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, 19 insertions, 9 deletions

diff --git a/include/sys/zcp.h b/include/sys/zcp.h
index df13bf230..b56eda552 100644
--- a/include/sys/zcp.h
+++ b/include/sys/zcp.h
@@ -38,20 +38,25 @@ extern uint64_t zfs_lua_max_memlimit;
 
 int zcp_argerror(lua_State *, int, const char *, ...);
 
-int zcp_eval(const char *, const char *, uint64_t, uint64_t, nvpair_t *,
-    nvlist_t *);
+int zcp_eval(const char *, const char *, boolean_t, uint64_t, uint64_t,
+    nvpair_t *, nvlist_t *);
 
 int zcp_load_list_lib(lua_State *);
 
 int zcp_load_synctask_lib(lua_State *, boolean_t);
 
 typedef void (zcp_cleanup_t)(void *);
+typedef struct zcp_cleanup_handler {
+	zcp_cleanup_t *zch_cleanup_func;
+	void *zch_cleanup_arg;
+	list_node_t zch_node;
+} zcp_cleanup_handler_t;
 
 typedef struct zcp_run_info {
 	dsl_pool_t	*zri_pool;
 
 	/*
-	 * An estimate of the total ammount of space consumed by all
+	 * An estimate of the total amount of space consumed by all
 	 * synctasks we have successfully performed so far in this
 	 * channel program. Used to generate ENOSPC errors for syncfuncs.
 	 */
@@ -89,16 +94,21 @@ typedef struct zcp_run_info {
 	boolean_t	zri_timed_out;
 
 	/*
-	 * The currently registered cleanup function, which will be called
-	 * with the stored argument if a fatal error occurs.
+	 * Boolean indicating whether or not we are running in syncing
+	 * context.
 	 */
-	zcp_cleanup_t	*zri_cleanup;
-	void		*zri_cleanup_arg;
+	boolean_t	zri_sync;
+
+	/*
+	 * List of currently registered cleanup handlers, which will be
+	 * triggered in the event of a fatal error.
+	 */
+	list_t		zri_cleanup_handlers;
 } zcp_run_info_t;
 
 zcp_run_info_t *zcp_run_info(lua_State *);
-void zcp_register_cleanup(lua_State *, zcp_cleanup_t, void *);
-void zcp_clear_cleanup(lua_State *);
+zcp_cleanup_handler_t *zcp_register_cleanup(lua_State *, zcp_cleanup_t, void *);
+void zcp_deregister_cleanup(lua_State *, zcp_cleanup_handler_t *);
 void zcp_cleanup(lua_State *);
 
 /*