OpenZFS 8677 - Open-Context Channel Programs

Authored by: Serapheim Dimitropoulos <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: Chris Williamson <[email protected]>
Reviewed by: Pavel Zakharov <[email protected]>
Approved by: Robert Mustacchi <[email protected]>
Ported-by: Don Brady <[email protected]>

We want to be able to run channel programs outside of synching
context. This would greatly improve performance for channel programs
that just gather information, as they won't have to wait for synching
context anymore.

=== What is implemented?

This feature introduces the following:
- A new command line flag in "zfs program" to specify our intention
  to run in open context. (The -n option)
- A new flag/option within the channel program ioctl which selects
  the context.
- Appropriate error handling whenever we try a channel program in
  open-context that contains zfs.sync* expressions.
- Documentation for the new feature in the manual pages.

=== How do we handle zfs.sync functions in open context?

When such a function is found by the interpreter and we are running
in open context we abort the script and we spit out a descriptive
runtime error. For example, given the script below ...

arg = ...
fs = arg["argv"][1]
err = zfs.sync.destroy(fs)
msg = "destroying " .. fs .. " err=" .. err
return msg

if we run it in open context, we will get back the following error:

Channel program execution failed:
[string "channel program"]:3: running functions from the zfs.sync
submodule requires passing sync=TRUE to lzc_channel_program()
(i.e. do not specify the "-n" command line argument)
stack traceback:
            [C]: in function 'destroy'
            [string "channel program"]:3: in main chunk

=== What about testing?

We've introduced new wrappers for all channel program tests that
run each channel program as both (startard & open-context) and
expect the appropriate behavior depending on the program using
the zfs.sync module.

OpenZFS-issue: https://www.illumos.org/issues/8677
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/17a49e15
Closes #6558

1 files changed, 15 insertions, 5 deletions

diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index cf31624f0..fce228a20 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
  * Copyright 2012 Milan Jurik. All rights reserved.
  * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  * Copyright (c) 2013 Steven Hartland.  All rights reserved.
@@ -340,7 +340,7 @@ get_usage(zfs_help_t idx)
 	case HELP_BOOKMARK:
 		return (gettext("\tbookmark <snapshot> <bookmark>\n"));
 	case HELP_CHANNEL_PROGRAM:
-		return (gettext("\tprogram [-t <instruction limit>] "
+		return (gettext("\tprogram [-n] [-t <instruction limit>] "
 		    "[-m <memory limit (b)>] <pool> <program file> "
 		    "[lua args...]\n"));
 	case HELP_LOAD_KEY:
@@ -7098,10 +7098,11 @@ zfs_do_channel_program(int argc, char **argv)
 	nvlist_t *outnvl;
 	uint64_t instrlimit = ZCP_DEFAULT_INSTRLIMIT;
 	uint64_t memlimit = ZCP_DEFAULT_MEMLIMIT;
+	boolean_t sync_flag = B_TRUE;
 	zpool_handle_t *zhp;
 
 	/* check options */
-	while ((c = getopt(argc, argv, "t:m:")) != -1) {
+	while ((c = getopt(argc, argv, "nt:m:")) != -1) {
 		switch (c) {
 		case 't':
 		case 'm': {
@@ -7139,6 +7140,10 @@ zfs_do_channel_program(int argc, char **argv)
 			}
 			break;
 		}
+		case 'n': {
+			sync_flag = B_FALSE;
+			break;
+		}
 		case '?':
 			(void) fprintf(stderr, gettext("invalid option '%c'\n"),
 			    optopt);
@@ -7210,8 +7215,13 @@ zfs_do_channel_program(int argc, char **argv)
 	nvlist_t *argnvl = fnvlist_alloc();
 	fnvlist_add_string_array(argnvl, ZCP_ARG_CLIARGV, argv + 2, argc - 2);
 
-	ret = lzc_channel_program(poolname, progbuf, instrlimit, memlimit,
-	    argnvl, &outnvl);
+	if (sync_flag) {
+		ret = lzc_channel_program(poolname, progbuf,
+		    instrlimit, memlimit, argnvl, &outnvl);
+	} else {
+		ret = lzc_channel_program_nosync(poolname, progbuf,
+		    instrlimit, memlimit, argnvl, &outnvl);
+	}
 
 	if (ret != 0) {
 		/*