Illumos #3603, #3604: bobj improvements

3603 panic from bpobj_enqueue_subobj()
3604 zdb should print bpobjs more verbosely
3871 GCC 4.5.3 does not like issue 3604 patch
Reviewed by: Henrik Mattson <henrik.mattson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Dan McDonald <danmcd@nexenta.com>

References:
  https://www.illumos.org/issues/3603
  https://www.illumos.org/issues/3604
  https://www.illumos.org/issues/3871
  illumos/illumos-gate@d04756377d

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

Note that the patch from Illumos issue 3871 is not accepted into Illumos
at the time of this writing. It is something that I wrote when porting
this. Documentation is in the Illumos issue.

module/zfs/bpobj.c

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
  */
 
 #include <sys/bpobj.h>
@@ -418,6 +418,12 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
 
 			VERIFY3U(0, ==, dmu_buf_hold(bpo->bpo_os, subsubobjs,
 			    0, FTAG, &subdb, 0));
+			/*
+			 * Make sure that we are not asking dmu_write()
+			 * to write more data than we have in our buffer.
+			 */
+			VERIFY3U(subdb->db_size, >=,
+			    numsubsub * sizeof (subobj));
 			dmu_write(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs,
 			    bpo->bpo_phys->bpo_num_subobjs * sizeof (subobj),
 			    numsubsub * sizeof (subobj), subdb->db_data, tx);