X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=module%2Fzfs%2Fddt.c;h=286f3bb60499e2d0b22447abc19da95815aaa65a;hb=refs%2Fheads%2Frertzinger%2Ffeature-zpool-get--p;hp=71833149676561796130db2e2a1ec5009e3d8bb7;hpb=572e285762521df27fe5b026f409ba1a21abb7ac;p=zfs.git

diff --git a/module/zfs/ddt.c b/module/zfs/ddt.c
index 7183314..286f3bb 100644
--- a/module/zfs/ddt.c
+++ b/module/zfs/ddt.c
@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -82,13 +83,14 @@ ddt_object_destroy(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 	spa_t *spa = ddt->ddt_spa;
 	objset_t *os = ddt->ddt_os;
 	uint64_t *objectp = &ddt->ddt_object[type][class];
+	uint64_t count;
 	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(ddt_object_count(ddt, type, class, &count) == 0 && count == 0);
 	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);
@@ -102,6 +104,7 @@ 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;
+	uint64_t count;
 	char name[DDT_NAMELEN];
 	int error;
 
@@ -120,9 +123,15 @@ ddt_object_load(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
 	/*
 	 * Seed the cached statistics.
 	 */
-	VERIFY(ddt_object_info(ddt, type, class, &doi) == 0);
+	error = ddt_object_info(ddt, type, class, &doi);
+	if (error)
+		return (error);
+
+	error = ddt_object_count(ddt, type, class, &count);
+	if (error)
+		return (error);
 
-	ddo->ddo_count = ddt_object_count(ddt, type, class);
+	ddo->ddo_count = count;
 	ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
 	ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
 
@@ -136,6 +145,7 @@ ddt_object_sync(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;
+	uint64_t count;
 	char name[DDT_NAMELEN];
 
 	ddt_object_name(ddt, type, class, name);
@@ -148,8 +158,9 @@ ddt_object_sync(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 	 * Cache DDT statistics; this is the only time they'll change.
 	 */
 	VERIFY(ddt_object_info(ddt, type, class, &doi) == 0);
+	VERIFY(ddt_object_count(ddt, type, class, &count) == 0);
 
-	ddo->ddo_count = ddt_object_count(ddt, type, class);
+	ddo->ddo_count = count;
 	ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
 	ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
 }
@@ -206,13 +217,14 @@ ddt_object_walk(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 	    ddt->ddt_object[type][class], dde, walk));
 }
 
-uint64_t
-ddt_object_count(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
+int
+ddt_object_count(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
+    uint64_t *count)
 {
 	ASSERT(ddt_object_exists(ddt, type, class));
 
 	return (ddt_ops[type]->ddt_op_count(ddt->ddt_os,
-	    ddt->ddt_object[type][class]));
+	    ddt->ddt_object[type][class], count));
 }
 
 int
@@ -244,9 +256,10 @@ ddt_object_name(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 void
 ddt_bp_fill(const ddt_phys_t *ddp, blkptr_t *bp, uint64_t txg)
 {
+	int d;
 	ASSERT(txg != 0);
 
-	for (int d = 0; d < SPA_DVAS_PER_BP; d++)
+	for (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);
 }
@@ -287,9 +300,10 @@ ddt_key_fill(ddt_key_t *ddk, const blkptr_t *bp)
 void
 ddt_phys_fill(ddt_phys_t *ddp, const blkptr_t *bp)
 {
+	int d;
 	ASSERT(ddp->ddp_phys_birth == 0);
 
-	for (int d = 0; d < SPA_DVAS_PER_BP; d++)
+	for (d = 0; d < SPA_DVAS_PER_BP; d++)
 		ddp->ddp_dva[d] = bp->blk_dva[d];
 	ddp->ddp_phys_birth = BP_PHYSICAL_BIRTH(bp);
 }
@@ -309,8 +323,10 @@ ddt_phys_addref(ddt_phys_t *ddp)
 void
 ddt_phys_decref(ddt_phys_t *ddp)
 {
-	ASSERT((int64_t)ddp->ddp_refcnt > 0);
-	ddp->ddp_refcnt--;
+	if (ddp) {
+		ASSERT(ddp->ddp_refcnt > 0);
+		ddp->ddp_refcnt--;
+	}
 }
 
 void
@@ -327,8 +343,9 @@ 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;
+	int p;
 
-	for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+	for (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);
@@ -340,8 +357,9 @@ uint64_t
 ddt_phys_total_refcnt(const ddt_entry_t *dde)
 {
 	uint64_t refcnt = 0;
+	int p;
 
-	for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++)
+	for (p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++)
 		refcnt += dde->dde_phys[p].ddp_refcnt;
 
 	return (refcnt);
@@ -355,17 +373,18 @@ ddt_stat_generate(ddt_t *ddt, ddt_entry_t *dde, ddt_stat_t *dds)
 	ddt_key_t *ddk = &dde->dde_key;
 	uint64_t lsize = DDK_GET_LSIZE(ddk);
 	uint64_t psize = DDK_GET_PSIZE(ddk);
+	int p, d;
 
 	bzero(dds, sizeof (*dds));
 
-	for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+	for (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++)
+		for (d = 0; d < SPA_DVAS_PER_BP; d++)
 			dsize += dva_get_dsize_sync(spa, &ddp->ddp_dva[d]);
 
 		dds->dds_blocks += 1;
@@ -413,16 +432,20 @@ ddt_stat_update(ddt_t *ddt, ddt_entry_t *dde, uint64_t neg)
 void
 ddt_histogram_add(ddt_histogram_t *dst, const ddt_histogram_t *src)
 {
-	for (int h = 0; h < 64; h++)
+	int h;
+
+	for (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)
 {
+	int h;
+
 	bzero(dds, sizeof (*dds));
 
-	for (int h = 0; h < 64; h++)
+	for (h = 0; h < 64; h++)
 		ddt_stat_add(dds, &ddh->ddh_stat[h], 0);
 }
 
@@ -442,11 +465,15 @@ ddt_histogram_empty(const ddt_histogram_t *ddh)
 void
 ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
 {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
+
 	/* Sum the statistics we cached in ddt_object_sync(). */
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	for (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;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				ddt_object_t *ddo =
 				    &ddt->ddt_object_stats[type][class];
@@ -467,10 +494,14 @@ ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
 void
 ddt_get_dedup_histogram(spa_t *spa, ddt_histogram_t *ddh)
 {
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
+
+	for (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;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				ddt_histogram_add(ddh,
 				    &ddt->ddt_histogram_cache[type][class]);
@@ -484,7 +515,8 @@ 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);
+	/* XXX: Move to a slab */
+	ddh_total = kmem_zalloc(sizeof (ddt_histogram_t), KM_PUSHPAGE);
 	ddt_get_dedup_histogram(spa, ddh_total);
 	ddt_histogram_stat(dds_total, ddh_total);
 	kmem_free(ddh_total, sizeof (ddt_histogram_t));
@@ -519,8 +551,9 @@ ddt_ditto_copies_needed(ddt_t *ddt, ddt_entry_t *dde, ddt_phys_t *ddp_willref)
 	uint64_t ditto = spa->spa_dedup_ditto;
 	int total_copies = 0;
 	int desired_copies = 0;
+	int p;
 
-	for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++) {
+	for (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 */
@@ -553,8 +586,9 @@ 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);
+	int d;
 
-	for (int d = 0; d < SPA_DVAS_PER_BP; d++, dva++)
+	for (d = 0; d < SPA_DVAS_PER_BP; d++, dva++)
 		if (DVA_IS_VALID(dva))
 			copies++;
 
@@ -630,7 +664,8 @@ ddt_alloc(const ddt_key_t *ddk)
 {
 	ddt_entry_t *dde;
 
-	dde = kmem_zalloc(sizeof (ddt_entry_t), KM_SLEEP);
+	/* XXX: Move to a slab */
+	dde = kmem_zalloc(sizeof (ddt_entry_t), KM_PUSHPAGE);
 	cv_init(&dde->dde_cv, NULL, CV_DEFAULT, NULL);
 
 	dde->dde_key = *ddk;
@@ -641,9 +676,11 @@ ddt_alloc(const ddt_key_t *ddk)
 static void
 ddt_free(ddt_entry_t *dde)
 {
+	int p;
+
 	ASSERT(!dde->dde_loading);
 
-	for (int p = 0; p < DDT_PHYS_TYPES; p++)
+	for (p = 0; p < DDT_PHYS_TYPES; p++)
 		ASSERT(dde->dde_lead_zio[p] == NULL);
 
 	if (dde->dde_repair_data != NULL)
@@ -731,6 +768,8 @@ ddt_prefetch(spa_t *spa, const blkptr_t *bp)
 {
 	ddt_t *ddt;
 	ddt_entry_t dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (!zfs_dedup_prefetch || bp == NULL || !BP_GET_DEDUP(bp))
 		return;
@@ -743,8 +782,8 @@ ddt_prefetch(spa_t *spa, const blkptr_t *bp)
 	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++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class < DDT_CLASSES; class++) {
 			ddt_object_prefetch(ddt, type, class, &dde);
 		}
 	}
@@ -757,8 +796,9 @@ ddt_entry_compare(const void *x1, const void *x2)
 	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;
+	int i;
 
-	for (int i = 0; i < DDT_KEY_WORDS; i++) {
+	for (i = 0; i < DDT_KEY_WORDS; i++) {
 		if (u1[i] < u2[i])
 			return (-1);
 		if (u1[i] > u2[i])
@@ -773,7 +813,8 @@ ddt_table_alloc(spa_t *spa, enum zio_checksum c)
 {
 	ddt_t *ddt;
 
-	ddt = kmem_zalloc(sizeof (*ddt), KM_SLEEP);
+	/* XXX: Move to a slab */
+	ddt = kmem_zalloc(sizeof (*ddt), KM_PUSHPAGE | KM_NODEBUG);
 
 	mutex_init(&ddt->ddt_lock, NULL, MUTEX_DEFAULT, NULL);
 	avl_create(&ddt->ddt_tree, ddt_entry_compare,
@@ -801,15 +842,20 @@ ddt_table_free(ddt_t *ddt)
 void
 ddt_create(spa_t *spa)
 {
+	enum zio_checksum c;
+
 	spa->spa_dedup_checksum = ZIO_DEDUPCHECKSUM;
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
 		spa->spa_ddt[c] = ddt_table_alloc(spa, c);
 }
 
 int
 ddt_load(spa_t *spa)
 {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
 	int error;
 
 	ddt_create(spa);
@@ -821,10 +867,10 @@ ddt_load(spa_t *spa)
 	if (error)
 		return (error == ENOENT ? 0 : error);
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	for (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;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				error = ddt_object_load(ddt, type, class);
 				if (error != 0 && error != ENOENT)
@@ -845,7 +891,9 @@ ddt_load(spa_t *spa)
 void
 ddt_unload(spa_t *spa)
 {
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	enum zio_checksum c;
+
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		if (spa->spa_ddt[c]) {
 			ddt_table_free(spa->spa_ddt[c]);
 			spa->spa_ddt[c] = NULL;
@@ -857,7 +905,9 @@ boolean_t
 ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 {
 	ddt_t *ddt;
-	ddt_entry_t dde;
+	ddt_entry_t *dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (!BP_GET_DEDUP(bp))
 		return (B_FALSE);
@@ -866,14 +916,20 @@ ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 		return (B_TRUE);
 
 	ddt = spa->spa_ddt[BP_GET_CHECKSUM(bp)];
+	dde = kmem_alloc(sizeof(ddt_entry_t), KM_PUSHPAGE);
 
-	ddt_key_fill(&dde.dde_key, 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)
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class <= max_class; class++) {
+			if (ddt_object_lookup(ddt, type, class, dde) == 0) {
+				kmem_free(dde, sizeof(ddt_entry_t));
 				return (B_TRUE);
+			}
+		}
+	}
 
+	kmem_free(dde, sizeof(ddt_entry_t));
 	return (B_FALSE);
 }
 
@@ -882,13 +938,15 @@ ddt_repair_start(ddt_t *ddt, const blkptr_t *bp)
 {
 	ddt_key_t ddk;
 	ddt_entry_t *dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	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++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (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,
@@ -938,11 +996,12 @@ ddt_repair_entry(ddt_t *ddt, ddt_entry_t *dde, ddt_entry_t *rdde, zio_t *rio)
 	ddt_key_t *rddk = &rdde->dde_key;
 	zio_t *zio;
 	blkptr_t blk;
+	int p;
 
 	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++) {
+	for (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)))
@@ -992,13 +1051,13 @@ ddt_sync_entry(ddt_t *ddt, ddt_entry_t *dde, dmu_tx_t *tx, uint64_t txg)
 	enum ddt_class oclass = dde->dde_class;
 	enum ddt_class nclass;
 	uint64_t total_refcnt = 0;
+	int p;
 
 	ASSERT(dde->dde_loaded);
 	ASSERT(!dde->dde_loading);
 
-	for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
+	for (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;
@@ -1054,6 +1113,8 @@ 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;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (avl_numnodes(&ddt->ddt_tree) == 0)
 		return;
@@ -1061,11 +1122,9 @@ ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
 	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);
+		spa->spa_ddt_stat_object = zap_create_link(ddt->ddt_os,
+		    DMU_OT_DDT_STATS, DMU_POOL_DIRECTORY_OBJECT,
+		    DMU_POOL_DDT_STATS, tx);
 	}
 
 	while ((dde = avl_destroy_nodes(&ddt->ddt_tree, &cookie)) != NULL) {
@@ -1073,15 +1132,17 @@ ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
 		ddt_free(dde);
 	}
 
-	for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-		uint64_t count = 0;
-		for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		uint64_t add, count = 0;
+		for (class = 0; class < DDT_CLASSES; class++) {
 			if (ddt_object_exists(ddt, type, class)) {
 				ddt_object_sync(ddt, type, class, tx);
-				count += ddt_object_count(ddt, type, class);
+				VERIFY(ddt_object_count(ddt, type, class,
+				    &add) == 0);
+				count += add;
 			}
 		}
-		for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+		for (class = 0; class < DDT_CLASSES; class++) {
 			if (count == 0 && ddt_object_exists(ddt, type, class))
 				ddt_object_destroy(ddt, type, class, tx);
 		}
@@ -1097,12 +1158,13 @@ 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);
+	enum zio_checksum c;
 
 	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++) {
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
 		if (ddt == NULL)
 			continue;
@@ -1144,3 +1206,8 @@ ddt_walk(spa_t *spa, ddt_bookmark_t *ddb, ddt_entry_t *dde)
 
 	return (ENOENT);
 }
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+module_param(zfs_dedup_prefetch, int, 0644);
+MODULE_PARM_DESC(zfs_dedup_prefetch,"Enable prefetching dedup-ed blks");
+#endif