svn commit: r222466 - head/sbin/umount

[Robert Watson]

On Sun, 29 May 2011, Rick Macklem wrote:

>  Modify the umount(8) command so that it doesn't do
>  a sync(2) syscall before unmount(2) for the "-f" case.
>  This avoids a forced dismount from getting stuck for
>  an NFS mountpoint in sync() when the server is not
>  responsive. With this commit, forced dismounts should
>  normally work for the NFS clients, but can take up to
>  about 1minute to complete.

I'm actually a bit confused about why umount(8) calls sync(2) at all: surely 
it's the responsibility of the file system, rather than the userland tool, to 
ensure consistency subject to file system configuration and unmount-time 
flags?

Robert