nfsd41: use sv_max_mesg for forechannel max sizes

ca_maxresponsesize and ca_maxrequest size include the RPC header.

sv_max_mesg is sv_max_payolad plus a page for overhead and is used in
svc_init_buffer to allocate server buffer space for both the request and reply.
Note that this means we can service an RPC compound that requires
ca_maxrequestsize (MAXWRITE) or ca_max_responsesize (MAXREAD) but that we do
not support an RPC compound that requires both ca_maxrequestsize and
ca_maxresponsesize.

Signed-off-by: Andy Adamson <andros@netapp.com>
[bfields@citi.umich.edu: more documentation updates]
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/filesystems/nfs41-server.txt b/Documentation/filesystems/nfs41-server.txt
index 1f95e7731886..1bd0d0c05171 100644
--- a/Documentation/filesystems/nfs41-server.txt
+++ b/Documentation/filesystems/nfs41-server.txt
@@ -213,3 +213,10 @@ The following cases aren't supported yet:
   DESTROY_CLIENTID, DESTROY_SESSION, EXCHANGE_ID.
 * DESTROY_SESSION MUST be the final operation in the COMPOUND request.
 
+Nonstandard compound limitations:
+* No support for a sessions fore channel RPC compound that requires both a
+  ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
+  fail to live up to the promise we made in CREATE_SESSION fore channel
+  negotiation.
+* No more than one IO operation (read, write, readdir) allowed per
+  compound.