> On Aug 3, 2016, at 1:47 PM, bfields@xxxxxxxxxxxx wrote:
>
> 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?
This simple fix eliminates the log noise:
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 2808d55..f94caf7 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -520,7 +520,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
char servername[48];
if (args->bc_xprt) {
- WARN_ON(args->protocol != XPRT_TRANSPORT_BC_TCP);
+ WARN_ON(!(args->protocol & XPRT_TRANSPORT_BC));
xprt = args->bc_xprt->xpt_bc_xprt;
if (xprt) {
xprt_get(xprt);
This code seems to come from:
commit d50039ea5ee63c589b0434baa5ecf6e5075bb6f9
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
AuthorDate: Mon May 16 17:03:42 2016 -0400
nfsd4/rpc: move backchannel create logic into rpc code
Where it may have been copied from:
-static struct rpc_clnt *create_backchannel_client(struct rpc_create_args *args)
-{
- struct rpc_xprt *xprt;
-
- if (args->protocol != XPRT_TRANSPORT_BC_TCP)
- return rpc_create(args);
-
- xprt = args->bc_xprt->xpt_bc_xprt;
- if (xprt) {
- xprt_get(xprt);
- return rpc_create_xprt(args, xprt);
- }
-
- return rpc_create(args);
-}
There's no warning here. In fact, protocol != BC_TCP seems to
be expected.
I'm wondering if the warning is needed at all?
--
Chuck Lever
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