P9P_INVALFID
((++(p9p->nextfid)) == P9P_INVALFID ? p9p->nextfid = 2 : p9p->nextfid)
if (mode & FREAD && p9n->fid_read == P9P_INVALFID) {
if (mode & FWRITE && p9n->fid_write == P9P_INVALFID) {
if (p9n->fid_read != P9P_INVALFID) {
p9n->fid_read = P9P_INVALFID;
if (p9n->fid_write != P9P_INVALFID) {
p9n->fid_write = P9P_INVALFID;
p9n->fid_base = P9P_INVALFID;
assert(p9n->fid_read == P9P_INVALFID && p9n->fid_write == P9P_INVALFID);