OpenZFS 8600 - ZFS channel programs - snapshot

Authored by: Chris Williamson <chris.williamson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Don Brady <don.brady@delphix.com>

ZFS channel programs should be able to create snapshots.
In addition to the base snapshot functionality, this entails extra
logic to handle edge cases which were formerly not possible, such as
creating then destroying a snapshot in the same transaction sync.

OpenZFS-issue: https://www.illumos.org/issues/8600
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/68089b8b

module/zfs/zcp.c

@@ -14,7 +14,7 @@
  */
 
 /*
- * Copyright (c) 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2016, 2017 by Delphix. All rights reserved.
  */
 
 /*
@@ -106,10 +106,15 @@
 #define	KM_NORMALPRI	0
 #endif
 
+#define	ZCP_NVLIST_MAX_DEPTH 20
+
 uint64_t zfs_lua_check_instrlimit_interval = 100;
 uint64_t zfs_lua_max_instrlimit = ZCP_MAX_INSTRLIMIT;
 uint64_t zfs_lua_max_memlimit = ZCP_MAX_MEMLIMIT;
 
+/*
+ * Forward declarations for mutually recursive functions
+ */
 static int zcp_nvpair_value_to_lua(lua_State *, nvpair_t *, char *, int);
 static int zcp_lua_to_nvlist_impl(lua_State *, int, nvlist_t *, const char *,
     int);
@@ -217,8 +222,6 @@ zcp_cleanup(lua_State *state)
 	}
 }
 
-#define	ZCP_NVLIST_MAX_DEPTH 20
-
 /*
  * Convert the lua table at the given index on the Lua stack to an nvlist
  * and return it.