[PATCH] drm/i915: Fix comparison bug

From: Rasmus Villemoes
Date: Mon Sep 28 2015 - 17:14:48 EST

->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.

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
drivers/gpu/drm/i915/i915_debugfs.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index e3ec9049081f..5207e681a987 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -258,7 +258,11 @@ 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)

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