tree 8397b0101b81828399b250871bbf0ab04911deec
parent df6aeb5235e982ef2facc81922fb8393dc1bc814
author Chuck Lever <chuck.lever@oracle.com> 1583178353 -0500
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1597152822 +0200

nfsd: Fix NFSv4 READ on RDMA when using readv

commit 412055398b9e67e07347a936fc4a6adddabe9cf4 upstream.

svcrdma expects that the payload falls precisely into the xdr_buf
page vector. This does not seem to be the case for
nfsd4_encode_readv().

This code is called only when fops->splice_read is missing or when
RQ_SPLICE_OK is clear, so it's not a noticeable problem in many
common cases.

Add new transport method: ->xpo_read_payload so that when a READ
payload does not fit exactly in rq_res's page vector, the XDR
encoder can inform the RPC transport exactly where that payload is,
without the payload's XDR pad.

That way, when a Write chunk is present, the transport knows what
byte range in the Reply message is supposed to be matched with the
chunk.

Note that the Linux NFS server implementation of NFS/RDMA can
currently handle only one Write chunk per RPC-over-RDMA message.
This simplifies the implementation of this fix.

Fixes: b04209806384 ("nfsd4: allow exotic read compounds")
Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=198053
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Timo Rothenpieler <timo@rothenpieler.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>