Re: [PATCH v11 20/25] drivers: convert shrinkers to new count/scan API

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index bd2a3b4..1746f30 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c

@@ -377,28 +377,26 @@ out:
 	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;
-}
-

  */
-static int ttm_pool_mm_shrink(struct shrinker *shrink,
-			      struct shrink_control *sc)
+static long
+ttm_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	static atomic_t start_pool = ATOMIC_INIT(0);
 	unsigned i;
 	unsigned pool_offset = atomic_add_return(1, &start_pool);
 	struct ttm_page_pool *pool;
 	int shrink_pages = sc->nr_to_scan;
+	long freed = 0;
 
 	pool_offset = pool_offset % NUM_POOLS;
 	/* select start pool in round robin fashion */

@@ -408,14 +406,28 @@ static int ttm_pool_mm_shrink(struct shrinker *shrink,
 			break;
 		pool = &_manager->pools[(i + pool_offset)%NUM_POOLS];
 		shrink_pages = ttm_page_pool_free(pool, nr_free);
+		freed += nr_free - shrink_pages;
 	}
-	/* return estimated number of unused pages in pool */
-	return ttm_pool_get_num_unused_pages();
+	return freed;
+}
+
+
+static long
+ttm_pool_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	unsigned i;
+	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);
 }

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index b8b3943..dc009f1 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c

@@ -918,19 +918,6 @@ int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(ttm_dma_populate);
 
-/* Get good estimation how many pages are free in pools */
-static int ttm_dma_pool_get_num_unused_pages(void)
-{
-	struct device_pools *p;
-	unsigned total = 0;
-
-	mutex_lock(&_manager->lock);
-	list_for_each_entry(p, &_manager->pools, pools)
-		total += p->pool->npages_free;
-	mutex_unlock(&_manager->lock);
-	return total;
-}
-
 /* Put all pages in pages list to correct pool to wait for reuse */
 void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 {

@@ -1002,18 +989,29 @@ EXPORT_SYMBOL_GPL(ttm_dma_unpopulate);
 
 /**
  * Callback for mm to request pool to reduce number of page held.
+ *
+ * XXX: (dchinner) Deadlock warning!
+ *
+ * ttm_dma_page_pool_free() does GFP_KERNEL memory allocation, and so attention
+ * needs to be paid to sc->gfp_mask to determine if this can be done or not.
+ * GFP_KERNEL memory allocation in a GFP_ATOMIC reclaim context woul dbe really
+ * bad.

  */
-static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
-				  struct shrink_control *sc)
+static long
+ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	static atomic_t start_pool = ATOMIC_INIT(0);
 	unsigned idx = 0;
 	unsigned pool_offset = atomic_add_return(1, &start_pool);
 	unsigned shrink_pages = sc->nr_to_scan;
 	struct device_pools *p;
+	long freed = 0;
 
 	if (list_empty(&_manager->pools))
-		return 0;
+		return SHRINK_STOP;
 
 	mutex_lock(&_manager->lock);
 	pool_offset = pool_offset % _manager->npools;

@@ -1029,18 +1027,33 @@ static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
 			continue;
 		nr_free = shrink_pages;
 		shrink_pages = ttm_dma_page_pool_free(p->pool, nr_free);
+		freed += nr_free - shrink_pages;
+
 		pr_debug("%s: (%s:%d) Asked to shrink %d, have %d more to go\n",
 			 p->pool->dev_name, p->pool->name, current->pid,
 			 nr_free, shrink_pages);
 	}
 	mutex_unlock(&_manager->lock);
-	/* return estimated number of unused pages in pool */
-	return ttm_dma_pool_get_num_unused_pages();
+	return freed;
+}

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index dcceed2..4ade8e3 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c

@@ -1140,23 +1140,19 @@ static bool zcache_freeze;
  * pageframes in use.  FIXME POLICY: Probably the writeback should only occur
  * if the eviction doesn't free enough pages.
  */
-static int shrink_zcache_memory(struct shrinker *shrink,
-				struct shrink_control *sc)
+static long scan_zcache_memory(struct shrinker *shrink,
+			       struct shrink_control *sc)
 {
 	static bool in_progress;
-	int ret = -1;
-	int nr = sc->nr_to_scan;
 	int nr_evict = 0;
 	int nr_writeback = 0;
 	struct page *page;
 	int  file_pageframes_inuse, anon_pageframes_inuse;
-
-	if (nr <= 0)
-		goto skip_evict;
+	long freed = 0;
 
 	/* don't allow more than one eviction thread at a time */
 	if (in_progress)
-		goto skip_evict;
+		return 0;
 
 	in_progress = true;
 

@@ -1176,6 +1172,7 @@ static int shrink_zcache_memory(struct shrinker *shrink,
 		if (page == NULL)
 			break;
 		zcache_free_page(page);
+		freed++;
 	}
 
 	zcache_last_active_anon_pageframes =

@@ -1192,13 +1189,22 @@ static int shrink_zcache_memory(struct shrinker *shrink,
 #ifdef CONFIG_ZCACHE_WRITEBACK
 		int writeback_ret;
 		writeback_ret = zcache_frontswap_writeback();
-		if (writeback_ret == -ENOMEM)
+		if (writeback_ret != -ENOMEM)
+			freed++;
+		else
 #endif
 			break;
 	}
 	in_progress = false;
 
-skip_evict:
+	return freed;
+}
+
+static long count_zcache_memory(struct shrinker *shrink,
+				struct shrink_control *sc)
+{
+	int ret = -1;
+
 	/* resample: has changed, but maybe not all the way yet */
 	zcache_last_active_file_pageframes =
 		global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);

@@ -1212,7 +1218,8 @@ skip_evict:
 }
 
 static struct shrinker zcache_shrinker = {
-	.shrink = shrink_zcache_memory,
+	.scan_objects = scan_zcache_memory,
+	.count_objects = count_zcache_memory,
 	.seeks = DEFAULT_SEEKS,
 };