WIP, draft2 (unfinished work)

5960 zfs recv should prefetch indirect blocks
5925 zfs receive -o origin=

Reviewed by: Prakash Surya <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>

depends on openzfs#3574 Illumos 5745 zfs set allows only one dataset property to be set at a time
depends on openzfs#3611 Illumos 5746 more checksumming in zfs send

diverged code base from Illumos:

[lib/libzfs/libzfs_sendrecv.c]
b8864a2 Fix gcc cast warnings
325f023 Add linux kernel device support
5c3f61e Increase Linux pipe buffer size on 'zfs receive'

[module/zfs/zfs_vnops.c]
3558fd7 Prototype/structure update for Linux
c12e3a5 Restructure zfs_readdir() to fix regressions

fc5bb51 Fix stack dbuf_hold_impl()
34229a2 Reduce stack usage for recursive traverse_visitbp()
module/zfs/dmu.c (c90 vs. c99)
37abac6 Illumos openzfs#2703: add mechanism to report ZFS send progress [module/zfs/dmu_send.c]

Ported-by: kernelOfTruth [email protected]

cmd/zdb/zdb.c

@@ -2488,6 +2488,9 @@ zdb_blkptr_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 	dmu_object_type_t type;
 	boolean_t is_metadata;
 
+	if (bp == NULL)
+		return (0);
+
 	if (dump_opt['b'] >= 5 && bp->blk_birth > 0) {
 		char blkbuf[BP_SPRINTF_LEN];
 		snprintf_blkptr(blkbuf, sizeof (blkbuf), bp);
@@ -2984,7 +2987,7 @@ zdb_ddt_add_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 	avl_index_t where;
 	zdb_ddt_entry_t *zdde, zdde_search;
 
-	if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp))
+	if (bp == NULL || BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp))
 		return (0);
 
 	if (dump_opt['S'] > 1 && zb->zb_level == ZB_ROOT_LEVEL) {