svcrdma: advertise the correct max payload

Svcrdma currently advertises 1MB, which is too large.  The correct value
is the minimum of RPCSVC_MAXPAYLOAD and 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@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 8 insertions, 1 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 374feb44afea..4e618808bc98 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 c419498b8f46..ac7fc9a31342 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -51,6 +51,7 @@
 #include <linux/sunrpc/clnt.h>          /* rpc_xprt */
 #include <linux/sunrpc/rpc_rdma.h>      /* RPC/RDMA protocol */
 #include <linux/sunrpc/xprtrdma.h>      /* xprt parameters */
+#include <linux/sunrpc/svc.h>           /* RPCSVC_MAXPAYLOAD */
 
 #define RDMA_RESOLVE_TIMEOUT    (5000)  /* 5 seconds */
 #define RDMA_CONNECT_RETRY_MAX  (2)     /* retries if no listener backlog */
@@ -392,4 +393,10 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
 /* Workqueue created in svc_rdma.c */
 extern struct workqueue_struct *svc_rdma_wq;
 
+#if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
+#define RPCSVC_MAXPAYLOAD_RDMA RPCSVC_MAXPAYLOAD
+#else
+#define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
+#endif
+
 #endif                          /* _LINUX_SUNRPC_XPRT_RDMA_H */