fbb550b94d
It was previously possible to round up one sector length if the start block
were not properly aligned.
Resolves PR kern/36716. This may also fix the following reported issues
on port-sgimips:
http://mail-index.netbsd.org/port-sgimips/2005/09/12/0000.html
http://mail-index.netbsd.org/port-sgimips/2005/09/14/0000.html
While here, be sure to put back allocated bufs, which previously appear
to have been leaked. Further, remove the dead write bounce code which never
got executed anyway.
No complaints on tech-kern.