Illumos openzfs#2882, openzfs#2883, openzfs#2900

2882 implement libzfs_core
2883 changing "canmount" property to "on" should not always remount dataset
2900 "zfs snapshot" should be able to create multiple, arbitrary snapshots at once

Reviewed by: George Wilson <[email protected]>
Reviewed by: Chris Siden <[email protected]>
Reviewed by: Garrett D'Amore <[email protected]>
Reviewed by: Bill Pijewski <[email protected]>
Reviewed by: Dan Kruchinin <[email protected]>
Approved by: Eric Schrock <[email protected]>

References:
  illumos/illumos-gate@4445fff

Ported-by: Tim Chase <[email protected]>
Closes openzfs#1293

Porting notes:

Add "nosleep" versions of the fnvlist_dup, fnvlist_merge, fnvlist_alloc
and fnvlist_pack functions with a suffix of "_nosleep".  They simply
perform their allocations with the KM_NOSLEEP flag.

Add zvol minor device creation to the new zfs_snapshot_nvl function.

Remove the logging of the "release" operation in
dsl_dataset_user_release_sync().  The logging caused a null dereference
because ds->ds_dir is zeroed in dsl_dataset_destroy_sync() and the
logging functions try to get the ds name via the dsl_dataset_name()
function. I've got no idea why this particular code would have worked
in Illumos.  This code has subsequently been completely reworked in
Illumos commit 3b2aab1 (3464 zfs synctask code needs restructuring).

Squash some "may be used uninitialized" warning/erorrs.

Fix some printf format warnings for %lld and %llu.

include/libzfs_core.h

@@ -0,0 +1,62 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (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
+ */
+
+/*
+ * Copyright (c) 2012 by Delphix. All rights reserved.
+ */
+
+#ifndef	_LIBZFS_CORE_H
+#define	_LIBZFS_CORE_H
+
+#include <libnvpair.h>
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/fs/zfs.h>
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+int libzfs_core_init(void);
+void libzfs_core_fini(void);
+
+int lzc_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t **errlist);
+int lzc_create(const char *fsname, dmu_objset_type_t type, nvlist_t *props);
+int lzc_clone(const char *fsname, const char *origin, nvlist_t *props);
+int lzc_destroy_snaps(nvlist_t *snaps, boolean_t defer, nvlist_t **errlist);
+
+int lzc_snaprange_space(const char *firstsnap, const char *lastsnap,
+    uint64_t *usedp);
+
+int lzc_send(const char *snapname, const char *fromsnap, int fd);
+int lzc_receive(const char *snapname, nvlist_t *props, const char *origin,
+    boolean_t force, int fd);
+int lzc_send_space(const char *snapname, const char *fromsnap,
+    uint64_t *result);
+
+boolean_t lzc_exists(const char *dataset);
+
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _LIBZFS_CORE_H */

lib/libzfs_core/Makefile.am

@@ -0,0 +1,15 @@
+include $(top_srcdir)/config/Rules.am
+
+DEFAULT_INCLUDES += \
+	-I$(top_srcdir)/include \
+	-I$(top_srcdir)/lib/libspl/include
+
+lib_LTLIBRARIES = libzfs_core.la
+
+libzfs_core_la_SOURCES = \
+	$(top_srcdir)/lib/libzfs_core/libzfs_core.c
+
+libzfs_core_la_LIBADD = \
+	$(top_builddir)/lib/libnvpair/libnvpair.la
+
+libzfs_core_la_LDFLAGS = -pthread -version-info 1:1:0