Re: [PATCH] zram: check compressor name before setting it

[Marcin Jabrzyk]

Hello Minchan,

On 22/05/15 15:14, Minchan Kim wrote:
> Hello Sergey,
>
> On Fri, May 22, 2015 at 09:44:11PM +0900, Sergey Senozhatsky wrote:
> > On (05/22/15 11:12), Marcin Jabrzyk wrote:
> > > > no.
> > > >
> > > > zram already complains about failed comp backend creation.
> > > > it's in dmesg (or syslog, etc.):
> > > >
> > > > 	"zram: Cannot initialise %s compressing backend"
> > > OK, now I see that. Sorry for the noise.
> > >
> > > > second, there is not much value in exposing zcomp internals,
> > > > especially when the result is just another line in dmesg output.
> > >
> > >  From the other hand, the only valid values that can be written are
> > > in 'comp_algorithm'.
> > > So when writing other one, returning -EINVAL seems to be reasonable.
> > > The user would get immediately information that he can't do that,
> > > now the information can be very deferred in time.
> >
> > it's not.
> > the error message appears in syslog right before we return -EINVAL
> > back to user.
>
> Although Marcin's description is rather misleading, I like the patch.
> Every admin doesn't watch dmesg output. Even people could change loglevel
> simply so KERN_INFO would be void in that case.
Sorry for being confusing, at the first time I've overlooked that error 
message in syslog.
I didn't thought about looking for handling exactly this error in 
completely different place.

> Instant error propagation is more strighforward for user point of view
> rather than delaying with depending on another event.

Yes this was my exact motivation.
Instant value can be detected in scripts etc. Easier to debug in
automated environment.

> Thanks.
>
> > 	-ss
> >
> > > I'm not for exposing more internals, but getting -EINVAL would be nice I

If this would be ok, I can prepare v2 with better description and with
less exposing zcomp internals.

Best regards,
Marcin Jabrzyk

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