Re: [PATCH V2] xfs: introduce CONFIG_XFS_WARN

Dave Chinner
2013-04-24T22:58:42Z

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.

There are roughly 1700 ASSERT statements in the XFS code, so
compiling them in unconditionally is a lot of extra code. Adding a
sysctl to make them conditional adds as many branches into the code
than in 99.99999% of calls are never going to evaluate as true. The
convenience of a sysctl is more than outweighed by the additional
overhead for the majortiy of people that don't need to diagnose
problems on their system.

Hence I don't think the overhead of unconditionally compiling in
ASSERT checks is worth while for the majority of users, especially
as most distros ship a debug kernel for exactly this purpose....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com