[PATCH 1/2] Introduce get_ioengine for external engines

[PATCH 1/2] Introduce get_ioengine for external engines

[Daniel Gollub]

This makes life easier for plugins written in C++
since they do not need to deal with struct initilization issues
with the ioengine_ops symbol.

With g++ a non-static ioengine_ops in global scope like this:

struct ioengine_ops ioengine = {
        .name           = "null",
        .version        = FIO_IOOPS_VERSION,
        .queue          = fio_null_queue,
        .commit         = fio_null_commit,
};

Results in:

cpp_null2.cc: At global scope:
cpp_null2.cc:112:1: error: C99 designator ‘name’ outside aggregate initializer
cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
$

Example get_iongine() symbol usage:

---8<---
extern "C" {
void get_ioengine(struct ioengine_ops **ioengine_ptr) {
        struct ioengine_ops *ioengine;
        *ioengine_ptr = (struct ioengine_ops *) malloc(sizeof(struct ioengine_ops));
        ioengine = *ioengine_ptr;

        strcpy(ioengine->name, "cpp_null");
        ioengine->version        = FIO_IOOPS_VERSION;
        ioengine->queue          = fio_null_queue;
        ioengine->commit         = fio_null_commit;
        ioengine->getevents      = fio_null_getevents;
        ioengine->event          = fio_null_event;
        ioengine->init           = fio_null_init;
        ioengine->cleanup        = fio_null_cleanup;
        ioengine->open_file      = fio_null_open;
        ioengine->flags          = FIO_DISKLESSIO;
}
}
--->8---

Signed-off-by: Daniel Gollub <d.gollub@telekom.de>
---
 ioengines.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/ioengines.c b/ioengines.c
index d71e372..c080da3 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -90,6 +90,7 @@ static struct ioengine_ops *dlopen_ioengine(struct thread_data *td,
 {
 	struct ioengine_ops *ops;
 	void *dlhandle;
+	typedef void (*get_ioengine_t)(struct ioengine_ops **);
 
 	dprint(FD_IO, "dload engine %s\n", engine_lib);
 
@@ -107,6 +108,19 @@ static struct ioengine_ops *dlopen_ioengine(struct thread_data *td,
 	ops = dlsym(dlhandle, engine_lib);
 	if (!ops)
 		ops = dlsym(dlhandle, "ioengine");
+
+	/*
+	 * For some external engines (like C++ ones) it is not that trivial
+	 * to provide a non-static ionengine structure that we can reference.
+	 * Instead we call a method which allocates the required ioengine
+	 * structure.
+	 */
+	if (!ops) {
+		get_ioengine_t get_ioengine = dlsym(dlhandle, "get_ioengine");
+		if (get_ioengine)
+			get_ioengine(&ops);
+	}
+
 	if (!ops) {
 		td_vmsg(td, -1, dlerror(), "dlsym");
 		dlclose(dlhandle);
-- 
1.7.10.4

[PATCH 2/2] engines/null: allow build as external C++ ioengine

[Daniel Gollub]

In first place to have a simple test candidate for external
ioengines using get_ioengine() method for retriving the
io_engine struct.

Can be compiled with:

g++ -O2 -g -shared -rdynamic -fPIC -o null.so null.c -DFIO_EXTERNAL_ENGINE

Signed-off-by: Daniel Gollub <d.gollub@telekom.de>
---
 engines/null.c |   46 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 7 deletions(-)

diff --git a/engines/null.c b/engines/null.c
index bf7885e..9f9d850 100644
--- a/engines/null.c
+++ b/engines/null.c
@@ -4,6 +4,10 @@
  * IO engine that doesn't do any real IO transfers, it just pretends to.
  * The main purpose is to test fio itself.
  *
+ * It also can act as external C++ engine - compiled with:
+ *
+ * g++ -O2 -g -shared -rdynamic -fPIC -o null.so null.c -DFIO_EXTERNAL_ENGINE
+ *
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -21,7 +25,7 @@ struct null_data {
 
 static struct io_u *fio_null_event(struct thread_data *td, int event)
 {
-	struct null_data *nd = td->io_ops->data;
+	struct null_data *nd = (struct null_data *) td->io_ops->data;
 
 	return nd->io_us[event];
 }
@@ -30,7 +34,7 @@ static int fio_null_getevents(struct thread_data *td, unsigned int min_events,
 			      unsigned int fio_unused max,
 			      struct timespec fio_unused *t)
 {
-	struct null_data *nd = td->io_ops->data;
+	struct null_data *nd = (struct null_data *) td->io_ops->data;
 	int ret = 0;
 	
 	if (min_events) {
@@ -43,10 +47,12 @@ static int fio_null_getevents(struct thread_data *td, unsigned int min_events,
 
 static int fio_null_commit(struct thread_data *td)
 {
-	struct null_data *nd = td->io_ops->data;
+	struct null_data *nd = (struct null_data *) td->io_ops->data;
 
 	if (!nd->events) {
+#ifndef FIO_EXTERNAL_ENGINE
 		io_u_mark_submit(td, nd->queued);
+#endif
 		nd->events = nd->queued;
 		nd->queued = 0;
 	}
@@ -56,7 +62,7 @@ static int fio_null_commit(struct thread_data *td)
 
 static int fio_null_queue(struct thread_data *td, struct io_u *io_u)
 {
-	struct null_data *nd = td->io_ops->data;
+	struct null_data *nd = (struct null_data *) td->io_ops->data;
 
 	fio_ro_check(td, io_u);
 
@@ -77,7 +83,7 @@ static int fio_null_open(struct thread_data fio_unused *td,
 
 static void fio_null_cleanup(struct thread_data *td)
 {
-	struct null_data *nd = td->io_ops->data;
+	struct null_data *nd = (struct null_data *) td->io_ops->data;
 
 	if (nd) {
 		if (nd->io_us)
@@ -88,12 +94,12 @@ static void fio_null_cleanup(struct thread_data *td)
 
 static int fio_null_init(struct thread_data *td)
 {
-	struct null_data *nd = malloc(sizeof(*nd));
+	struct null_data *nd = (struct null_data *) malloc(sizeof(*nd));
 
 	memset(nd, 0, sizeof(*nd));
 
 	if (td->o.iodepth != 1) {
-		nd->io_us = malloc(td->o.iodepth * sizeof(struct io_u *));
+		nd->io_us = (struct io_u **) malloc(td->o.iodepth * sizeof(struct io_u *));
 		memset(nd->io_us, 0, td->o.iodepth * sizeof(struct io_u *));
 	} else
 		td->io_ops->flags |= FIO_SYNCIO;
@@ -102,6 +108,7 @@ static int fio_null_init(struct thread_data *td)
 	return 0;
 }
 
+#ifndef __cplusplus
 static struct ioengine_ops ioengine = {
 	.name		= "null",
 	.version	= FIO_IOOPS_VERSION,
@@ -124,3 +131,28 @@ static void fio_exit fio_null_unregister(void)
 {
 	unregister_ioengine(&ioengine);
 }
+
+#else
+
+#ifdef FIO_EXTERNAL_ENGINE
+extern "C" {
+void get_ioengine(struct ioengine_ops **ioengine_ptr) {
+	struct ioengine_ops *ioengine;
+	*ioengine_ptr = (struct ioengine_ops *) malloc(sizeof(struct ioengine_ops));
+	ioengine = *ioengine_ptr;
+
+	strcpy(ioengine->name, "cpp_null");
+	ioengine->version        = FIO_IOOPS_VERSION;
+	ioengine->queue          = fio_null_queue;
+	ioengine->commit         = fio_null_commit;
+	ioengine->getevents      = fio_null_getevents;
+	ioengine->event          = fio_null_event;
+	ioengine->init           = fio_null_init;
+	ioengine->cleanup        = fio_null_cleanup;
+	ioengine->open_file      = fio_null_open;
+	ioengine->flags	         = FIO_DISKLESSIO;
+}
+}
+#endif /* FIO_EXTERNAL_ENGINE */
+
+#endif /* __cplusplus */
-- 
1.7.10.4

Re: [PATCH 2/2] engines/null: allow build as external C++ ioengine

[Jens Axboe]

On 2014-02-12 12:13, Daniel Gollub wrote:
> In first place to have a simple test candidate for external
> ioengines using get_ioengine() method for retriving the
> io_engine struct.
>
> Can be compiled with:
>
> g++ -O2 -g -shared -rdynamic -fPIC -o null.so null.c -DFIO_EXTERNAL_ENGINE

I'm assuming this is just an example of how you'd build your external 
engine? Look OK to me with that in mind.

-- 
Jens Axboe

Re: [PATCH 2/2] engines/null: allow build as external C++ ioengine

[Daniel Gollub]

On Wed, 12 Feb 2014 21:13:14 -0700, Jens Axboe wrote:
> On 2014-02-12 12:13, Daniel Gollub wrote:
> > In first place to have a simple test candidate for external
> > ioengines using get_ioengine() method for retriving the
> > io_engine struct.
> >
> > Can be compiled with:
> >
> > g++ -O2 -g -shared -rdynamic -fPIC -o null.so null.c
> > -DFIO_EXTERNAL_ENGINE
> 
> I'm assuming this is just an example of how you'd build your external 
> engine? Look OK to me with that in mind.
> 

Yes it is. I although thought about integrating the build (of the null
C++/external variant) as kind of a build/compile test (not by default)
so we can spot changes on fio.h (or headers which are included by fio.h)
which break builds for external C++ based ioengines.

Something like ./configure --example-external-ioengines which
would also build skeleton_external (plain C) and cpp_null.so (if g++ is
available).

-- 
Daniel Gollub

Re: [PATCH 1/2] Introduce get_ioengine for external engines

[Jens Axboe]

On 2014-02-12 12:13, Daniel Gollub wrote:
> This makes life easier for plugins written in C++
> since they do not need to deal with struct initilization issues
> with the ioengine_ops symbol.
>
> With g++ a non-static ioengine_ops in global scope like this:
>
> struct ioengine_ops ioengine = {
>          .name           = "null",
>          .version        = FIO_IOOPS_VERSION,
>          .queue          = fio_null_queue,
>          .commit         = fio_null_commit,
> };
>
> Results in:
>
> cpp_null2.cc: At global scope:
> cpp_null2.cc:112:1: error: C99 designator ‘name’ outside aggregate initializer
> cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
> cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
> cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
> cpp_null2.cc:112:1: sorry, unimplemented: non-trivial designated initializers not supported
> $
>
> Example get_iongine() symbol usage:
>
> ---8<---
> extern "C" {
> void get_ioengine(struct ioengine_ops **ioengine_ptr) {
>          struct ioengine_ops *ioengine;
>          *ioengine_ptr = (struct ioengine_ops *) malloc(sizeof(struct ioengine_ops));
>          ioengine = *ioengine_ptr;
>
>          strcpy(ioengine->name, "cpp_null");
>          ioengine->version        = FIO_IOOPS_VERSION;
>          ioengine->queue          = fio_null_queue;
>          ioengine->commit         = fio_null_commit;
>          ioengine->getevents      = fio_null_getevents;
>          ioengine->event          = fio_null_event;
>          ioengine->init           = fio_null_init;
>          ioengine->cleanup        = fio_null_cleanup;
>          ioengine->open_file      = fio_null_open;
>          ioengine->flags          = FIO_DISKLESSIO;
> }
> }
> --->8---
>
> Signed-off-by: Daniel Gollub <d.gollub@telekom.de>
> ---
>   ioengines.c |   14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
> diff --git a/ioengines.c b/ioengines.c
> index d71e372..c080da3 100644
> --- a/ioengines.c
> +++ b/ioengines.c
> @@ -90,6 +90,7 @@ static struct ioengine_ops *dlopen_ioengine(struct thread_data *td,
>   {
>   	struct ioengine_ops *ops;
>   	void *dlhandle;
> +	typedef void (*get_ioengine_t)(struct ioengine_ops **);
>
>   	dprint(FD_IO, "dload engine %s\n", engine_lib);
>
> @@ -107,6 +108,19 @@ static struct ioengine_ops *dlopen_ioengine(struct thread_data *td,
>   	ops = dlsym(dlhandle, engine_lib);
>   	if (!ops)
>   		ops = dlsym(dlhandle, "ioengine");
> +
> +	/*
> +	 * For some external engines (like C++ ones) it is not that trivial
> +	 * to provide a non-static ionengine structure that we can reference.
> +	 * Instead we call a method which allocates the required ioengine
> +	 * structure.
> +	 */
> +	if (!ops) {
> +		get_ioengine_t get_ioengine = dlsym(dlhandle, "get_ioengine");
> +		if (get_ioengine)
> +			get_ioengine(&ops);
> +	}
> +
>   	if (!ops) {
>   		td_vmsg(td, -1, dlerror(), "dlsym");
>   		dlclose(dlhandle);
>

This looks fine, but lets put that typedef in ioengine.h instead.

-- 
Jens Axboe