Illumos #3498 panic in arc_read()

3498 panic in arc_read(): !refcount_is_zero(&pbuf->b_hdr->b_refcnt)
Reviewed by: Adam Leventhal <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Approved by: Richard Lowe <[email protected]>

References:
  illumos/illumos-gate@1b912ec7100c10e7243bf0879af0fe580e08c73d
  https://www.illumos.org/issues/3498

Ported-by: Brian Behlendorf <[email protected]>
Closes #1249

12 files changed, 70 insertions, 177 deletions

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 26677255d..de869666b 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -884,7 +884,6 @@ buf_cons(void *vbuf, void *unused, int kmflag)
 
 	bzero(buf, sizeof (arc_buf_t));
 	mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
-	rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL);
 	arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
 
 	return (0);
@@ -914,7 +913,6 @@ buf_dest(void *vbuf, void *unused)
 	arc_buf_t *buf = vbuf;
 
 	mutex_destroy(&buf->b_evict_lock);
-	rw_destroy(&buf->b_data_lock);
 	arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
 }
 
@@ -2907,42 +2905,11 @@ arc_read_done(zio_t *zio)
  *
  * arc_read_done() will invoke all the requested "done" functions
  * for readers of this block.
- *
- * Normal callers should use arc_read and pass the arc buffer and offset
- * for the bp.  But if you know you don't need locking, you can use
- * arc_read_bp.
  */
 int
-arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf,
-    arc_done_func_t *done, void *private, int priority, int zio_flags,
-    uint32_t *arc_flags, const zbookmark_t *zb)
-{
-	int err;
-
-	if (pbuf == NULL) {
-		/*
-		 * XXX This happens from traverse callback funcs, for
-		 * the objset_phys_t block.
-		 */
-		return (arc_read_nolock(pio, spa, bp, done, private, priority,
-		    zio_flags, arc_flags, zb));
-	}
-
-	ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
-	ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
-	rw_enter(&pbuf->b_data_lock, RW_READER);
-
-	err = arc_read_nolock(pio, spa, bp, done, private, priority,
-	    zio_flags, arc_flags, zb);
-	rw_exit(&pbuf->b_data_lock);
-
-	return (err);
-}
-
-int
-arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
-    arc_done_func_t *done, void *private, int priority, int zio_flags,
-    uint32_t *arc_flags, const zbookmark_t *zb)
+arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
+    void *private, int priority, int zio_flags, uint32_t *arc_flags,
+    const zbookmark_t *zb)
 {
 	arc_buf_hdr_t *hdr;
 	arc_buf_t *buf = NULL;
@@ -3480,19 +3447,6 @@ arc_release(arc_buf_t *buf, void *tag)
 	}
 }
 
-/*
- * Release this buffer.  If it does not match the provided BP, fill it
- * with that block's contents.
- */
-/* ARGSUSED */
-int
-arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa,
-    zbookmark_t *zb)
-{
-	arc_release(buf, tag);
-	return (0);
-}
-
 int
 arc_released(arc_buf_t *buf)
 {
diff --git a/module/zfs/bptree.c b/module/zfs/bptree.c
index 1a009cfe5..73922db88 100644
--- a/module/zfs/bptree.c
+++ b/module/zfs/bptree.c
@@ -135,7 +135,7 @@ bptree_add(objset_t *os, uint64_t obj, blkptr_t *bp, uint64_t birth_txg,
 
 /* ARGSUSED */
 static int
-bptree_visit_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
+bptree_visit_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	int err;
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 83a8035dd..46f42dd7c 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -559,7 +559,6 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 	spa_t *spa;
 	zbookmark_t zb;
 	uint32_t aflags = ARC_NOWAIT;
-	arc_buf_t *pbuf;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
@@ -621,14 +620,8 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 	    db->db.db_object, db->db_level, db->db_blkid);
 
 	dbuf_add_ref(db, NULL);
-	/* ZIO_FLAG_CANFAIL callers have to check the parent zio's error */
 
-	if (db->db_parent)
-		pbuf = db->db_parent->db_buf;
-	else
-		pbuf = db->db_objset->os_phys_buf;
-
-	(void) dsl_read(zio, spa, db->db_blkptr, pbuf,
+	(void) arc_read(zio, spa, db->db_blkptr,
 	    dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ,
 	    (*flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
 	    &aflags, &zb);
@@ -1026,7 +1019,6 @@ void
 dbuf_release_bp(dmu_buf_impl_t *db)
 {
 	objset_t *os;
-	zbookmark_t zb;
 
 	DB_GET_OBJSET(&os, db);
 	ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
@@ -1034,13 +1026,7 @@ dbuf_release_bp(dmu_buf_impl_t *db)
 	    list_link_active(&os->os_dsl_dataset->ds_synced_link));
 	ASSERT(db->db_parent == NULL || arc_released(db->db_parent->db_buf));
 
-	zb.zb_objset = os->os_dsl_dataset ?
-	    os->os_dsl_dataset->ds_object : 0;
-	zb.zb_object = db->db.db_object;
-	zb.zb_level = db->db_level;
-	zb.zb_blkid = db->db_blkid;
-	(void) arc_release_bp(db->db_buf, db,
-	    db->db_blkptr, os->os_spa, &zb);
+	(void) arc_release(db->db_buf, db);
 }
 
 dbuf_dirty_record_t *
@@ -1886,7 +1872,6 @@ dbuf_prefetch(dnode_t *dn, uint64_t blkid)
 		if (bp && !BP_IS_HOLE(bp)) {
 			int priority = dn->dn_type == DMU_OT_DDT_ZAP ?
 			    ZIO_PRIORITY_DDT_PREFETCH : ZIO_PRIORITY_ASYNC_READ;
-			arc_buf_t *pbuf;
 			dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
 			uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
 			zbookmark_t zb;
@@ -1894,13 +1879,8 @@ dbuf_prefetch(dnode_t *dn, uint64_t blkid)
 			SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
 			    dn->dn_object, 0, blkid);
 
-			if (db)
-				pbuf = db->db_buf;
-			else
-				pbuf = dn->dn_objset->os_phys_buf;
-
-			(void) dsl_read(NULL, dn->dn_objset->os_spa,
-			    bp, pbuf, NULL, NULL, priority,
+			(void) arc_read(NULL, dn->dn_objset->os_spa,
+			    bp, NULL, NULL, priority,
 			    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
 			    &aflags, &zb);
 		}
diff --git a/module/zfs/dmu_diff.c b/module/zfs/dmu_diff.c
index 22340ebc5..dc237780c 100644
--- a/module/zfs/dmu_diff.c
+++ b/module/zfs/dmu_diff.c
@@ -105,7 +105,7 @@ report_dnode(struct diffarg *da, uint64_t object, dnode_phys_t *dnp)
 
 /* ARGSUSED */
 static int
-diff_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
+diff_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	struct diffarg *da = arg;
@@ -132,9 +132,9 @@ diff_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
 		int blksz = BP_GET_LSIZE(bp);
 		int i;
 
-		if (dsl_read(NULL, spa, bp, pbuf,
-		    arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
-		    ZIO_FLAG_CANFAIL, &aflags, zb) != 0)
+		if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
+		    &aflags, zb) != 0)
 			return (EIO);
 
 		blk = abuf->b_data;
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 50673dc97..ca75e525b 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -276,12 +276,7 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
 			aflags |= ARC_L2CACHE;
 
 		dprintf_bp(os->os_rootbp, "reading %s", "");
-		/*
-		 * XXX when bprewrite scrub can change the bp,
-		 * and this is called from dmu_objset_open_ds_os, the bp
-		 * could change, and we'll need a lock.
-		 */
-		err = dsl_read_nolock(NULL, spa, os->os_rootbp,
+		err = arc_read(NULL, spa, os->os_rootbp,
 		    arc_getbuf_func, &os->os_phys_buf,
 		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
 		if (err) {
@@ -1119,8 +1114,7 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
 	SET_BOOKMARK(&zb, os->os_dsl_dataset ?
 	    os->os_dsl_dataset->ds_object : DMU_META_OBJSET,
 	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
-	VERIFY3U(0, ==, arc_release_bp(os->os_phys_buf, &os->os_phys_buf,
-	    os->os_rootbp, os->os_spa, &zb));
+	arc_release(os->os_phys_buf, &os->os_phys_buf);
 
 	dmu_write_policy(os, NULL, 0, 0, &zp);
 
@@ -1765,7 +1759,7 @@ dmu_objset_prefetch(const char *name, void *arg)
 			SET_BOOKMARK(&zb, ds->ds_object, ZB_ROOT_OBJECT,
 			    ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
 
-			(void) dsl_read_nolock(NULL, dsl_dataset_get_spa(ds),
+			(void) arc_read(NULL, dsl_dataset_get_spa(ds),
 			    &ds->ds_phys->ds_bp, NULL, NULL,
 			    ZIO_PRIORITY_ASYNC_READ,
 			    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index b25680360..54e75971d 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -330,7 +330,7 @@ dump_dnode(dmu_sendarg_t *dsp, uint64_t object, dnode_phys_t *dnp)
 
 /* ARGSUSED */
 static int
-backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
+backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	dmu_sendarg_t *dsp = arg;
@@ -359,9 +359,9 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
 		uint32_t aflags = ARC_WAIT;
 		arc_buf_t *abuf;
 
-		if (dsl_read(NULL, spa, bp, pbuf,
-		    arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
-		    ZIO_FLAG_CANFAIL, &aflags, zb) != 0)
+		if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
+		    &aflags, zb) != 0)
 			return (EIO);
 
 		blk = abuf->b_data;
@@ -378,9 +378,9 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
 		arc_buf_t *abuf;
 		int blksz = BP_GET_LSIZE(bp);
 
-		if (arc_read_nolock(NULL, spa, bp,
-		    arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
-		    ZIO_FLAG_CANFAIL, &aflags, zb) != 0)
+		if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
+		    &aflags, zb) != 0)
 			return (EIO);
 
 		err = dump_spill(dsp, zb->zb_object, blksz, abuf->b_data);
@@ -390,9 +390,9 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
 		arc_buf_t *abuf;
 		int blksz = BP_GET_LSIZE(bp);
 
-		if (dsl_read(NULL, spa, bp, pbuf,
-		    arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
-		    ZIO_FLAG_CANFAIL, &aflags, zb) != 0) {
+		if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
+		    &aflags, zb) != 0) {
 			if (zfs_send_corrupt_data) {
 				uint64_t *ptr;
 				/* Send a block filled with 0x"zfs badd bloc" */
diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c
index 370a28aeb..1c3972371 100644
--- a/module/zfs/dmu_traverse.c
+++ b/module/zfs/dmu_traverse.c
@@ -62,9 +62,9 @@ typedef struct traverse_data {
 } traverse_data_t;
 
 static int traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
-    arc_buf_t *buf, uint64_t objset, uint64_t object);
+    uint64_t objset, uint64_t object);
 static void prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *,
-    arc_buf_t *buf, uint64_t objset, uint64_t object);
+    uint64_t objset, uint64_t object);
 
 static int
 traverse_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
@@ -81,7 +81,7 @@ traverse_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
 	SET_BOOKMARK(&zb, td->td_objset, ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
 	    bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
 
-	(void) td->td_func(td->td_spa, zilog, bp, NULL, &zb, NULL, td->td_arg);
+	(void) td->td_func(td->td_spa, zilog, bp, &zb, NULL, td->td_arg);
 
 	return (0);
 }
@@ -105,7 +105,7 @@ traverse_zil_record(zilog_t *zilog, lr_t *lrc, void *arg, uint64_t claim_txg)
 		SET_BOOKMARK(&zb, td->td_objset, lr->lr_foid,
 		    ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
 
-		(void) td->td_func(td->td_spa, zilog, bp, NULL, &zb, NULL,
+		(void) td->td_func(td->td_spa, zilog, bp, &zb, NULL,
 		    td->td_arg);
 	}
 	return (0);
@@ -182,7 +182,7 @@ traverse_pause(traverse_data_t *td, const zbookmark_t *zb)
 
 static void
 traverse_prefetch_metadata(traverse_data_t *td,
-    arc_buf_t *pbuf, const blkptr_t *bp, const zbookmark_t *zb)
+    const blkptr_t *bp, const zbookmark_t *zb)
 {
 	uint32_t flags = ARC_NOWAIT | ARC_PREFETCH;
 
@@ -200,14 +200,13 @@ traverse_prefetch_metadata(traverse_data_t *td,
 	if (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_DNODE)
 		return;
 
-	(void) arc_read(NULL, td->td_spa, bp,
-	    pbuf, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
-	    ZIO_FLAG_CANFAIL, &flags, zb);
+	(void) arc_read(NULL, td->td_spa, bp, NULL, NULL,
+	    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
 }
 
 static int
 traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
-    arc_buf_t *pbuf, const blkptr_t *bp, const zbookmark_t *zb)
+    const blkptr_t *bp, const zbookmark_t *zb)
 {
 	zbookmark_t czb;
 	int err = 0, lasterr = 0;
@@ -228,8 +227,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 	}
 
 	if (BP_IS_HOLE(bp)) {
-		err = td->td_func(td->td_spa, NULL, NULL, pbuf, zb, dnp,
-		    td->td_arg);
+		err = td->td_func(td->td_spa, NULL, NULL, zb, dnp, td->td_arg);
 		return (err);
 	}
 
@@ -249,7 +247,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 	}
 
 	if (td->td_flags & TRAVERSE_PRE) {
-		err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp,
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp,
 		    td->td_arg);
 		if (err == TRAVERSE_VISIT_NO_CHILDREN)
 			return (0);
@@ -265,8 +263,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		blkptr_t *cbp;
 		int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
 
-		err = dsl_read(NULL, td->td_spa, bp, pbuf,
-		    arc_getbuf_func, &buf,
+		err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
 		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
 		if (err)
 			return (err);
@@ -276,7 +273,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 			SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
 			    zb->zb_level - 1,
 			    zb->zb_blkid * epb + i);
-			traverse_prefetch_metadata(td, buf, &cbp[i], &czb);
+			traverse_prefetch_metadata(td, &cbp[i], &czb);
 		}
 
 		/* recursively visitbp() blocks below this */
@@ -284,7 +281,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 			SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
 			    zb->zb_level - 1,
 			    zb->zb_blkid * epb + i);
-			err = traverse_visitbp(td, dnp, buf, &cbp[i], &czb);
+			err = traverse_visitbp(td, dnp, &cbp[i], &czb);
 			if (err) {
 				if (!hard)
 					break;
@@ -296,21 +293,20 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		int i;
 		int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
 
-		err = dsl_read(NULL, td->td_spa, bp, pbuf,
-		    arc_getbuf_func, &buf,
+		err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
 		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
 		if (err)
 			return (err);
 		dnp = buf->b_data;
 
 		for (i = 0; i < epb; i++) {
-			prefetch_dnode_metadata(td, &dnp[i], buf, zb->zb_objset,
+			prefetch_dnode_metadata(td, &dnp[i], zb->zb_objset,
 			    zb->zb_blkid * epb + i);
 		}
 
 		/* recursively visitbp() blocks below this */
 		for (i = 0; i < epb; i++) {
-			err = traverse_dnode(td, &dnp[i], buf, zb->zb_objset,
+			err = traverse_dnode(td, &dnp[i], zb->zb_objset,
 			    zb->zb_blkid * epb + i);
 			if (err) {
 				if (!hard)
@@ -323,24 +319,23 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		objset_phys_t *osp;
 		dnode_phys_t *dnp;
 
-		err = dsl_read_nolock(NULL, td->td_spa, bp,
-		    arc_getbuf_func, &buf,
+		err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
 		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
 		if (err)
 			return (err);
 
 		osp = buf->b_data;
 		dnp = &osp->os_meta_dnode;
-		prefetch_dnode_metadata(td, dnp, buf, zb->zb_objset,
+		prefetch_dnode_metadata(td, dnp, zb->zb_objset,
 		    DMU_META_DNODE_OBJECT);
 		if (arc_buf_size(buf) >= sizeof (objset_phys_t)) {
 			prefetch_dnode_metadata(td, &osp->os_userused_dnode,
-			    buf, zb->zb_objset, DMU_USERUSED_OBJECT);
+			    zb->zb_objset, DMU_USERUSED_OBJECT);
 			prefetch_dnode_metadata(td, &osp->os_groupused_dnode,
-			    buf, zb->zb_objset, DMU_USERUSED_OBJECT);
+			    zb->zb_objset, DMU_USERUSED_OBJECT);
 		}
 
-		err = traverse_dnode(td, dnp, buf, zb->zb_objset,
+		err = traverse_dnode(td, dnp, zb->zb_objset,
 		    DMU_META_DNODE_OBJECT);
 		if (err && hard) {
 			lasterr = err;
@@ -348,7 +343,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		}
 		if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
 			dnp = &osp->os_userused_dnode;
-			err = traverse_dnode(td, dnp, buf, zb->zb_objset,
+			err = traverse_dnode(td, dnp, zb->zb_objset,
 			    DMU_USERUSED_OBJECT);
 		}
 		if (err && hard) {
@@ -357,7 +352,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		}
 		if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
 			dnp = &osp->os_groupused_dnode;
-			err = traverse_dnode(td, dnp, buf, zb->zb_objset,
+			err = traverse_dnode(td, dnp, zb->zb_objset,
 			    DMU_GROUPUSED_OBJECT);
 		}
 	}
@@ -367,8 +362,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 
 post:
 	if (err == 0 && lasterr == 0 && (td->td_flags & TRAVERSE_POST)) {
-		err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp,
-		    td->td_arg);
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
 		if (err == ERESTART)
 			pause = B_TRUE;
 	}
@@ -384,25 +378,25 @@ post:
 
 static void
 prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *dnp,
-    arc_buf_t *buf, uint64_t objset, uint64_t object)
+    uint64_t objset, uint64_t object)
 {
 	int j;
 	zbookmark_t czb;
 
 	for (j = 0; j < dnp->dn_nblkptr; j++) {
 		SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
-		traverse_prefetch_metadata(td, buf, &dnp->dn_blkptr[j], &czb);
+		traverse_prefetch_metadata(td, &dnp->dn_blkptr[j], &czb);
 	}
 
 	if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
 		SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
-		traverse_prefetch_metadata(td, buf, &dnp->dn_spill, &czb);
+		traverse_prefetch_metadata(td, &dnp->dn_spill, &czb);
 	}
 }
 
 static int
 traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
-    arc_buf_t *buf, uint64_t objset, uint64_t object)
+    uint64_t objset, uint64_t object)
 {
 	int j, err = 0, lasterr = 0;
 	zbookmark_t czb;
@@ -410,7 +404,7 @@ traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
 
 	for (j = 0; j < dnp->dn_nblkptr; j++) {
 		SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
-		err = traverse_visitbp(td, dnp, buf, &dnp->dn_blkptr[j], &czb);
+		err = traverse_visitbp(td, dnp, &dnp->dn_blkptr[j], &czb);
 		if (err) {
 			if (!hard)
 				break;
@@ -420,7 +414,7 @@ traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
 
 	if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
 		SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
-		err = traverse_visitbp(td, dnp, buf, &dnp->dn_spill, &czb);
+		err = traverse_visitbp(td, dnp, &dnp->dn_spill, &czb);
 		if (err) {
 			if (!hard)
 				return (err);
@@ -433,8 +427,7 @@ traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
 /* ARGSUSED */
 static int
 traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
-    arc_buf_t *pbuf, const zbookmark_t *zb, const dnode_phys_t *dnp,
-    void *arg)
+    const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	prefetch_data_t *pfd = arg;
 	uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
@@ -455,10 +448,8 @@ traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 	cv_broadcast(&pfd->pd_cv);
 	mutex_exit(&pfd->pd_mtx);
 
-	(void) dsl_read(NULL, spa, bp, pbuf, NULL, NULL,
-	    ZIO_PRIORITY_ASYNC_READ,
-	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
-	    &aflags, zb);
+	(void) arc_read(NULL, spa, bp, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
+	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &aflags, zb);
 
 	return (0);
 }
@@ -476,7 +467,7 @@ traverse_prefetch_thread(void *arg)
 
 	SET_BOOKMARK(&czb, td.td_objset,
 	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
-	(void) traverse_visitbp(&td, NULL, NULL, td.td_rootbp, &czb);
+	(void) traverse_visitbp(&td, NULL, td.td_rootbp, &czb);
 
 	mutex_enter(&td_main->td_pfd->pd_mtx);
 	td_main->td_pfd->pd_exited = B_TRUE;
@@ -544,7 +535,7 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 
 	SET_BOOKMARK(czb, td->td_objset,
 	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
-	err = traverse_visitbp(td, NULL, NULL, rootbp, czb);
+	err = traverse_visitbp(td, NULL, rootbp, czb);
 
 	mutex_enter(&pd->pd_mtx);
 	pd->pd_cancel = B_TRUE;
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index c1a029be7..d9e8bd30f 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -1271,7 +1271,7 @@ struct killarg {
 
 /* ARGSUSED */
 static int
-kill_blkptr(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
+kill_blkptr(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	struct killarg *ka = arg;
diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index 297caa067..34a4f0382 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -363,24 +363,6 @@ dsl_free_sync(zio_t *pio, dsl_pool_t *dp, uint64_t txg, const blkptr_t *bpp)
 	zio_nowait(zio_free_sync(pio, dp->dp_spa, txg, bpp, pio->io_flags));
 }
 
-int
-dsl_read(zio_t *pio, spa_t *spa, const blkptr_t *bpp, arc_buf_t *pbuf,
-    arc_done_func_t *done, void *private, int priority, int zio_flags,
-    uint32_t *arc_flags, const zbookmark_t *zb)
-{
-	return (arc_read(pio, spa, bpp, pbuf, done, private,
-	    priority, zio_flags, arc_flags, zb));
-}
-
-int
-dsl_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bpp,
-    arc_done_func_t *done, void *private, int priority, int zio_flags,
-    uint32_t *arc_flags, const zbookmark_t *zb)
-{
-	return (arc_read_nolock(pio, spa, bpp, done, private,
-	    priority, zio_flags, arc_flags, zb));
-}
-
 static uint64_t
 dsl_scan_ds_maxtxg(dsl_dataset_t *ds)
 {
@@ -551,12 +533,8 @@ dsl_scan_prefetch(dsl_scan_t *scn, arc_buf_t *buf, blkptr_t *bp,
 
 	SET_BOOKMARK(&czb, objset, object, BP_GET_LEVEL(bp), blkid);
 
-	/*
-	 * XXX need to make sure all of these arc_read() prefetches are
-	 * done before setting xlateall (similar to dsl_read())
-	 */
 	(void) arc_read(scn->scn_zio_root, scn->scn_dp->dp_spa, bp,
-	    buf, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
+	    NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SCAN_THREAD, &flags, &czb);
 }
 
@@ -614,8 +592,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 		blkptr_t *cbp;
 		int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
 
-		err = arc_read_nolock(NULL, dp->dp_spa, bp,
-		    arc_getbuf_func, bufp,
+		err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 		    ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 		if (err) {
 			scn->scn_phys.scn_errors++;
@@ -637,8 +614,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 	} else if (BP_GET_TYPE(bp) == DMU_OT_USERGROUP_USED) {
 		uint32_t flags = ARC_WAIT;
 
-		err = arc_read_nolock(NULL, dp->dp_spa, bp,
-		    arc_getbuf_func, bufp,
+		err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 		    ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 		if (err) {
 			scn->scn_phys.scn_errors++;
@@ -650,8 +626,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 		int i, j;
 		int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
 
-		err = arc_read_nolock(NULL, dp->dp_spa, bp,
-		    arc_getbuf_func, bufp,
+		err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 		    ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 		if (err) {
 			scn->scn_phys.scn_errors++;
@@ -673,8 +648,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 		uint32_t flags = ARC_WAIT;
 		objset_phys_t *osp;
 
-		err = arc_read_nolock(NULL, dp->dp_spa, bp,
-		    arc_getbuf_func, bufp,
+		err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 		    ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 		if (err) {
 			scn->scn_phys.scn_errors++;
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index c885e3e41..e986e924d 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -1856,7 +1856,7 @@ spa_load_verify_done(zio_t *zio)
 /*ARGSUSED*/
 static int
 spa_load_verify_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
-    arc_buf_t *pbuf, const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
+    const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	if (bp != NULL) {
 		zio_t *rio = arg;
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index 64de856f0..c1796937b 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -212,7 +212,7 @@ zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, blkptr_t *nbp, void *dst,
 	SET_BOOKMARK(&zb, bp->blk_cksum.zc_word[ZIL_ZC_OBJSET],
 	    ZB_ZIL_OBJECT, ZB_ZIL_LEVEL, bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
 
-	error = dsl_read_nolock(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
+	error = arc_read(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
 	    ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
 
 	if (error == 0) {
@@ -288,7 +288,7 @@ zil_read_log_data(zilog_t *zilog, const lr_write_t *lr, void *wbuf)
 	SET_BOOKMARK(&zb, dmu_objset_id(zilog->zl_os), lr->lr_foid,
 	    ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
 
-	error = arc_read_nolock(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
+	error = arc_read(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
 	    ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
 
 	if (error == 0) {
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 2e1170920..8cf040850 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -2051,7 +2051,7 @@ zio_ddt_collision(zio_t *zio, ddt_t *ddt, ddt_entry_t *dde)
 
 			ddt_exit(ddt);
 
-			error = arc_read_nolock(NULL, spa, &blk,
+			error = arc_read(NULL, spa, &blk,
 			    arc_getbuf_func, &abuf, ZIO_PRIORITY_SYNC_READ,
 			    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
 			    &aflags, &zio->io_bookmark);