ioengines: improve "is this the same IO engine" check

We can't just compare the name, that assumes that name and filename
match for an IO engine. While that's generally the case for the
engines that fio ships with, it's not a requirement, and it's
definitely not true for external engines.

Fixup the check by re-loading the engine and checking the OPS
instead. That should be bullet proof.

Fixes: 800334d ("Correctly detect whether ioengine_load can exit early")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/init.c b/init.c
index b9da71335a7fc34aece77d4678949c35a276cdd1..03cdf902261f51d6d4dc33360bdcb67bd9fe88c9 100644 (file)
--- a/init.c
+++ b/init.c
@@ -11,6 +11,7 @@
 #include <sys/ipc.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <dlfcn.h>
 
 #include "fio.h"
 #ifndef FIO_NO_HAVE_SHM_H
@@ -1064,6 +1065,9 @@ int ioengine_load(struct thread_data *td)
        }
 
        if (td->io_ops) {
+               struct ioengine_ops *ops;
+               void *dlhandle;
+
                /* An engine is loaded, but the requested ioengine
                 * may have changed.
                 */
@@ -1072,6 +1076,19 @@ int ioengine_load(struct thread_data *td)
                        return 0;
                }
 
+               /*
+                * Name of file and engine may be different, load ops
+                * for this name and see if they match. If they do, then
+                * the engine is unchanged.
+                */
+               dlhandle = td->io_ops_dlhandle;
+               ops = load_ioengine(td);
+               if (ops == td->io_ops && dlhandle == td->io_ops_dlhandle)
+                       return 0;
+
+               if (dlhandle && dlhandle != td->io_ops_dlhandle)
+                       dlclose(dlhandle);
+
                /* Unload the old engine. */
                free_ioengine(td);
        }