On Mon, 30 May 2011, Kostik Belousov wrote:
On Mon, May 30, 2011 at 01:48:53PM +0100, Robert Watson wrote:
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?
This call is from the same department as triple-sync before reboot, IMO.
No doubt. :-)
If the sync(2) has actual consistency and reliability benefits, it should
probably be done by the umount(2) system call, so that other future
auto-mounters, etc, also get the same result, rather than having to encode it
in every application. If it's done on blind faith, perhaps it shouldn't be
done at all.
Robert
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