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Re: [PATCH V2] xfs: introduce CONFIG_XFS_WARN

To: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Subject: Re: [PATCH V2] xfs: introduce CONFIG_XFS_WARN
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 26 Apr 2013 07:44:05 +1000
Cc: Brian Foster <bfoster@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1366898869.3762.32410.camel@xxxxxxxxxxxxxxxxxx>
References: <1366699138-24055-1-git-send-email-david@xxxxxxxxxxxxx> <5176833C.8070305@xxxxxxxxxx> <20130423210226.GN10481@dastard> <20130424085546.GQ10481@dastard> <1366828792.3762.32405.camel@xxxxxxxxxxxxxxxxxx> <20130424225821.GV10481@dastard> <1366898869.3762.32410.camel@xxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Apr 25, 2013 at 09:07:49AM -0500, Chandra Seetharaman wrote:
> On Thu, 2013-04-25 at 08:58 +1000, Dave Chinner wrote:
> > On Wed, Apr 24, 2013 at 01:39:52PM -0500, Chandra Seetharaman wrote:
> > > Hi Dave,
> > > 
> > > Since this solution is for production environment, would it be valuable
> > > to have a sysctl variable to allow enabling/disabling XFS_WARN, as
> > > opposed to needing to recompile the module afresh ?
> > 
> > The idea is that distros enable it on the debug kernel packages
> > rather than using CONFIG_XFS_DEBUG=y. Hence if someone has a
> > problem, they just install the debug kernel and they get all this
> > additional checking.
> 
> Thanks for the clarification.
> 
> I was thinking that CONFIG_XFS_DEBUG would be enabled in the distro's
> debug kernel and this new option is in addition to that. Hence, my
> question.

If you are shipping a debug kernel with CONFIG_XFS_DEBUG, then you
don't want your customers running that debug kernel for very long.
CONFIG_XFS_DEBUG changes allocation algorithms to improve test
coverage and this causes accelerated filesystem aging....

CONFIG_XFS_WARN is designed to be used instead of CONFIG_XFS_DEBUG
in these situations - we get more verbose checking, but without the
down sides associated with all the algorithmic changes in
XFS_DEBUG...

> So, with this new config option, CONFIG_XFS_DEBUG will only be used in
> development environment, correct ?

That's what I has always been intended for.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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