwe)
                DDT_LOG_ENTRY_TO_LIGHTWEIGHT(ddt, ddle, ddlwe);
        return (B_TRUE);
}

void
ddt_log_checkpoint(ddt_t *ddt, ddt_lightweight_entry_t *ddlwe, dmu_tx_t *tx)
{
        ddt_log_t *ddl = ddt->ddt_log_flushing;

        ASSERT3U(ddl->ddl_object, !=, 0);

#ifdef ZFS_DEBUG
        /*
         * There should not be any entries on the log tree before the given
         * checkpoint. Assert that this is the case.
         */
        ddt_log_entry_t *ddle = avl_first(&ddl->ddl_tree);
        if (ddle != NULL)
                VERIFY3U(ddt_key_compare(&ddle->ddle_key, &ddlwe->ddlwe_key),
                    >, 0);
#endif

        ddl->ddl_flags |= DDL_FLAG_CHECKPOINT;
        ddl->ddl_checkpoint = ddlwe->ddlwe_key;
        ddt_log_update_header(ddt, ddl, tx);

        ddt_log_update_stats(ddt);
}

void
ddt_log_truncate(ddt_t *ddt, dmu_tx_t *tx)
{
        ddt_log_t *ddl = ddt->ddt_log_flushing;

        if (ddl->ddl_object == 0)
                return;

        ASSERT(avl_is_empty(&ddl->ddl_tree));

        /* Eject the entire object */
        dmu_free_range(ddt->ddt_os, ddl->ddl_object, 0, DMU_OBJECT_END, tx);

        ddl->ddl_length = 0;
        ddl->ddl_flags &= ~DDL_FLAG_CHECKPOINT;
        memset(&ddl->ddl_checkpoint, 0, sizeof (ddt_key_t));
        ddt_log_update_header(ddt, ddl, tx);

        ddt_log_update_stats(ddt);
}

boolean_t
ddt_log_swap(ddt_t *ddt, dmu_tx_t *tx)
{
        /* Swap the logs. The old flushing one must be empty */
        VERIFY(avl_is_empty(&ddt->ddt_log_flushing->ddl_tree));

        /*
         * If there are still blocks on the flushing log, truncate it first.
         * This can happen if there were entries on the flushing log that were
         * removed in memory via ddt_lookup(); their vestigal remains are
         * on disk.
         */
        if (ddt->ddt_log_flushing->ddl_length > 0)
                ddt_log_truncate(ddt, tx);

        /*
         * Swap policy. We swap the logs (and so begin flushing) when the
         * active tree grows too large, or when we haven't swapped it in
         * some amount of time, or if something has requested the logs be
         * flushed ASAP (see ddt_walk_init()).
         */

        /*
         * The log tree is too large if the memory usage of its entries is over
         * half of the memory limit. This effectively gives each log tree half
         * the available memory.
         */
        const boolean_t too_large =
            (avl_numnodes(&ddt->ddt_log_active->ddl_tree) *
            DDT_LOG_ENTRY_SIZE(ddt)) >= (zfs_dedup_log_mem_max >> 1);

        const boolean_t too_old =
            tx->tx_txg >=
            (ddt->ddt_log_active->ddl_first_txg +
            MAX(1, zfs_dedup_log_txg_max));

        const boolean_t force =
            ddt->ddt_log_active->ddl_first_txg <= ddt->ddt_flush_force_txg;

        if (!(too_large || too_old || force))
                return (B_FALSE);

        ddt_log_t *swap = ddt->ddt_log_active;
        ddt->ddt_log_active = ddt->ddt_log_flushing;
        ddt->ddt_log_flushing = swap;

        ASSERT(ddt->ddt_log_active->ddl_flags & DDL_FLAG_FLUSHING);
        ddt->ddt_log_active->ddl_flags &=
            ~(DDL_FLAG_FLUSHING | DDL_FLAG_CHECKPOINT);

        ASSERT(!(ddt->ddt_log_flushing->ddl_flags & DDL_FLAG_FLUSHING));
        ddt->ddt_log_flushing->ddl_flags |= DDL_FLAG_FLUSHING;

        ddt->ddt_log_active->ddl_first_txg = tx->tx_txg;

        ddt_log_update_header(ddt, ddt->ddt_log_active, tx);
        ddt_log_update_header(ddt, ddt->ddt_log_flushing, tx);

        ddt_log_update_stats(ddt);

        return (B_TRUE);
}

static inline void
ddt_log_load_entry(ddt_t *ddt, ddt_log_t *ddl, ddt_log_record_t *dlr,
    const ddt_key_t *checkpoint)
{
        ASSERT3U(DLR_GET_TYPE(dlr), ==, DLR_ENTRY);

        ddt_log_record_entry_t *dlre =
            (ddt_log_record_entry_t *)dlr->dlr_payload;
        if (checkpoint != NULL &&
            ddt_key_compare(&dlre->dlre_key, checkpoint) <= 0) {
                /* Skip pre-checkpoint entries; they're already flushed. */
                return;
        }

        ddt_lightweight_entry_t ddlwe;
        ddlwe.ddlwe_type = DLR_GET_ENTRY_TYPE(dlr);
        ddlwe.ddlwe_class = DLR_GET_ENTRY_CLASS(dlr);

        ddlwe.ddlwe_key = dlre->dlre_key;
        memcpy(&ddlwe.ddlwe_phys, dlre->dlre_phys, DDT_PHYS_SIZE(ddt));

        ddt_log_update_entry(ddt, ddl, &ddlwe);
}

static void
ddt_log_empty(ddt_t *ddt, ddt_log_t *ddl)
{
        void *cookie = NULL;
        ddt_log_entry_t *ddle;
        IMPLY(ddt->ddt_version == UINT64_MAX, avl_is_empty(&ddl->ddl_tree));
        while ((ddle =
            avl_destroy_nodes(&ddl->ddl_tree, &cookie)) != NULL) {
                kmem_cache_free(ddt->ddt_flags & DDT_FLAG_FLAT ?
                    ddt_log_entry_flat_cache : ddt_log_entry_trad_cache, ddle);
        }
        ASSERT(avl_is_empty(&ddl->ddl_tree));
}

static int
ddt_log_load_one(ddt_t *ddt, uint_t n)
{
        ASSERT3U(n, <, 2);

        ddt_log_t *ddl = &ddt->ddt_log[n];

        char name[DDT_NAMELEN];
        ddt_log_name(ddt, name, n);

        uint64_t obj;
        int err = zap_lookup(ddt->ddt_os, ddt->ddt_dir_object, name,
            sizeof (uint64_t), 1, &obj);
        if (err == ENOENT)
                return (0);
        if (err != 0)
                return (err);

        dnode_t *dn;
        err = dnode_hold(ddt->ddt_os, obj, FTAG, &dn);
        if (err != 0)
                return (err);

        ddt_log_header_t hdr;
        dmu_buf_t *db;
        err = dmu_bonus_hold_by_dnode(dn, FTAG, &db, DMU_READ_NO_PREFETCH);
        if (err != 0) {
                dnode_rele(dn, FTAG);
                return (err);
        }
        memcpy(&hdr, db->db_data, sizeof (ddt_log_header_t));
        dmu_buf_rele(db, FTAG);

        if (DLH_GET_VERSION(&hdr) != 1) {
                dnode_rele(dn, FTAG);
                zfs_dbgmsg("ddt_log_load: spa=%s ddt_log=%s "
                    "unknown version=%llu", spa_name(ddt->ddt_spa), name,
                    (u_longlong_t)DLH_GET_VERSION(&hdr));
                return (SET_ERROR(EINVAL));
        }

        ddt_key_t *checkpoint = NULL;
        if (DLH_GET_FLAGS(&hdr) & DDL_FLAG_CHECKPOINT) {
                /*
                 * If the log has a checkpoint, then we can ignore any entries
                 * that have already been flushed.
                 */
                ASSERT(DLH_GET_FLAGS(&hdr) & DDL_FLAG_FLUSHING);
                checkpoint = &hdr.dlh_checkpoint;
        }

        if (hdr.dlh_length > 0) {
                dmu_prefetch_by_dnode(dn, 0, 0, hdr.dlh_length,
                    ZIO_PRIORITY_SYNC_READ);

                for (uint64_t offset = 0; offset < hdr.dlh_length;
                    offset += dn->dn_datablksz) {
                        err = dmu_buf_hold_by_dnode(dn, offset, FTAG, &db,
                            DMU_READ_PREFETCH);
                        if (err != 0) {
                                dnode_rele(dn, FTAG);
                                ddt_log_empty(ddt, ddl);
                                return (err);
                        }

                        uint64_t boffset = 0;
                        while (boffset < db->db_size) {
                                ddt_log_record_t *dlr =
                                    (ddt_log_record_t *)(db->db_data + boffset);

                                /* Partially-filled block, skip the rest */
                                if (DLR_GET_TYPE(dlr) == DLR_INVALID)
                                        break;

                                switch (DLR_GET_TYPE(dlr)) {
                                case DLR_ENTRY:
                                        ddt_log_load_entry(ddt, ddl, dlr,
                                            checkpoint);
                                        break;

                                default:
                                        dmu_buf_rele(db, FTAG);
                                        dnode_rele(dn, FTAG);
                                        ddt_log_empty(ddt, ddl);
                                        return (SET_ERROR(EINVAL));
                                }

                                boffset += DLR_GET_RECLEN(dlr);
                        }

                        dmu_buf_rele(db, FTAG);
                }
        }

        dnode_rele(dn, FTAG);

        ddl->ddl_object = obj;
        ddl->ddl_flags = DLH_GET_FLAGS(&hdr);
        ddl->ddl_length = hdr.dlh_length;
        ddl->ddl_first_txg = hdr.dlh_first_txg;

        if (ddl->ddl_flags & DDL_FLAG_FLUSHING)
                ddt->ddt_log_flushing = ddl;
        else
                ddt->ddt_log_active = ddl;

        return (0);
}

int
ddt_log_load(ddt_t *ddt)
{
        int err;

        if (spa_load_state(ddt->ddt_spa) == SPA_LOAD_TRYIMPORT) {
                /*
                 * The DDT is going to be freed again in a moment, so there's
                 * no point loading the log; it'll just slow down import.
                 */
                return (0);
        }

        ASSERT0(ddt->ddt_log[0].ddl_object);
        ASSERT0(ddt->ddt_log[1].ddl_object);
        if (ddt->ddt_dir_object == 0) {
                /*
                 * If we're configured but the containing dir doesn't exist
                 * yet, then the log object can't possibly exist either.
                 */
                ASSERT3U(ddt->ddt_version, !=, UINT64_MAX);
                return (SET_ERROR(ENOENT));
        }

        if ((err = ddt_log_load_one(ddt, 0)) != 0)
                return (err);
        if ((err = ddt_log_load_one(ddt, 1)) != 0)
                return (err);

        VERIFY3P(ddt->ddt_log_active, !=, ddt->ddt_log_flushing);
        VERIFY(!(ddt->ddt_log_active->ddl_flags & DDL_FLAG_FLUSHING));
        VERIFY(!(ddt->ddt_log_active->ddl_flags & DDL_FLAG_CHECKPOINT));
        VERIFY(ddt->ddt_log_flushing->ddl_flags & DDL_FLAG_FLUSHING);

        /*
         * We have two finalisation tasks:
         *
         * - rebuild the histogram. We do this at the end rather than while
         *   we're loading so we don't need to uncount and recount entries that
         *   appear multiple times in the log.
         *
         * - remove entries from the flushing tree that are on both trees. This
         *   happens when ddt_lookup() rehydrates an entry from the flushing
         *   tree, as ddt_log_take_key() removes the entry from the in-memory
         *   tree but doesn't remove it from disk.
         */

        /*
         * We don't technically need a config lock here, since there shouldn't
         * be pool config changes during DDT load. dva_get_dsize_sync() via
         * ddt_stat_generate() is expecting it though, and it won't hurt
         * anything, so we take it.
         */
        spa_config_enter(ddt->ddt_spa, SCL_STATE, FTAG, RW_READER);

        avl_tree_t *al = &ddt->ddt_log_active->ddl_tree;
        avl_tree_t *fl = &ddt->ddt_log_flushing->ddl_tree;
        ddt_log_entry_t *ae = avl_first(al);
        ddt_log_entry_t *fe = avl_first(fl);
        while (ae != NULL || fe != NULL) {
                ddt_log_entry_t *ddle;
                if (ae == NULL) {
                        /* active exhausted, take flushing */
                        ddle = fe;
                        fe = AVL_NEXT(fl, fe);
                } else if (fe == NULL) {
                        /* flushing exuhausted, take active */
                        ddle = ae;
                        ae = AVL_NEXT(al, ae);
                } else {
                        /* compare active and flushing */
                        int c = ddt_key_compare(&ae->ddle_key, &fe->ddle_key);
                        if (c < 0) {
                                /* active behind, take and advance */
                                ddle = ae;
                                ae = AVL_NEXT(al, ae);
                        } else if (c > 0) {
                                /* flushing behind, take and advance */
                                ddle = fe;
                                fe = AVL_NEXT(fl, fe);
                        } else {
                                /* match. remove from flushing, take active */
                                ddle = fe;
                                fe = AVL_NEXT(fl, fe);
                                avl_remove(fl, ddle);

                                ddle = ae;
                                ae = AVL_NEXT(al, ae);
                        }
                }

                ddt_lightweight_entry_t ddlwe;
                DDT_LOG_ENTRY_TO_LIGHTWEIGHT(ddt, ddle, &ddlwe);
                ddt_histogram_add_entry(ddt, &ddt->ddt_log_histogram, &ddlwe);
        }

        spa_config_exit(ddt->ddt_spa, SCL_STATE, FTAG);

        ddt_log_update_stats(ddt);

        return (0);
}

void
ddt_log_alloc(ddt_t *ddt)
{
        ASSERT3P(ddt->ddt_log_active, ==, NULL);
        ASSERT3P(ddt->ddt_log_flushing, ==, NULL);

        avl_create(&ddt->ddt_log[0].ddl_tree, ddt_key_compare,
            sizeof (ddt_log_entry_t), offsetof(ddt_log_entry_t, ddle_node));
        avl_create(&ddt->ddt_log[1].ddl_tree, ddt_key_compare,
            sizeof (ddt_log_entry_t), offsetof(ddt_log_entry_t, ddle_node));
        ddt->ddt_log_active = &ddt->ddt_log[0];
        ddt->ddt_log_flushing = &ddt->ddt_log[1];
        ddt->ddt_log_flushing->ddl_flags |= DDL_FLAG_FLUSHING;
}

void
ddt_log_free(ddt_t *ddt)
{
        ddt_log_empty(ddt, &ddt->ddt_log[0]);
        ddt_log_empty(ddt, &ddt->ddt_log[1]);
        avl_destroy(&ddt->ddt_log[0].ddl_tree);
        avl_destroy(&ddt->ddt_log[1].ddl_tree);
}

ZFS_MODULE_PARAM(zfs_dedup, zfs_dedup_, log_txg_max, UINT, ZMOD_RW,
        "Max transactions before starting to flush dedup logs");

ZFS_MODULE_PARAM(zfs_dedup, zfs_dedup_, log_mem_max, U64, ZMOD_RD,
        "Max memory for dedup logs");

ZFS_MODULE_PARAM(zfs_dedup, zfs_dedup_, log_mem_max_percent, UINT, ZMOD_RD,
        "Max memory for dedup logs, as % of total memory");