2013-07-23 19:18:16

by Artem Savkov

Subject: [PATCH] drm: i915_gem_inactive_scan: insufficient nr_to_scan size

nr_to_scan needs to be (unsigned) long, not int, otherwise we get negative
values on 32bit systems during shrink resulting in lots of messages like one
below.

[ 4078.989603] shrink_slab: i915_gem_inactive_scan+0x0/0xc0 negative objects to delete nr=-289580136

Introduced in "drivers: convert shrinkers to new count/scan API"
(383e4f4a4cdeb2dd552e90811089bcb4d41eb32e in linux-next.git)

Signed-off-by: Artem Savkov <[email protected]>
---
drivers/gpu/drm/i915/i915_gem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4635354..b3b4891b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4649,7 +4649,7 @@ i915_gem_inactive_scan(struct shrinker *shrinker, struct shrink_control *sc)
struct drm_i915_private,
mm.inactive_shrinker);
struct drm_device *dev = dev_priv->dev;
- int nr_to_scan = sc->nr_to_scan;
+ unsigned long nr_to_scan = sc->nr_to_scan;
unsigned long freed;
bool unlock = true;

--
1.8.3.3

2013-07-23 19:29:47

by Artem Savkov

Subject: Re: [PATCH] drm: i915_gem_inactive_scan: insufficient nr_to_scan size

On Tue, Jul 23, 2013 at 11:18:06PM +0400, Artem Savkov wrote:
> nr_to_scan needs to be (unsigned) long, not int, otherwise we get negative
> values on 32bit systems during shrink resulting in lots of messages like one
> below.
>
> [ 4078.989603] shrink_slab: i915_gem_inactive_scan+0x0/0xc0 negative objects to delete nr=-289580136
>
> Introduced in "drivers: convert shrinkers to new count/scan API"
> (383e4f4a4cdeb2dd552e90811089bcb4d41eb32e in linux-next.git)

Sorry, looks like my analysis was wrong, I can still see the issue with this
patch.

--
Regards,
Artem