[PATCH 2/3] SUNRPC: Fix large reads on NFS/RDMA

[Chuck Lever <chuck.lever@oracle.com>]

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 stopped working.  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>
Cc: <stable@vger.kernel.org> # 3.7+
---

 net/sunrpc/xprtrdma/rpc_rdma.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index e03725b..96ead52 100644
--- 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;