drm/i915: Fix comparison bug

->stolen->start has type u64 aka unsigned long long; relying on the
difference (effectively cast to int) for sorting is wrong.

It wouldn't be a problem in practice if the values compared are always
within INT_MAX of each other (so that the difference is actually
representable in an int), but 440fd5283a87 ("drm/mm: Support 4 GiB and
larger ranges") strongly suggests that's not the case.

Note: atm we don't support more than about 1G of stolen, so this is
impossible currenlty.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
[danvet: Add note that this is impossible currently.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index afa79827f1f752a24d1be7320883f86a0a41e040..9839831dd6e58c0a418be2122c4a9187f0d6026a 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -253,7 +253,11 @@ static int obj_rank_by_stolen(void *priv,
        struct drm_i915_gem_object *b =
                container_of(B, struct drm_i915_gem_object, obj_exec_link);
 
-       return a->stolen->start - b->stolen->start;
+       if (a->stolen->start < b->stolen->start)
+               return -1;
+       if (a->stolen->start > b->stolen->start)
+               return 1;
+       return 0;
 }
 
 static int i915_gem_stolen_list_info(struct seq_file *m, void *data)