On Wed, Aug 03, 2016 at 11:27:47AM -0400, Chuck Lever wrote:
> Hi Bruce-
>
> I see that commit 39a9beab5acb83176e8b9a4f0778749a09341f1f
> Author: J. Bruce Fields <bfields@xxxxxxxxxx>
> AuthorDate: Tue May 17 12:38:21 2016 -0400
>
> rpc: share one xps between all backchannels
>
> has added this piece of code:
>
> @@ -452,10 +452,20 @@ static struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
> struct rpc_clnt *clnt = NULL;
> struct rpc_xprt_switch *xps;
>
> - xps = xprt_switch_alloc(xprt, GFP_KERNEL);
> - if (xps == NULL) {
> - xprt_put(xprt);
> - return ERR_PTR(-ENOMEM);
> + if (args->bc_xprt && args->bc_xprt->xpt_bc_xps) {
> + WARN_ON(args->protocol != XPRT_TRANSPORT_BC_TCP);
> + xps = args->bc_xprt->xpt_bc_xps;
> + xprt_switch_get(xps);
> + } else {
>
>
> the WARN_ON here fires on the server whenever I use NFSv4.1 on RDMA.
>
> Can you say why it was added? Is there something RPC/RDMA needs to
> do to make the code safe?
What is args->protocol in this case?
Digging around... OK, I missed that BC_TCP and BC_RDMA were defined as
OR's of an XPRT_TRANSPORT_BC bit with the identifier of the underlying
transport. That makes sense.
So, I should have just used XPRT_TRANSPORT_BC there--I think all I meant
was "is this a backchannel".
Does that fix the problem?
--b.
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