Re: [PATCH] svcrdma: Advertise the correct max payload

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 9/22/2014 1:39 PM, J. Bruce Fields wrote:
> On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
>> Svcrdma currently advertises 1MB, which is too large.  The correct value
>> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
>> size. This bug is usually benign because the Linux X64 NFSRDMA client
>> correctly limits the payload size to the correct value (64*4096 = 256KB).
>> But if the Linux client is PPC64 with a 64KB page size, then the client
>> will indeed use a payload size that will overflow the server.
>>
>> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
>> ---
>>
>>   net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>>   net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>>   2 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> index 374feb4..4e61880 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>>   	.xcl_name = "rdma",
>>   	.xcl_owner = THIS_MODULE,
>>   	.xcl_ops = &svc_rdma_ops,
>> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
>> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>>   	.xcl_ident = XPRT_TRANSPORT_RDMA,
>>   };
>>   
>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>> index c419498..467a77c 100644
>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>>   /* Workqueue created in svc_rdma.c */
>>   extern struct workqueue_struct *svc_rdma_wq;
>>   
>> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> Do you want to define this as the minimum of this and
> RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
> day?

Why would it need to be limited by MAXPAYLOAD_TCP?

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html