Introduce get_ioengine for external engines
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>
Moved get_ioengine_t typedef to ioengine.h.
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/ioengines.c b/ioengines.c
index d71e372..3c75fa6 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -107,6 +107,20 @@
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);