[PATCH] drm/ttm: fix missing NULL check in ttm_device_swapout

[Felix Kuehling <Felix.Kuehling@amd.com>]

Backport of Christian's patch 81b0d0e4f811 to amd-staging-drm-next. This
branch may be nearly obsolete, but this patch may still be worth
applying as it can serve as a template for backports to some release
branches. It fixes intermittent kernel oopses when memory is severely
overcommitted.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
 drivers/gpu/drm/ttm/ttm_device.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index be24bb6cefd0..165a6cbb45d5 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -157,6 +157,9 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 			list_for_each_entry(bo, &man->lru[j], lru) {
 				uint32_t num_pages = PFN_UP(bo->base.size);
 
+				if (!bo->resource)
+					continue;
+
 				ret = ttm_bo_swapout(bo, ctx, gfp_flags);
 				/* ttm_bo_swapout has dropped the lru_lock */
 				if (!ret)
-- 
2.32.0