[PATCH] io_uring: only call kfree() for a non-zero pointer

[Jens Axboe <axboe@kernel.dk>]

It's safe to call kfree() with a NULL pointer, but it's also pointless.
Most of the time we don't have any data to free, and at millions of
requests per second, the redundant function call adds noticeable
overhead (about 1.3% of the runtime).

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

---

Kinda silly, this is 100% reproducible. Actually somewhat baffled
that kfree() isn't a inline, to avoid a function call if the pointer
is NULL.

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 14168fbc7d79..51ff88330f9a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1519,7 +1519,8 @@ static void io_dismantle_req(struct io_kiocb *req)
 	if (req->flags & REQ_F_NEED_CLEANUP)
 		io_cleanup_req(req);
 
-	kfree(req->io);
+	if (req->io)
+		kfree(req->io);
 	if (req->file)
 		io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));
 	__io_put_req_task(req);

-- 
Jens Axboe