From 48ff7df9daea86c82a572b0a840bb8371b6b1a29 Mon Sep 17 00:00:00 2001

From: Eric Sandeen <sandeen@redhat.com>

Date: Mon, 25 Jan 2021 13:23:48 -0600

Subject: [PATCH] fio: fix dlopen refcounting of dynamic engines

ioengine_load() will dlclose the dynamic library if it matches one

that we've already got open, but this defeats the built-in refcounting

done by dlopen/dlclose.  As each thread exits, it calls free_ioengine(),

and this may do a final dlclose on a dynamic ioengine that is still

in use if we don't have the proper reference count.

Fix this by dropping the explicit dlclose of a "matching" dlopened

dynamic engine library, and let each dlclose decrement the refcount

on the engine library as is normal.

This also adds/modifies a couple of debug messages to help track this.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

 init.c      | 5 +----

 ioengines.c | 8 ++++++--

 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/init.c b/init.c

index ab38b334..d6dbaf7c 100644

--- a/init.c

+++ b/init.c

@@ -1109,11 +1109,8 @@ int ioengine_load(struct thread_data *td)

 		if (!ops)

 			goto fail;

-		if (ops == td->io_ops && dlhandle == td->io_ops->dlhandle) {

-			if (dlhandle)

-				dlclose(dlhandle);

+		if (ops == td->io_ops && dlhandle == td->io_ops->dlhandle)

 			return 0;

-		}

 		if (dlhandle && dlhandle != td->io_ops->dlhandle)

 			dlclose(dlhandle);

diff --git a/ioengines.c b/ioengines.c

index dcc9496d..f88b0537 100644

--- a/ioengines.c

+++ b/ioengines.c

@@ -95,6 +95,7 @@ static void *dlopen_external(struct thread_data *td, const char *engine)

 	sprintf(engine_path, "%s/fio-%s.so", FIO_EXT_ENG_DIR, engine);

+	dprint(FD_IO, "dlopen external %s\n", engine_path);

 	dlhandle = dlopen(engine_path, RTLD_LAZY);

 	if (!dlhandle)

 		log_info("Engine %s not found; Either name is invalid, was not built, or fio-engine-%s package is missing.\n",

@@ -116,7 +117,7 @@ static struct ioengine_ops *dlopen_ioengine(struct thread_data *td,

 	    !strncmp(engine_lib, "aio", 3))

 		engine_lib = "libaio";

-	dprint(FD_IO, "dload engine %s\n", engine_lib);

+	dprint(FD_IO, "dlopen engine %s\n", engine_lib);

 	dlerror();

 	dlhandle = dlopen(engine_lib, RTLD_LAZY);

@@ -194,7 +195,9 @@ struct ioengine_ops *load_ioengine(struct thread_data *td)

 	 * so as not to break job files not using the prefix.

 	 */

 	ops = __load_ioengine(td->o.ioengine);

-	if (!ops)

+

+	/* We do re-dlopen existing handles, for reference counting */

+	if (!ops || ops->dlhandle)

 		ops = dlopen_ioengine(td, name);

 	/*

@@ -229,6 +232,7 @@ void free_ioengine(struct thread_data *td)

 	}

 	if (td->io_ops->dlhandle) {

+		dprint(FD_IO, "dlclose ioengine %s\n", td->io_ops->name);

 		dlclose(td->io_ops->dlhandle);

 		td->io_ops->dlhandle = NULL;

 	}

-- 

2.26.2