drm/amdgpu: fix lru size grouping v2

Adding a BO can make it the insertion point for larger sizes as well.

v2: add a comment about the guard structure.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -946,6 +946,8 @@ static struct list_head *amdgpu_ttm_lru_tail(struct ttm_buffer_object *tbo)
 	struct list_head *res = lru->lru[tbo->mem.mem_type];
 
 	lru->lru[tbo->mem.mem_type] = &tbo->lru;
+	while ((++lru)->lru[tbo->mem.mem_type] == res)
+		lru->lru[tbo->mem.mem_type] = &tbo->lru;
 
 	return res;
 }
@@ -956,6 +958,8 @@ static struct list_head *amdgpu_ttm_swap_lru_tail(struct ttm_buffer_object *tbo)
 	struct list_head *res = lru->swap_lru;
 
 	lru->swap_lru = &tbo->swap;
+	while ((++lru)->swap_lru == res)
+		lru->swap_lru = &tbo->swap;
 
 	return res;
 }
@@ -1003,6 +1007,10 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 		lru->swap_lru = &adev->mman.bdev.glob->swap_lru;
 	}
 
+	for (j = 0; j < TTM_NUM_MEM_TYPES; ++j)
+		adev->mman.guard.lru[j] = NULL;
+	adev->mman.guard.swap_lru = NULL;
+
 	adev->mman.initialized = true;
 	r = ttm_bo_init_mm(&adev->mman.bdev, TTM_PL_VRAM,
 				adev->mc.real_vram_size >> PAGE_SHIFT);

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

@@ -61,6 +61,8 @@ struct amdgpu_mman {
 
 	/* custom LRU management */
 	struct amdgpu_mman_lru			log2_size[AMDGPU_TTM_LRU_SIZE];
+	/* guard for log2_size array, don't add anything in between */
+	struct amdgpu_mman_lru			guard;
 };
 
 int amdgpu_copy_buffer(struct amdgpu_ring *ring,