Re: [linux-next:master] [io_uring/rw] 8cf0c45999: fio.read_bw_MBps 51.1% regression

[Jens Axboe <axboe@kernel.dk>]

On 12/26/24 8:13 PM, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed a 51.1% regression of fio.read_bw_MBps on:
> 
> 
> commit: 8cf0c459993ee2911f4f01fba21b1987b102c887 ("io_uring/rw: Allocate async data through helper")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> 
> [test failed on linux-next/master 8155b4ef3466f0e289e8fcc9e6e62f3f4dceeac2]

Took a quick look, and I think that patch forgets to clear ->bytes_done
when we don't have a free_iovec. That looks like a mistake, it should
always get cleared, it has no dependence on ->free_iovec.

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 75f70935ccf4..ca1b19d3d142 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -228,8 +228,8 @@ static int io_rw_alloc_async(struct io_kiocb *req)
 		kasan_mempool_unpoison_object(rw->free_iovec,
 					      rw->free_iov_nr * sizeof(struct iovec));
 		req->flags |= REQ_F_NEED_CLEANUP;
-		rw->bytes_done = 0;
 	}
+	rw->bytes_done = 0;
 	return 0;
 }
 

-- 
Jens Axboe