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

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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 14168fbc7d797da444a72bddb2a10b645e64c346..51ff88330f9a8829c3de10dafc7d78f78fafa9c9 100644 (file)
--- 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);