gpu: ion: Add ion_page_pool.

This patch adds a new utility heaps can use to manage
memory.  In the past we have found it can be very
expensive to manage the caches when allocating memory,
but it is imposible to know whether a previous user of a
given memory allocation had a cached mapping. This patch
adds the ability to store a pool of pages that were
previously used uncached so that cache maintenance
only need be done when growing this pool.  The pool also
contains a shrinker so memory from the pool can be
recovered in low memory conditions.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 163 insertions, 0 deletions

diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c
new file mode 100644
index 0000000..78f39f7
--- /dev/null
+++ b/drivers/staging/android/ion/ion_page_pool.c
@@ -0,0 +1,163 @@
+/*
+ * drivers/staging/android/ion/ion_mem_pool.c
+ *
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/shrinker.h>
+#include "ion_priv.h"
+
+struct ion_page_pool_item {
+	struct page *page;
+	struct list_head list;
+};
+
+static void *ion_page_pool_alloc_pages(struct ion_page_pool *pool)
+{
+	struct page *page = alloc_pages(pool->gfp_mask, pool->order);
+
+	if (!page)
+		return NULL;
+	/* this is only being used to flush the page for dma,
+	   this api is not really suitable for calling from a driver
+	   but no better way to flush a page for dma exist at this time */
+	__dma_page_cpu_to_dev(page, 0, PAGE_SIZE << pool->order,
+			      DMA_BIDIRECTIONAL);
+	return page;
+}
+
+static void ion_page_pool_free_pages(struct ion_page_pool *pool,
+				     struct page *page)
+{
+	__free_pages(page, pool->order);
+}
+
+static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
+{
+	struct ion_page_pool_item *item;
+
+	item = kmalloc(sizeof(struct ion_page_pool_item), GFP_KERNEL);
+	if (!item)
+		return -ENOMEM;
+	item->page = page;
+	list_add_tail(&item->list, &pool->items);
+	pool->count++;
+	return 0;
+}
+
+static struct page *ion_page_pool_remove(struct ion_page_pool *pool)
+{
+	struct ion_page_pool_item *item;
+	struct page *page;
+
+	BUG_ON(!pool->count);
+	BUG_ON(list_empty(&pool->items));
+
+	item = list_first_entry(&pool->items, struct ion_page_pool_item, list);
+	list_del(&item->list);
+	page = item->page;
+	kfree(item);
+	pool->count--;
+	return page;
+}
+
+void *ion_page_pool_alloc(struct ion_page_pool *pool)
+{
+	struct page *page = NULL;
+
+	BUG_ON(!pool);
+
+	mutex_lock(&pool->mutex);
+	if (pool->count)
+		page = ion_page_pool_remove(pool);
+	else
+		page = ion_page_pool_alloc_pages(pool);
+	mutex_unlock(&pool->mutex);
+
+	return page;
+}
+
+void ion_page_pool_free(struct ion_page_pool *pool, struct page* page)
+{
+	int ret;
+
+	mutex_lock(&pool->mutex);
+	ret = ion_page_pool_add(pool, page);
+	if (ret)
+		ion_page_pool_free_pages(pool, page);
+	mutex_unlock(&pool->mutex);
+}
+
+static int ion_page_pool_shrink(struct shrinker *shrinker,
+				 struct shrink_control *sc)
+{
+	struct ion_page_pool *pool = container_of(shrinker,
+						 struct ion_page_pool,
+						 shrinker);
+	int nr_freed = 0;
+	int i;
+
+	if (sc->nr_to_scan == 0)
+		return pool->count * (1 << pool->order);
+
+	mutex_lock(&pool->mutex);
+	for (i = 0; i < sc->nr_to_scan && pool->count; i++) {
+		struct ion_page_pool_item *item;
+		struct page *page;
+
+		item = list_first_entry(&pool->items, struct ion_page_pool_item, list);
+		page = item->page;
+		if (PageHighMem(page) && !(sc->gfp_mask & __GFP_HIGHMEM)) {
+			list_move_tail(&item->list, &pool->items);
+			continue;
+		}
+		BUG_ON(page != ion_page_pool_remove(pool));
+		ion_page_pool_free_pages(pool, page);
+		nr_freed += (1 << pool->order);
+	}
+	pr_info("%s: shrunk page_pool of order %d by %d pages\n", __func__,
+		pool->order, nr_freed);
+	mutex_unlock(&pool->mutex);
+
+	return pool->count * (1 << pool->order);
+}
+
+struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order)
+{
+	struct ion_page_pool *pool = kmalloc(sizeof(struct ion_page_pool),
+					     GFP_KERNEL);
+	if (!pool)
+		return NULL;
+	pool->count = 0;
+	INIT_LIST_HEAD(&pool->items);
+	pool->shrinker.shrink = ion_page_pool_shrink;
+	pool->shrinker.seeks = DEFAULT_SEEKS * 16;
+	pool->shrinker.batch = 0;
+	register_shrinker(&pool->shrinker);
+	pool->gfp_mask = gfp_mask;
+	pool->order = order;
+	mutex_init(&pool->mutex);
+
+	return pool;
+}
+
+void ion_page_pool_destroy(struct ion_page_pool *pool)
+{
+	unregister_shrinker(&pool->shrinker);
+	kfree(pool);
+}
+