Illumos 3897 - zfs filesystem and snapshot limits

3897 zfs filesystem and snapshot limits
Author: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://www.illumos.org/issues/3897
  https://github.com/illumos/illumos-gate/commit/a2afb61

Porting Notes:

dsl_dataset_snapshot_check(): reduce stack usage using kmem_alloc().

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

lib/libspl/include/sys/Makefile.am

@@ -31,6 +31,7 @@ libspl_HEADERS = \
 	$(top_srcdir)/lib/libspl/include/sys/mount.h \
 	$(top_srcdir)/lib/libspl/include/sys/note.h \
 	$(top_srcdir)/lib/libspl/include/sys/param.h \
+	$(top_srcdir)/lib/libspl/include/sys/policy.h \
 	$(top_srcdir)/lib/libspl/include/sys/priv.h \
 	$(top_srcdir)/lib/libspl/include/sys/processor.h \
 	$(top_srcdir)/lib/libspl/include/sys/stack.h \

lib/libspl/include/sys/policy.h

@@ -0,0 +1,26 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (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
+ */
+
+#ifndef	_LIBSYS_SYS_POLICY_H
+#define	_LIBSYS_SYS_POLICY_H
+
+#endif	/* _LIBSYS_SYS_POLICY_H */