8830bbca9f
got a panic in uvm_fault from ffs_write. I believe this is because cp used mmap, the container file page was not in core, and uvm_fault objected to the container file vnode and the coda vnode not matching. I have long been plagued by crashes on cp from coda, and this was the first time I got and understood a backtrace. Clean up old comments that are no longer accurate. Document refcounting better. Note some questionable behaviors with XXX. Clean up PNBUF_PUT and SAVESTART. Only do this where vnodeops(9) says we should, and do it on error also. In symlink, vput parent and free namebuf even in error cases.