--- zzzz-none-000/linux-3.10.107/drivers/gpu/drm/ttm/ttm_page_alloc.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/gpu/drm/ttm/ttm_page_alloc.c	2021-02-04 17:41:59.000000000 +0000
@@ -297,9 +297,12 @@
  *
  * @pool: to free the pages from
  * @free_all: If set to true will free all pages in pool
+ * @use_static: Safe to use static buffer
  **/
-static int ttm_page_pool_free(struct ttm_page_pool *pool, unsigned nr_free)
+static int ttm_page_pool_free(struct ttm_page_pool *pool, unsigned nr_free,
+			      bool use_static)
 {
+	static struct page *static_buf[NUM_PAGES_TO_ALLOC];
 	unsigned long irq_flags;
 	struct page *p;
 	struct page **pages_to_free;
@@ -309,8 +312,11 @@
 	if (NUM_PAGES_TO_ALLOC < nr_free)
 		npages_to_free = NUM_PAGES_TO_ALLOC;
 
-	pages_to_free = kmalloc(npages_to_free * sizeof(struct page *),
-			GFP_KERNEL);
+	if (use_static)
+		pages_to_free = static_buf;
+	else
+		pages_to_free = kmalloc(npages_to_free * sizeof(struct page *),
+					GFP_KERNEL);
 	if (!pages_to_free) {
 		pr_err("Failed to allocate memory for pool free operation\n");
 		return 0;
@@ -373,49 +379,63 @@
 	if (freed_pages)
 		ttm_pages_put(pages_to_free, freed_pages);
 out:
-	kfree(pages_to_free);
+	if (pages_to_free != static_buf)
+		kfree(pages_to_free);
 	return nr_free;
 }
 
-/* Get good estimation how many pages are free in pools */
-static int ttm_pool_get_num_unused_pages(void)
-{
-	unsigned i;
-	int total = 0;
-	for (i = 0; i < NUM_POOLS; ++i)
-		total += _manager->pools[i].npages;
-
-	return total;
-}
-
 /**
  * Callback for mm to request pool to reduce number of page held.
+ *
+ * XXX: (dchinner) Deadlock warning!
+ *
+ * This code is crying out for a shrinker per pool....
  */
-static int ttm_pool_mm_shrink(struct shrinker *shrink,
-			      struct shrink_control *sc)
+static unsigned long
+ttm_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
-	static atomic_t start_pool = ATOMIC_INIT(0);
+	static DEFINE_MUTEX(lock);
+	static unsigned start_pool;
 	unsigned i;
-	unsigned pool_offset = atomic_add_return(1, &start_pool);
+	unsigned pool_offset;
 	struct ttm_page_pool *pool;
 	int shrink_pages = sc->nr_to_scan;
+	unsigned long freed = 0;
 
-	pool_offset = pool_offset % NUM_POOLS;
+	if (!mutex_trylock(&lock))
+		return SHRINK_STOP;
+	pool_offset = ++start_pool % NUM_POOLS;
 	/* select start pool in round robin fashion */
 	for (i = 0; i < NUM_POOLS; ++i) {
 		unsigned nr_free = shrink_pages;
 		if (shrink_pages == 0)
 			break;
 		pool = &_manager->pools[(i + pool_offset)%NUM_POOLS];
-		shrink_pages = ttm_page_pool_free(pool, nr_free);
+		/* OK to use static buffer since global mutex is held. */
+		shrink_pages = ttm_page_pool_free(pool, nr_free, true);
+		freed += nr_free - shrink_pages;
 	}
-	/* return estimated number of unused pages in pool */
-	return ttm_pool_get_num_unused_pages();
+	mutex_unlock(&lock);
+	return freed;
+}
+
+
+static unsigned long
+ttm_pool_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	unsigned i;
+	unsigned long count = 0;
+
+	for (i = 0; i < NUM_POOLS; ++i)
+		count += _manager->pools[i].npages;
+
+	return count;
 }
 
 static void ttm_pool_mm_shrink_init(struct ttm_pool_manager *manager)
 {
-	manager->mm_shrink.shrink = &ttm_pool_mm_shrink;
+	manager->mm_shrink.count_objects = ttm_pool_shrink_count;
+	manager->mm_shrink.scan_objects = ttm_pool_shrink_scan;
 	manager->mm_shrink.seeks = 1;
 	register_shrinker(&manager->mm_shrink);
 }
@@ -694,7 +714,7 @@
 	}
 	spin_unlock_irqrestore(&pool->lock, irq_flags);
 	if (npages)
-		ttm_page_pool_free(pool, npages);
+		ttm_page_pool_free(pool, npages, false);
 }
 
 /*
@@ -778,7 +798,7 @@
 	return 0;
 }
 
-static void ttm_page_pool_init_locked(struct ttm_page_pool *pool, int flags,
+static void ttm_page_pool_init_locked(struct ttm_page_pool *pool, gfp_t flags,
 		char *name)
 {
 	spin_lock_init(&pool->lock);
@@ -833,8 +853,9 @@
 	pr_info("Finalizing pool allocator\n");
 	ttm_pool_mm_shrink_fini(_manager);
 
+	/* OK to use static buffer since global mutex is no longer used. */
 	for (i = 0; i < NUM_POOLS; ++i)
-		ttm_page_pool_free(&_manager->pools[i], FREE_ALL_PAGES);
+		ttm_page_pool_free(&_manager->pools[i], FREE_ALL_PAGES, true);
 
 	kobject_put(&_manager->kobj);
 	_manager = NULL;