[Intel-gfx] [PATCH 4/5] drm: WARN when removing unallocated node

[Chris Wilson]

On Fri, Aug 09, 2013 at 10:12:15PM -0700, Ben Widawsky wrote:
> The conditional is usually a recoverable driver bug, and so WARNing, and
> preventing the drm_mm code from doing potential damage (BUG) is
> desirable.
> 
> This issue was hit and fixed twice while developing the i915 multiple
> address space code. The first fix is the patch just before this, and is
> hit on an not frequently occuring error path. Another was fixed during
> patch iteration, so it's hard to see from the patch:
> 
> commit c6cfb325677ea6305fb19acf3a4d14ea267f923e
> Author: Ben Widawsky <ben at bwidawsk.net>
> Date:   Fri Jul 5 14:41:06 2013 -0700
> 
>     drm/i915: Embed drm_mm_node in i915 gem obj
> 
> From the intel-gfx mailing list, we discussed this:
> References: <20130705191235.GA3057 at bwidawsk.net>
> 
> Cc: Dave Airlie <airlied at redhat.com>
> CC: <dri-devel at lists.freedesktop.org>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>

On the other hand, if we end up with a proliferation of
  if (drm_mm_node_allocated(node))
    drm_mm_remove_node(node)
in the drivers, putting the guard into remove_node is preferrable. At
the moment we only have the one error path in i915.ko where we need to
double check so it is not much of a concern.

Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre