[Devel] [PATCH VZ9] fs/fuse kio: add debug info to catch unexpected event

[Alexey Kuznetsov]

Ack

On Wed, May 28, 2025 at 11:11 AM Liu Kui <kui.liu at virtuozzo.com> wrote:
>
> We encountered a very strange problem that krpc returns a response
> msg without error, however the userspace still sees the original
> request msg header in the tx buf instead of the response msg header.
> We don't know how it happened, as there's no info from kernel. So
> here we try to catch such event by printing a warn message only,
> letting userpsace handle such exception.
>
> Related to #VSTOR-107235
> https://virtuozzo.atlassian.net/browse/VSTOR-107235
>
> Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
> ---
>  fs/fuse/kio/pcs/pcs_krpc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/fs/fuse/kio/pcs/pcs_krpc.c b/fs/fuse/kio/pcs/pcs_krpc.c
> index 0b47afb9bb01..e8c924c1a5da 100644
> --- a/fs/fuse/kio/pcs/pcs_krpc.c
> +++ b/fs/fuse/kio/pcs/pcs_krpc.c
> @@ -85,10 +85,17 @@ static void krpc_req_complete(struct krpc_req *kreq, int error)
>  {
>         struct krpc_completion *comp = &kreq->completion;
>         struct pcs_krpc *krpc = kreq->krpc;
> +       struct pcs_rpc_hdr *h = (struct pcs_rpc_hdr *)kreq->hdr_buf;
>
>         BUG_ON(!comp->xid);
>
>         comp->result = error;
> +       if (!comp->result && !(RPC_IS_RESPONSE(h->type))) {
> +               /*
> +                * This should never happen, catch the event if it happens.
> +                */
> +               WARN_ON_ONCE(1);
> +       }
>
>         kreq_release_data_chunks(kreq);
>         if (kreq->hdr_chunk.mr)
> --
> 2.39.5 (Apple Git-154)