Re: Why is one sync() not enough?

[Andrew Morton <akpm@osdl.org>]

Nico Schottelius <nico-kernel@schottelius.org> wrote:
>
> Hello Andrew,
> 
> you wrote:
> > What filesystem?
> 
> jfs

It would be useful to test with a different filesystem (ext3 mounted with
data=writeback is close to equivalent).  That'll help us identify the bug.

> > What kernel version?
> 
> 2.6.11.11
> 
> > Any unusual bind mounts, loopback
> > mounts, etc?  There must be something there...>
> 
> Yes, dm-crypt-mounted-jfs.

Again, if you can temporarily eliminate dm-crypt as well it will help
narrow it down.

> So if I understood everything correctly, a simple umount() without
> a sync() before should be enough?

Yes.

> If so, I'll try that, I am happy about every less function call
> I need to do.

OK.  sync()+umount() shouldn't take any longer than a bare umount() (which
has to do a sync too).  Unless you have multiple disks, in which case
there's no point in syncing the disks which aren't being umounted.  But
then, I have a feeling that standard util-linux umount(8) does a global
sync anyway.