Re: [RFC PATCH 0/2] return value from shrinkers

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 13 May 2013 16:16:33 +0200 Oskar Andero <oskar.andero@sonymobile.com> wrote:

> In a previous discussion on lkml it was noted that the shrinkers use the
> magic value "-1" to signal that something went wrong.
> 
> This patch-set implements the suggestion of instead using errno.h values
> to return something more meaningful.
> 
> The first patch simply changes the check from -1 to any negative value and
> updates the comment accordingly.
> 
> The second patch updates the shrinkers to return an errno.h value instead
> of -1. Since this one spans over many different areas I need input on what is
> a meaningful return value. Right now I used -EBUSY on everything for consitency.
> 
> What do you say? Is this a good idea or does it make no sense at all?

I don't see much point in it, really.  Returning an errno implies that
the errno will eventually be returned to userspace.  But that isn't the
case, so such a change is somewhat misleading.

If we want the capability to return more than a binary yes/no message
to callers then yes, we could/should enumerate the shrinker return
values.  But as that is a different concept from errnos, it should be
done with a different and shrinker-specific namespace.