SUNRPC: Fix large reads on NFS/RDMA

After commit a11a2bf4, "SUNRPC: Optimise away unnecessary data moves
in xdr_align_pages", Thu Aug 2 13:21:43 2012, READs larger than a
few hundred bytes via NFS/RDMA no longer work.  This commit exposed
a long-standing bug in rpcrdma_inline_fixup().

I reproduce this with an rsize=4096 mount using the cthon04 basic
tests.  Test 5 fails with an EIO error.

For my reproducer, kernel log shows:

  NFS: server cheating in read reply: count 4096 > recvd 0

rpcrdma_inline_fixup() is zeroing the xdr_stream::page_len field,
and xdr_align_pages() is now returning that value to the READ XDR
decoder function.

That field is set up by xdr_inline_pages() by the READ XDR encoder
function.  As far as I can tell, it is supposed to be left alone
after that, as it describes the dimensions of the reply xdr_stream,
not the contents of that stream.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=68391
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index e03725b..96ead52 100644 (file)
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -649,9 +649,7 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
                                break;
                        page_base = 0;
                }
-               rqst->rq_rcv_buf.page_len = olen - copy_len;
-       } else
-               rqst->rq_rcv_buf.page_len = 0;
+       }
 
        if (copy_len && rqst->rq_rcv_buf.tail[0].iov_len) {
                curlen = copy_len;