drm/ttm: handle OOM in ttm_tt_swapout

- Without this change I get a general protection fault.
- Also use PTR_ERR where applicable.
Signed-off-by: Maarten Maathuis <madman2003@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Acked-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ttm/ttm_tt.c

@@ -476,7 +476,7 @@ static int ttm_tt_swapin(struct ttm_tt *ttm)
 	void *from_virtual;
 	void *to_virtual;
 	int i;
-	int ret;
+	int ret = -ENOMEM;
 
 	if (ttm->page_flags & TTM_PAGE_FLAG_USER) {
 		ret = ttm_tt_set_user(ttm, ttm->tsk, ttm->start,
@@ -495,8 +495,10 @@ static int ttm_tt_swapin(struct ttm_tt *ttm)
 
 	for (i = 0; i < ttm->num_pages; ++i) {
 		from_page = read_mapping_page(swap_space, i, NULL);
-		if (IS_ERR(from_page))
+		if (IS_ERR(from_page)) {
+			ret = PTR_ERR(from_page);
 			goto out_err;
+		}
 		to_page = __ttm_tt_get_page(ttm, i);
 		if (unlikely(to_page == NULL))
 			goto out_err;
@@ -519,7 +521,7 @@ static int ttm_tt_swapin(struct ttm_tt *ttm)
 	return 0;
 out_err:
 	ttm_tt_free_alloced_pages(ttm);
-	return -ENOMEM;
+	return ret;
 }
 
 int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistant_swap_storage)
@@ -531,6 +533,7 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistant_swap_storage)
 	void *from_virtual;
 	void *to_virtual;
 	int i;
+	int ret = -ENOMEM;
 
 	BUG_ON(ttm->state != tt_unbound && ttm->state != tt_unpopulated);
 	BUG_ON(ttm->caching_state != tt_cached);
@@ -553,7 +556,7 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistant_swap_storage)
 						0);
 		if (unlikely(IS_ERR(swap_storage))) {
 			printk(KERN_ERR "Failed allocating swap storage.\n");
-			return -ENOMEM;
+			return PTR_ERR(swap_storage);
 		}
 	} else
 		swap_storage = persistant_swap_storage;
@@ -565,9 +568,10 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistant_swap_storage)
 		if (unlikely(from_page == NULL))
 			continue;
 		to_page = read_mapping_page(swap_space, i, NULL);
-		if (unlikely(to_page == NULL))
+		if (unlikely(IS_ERR(to_page))) {
+			ret = PTR_ERR(to_page);
 			goto out_err;
-
+		}
 		preempt_disable();
 		from_virtual = kmap_atomic(from_page, KM_USER0);
 		to_virtual = kmap_atomic(to_page, KM_USER1);
@@ -591,5 +595,5 @@ out_err:
 	if (!persistant_swap_storage)
 		fput(swap_storage);
 
-	return -ENOMEM;
+	return ret;
 }