From d4550bbee66f4ba5a5e9bbe8055006332ebfc58b Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Mon, 11 Feb 2019 11:23:49 -0500 Subject: 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 Signed-off-by: Anna Schumaker --- net/sunrpc/xprtrdma/rpc_rdma.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'net/sunrpc/xprtrdma') 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; else wtype = rpcrdma_replych; -- cgit v1.2.3