path: root/net/sunrpc
diff options
authorChuck Lever <chuck.lever@oracle.com>2019-02-11 11:23:49 -0500
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2019-02-13 10:19:06 -0500
commitd4550bbee66f4ba5a5e9bbe8055006332ebfc58b (patch)
tree38770a38bc030fe76aa5320a73538611973eba7b /net/sunrpc
parentxprtrdma: Fix sparse warnings (diff)
xprtrdma: Check inline size before providing a Write chunk
In very rare cases, an NFS READ operation might predict that the non-payload part of the RPC Call is large. For instance, an NFSv4 COMPOUND with a large GETATTR result, in combination with a large Kerberos credential, could push the non-payload part to be several kilobytes. If the non-payload part is larger than the connection's inline threshold, the client is required to provision a Reply chunk. The current Linux client does not check for this case. There are two obvious ways to handle it: a. Provision a Write chunk for the payload and a Reply chunk for the non-payload part b. Provision a Reply chunk for the whole RPC Reply Some testing at a recent NFS bake-a-thon showed that servers can mostly handle a. but there are some corner cases that do not work yet. b. already works (it has to, to handle krb5i/p), but could be somewhat less efficient. However, I expect this scenario to be very rare -- no-one has reported a problem yet. So I'm going to implement b. Sometime later I will provide some patches to help make b. a little more efficient by more carefully choosing the Reply chunk's segment sizes to ensure the payload is optimally aligned. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc')
1 files changed, 17 insertions, 1 deletions
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index d18614e02b4e..7774aee7c013 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -164,6 +164,21 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
return rqst->rq_rcv_buf.buflen <= ia->ri_max_inline_read;
+/* The client is required to provide a Reply chunk if the maximum
+ * size of the non-payload part of the RPC Reply is larger than
+ * the inline threshold.
+ */
+static bool
+rpcrdma_nonpayload_inline(const struct rpcrdma_xprt *r_xprt,
+ const struct rpc_rqst *rqst)
+ const struct xdr_buf *buf = &rqst->rq_rcv_buf;
+ const struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+ return buf->head[0].iov_len + buf->tail[0].iov_len <
+ ia->ri_max_inline_read;
/* Split @vec on page boundaries into SGEs. FMR registers pages, not
* a byte range. Other modes coalesce these SGEs into a single MR
* when they can.
@@ -762,7 +777,8 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
if (rpcrdma_results_inline(r_xprt, rqst))
wtype = rpcrdma_noch;
- else if (ddp_allowed && rqst->rq_rcv_buf.flags & XDRBUF_READ)
+ else if ((ddp_allowed && rqst->rq_rcv_buf.flags & XDRBUF_READ) &&
+ rpcrdma_nonpayload_inline(r_xprt, rqst))
wtype = rpcrdma_writech;
wtype = rpcrdma_replych;