Re: [PATCH 1/3] SUNRPC: The TCP back channel mustn't disappear while requests are outstanding

J. Bruce Fields
2019-10-16T21:38:15Z

These make sense to me. (But I'll confess I haven't been following the
back and forth with Neil.)

On Wed, Oct 16, 2019 at 10:15:44AM -0400, Trond Myklebust wrote:
> If there are TCP back channel requests either being processed by the

In this patch and the next, is the "either" unnecessary, or was there
some other condition you meant to mention?

--b.

> server threads, then we should hold a reference to the transport
> to ensure it doesn't get freed from underneath us.
>
> Reported-by: Neil Brown <neilb@suse.de>
> Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..")
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
> net/sunrpc/backchannel_rqst.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> index 339e8c077c2d..7eb251372f94 100644
> --- a/net/sunrpc/backchannel_rqst.c
> +++ b/net/sunrpc/backchannel_rqst.c
> @@ -307,8 +307,8 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
> */
> dprintk("RPC: Last session removed req=%p\n", req);
> xprt_free_allocation(req);
> - return;
> }
> + xprt_put(xprt);
> }
>
> /*
> @@ -339,7 +339,7 @@ struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
> spin_unlock(&xprt->bc_pa_lock);
> if (new) {
> if (req != new)
> - xprt_free_bc_rqst(new);
> + xprt_free_allocation(new);
> break;
> } else if (req)
> break;
> @@ -368,6 +368,7 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
> set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
>
> dprintk("RPC: add callback request to list\n");
> + xprt_get(xprt);
> spin_lock(&bc_serv->sv_cb_lock);
> list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
> wake_up(&bc_serv->sv_cb_waitq);
> --
> 2.21.0
>