P9_IOHDRSZ
v9ses->maxdata = v9ses->clnt->msize - P9_IOHDRSZ;
rreq->wsize = fid->clnt->msize - P9_IOHDRSZ;
wreq->wsize = fid->clnt->msize - P9_IOHDRSZ;
buflen = fid->clnt->msize - P9_IOHDRSZ;
#define DEFAULT_MSIZE ((128 * 1024) + P9_IOHDRSZ)
if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
rsize = clnt->msize - P9_IOHDRSZ;
if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
rsize = clnt->msize - P9_IOHDRSZ;