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

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Message-ID: <5192523B.7030805@parallels.com>
Date:	Tue, 14 May 2013 19:03:23 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Oskar Andero <oskar.andero@...ymobile.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	Hugh Dickins <hughd@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Radovan Lekanovic <radovan.lekanovic@...ymobile.com>,
	David Rientjes <rientjes@...gle.com>,
	Dave Chinner <david@...morbit.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [RFC PATCH 0/2] return value from shrinkers

On 05/13/2013 06:16 PM, Oskar Andero wrote:
> Hi,
> 
> 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?
> 
> Thanks!
> 

Right now me and Dave are completely reworking the way shrinkers
operate. I suggest, first of all, that you take a look at that cautiously.

On the specifics of what you are doing here, what would be the benefit
of returning something other than -1 ? Is there anything we would do
differently for a return value lesser than 1?

So far, shrink_slab behaves the same, you are just expanding the test.
If you really want to push this through, I would suggest coming up with
a more concrete reason for why this is wanted.

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