drm/i915: Limit the scattergather coalescing to 32bits

The scattergather list uses a 32bit size counter, we should avoid
exceeding it.

v2: Also we should use unsigned int to match sg->length.

Fixes: 871dfbd67d4e ("drm/i915: Allow compaction upto SWIOTLB max segment size")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161018120251.25043-3-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6165a3b..9bb72e5 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2205,7 +2205,7 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
        return 0;
 }
 
-static unsigned long swiotlb_max_size(void)
+static unsigned int swiotlb_max_size(void)
 {
 #if IS_ENABLED(CONFIG_SWIOTLB)
        return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE);
@@ -2225,7 +2225,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
        struct sgt_iter sgt_iter;
        struct page *page;
        unsigned long last_pfn = 0;     /* suppress gcc warning */
-       unsigned long max_segment;
+       unsigned int max_segment;
        int ret;
        gfp_t gfp;
 
@@ -2238,7 +2238,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 
        max_segment = swiotlb_max_size();
        if (!max_segment)
-               max_segment = obj->base.size;
+               max_segment = rounddown(UINT_MAX, PAGE_SIZE);
 
        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (st == NULL)