Private parameters for ioengines

Here is the polished version of the engine private options patch.  As
discussed, the global section only ever tracks the private options for
the globally defined ioengine.  For command line parameters, the
ioengine must be selected before any private options are used.  (IE
--ioengine=libaio --userspace_reap will work, but --userspace_reap
--ioengine=libaio will not.)

The userspace_reap option from libaio has been moved over to this new
option method, usage should be identical to before.
The net ioengine has been modified to use parameters, with hostname,
port, protocol and listen defined as ioengine private parameters.  The
old style of hostname=host,port,protocol no longer works, so usage
will need to be updated.  (It will spit out an error that should be
clear enough that it changed if this is tried.)  Also, with the new
way for specifying parameters, the net IO engine now allows data to
flow in either direction on TCP connections, regardless of which end
initiates the connection.

There's also a new command line argument --enghelp which can be used
to get help on ioengine private parameters, similar to --cmdhelp.
With no argument, it lists all built-in ioengine.  The argument is an
ioengine name (Or path to .so) and optionally a comma followed by a
command name, which behaves identically to --cmdhelp.

For ioengine authorship, if options are supplied, both the options
structure and the size of the storage needed must be supplied, and the
storage must be large enough to hold a pointer to struct thread_data;
that is because the options callback doesn't explicitly have a pointer
to the thread data (Normally it relies on the fact that the options
struct is the start of the thread data), so the offset 0 of the struct
must point to the thread data, and is filled in automatically.  (This
also neatly provides a guarantee that offset 0 is reserved in the
options data, so it can be safely used as a test of undefined.)

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.h b/fio.h
index a5405e3..cc1f65f 100644
--- a/fio.h
+++ b/fio.h
@@ -245,8 +245,6 @@
 	unsigned int gid;
 
 	unsigned int sync_file_range;
-
-	unsigned int userspace_libaio_reap;
 };
 
 /*
@@ -254,6 +252,7 @@
  */
 struct thread_data {
 	struct thread_options o;
+	void *eo;
 	char verror[FIO_VERROR_SIZE];
 	pthread_t thread;
 	int thread_number;
@@ -551,16 +550,20 @@
 extern int fio_options_parse(struct thread_data *, char **, int);
 extern void fio_keywords_init(void);
 extern int fio_cmd_option_parse(struct thread_data *, const char *, char *);
+extern int fio_cmd_ioengine_option_parse(struct thread_data *, const char *, char *);
 extern void fio_fill_default_options(struct thread_data *);
 extern int fio_show_option_help(const char *);
+extern void fio_options_set_ioengine_opts(struct option *long_options, struct thread_data *td);
 extern void fio_options_dup_and_init(struct option *);
-extern void options_mem_dupe(struct thread_data *);
-extern void options_mem_free(struct thread_data *);
+extern void fio_options_mem_dupe(struct thread_data *);
+extern void options_mem_dupe(void *data, struct fio_option *options);
 extern void td_fill_rand_seeds(struct thread_data *);
 extern void add_job_opts(const char **);
 extern char *num2str(unsigned long, int, int, int);
+extern int ioengine_load(struct thread_data *);
 
-#define FIO_GETOPT_JOB		0x89988998
+#define FIO_GETOPT_JOB		0x89000000
+#define FIO_GETOPT_IOENGINE	0x98000000
 #define FIO_NR_OPTIONS		(FIO_MAX_OPTS + 128)
 
 /*