revert/rework 81647a9a('fix load_ioengine() not to support no "external:" prefix')

[fio.git] / ioengines.c

diff --git a/ioengines.c b/ioengines.c
index e78b4f79acadc87a30808e54a7e78b55155318f6..fa4acab2b3fa349a57993d086048a4709cb9b68a 100644 (file)
--- a/ioengines.c
+++ b/ioengines.c
@@ -143,17 +143,30 @@ static struct ioengine_ops *__load_ioengine(const char *name)
 struct ioengine_ops *load_ioengine(struct thread_data *td)
 {
        struct ioengine_ops *ops = NULL;
-       const char *name = NULL;
+       const char *name;
 
-       if (strcmp(td->o.ioengine, "external")) {
-               name = td->o.ioengine;
-               ops = __load_ioengine(name);
-       } else if (td->o.ioengine_so_path) {
-               name = td->o.ioengine_so_path;
+       /*
+        * Use ->ioengine_so_path if an external ioengine path is specified.
+        * In this case, ->ioengine is "external" which also means the prefix
+        * for external ioengines "external:" is properly used.
+        */
+       name = td->o.ioengine_so_path ?: td->o.ioengine;
+
+       /*
+        * Try to load ->ioengine first, and if failed try to dlopen(3) either
+        * ->ioengine or ->ioengine_so_path.  This is redundant for an external
+        * ioengine with prefix, and also leaves the possibility of unexpected
+        * behavior (e.g. if the "external" ioengine exists), but we do this
+        * so as not to break job files not using the prefix.
+        */
+       ops = __load_ioengine(td->o.ioengine);
+       if (!ops)
                ops = dlopen_ioengine(td, name);
-       } else
-               log_err("fio: missing external ioengine path\n");
 
+       /*
+        * If ops is NULL, we failed to load ->ioengine, and also failed to
+        * dlopen(3) either ->ioengine or ->ioengine_so_path as a path.
+        */
        if (!ops) {
                log_err("fio: engine %s not loadable\n", name);
                return NULL;