Update core ZFS code from build 121 to build 141.
[zfs.git] / module / zfs / ddt.c
diff --git a/module/zfs/ddt.c b/module/zfs/ddt.c
new file mode 100644 (file)
index 0000000..926b4df
--- /dev/null
@@ -0,0 +1,1140 @@
+/*
+ * 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 http://www.opensolaris.org/os/licensing.
+ * 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) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/spa.h>
+#include <sys/spa_impl.h>
+#include <sys/zio.h>
+#include <sys/ddt.h>
+#include <sys/zap.h>
+#include <sys/dmu_tx.h>
+#include <sys/arc.h>
+#include <sys/dsl_pool.h>
+#include <sys/zio_checksum.h>
+#include <sys/zio_compress.h>
+#include <sys/dsl_scan.h>
+
+static const ddt_ops_t *ddt_ops[DDT_TYPES] = {
+       &ddt_zap_ops,
+};
+
+static const char *ddt_class_name[DDT_CLASSES] = {
+       "ditto",
+       "duplicate",
+       "unique",
+};
+
+static void
+ddt_object_create(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    dmu_tx_t *tx)
+{
+       spa_t *spa = ddt->ddt_spa;
+       objset_t *os = ddt->ddt_os;
+       uint64_t *objectp = &ddt->ddt_object[type][class];
+       boolean_t prehash = zio_checksum_table[ddt->ddt_checksum].ci_dedup;
+       char name[DDT_NAMELEN];
+
+       ddt_object_name(ddt, type, class, name);
+
+       ASSERT(*objectp == 0);
+       VERIFY(ddt_ops[type]->ddt_op_create(os, objectp, tx, prehash) == 0);
+       ASSERT(*objectp != 0);
+
+       VERIFY(zap_add(os, DMU_POOL_DIRECTORY_OBJECT, name,
+           sizeof (uint64_t), 1, objectp, tx) == 0);
+
+       VERIFY(zap_add(os, spa->spa_ddt_stat_object, name,
+           sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
+           &ddt->ddt_histogram[type][class], tx) == 0);
+}
+
+static void
+ddt_object_destroy(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    dmu_tx_t *tx)
+{
+       spa_t *spa = ddt->ddt_spa;
+       objset_t *os = ddt->ddt_os;
+       uint64_t *objectp = &ddt->ddt_object[type][class];
+       char name[DDT_NAMELEN];
+
+       ddt_object_name(ddt, type, class, name);
+
+       ASSERT(*objectp != 0);
+       ASSERT(ddt_object_count(ddt, type, class) == 0);
+       ASSERT(ddt_histogram_empty(&ddt->ddt_histogram[type][class]));
+       VERIFY(zap_remove(os, DMU_POOL_DIRECTORY_OBJECT, name, tx) == 0);
+       VERIFY(zap_remove(os, spa->spa_ddt_stat_object, name, tx) == 0);
+       VERIFY(ddt_ops[type]->ddt_op_destroy(os, *objectp, tx) == 0);
+       bzero(&ddt->ddt_object_stats[type][class], sizeof (ddt_object_t));
+
+       *objectp = 0;
+}
+
+static int
+ddt_object_load(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
+{
+       ddt_object_t *ddo = &ddt->ddt_object_stats[type][class];
+       dmu_object_info_t doi;
+       char name[DDT_NAMELEN];
+       int error;
+
+       ddt_object_name(ddt, type, class, name);
+
+       error = zap_lookup(ddt->ddt_os, DMU_POOL_DIRECTORY_OBJECT, name,
+           sizeof (uint64_t), 1, &ddt->ddt_object[type][class]);
+
+       if (error)
+               return (error);
+
+       error = zap_lookup(ddt->ddt_os, ddt->ddt_spa->spa_ddt_stat_object, name,
+           sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
+           &ddt->ddt_histogram[type][class]);
+
+       /*
+        * Seed the cached statistics.
+        */
+       VERIFY(ddt_object_info(ddt, type, class, &doi) == 0);
+
+       ddo->ddo_count = ddt_object_count(ddt, type, class);
+       ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
+       ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
+
+       ASSERT(error == 0);
+       return (error);
+}
+
+static void
+ddt_object_sync(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    dmu_tx_t *tx)
+{
+       ddt_object_t *ddo = &ddt->ddt_object_stats[type][class];
+       dmu_object_info_t doi;
+       char name[DDT_NAMELEN];
+
+       ddt_object_name(ddt, type, class, name);
+
+       VERIFY(zap_update(ddt->ddt_os, ddt->ddt_spa->spa_ddt_stat_object, name,
+           sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
+           &ddt->ddt_histogram[type][class], tx) == 0);
+
+       /*
+        * Cache DDT statistics; this is the only time they'll change.
+        */
+       VERIFY(ddt_object_info(ddt, type, class, &doi) == 0);
+
+       ddo->ddo_count = ddt_object_count(ddt, type, class);
+       ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
+       ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
+}
+
+static int
+ddt_object_lookup(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    ddt_entry_t *dde)
+{
+       if (!ddt_object_exists(ddt, type, class))
+               return (ENOENT);
+
+       return (ddt_ops[type]->ddt_op_lookup(ddt->ddt_os,
+           ddt->ddt_object[type][class], dde));
+}
+
+static void
+ddt_object_prefetch(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    ddt_entry_t *dde)
+{
+       if (!ddt_object_exists(ddt, type, class))
+               return;
+
+       ddt_ops[type]->ddt_op_prefetch(ddt->ddt_os,
+           ddt->ddt_object[type][class], dde);
+}
+
+int
+ddt_object_update(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    ddt_entry_t *dde, dmu_tx_t *tx)
+{
+       ASSERT(ddt_object_exists(ddt, type, class));
+
+       return (ddt_ops[type]->ddt_op_update(ddt->ddt_os,
+           ddt->ddt_object[type][class], dde, tx));
+}
+
+static int
+ddt_object_remove(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    ddt_entry_t *dde, dmu_tx_t *tx)
+{
+       ASSERT(ddt_object_exists(ddt, type, class));
+
+       return (ddt_ops[type]->ddt_op_remove(ddt->ddt_os,
+           ddt->ddt_object[type][class], dde, tx));
+}
+
+int
+ddt_object_walk(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    uint64_t *walk, ddt_entry_t *dde)
+{
+       ASSERT(ddt_object_exists(ddt, type, class));
+
+       return (ddt_ops[type]->ddt_op_walk(ddt->ddt_os,
+           ddt->ddt_object[type][class], dde, walk));
+}
+
+uint64_t
+ddt_object_count(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
+{
+       ASSERT(ddt_object_exists(ddt, type, class));
+
+       return (ddt_ops[type]->ddt_op_count(ddt->ddt_os,
+           ddt->ddt_object[type][class]));
+}
+
+int
+ddt_object_info(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    dmu_object_info_t *doi)
+{
+       if (!ddt_object_exists(ddt, type, class))
+               return (ENOENT);
+
+       return (dmu_object_info(ddt->ddt_os, ddt->ddt_object[type][class],
+           doi));
+}
+
+boolean_t
+ddt_object_exists(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
+{
+       return (!!ddt->ddt_object[type][class]);
+}
+
+void
+ddt_object_name(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    char *name)
+{
+       (void) sprintf(name, DMU_POOL_DDT,
+           zio_checksum_table[ddt->ddt_checksum].ci_name,
+           ddt_ops[type]->ddt_op_name, ddt_class_name[class]);
+}
+
+void
+ddt_bp_fill(const ddt_phys_t *ddp, blkptr_t *bp, uint64_t txg)
+{
+       ASSERT(txg != 0);
+
+       for (int d = 0; d < SPA_DVAS_PER_BP; d++)
+               bp->blk_dva[d] = ddp->ddp_dva[d];
+       BP_SET_BIRTH(bp, txg, ddp->ddp_phys_birth);
+}
+
+void
+ddt_bp_create(enum zio_checksum checksum,
+    const ddt_key_t *ddk, const ddt_phys_t *ddp, blkptr_t *bp)
+{
+       BP_ZERO(bp);
+
+       if (ddp != NULL)
+               ddt_bp_fill(ddp, bp, ddp->ddp_phys_birth);
+
+       bp->blk_cksum = ddk->ddk_cksum;
+       bp->blk_fill = 1;
+
+       BP_SET_LSIZE(bp, DDK_GET_LSIZE(ddk));
+       BP_SET_PSIZE(bp, DDK_GET_PSIZE(ddk));
+       BP_SET_COMPRESS(bp, DDK_GET_COMPRESS(ddk));
+       BP_SET_CHECKSUM(bp, checksum);
+       BP_SET_TYPE(bp, DMU_OT_DEDUP);
+       BP_SET_LEVEL(bp, 0);
+       BP_SET_DEDUP(bp, 0);
+       BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
+}
+
+void
+ddt_key_fill(ddt_key_t *ddk, const blkptr_t *bp)
+{
+       ddk->ddk_cksum = bp->blk_cksum;
+       ddk->ddk_prop = 0;
+
+       DDK_SET_LSIZE(ddk, BP_GET_LSIZE(bp));
+       DDK_SET_PSIZE(ddk, BP_GET_PSIZE(bp));
+       DDK_SET_COMPRESS(ddk, BP_GET_COMPRESS(bp));
+}
+
+void
+ddt_phys_fill(ddt_phys_t *ddp, const blkptr_t *bp)
+{
+       ASSERT(ddp->ddp_phys_birth == 0);
+
+       for (int d = 0; d < SPA_DVAS_PER_BP; d++)
+               ddp->ddp_dva[d] = bp->blk_dva[d];
+       ddp->ddp_phys_birth = BP_PHYSICAL_BIRTH(bp);
+}
+
+void
+ddt_phys_clear(ddt_phys_t *ddp)
+{
+       bzero(ddp, sizeof (*ddp));
+}
+
+void
+ddt_phys_addref(ddt_phys_t *ddp)
+{
+       ddp->ddp_refcnt++;
+}
+
+void
+ddt_phys_decref(ddt_phys_t *ddp)
+{
+       ASSERT((int64_t)ddp->ddp_refcnt > 0);
+       ddp->ddp_refcnt--;
+}
+
+void
+ddt_phys_free(ddt_t *ddt, ddt_key_t *ddk, ddt_phys_t *ddp, uint64_t txg)
+{
+       blkptr_t blk;
+
+       ddt_bp_create(ddt->ddt_checksum, ddk, ddp, &blk);
+       ddt_phys_clear(ddp);
+       zio_free(ddt->ddt_spa, txg, &blk);
+}
+
+ddt_phys_t *
+ddt_phys_select(const ddt_entry_t *dde, const blkptr_t *bp)
+{
+       ddt_phys_t *ddp = (ddt_phys_t *)dde->dde_phys;
+
+       for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+               if (DVA_EQUAL(BP_IDENTITY(bp), &ddp->ddp_dva[0]) &&
+                   BP_PHYSICAL_BIRTH(bp) == ddp->ddp_phys_birth)
+                       return (ddp);
+       }
+       return (NULL);
+}
+
+uint64_t
+ddt_phys_total_refcnt(const ddt_entry_t *dde)
+{
+       uint64_t refcnt = 0;
+
+       for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++)
+               refcnt += dde->dde_phys[p].ddp_refcnt;
+
+       return (refcnt);
+}
+
+static void
+ddt_stat_generate(ddt_t *ddt, ddt_entry_t *dde, ddt_stat_t *dds)
+{
+       spa_t *spa = ddt->ddt_spa;
+       ddt_phys_t *ddp = dde->dde_phys;
+       ddt_key_t *ddk = &dde->dde_key;
+       uint64_t lsize = DDK_GET_LSIZE(ddk);
+       uint64_t psize = DDK_GET_PSIZE(ddk);
+
+       bzero(dds, sizeof (*dds));
+
+       for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+               uint64_t dsize = 0;
+               uint64_t refcnt = ddp->ddp_refcnt;
+
+               if (ddp->ddp_phys_birth == 0)
+                       continue;
+
+               for (int d = 0; d < SPA_DVAS_PER_BP; d++)
+                       dsize += dva_get_dsize_sync(spa, &ddp->ddp_dva[d]);
+
+               dds->dds_blocks += 1;
+               dds->dds_lsize += lsize;
+               dds->dds_psize += psize;
+               dds->dds_dsize += dsize;
+
+               dds->dds_ref_blocks += refcnt;
+               dds->dds_ref_lsize += lsize * refcnt;
+               dds->dds_ref_psize += psize * refcnt;
+               dds->dds_ref_dsize += dsize * refcnt;
+       }
+}
+
+void
+ddt_stat_add(ddt_stat_t *dst, const ddt_stat_t *src, uint64_t neg)
+{
+       const uint64_t *s = (const uint64_t *)src;
+       uint64_t *d = (uint64_t *)dst;
+       uint64_t *d_end = (uint64_t *)(dst + 1);
+
+       ASSERT(neg == 0 || neg == -1ULL);       /* add or subtract */
+
+       while (d < d_end)
+               *d++ += (*s++ ^ neg) - neg;
+}
+
+static void
+ddt_stat_update(ddt_t *ddt, ddt_entry_t *dde, uint64_t neg)
+{
+       ddt_stat_t dds;
+       ddt_histogram_t *ddh;
+       int bucket;
+
+       ddt_stat_generate(ddt, dde, &dds);
+
+       bucket = highbit(dds.dds_ref_blocks) - 1;
+       ASSERT(bucket >= 0);
+
+       ddh = &ddt->ddt_histogram[dde->dde_type][dde->dde_class];
+
+       ddt_stat_add(&ddh->ddh_stat[bucket], &dds, neg);
+}
+
+void
+ddt_histogram_add(ddt_histogram_t *dst, const ddt_histogram_t *src)
+{
+       for (int h = 0; h < 64; h++)
+               ddt_stat_add(&dst->ddh_stat[h], &src->ddh_stat[h], 0);
+}
+
+void
+ddt_histogram_stat(ddt_stat_t *dds, const ddt_histogram_t *ddh)
+{
+       bzero(dds, sizeof (*dds));
+
+       for (int h = 0; h < 64; h++)
+               ddt_stat_add(dds, &ddh->ddh_stat[h], 0);
+}
+
+boolean_t
+ddt_histogram_empty(const ddt_histogram_t *ddh)
+{
+       const uint64_t *s = (const uint64_t *)ddh;
+       const uint64_t *s_end = (const uint64_t *)(ddh + 1);
+
+       while (s < s_end)
+               if (*s++ != 0)
+                       return (B_FALSE);
+
+       return (B_TRUE);
+}
+
+void
+ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
+{
+       /* Sum the statistics we cached in ddt_object_sync(). */
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+               ddt_t *ddt = spa->spa_ddt[c];
+               for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+                       for (enum ddt_class class = 0; class < DDT_CLASSES;
+                           class++) {
+                               ddt_object_t *ddo =
+                                   &ddt->ddt_object_stats[type][class];
+                               ddo_total->ddo_count += ddo->ddo_count;
+                               ddo_total->ddo_dspace += ddo->ddo_dspace;
+                               ddo_total->ddo_mspace += ddo->ddo_mspace;
+                       }
+               }
+       }
+
+       /* ... and compute the averages. */
+       if (ddo_total->ddo_count != 0) {
+               ddo_total->ddo_dspace /= ddo_total->ddo_count;
+               ddo_total->ddo_mspace /= ddo_total->ddo_count;
+       } else {
+               ASSERT(ddo_total->ddo_dspace == 0);
+               ASSERT(ddo_total->ddo_mspace == 0);
+       }
+}
+
+void
+ddt_get_dedup_histogram(spa_t *spa, ddt_histogram_t *ddh)
+{
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+               ddt_t *ddt = spa->spa_ddt[c];
+               for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+                       for (enum ddt_class class = 0; class < DDT_CLASSES;
+                           class++) {
+                               ddt_histogram_add(ddh,
+                                   &ddt->ddt_histogram_cache[type][class]);
+                       }
+               }
+       }
+}
+
+void
+ddt_get_dedup_stats(spa_t *spa, ddt_stat_t *dds_total)
+{
+       ddt_histogram_t *ddh_total;
+
+       ddh_total = kmem_zalloc(sizeof (ddt_histogram_t), KM_SLEEP);
+       ddt_get_dedup_histogram(spa, ddh_total);
+       ddt_histogram_stat(dds_total, ddh_total);
+       kmem_free(ddh_total, sizeof (ddt_histogram_t));
+}
+
+uint64_t
+ddt_get_dedup_dspace(spa_t *spa)
+{
+       ddt_stat_t dds_total = { 0 };
+
+       ddt_get_dedup_stats(spa, &dds_total);
+       return (dds_total.dds_ref_dsize - dds_total.dds_dsize);
+}
+
+uint64_t
+ddt_get_pool_dedup_ratio(spa_t *spa)
+{
+       ddt_stat_t dds_total = { 0 };
+
+       ddt_get_dedup_stats(spa, &dds_total);
+       if (dds_total.dds_dsize == 0)
+               return (100);
+
+       return (dds_total.dds_ref_dsize * 100 / dds_total.dds_dsize);
+}
+
+int
+ddt_ditto_copies_needed(ddt_t *ddt, ddt_entry_t *dde, ddt_phys_t *ddp_willref)
+{
+       spa_t *spa = ddt->ddt_spa;
+       uint64_t total_refcnt = 0;
+       uint64_t ditto = spa->spa_dedup_ditto;
+       int total_copies = 0;
+       int desired_copies = 0;
+
+       for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++) {
+               ddt_phys_t *ddp = &dde->dde_phys[p];
+               zio_t *zio = dde->dde_lead_zio[p];
+               uint64_t refcnt = ddp->ddp_refcnt;      /* committed refs */
+               if (zio != NULL)
+                       refcnt += zio->io_parent_count; /* pending refs */
+               if (ddp == ddp_willref)
+                       refcnt++;                       /* caller's ref */
+               if (refcnt != 0) {
+                       total_refcnt += refcnt;
+                       total_copies += p;
+               }
+       }
+
+       if (ditto == 0 || ditto > UINT32_MAX)
+               ditto = UINT32_MAX;
+
+       if (total_refcnt >= 1)
+               desired_copies++;
+       if (total_refcnt >= ditto)
+               desired_copies++;
+       if (total_refcnt >= ditto * ditto)
+               desired_copies++;
+
+       return (MAX(desired_copies, total_copies) - total_copies);
+}
+
+int
+ddt_ditto_copies_present(ddt_entry_t *dde)
+{
+       ddt_phys_t *ddp = &dde->dde_phys[DDT_PHYS_DITTO];
+       dva_t *dva = ddp->ddp_dva;
+       int copies = 0 - DVA_GET_GANG(dva);
+
+       for (int d = 0; d < SPA_DVAS_PER_BP; d++, dva++)
+               if (DVA_IS_VALID(dva))
+                       copies++;
+
+       ASSERT(copies >= 0 && copies < SPA_DVAS_PER_BP);
+
+       return (copies);
+}
+
+size_t
+ddt_compress(void *src, uchar_t *dst, size_t s_len, size_t d_len)
+{
+       uchar_t *version = dst++;
+       int cpfunc = ZIO_COMPRESS_ZLE;
+       zio_compress_info_t *ci = &zio_compress_table[cpfunc];
+       size_t c_len;
+
+       ASSERT(d_len >= s_len + 1);     /* no compression plus version byte */
+
+       c_len = ci->ci_compress(src, dst, s_len, d_len - 1, ci->ci_level);
+
+       if (c_len == s_len) {
+               cpfunc = ZIO_COMPRESS_OFF;
+               bcopy(src, dst, s_len);
+       }
+
+       *version = (ZFS_HOST_BYTEORDER & DDT_COMPRESS_BYTEORDER_MASK) | cpfunc;
+
+       return (c_len + 1);
+}
+
+void
+ddt_decompress(uchar_t *src, void *dst, size_t s_len, size_t d_len)
+{
+       uchar_t version = *src++;
+       int cpfunc = version & DDT_COMPRESS_FUNCTION_MASK;
+       zio_compress_info_t *ci = &zio_compress_table[cpfunc];
+
+       if (ci->ci_decompress != NULL)
+               (void) ci->ci_decompress(src, dst, s_len, d_len, ci->ci_level);
+       else
+               bcopy(src, dst, d_len);
+
+       if ((version ^ ZFS_HOST_BYTEORDER) & DDT_COMPRESS_BYTEORDER_MASK)
+               byteswap_uint64_array(dst, d_len);
+}
+
+ddt_t *
+ddt_select_by_checksum(spa_t *spa, enum zio_checksum c)
+{
+       return (spa->spa_ddt[c]);
+}
+
+ddt_t *
+ddt_select(spa_t *spa, const blkptr_t *bp)
+{
+       return (spa->spa_ddt[BP_GET_CHECKSUM(bp)]);
+}
+
+void
+ddt_enter(ddt_t *ddt)
+{
+       mutex_enter(&ddt->ddt_lock);
+}
+
+void
+ddt_exit(ddt_t *ddt)
+{
+       mutex_exit(&ddt->ddt_lock);
+}
+
+static ddt_entry_t *
+ddt_alloc(const ddt_key_t *ddk)
+{
+       ddt_entry_t *dde;
+
+       dde = kmem_zalloc(sizeof (ddt_entry_t), KM_SLEEP);
+       cv_init(&dde->dde_cv, NULL, CV_DEFAULT, NULL);
+
+       dde->dde_key = *ddk;
+
+       return (dde);
+}
+
+static void
+ddt_free(ddt_entry_t *dde)
+{
+       ASSERT(!dde->dde_loading);
+
+       for (int p = 0; p < DDT_PHYS_TYPES; p++)
+               ASSERT(dde->dde_lead_zio[p] == NULL);
+
+       if (dde->dde_repair_data != NULL)
+               zio_buf_free(dde->dde_repair_data,
+                   DDK_GET_PSIZE(&dde->dde_key));
+
+       cv_destroy(&dde->dde_cv);
+       kmem_free(dde, sizeof (*dde));
+}
+
+void
+ddt_remove(ddt_t *ddt, ddt_entry_t *dde)
+{
+       ASSERT(MUTEX_HELD(&ddt->ddt_lock));
+
+       avl_remove(&ddt->ddt_tree, dde);
+       ddt_free(dde);
+}
+
+ddt_entry_t *
+ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add)
+{
+       ddt_entry_t *dde, dde_search;
+       enum ddt_type type;
+       enum ddt_class class;
+       avl_index_t where;
+       int error;
+
+       ASSERT(MUTEX_HELD(&ddt->ddt_lock));
+
+       ddt_key_fill(&dde_search.dde_key, bp);
+
+       dde = avl_find(&ddt->ddt_tree, &dde_search, &where);
+       if (dde == NULL) {
+               if (!add)
+                       return (NULL);
+               dde = ddt_alloc(&dde_search.dde_key);
+               avl_insert(&ddt->ddt_tree, dde, where);
+       }
+
+       while (dde->dde_loading)
+               cv_wait(&dde->dde_cv, &ddt->ddt_lock);
+
+       if (dde->dde_loaded)
+               return (dde);
+
+       dde->dde_loading = B_TRUE;
+
+       ddt_exit(ddt);
+
+       error = ENOENT;
+
+       for (type = 0; type < DDT_TYPES; type++) {
+               for (class = 0; class < DDT_CLASSES; class++) {
+                       error = ddt_object_lookup(ddt, type, class, dde);
+                       if (error != ENOENT)
+                               break;
+               }
+               if (error != ENOENT)
+                       break;
+       }
+
+       ASSERT(error == 0 || error == ENOENT);
+
+       ddt_enter(ddt);
+
+       ASSERT(dde->dde_loaded == B_FALSE);
+       ASSERT(dde->dde_loading == B_TRUE);
+
+       dde->dde_type = type;   /* will be DDT_TYPES if no entry found */
+       dde->dde_class = class; /* will be DDT_CLASSES if no entry found */
+       dde->dde_loaded = B_TRUE;
+       dde->dde_loading = B_FALSE;
+
+       if (error == 0)
+               ddt_stat_update(ddt, dde, -1ULL);
+
+       cv_broadcast(&dde->dde_cv);
+
+       return (dde);
+}
+
+void
+ddt_prefetch(spa_t *spa, const blkptr_t *bp)
+{
+       ddt_t *ddt;
+       ddt_entry_t dde;
+
+       if (!BP_GET_DEDUP(bp))
+               return;
+
+       /*
+        * We remove the DDT once it's empty and only prefetch dedup blocks
+        * when there are entries in the DDT.  Thus no locking is required
+        * as the DDT can't disappear on us.
+        */
+       ddt = ddt_select(spa, bp);
+       ddt_key_fill(&dde.dde_key, bp);
+
+       for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+               for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+                       ddt_object_prefetch(ddt, type, class, &dde);
+               }
+       }
+}
+
+int
+ddt_entry_compare(const void *x1, const void *x2)
+{
+       const ddt_entry_t *dde1 = x1;
+       const ddt_entry_t *dde2 = x2;
+       const uint64_t *u1 = (const uint64_t *)&dde1->dde_key;
+       const uint64_t *u2 = (const uint64_t *)&dde2->dde_key;
+
+       for (int i = 0; i < DDT_KEY_WORDS; i++) {
+               if (u1[i] < u2[i])
+                       return (-1);
+               if (u1[i] > u2[i])
+                       return (1);
+       }
+
+       return (0);
+}
+
+static ddt_t *
+ddt_table_alloc(spa_t *spa, enum zio_checksum c)
+{
+       ddt_t *ddt;
+
+       ddt = kmem_zalloc(sizeof (*ddt), KM_SLEEP);
+
+       mutex_init(&ddt->ddt_lock, NULL, MUTEX_DEFAULT, NULL);
+       avl_create(&ddt->ddt_tree, ddt_entry_compare,
+           sizeof (ddt_entry_t), offsetof(ddt_entry_t, dde_node));
+       avl_create(&ddt->ddt_repair_tree, ddt_entry_compare,
+           sizeof (ddt_entry_t), offsetof(ddt_entry_t, dde_node));
+       ddt->ddt_checksum = c;
+       ddt->ddt_spa = spa;
+       ddt->ddt_os = spa->spa_meta_objset;
+
+       return (ddt);
+}
+
+static void
+ddt_table_free(ddt_t *ddt)
+{
+       ASSERT(avl_numnodes(&ddt->ddt_tree) == 0);
+       ASSERT(avl_numnodes(&ddt->ddt_repair_tree) == 0);
+       avl_destroy(&ddt->ddt_tree);
+       avl_destroy(&ddt->ddt_repair_tree);
+       mutex_destroy(&ddt->ddt_lock);
+       kmem_free(ddt, sizeof (*ddt));
+}
+
+void
+ddt_create(spa_t *spa)
+{
+       spa->spa_dedup_checksum = ZIO_DEDUPCHECKSUM;
+
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
+               spa->spa_ddt[c] = ddt_table_alloc(spa, c);
+}
+
+int
+ddt_load(spa_t *spa)
+{
+       int error;
+
+       ddt_create(spa);
+
+       error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+           DMU_POOL_DDT_STATS, sizeof (uint64_t), 1,
+           &spa->spa_ddt_stat_object);
+
+       if (error)
+               return (error == ENOENT ? 0 : error);
+
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+               ddt_t *ddt = spa->spa_ddt[c];
+               for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+                       for (enum ddt_class class = 0; class < DDT_CLASSES;
+                           class++) {
+                               error = ddt_object_load(ddt, type, class);
+                               if (error != 0 && error != ENOENT)
+                                       return (error);
+                       }
+               }
+
+               /*
+                * Seed the cached histograms.
+                */
+               bcopy(ddt->ddt_histogram, &ddt->ddt_histogram_cache,
+                   sizeof (ddt->ddt_histogram));
+       }
+
+       return (0);
+}
+
+void
+ddt_unload(spa_t *spa)
+{
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+               if (spa->spa_ddt[c]) {
+                       ddt_table_free(spa->spa_ddt[c]);
+                       spa->spa_ddt[c] = NULL;
+               }
+       }
+}
+
+boolean_t
+ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
+{
+       ddt_t *ddt;
+       ddt_entry_t dde;
+
+       if (!BP_GET_DEDUP(bp))
+               return (B_FALSE);
+
+       if (max_class == DDT_CLASS_UNIQUE)
+               return (B_TRUE);
+
+       ddt = spa->spa_ddt[BP_GET_CHECKSUM(bp)];
+
+       ddt_key_fill(&dde.dde_key, bp);
+
+       for (enum ddt_type type = 0; type < DDT_TYPES; type++)
+               for (enum ddt_class class = 0; class <= max_class; class++)
+                       if (ddt_object_lookup(ddt, type, class, &dde) == 0)
+                               return (B_TRUE);
+
+       return (B_FALSE);
+}
+
+ddt_entry_t *
+ddt_repair_start(ddt_t *ddt, const blkptr_t *bp)
+{
+       ddt_key_t ddk;
+       ddt_entry_t *dde;
+
+       ddt_key_fill(&ddk, bp);
+
+       dde = ddt_alloc(&ddk);
+
+       for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+               for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+                       /*
+                        * We can only do repair if there are multiple copies
+                        * of the block.  For anything in the UNIQUE class,
+                        * there's definitely only one copy, so don't even try.
+                        */
+                       if (class != DDT_CLASS_UNIQUE &&
+                           ddt_object_lookup(ddt, type, class, dde) == 0)
+                               return (dde);
+               }
+       }
+
+       bzero(dde->dde_phys, sizeof (dde->dde_phys));
+
+       return (dde);
+}
+
+void
+ddt_repair_done(ddt_t *ddt, ddt_entry_t *dde)
+{
+       avl_index_t where;
+
+       ddt_enter(ddt);
+
+       if (dde->dde_repair_data != NULL && spa_writeable(ddt->ddt_spa) &&
+           avl_find(&ddt->ddt_repair_tree, dde, &where) == NULL)
+               avl_insert(&ddt->ddt_repair_tree, dde, where);
+       else
+               ddt_free(dde);
+
+       ddt_exit(ddt);
+}
+
+static void
+ddt_repair_entry_done(zio_t *zio)
+{
+       ddt_entry_t *rdde = zio->io_private;
+
+       ddt_free(rdde);
+}
+
+static void
+ddt_repair_entry(ddt_t *ddt, ddt_entry_t *dde, ddt_entry_t *rdde, zio_t *rio)
+{
+       ddt_phys_t *ddp = dde->dde_phys;
+       ddt_phys_t *rddp = rdde->dde_phys;
+       ddt_key_t *ddk = &dde->dde_key;
+       ddt_key_t *rddk = &rdde->dde_key;
+       zio_t *zio;
+       blkptr_t blk;
+
+       zio = zio_null(rio, rio->io_spa, NULL,
+           ddt_repair_entry_done, rdde, rio->io_flags);
+
+       for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++, rddp++) {
+               if (ddp->ddp_phys_birth == 0 ||
+                   ddp->ddp_phys_birth != rddp->ddp_phys_birth ||
+                   bcmp(ddp->ddp_dva, rddp->ddp_dva, sizeof (ddp->ddp_dva)))
+                       continue;
+               ddt_bp_create(ddt->ddt_checksum, ddk, ddp, &blk);
+               zio_nowait(zio_rewrite(zio, zio->io_spa, 0, &blk,
+                   rdde->dde_repair_data, DDK_GET_PSIZE(rddk), NULL, NULL,
+                   ZIO_PRIORITY_SYNC_WRITE, ZIO_DDT_CHILD_FLAGS(zio), NULL));
+       }
+
+       zio_nowait(zio);
+}
+
+static void
+ddt_repair_table(ddt_t *ddt, zio_t *rio)
+{
+       spa_t *spa = ddt->ddt_spa;
+       ddt_entry_t *dde, *rdde_next, *rdde;
+       avl_tree_t *t = &ddt->ddt_repair_tree;
+       blkptr_t blk;
+
+       if (spa_sync_pass(spa) > 1)
+               return;
+
+       ddt_enter(ddt);
+       for (rdde = avl_first(t); rdde != NULL; rdde = rdde_next) {
+               rdde_next = AVL_NEXT(t, rdde);
+               avl_remove(&ddt->ddt_repair_tree, rdde);
+               ddt_exit(ddt);
+               ddt_bp_create(ddt->ddt_checksum, &rdde->dde_key, NULL, &blk);
+               dde = ddt_repair_start(ddt, &blk);
+               ddt_repair_entry(ddt, dde, rdde, rio);
+               ddt_repair_done(ddt, dde);
+               ddt_enter(ddt);
+       }
+       ddt_exit(ddt);
+}
+
+static void
+ddt_sync_entry(ddt_t *ddt, ddt_entry_t *dde, dmu_tx_t *tx, uint64_t txg)
+{
+       dsl_pool_t *dp = ddt->ddt_spa->spa_dsl_pool;
+       ddt_phys_t *ddp = dde->dde_phys;
+       ddt_key_t *ddk = &dde->dde_key;
+       enum ddt_type otype = dde->dde_type;
+       enum ddt_type ntype = DDT_TYPE_CURRENT;
+       enum ddt_class oclass = dde->dde_class;
+       enum ddt_class nclass;
+       uint64_t total_refcnt = 0;
+
+       ASSERT(dde->dde_loaded);
+       ASSERT(!dde->dde_loading);
+
+       for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+               ASSERT(dde->dde_lead_zio[p] == NULL);
+               ASSERT((int64_t)ddp->ddp_refcnt >= 0);
+               if (ddp->ddp_phys_birth == 0) {
+                       ASSERT(ddp->ddp_refcnt == 0);
+                       continue;
+               }
+               if (p == DDT_PHYS_DITTO) {
+                       if (ddt_ditto_copies_needed(ddt, dde, NULL) == 0)
+                               ddt_phys_free(ddt, ddk, ddp, txg);
+                       continue;
+               }
+               if (ddp->ddp_refcnt == 0)
+                       ddt_phys_free(ddt, ddk, ddp, txg);
+               total_refcnt += ddp->ddp_refcnt;
+       }
+
+       if (dde->dde_phys[DDT_PHYS_DITTO].ddp_phys_birth != 0)
+               nclass = DDT_CLASS_DITTO;
+       else if (total_refcnt > 1)
+               nclass = DDT_CLASS_DUPLICATE;
+       else
+               nclass = DDT_CLASS_UNIQUE;
+
+       if (otype != DDT_TYPES &&
+           (otype != ntype || oclass != nclass || total_refcnt == 0)) {
+               VERIFY(ddt_object_remove(ddt, otype, oclass, dde, tx) == 0);
+               ASSERT(ddt_object_lookup(ddt, otype, oclass, dde) == ENOENT);
+       }
+
+       if (total_refcnt != 0) {
+               dde->dde_type = ntype;
+               dde->dde_class = nclass;
+               ddt_stat_update(ddt, dde, 0);
+               if (!ddt_object_exists(ddt, ntype, nclass))
+                       ddt_object_create(ddt, ntype, nclass, tx);
+               VERIFY(ddt_object_update(ddt, ntype, nclass, dde, tx) == 0);
+
+               /*
+                * If the class changes, the order that we scan this bp
+                * changes.  If it decreases, we could miss it, so
+                * scan it right now.  (This covers both class changing
+                * while we are doing ddt_walk(), and when we are
+                * traversing.)
+                */
+               if (nclass < oclass) {
+                       dsl_scan_ddt_entry(dp->dp_scan,
+                           ddt->ddt_checksum, dde, tx);
+               }
+       }
+}
+
+static void
+ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
+{
+       spa_t *spa = ddt->ddt_spa;
+       ddt_entry_t *dde;
+       void *cookie = NULL;
+
+       if (avl_numnodes(&ddt->ddt_tree) == 0)
+               return;
+
+       ASSERT(spa->spa_uberblock.ub_version >= SPA_VERSION_DEDUP);
+
+       if (spa->spa_ddt_stat_object == 0) {
+               spa->spa_ddt_stat_object = zap_create(ddt->ddt_os,
+                   DMU_OT_DDT_STATS, DMU_OT_NONE, 0, tx);
+               VERIFY(zap_add(ddt->ddt_os, DMU_POOL_DIRECTORY_OBJECT,
+                   DMU_POOL_DDT_STATS, sizeof (uint64_t), 1,
+                   &spa->spa_ddt_stat_object, tx) == 0);
+       }
+
+       while ((dde = avl_destroy_nodes(&ddt->ddt_tree, &cookie)) != NULL) {
+               ddt_sync_entry(ddt, dde, tx, txg);
+               ddt_free(dde);
+       }
+
+       for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
+               for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+                       if (!ddt_object_exists(ddt, type, class))
+                               continue;
+                       ddt_object_sync(ddt, type, class, tx);
+                       if (ddt_object_count(ddt, type, class) == 0)
+                               ddt_object_destroy(ddt, type, class, tx);
+               }
+       }
+
+       bcopy(ddt->ddt_histogram, &ddt->ddt_histogram_cache,
+           sizeof (ddt->ddt_histogram));
+}
+
+void
+ddt_sync(spa_t *spa, uint64_t txg)
+{
+       dmu_tx_t *tx;
+       zio_t *rio = zio_root(spa, NULL, NULL,
+           ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE);
+
+       ASSERT(spa_syncing_txg(spa) == txg);
+
+       tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
+
+       for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+               ddt_t *ddt = spa->spa_ddt[c];
+               if (ddt == NULL)
+                       continue;
+               ddt_sync_table(ddt, tx, txg);
+               ddt_repair_table(ddt, rio);
+       }
+
+       (void) zio_wait(rio);
+
+       dmu_tx_commit(tx);
+}
+
+int
+ddt_walk(spa_t *spa, ddt_bookmark_t *ddb, ddt_entry_t *dde)
+{
+       do {
+               do {
+                       do {
+                               ddt_t *ddt = spa->spa_ddt[ddb->ddb_checksum];
+                               int error = ENOENT;
+                               if (ddt_object_exists(ddt, ddb->ddb_type,
+                                   ddb->ddb_class)) {
+                                       error = ddt_object_walk(ddt,
+                                           ddb->ddb_type, ddb->ddb_class,
+                                           &ddb->ddb_cursor, dde);
+                               }
+                               dde->dde_type = ddb->ddb_type;
+                               dde->dde_class = ddb->ddb_class;
+                               if (error == 0)
+                                       return (0);
+                               if (error != ENOENT)
+                                       return (error);
+                               ddb->ddb_cursor = 0;
+                       } while (++ddb->ddb_checksum < ZIO_CHECKSUM_FUNCTIONS);
+                       ddb->ddb_checksum = 0;
+               } while (++ddb->ddb_type < DDT_TYPES);
+               ddb->ddb_type = 0;
+       } while (++ddb->ddb_class < DDT_CLASSES);
+
+       return (ENOENT);
+}