[PATCH 08/12] drm/ttm: use dma_resv reference in ttm_device_clear_lru_dma_mappings

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Instead of trying to grab a BO reference.

Also lock the dma_resv object, that TT unpopulate is done without
holding the lock looks extremely suspicious.

Only compile tested!

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/ttm/ttm_device.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index e4188e2ee7ab1..be6fc42772f9d 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -293,19 +293,29 @@ static void ttm_device_clear_lru_dma_mappings(struct ttm_device *bdev,
 
 	spin_lock(&bdev->lru_lock);
 	while ((res = ttm_lru_first_res_or_null(list))) {
-		struct ttm_buffer_object *bo = res->bo;
+		struct dma_resv *resv;
 
 		/* Take ref against racing releases once lru_lock is unlocked */
-		if (!ttm_bo_get_unless_zero(bo))
-			continue;
+		resv = dma_resv_get(res->bo->base.resv);
+		spin_unlock(&bdev->lru_lock);
+
+		dma_resv_lock(resv, NULL);
 
-		list_del_init(&bo->resource->lru.link);
+		/* Double check that res and bo is still valid */
+		spin_lock(&bdev->lru_lock);
+		if (res != ttm_lru_first_res_or_null(list)) {
+			dma_resv_unlock(resv);
+			dma_resv_put(resv);
+			continue;
+		}
+		list_del_init(&res->lru.link);
 		spin_unlock(&bdev->lru_lock);
 
-		if (bo->ttm)
-			ttm_tt_unpopulate(bo->bdev, bo->ttm);
+		if (res->bo->ttm)
+			ttm_tt_unpopulate(res->bo->bdev, res->bo->ttm);
 
-		ttm_bo_put(bo);
+		dma_resv_unlock(resv);
+		dma_resv_put(resv);
 		spin_lock(&bdev->lru_lock);
 	}
 	spin_unlock(&bdev->lru_lock);
-- 
2.43.0