Re: [PATCH] block: rnbd: rnbd-srv: silence uninitialized variable warning

[Nathan Chancellor]

On Tue, Aug 18, 2020 at 12:03:18AM -0400, Brooke Basile wrote:
> Clang warns:
>       drivers/block/rnbd/rnbd-srv.c:150:6: warning: variable 'err' is used
>       uninitialized whenever 'if' condition is true 
> [-Wsometimes-uninitialized]
>               if (IS_ERR(bio)) {
>               ^~~~~~~~~~~
>       drivers/block/rnbd/rnbd-srv.c:177:9: note: uninitialized use occurs here
>               return err;
>               ^~~
>       drivers/block/rnbd/rnbd-srv.c:126:9: note: initialize the variable 'err'
>       to silence this warning
>               int err;
>                       ^
>                       = 0
> 
> Silence this by replacing `err` with `ret`, returning ret = 0 upon
> success.
> 
> Signed-off-by: Brooke Basile <brookebas...@gmail.com>
> ---
>  drivers/block/rnbd/rnbd-srv.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
> index 0fb94843a495..f515d1a048a9 100644
> --- a/drivers/block/rnbd/rnbd-srv.c
> +++ b/drivers/block/rnbd/rnbd-srv.c
> @@ -123,10 +123,10 @@ static int process_rdma(struct rtrs_srv *sess,
>       struct rnbd_io_private *priv;
>       struct rnbd_srv_sess_dev *sess_dev;
>       u32 dev_id;
> -     int err;
>       struct rnbd_dev_blk_io *io;
>       struct bio *bio;
>       short prio;
> +     int ret = 0;
>  
>       priv = kmalloc(sizeof(*priv), GFP_KERNEL);
>       if (!priv)
> @@ -138,7 +138,7 @@ static int process_rdma(struct rtrs_srv *sess,
>       if (IS_ERR(sess_dev)) {
>               pr_err_ratelimited("Got I/O request on session %s for unknown 
> device id %d\n",
>                                  srv_sess->sessname, dev_id);
> -             err = -ENOTCONN;
> +             ret = -ENOTCONN;
>               goto err;
>       }
>  
> @@ -168,13 +168,13 @@ static int process_rdma(struct rtrs_srv *sess,
>  
>       submit_bio(bio);
>  
> -     return 0;
> +     return ret;
>  
>  sess_dev_put:
>       rnbd_put_sess_dev(sess_dev);
>  err:
>       kfree(priv);
> -     return err;
> +     return ret;
>  }
>  
>  static void destroy_device(struct rnbd_srv_dev *dev)
> -- 
> 2.28.0
> 

I don't think this is a proper fix since the root cause of the warning
appears to be that we are ignoring the return value of
rnbd_bio_map_kern. Should we not set err to that value like this
(completely untested)?

Cheers,
Nathan

diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
index 0fb94843a495..1b71cb2a885d 100644
--- a/drivers/block/rnbd/rnbd-srv.c
+++ b/drivers/block/rnbd/rnbd-srv.c
@@ -148,7 +148,8 @@ static int process_rdma(struct rtrs_srv *sess,
        /* Generate bio with pages pointing to the rdma buffer */
        bio = rnbd_bio_map_kern(data, sess_dev->rnbd_dev->ibd_bio_set, datalen, 
GFP_KERNEL);
        if (IS_ERR(bio)) {
-               rnbd_srv_err(sess_dev, "Failed to generate bio, err: %ld\n", 
PTR_ERR(bio));
+               err = PTR_ERR(bio);
+               rnbd_srv_err(sess_dev, "Failed to generate bio, err: %ld\n", 
err);
                goto sess_dev_put;
        }