Re: Scrub resume regression

[David Sterba <dsterba@suse.cz>]

On Wed, Jan 15, 2020 at 02:10:42PM +0100, Holger Hoffstätte wrote:
> On 1/15/20 1:51 PM, David Sterba wrote:
> >> It is important that scrub always returns the stats, even when it
> >> returns an error. This is critical for cancel, as that is how
> >> cancel/resume works, but it should also apply in case of other errors so
> >> that the user can see how much of the scrub was done before the fatal error.
> > 
> > That's something we need to document in code and perhaps in the manual
> > pages too.
> 
> Isn't the real problem that cancel does not actually mean cancel,
> but rather also implies "..and maybe continue"? IMHO cancel should cancel
> (and say how much work was performed), while the intention to resume should
> be called e.g. "pause". This makes the behaviour clear and prevents
> accidental semantic overlap.

We can add 'pause', but for backward compatibility, cancel has to stay
as is. I personally think that saving the last position after cancel is
not a big deal. With 'pause' it will be less confusing for users and
will have also parity with balance commands.

start - pause - resume
start - cancel

One difference is that cancelling balance will also delete the state
(stored inside the filesystem metadata). If scrub start follows cancel,
the state is reset at the beginning. I'm not sure if adding an extra
option eg. 'scrub cancel --reset' is worth.