/*
 * Copyright (C) 2016 Red Hat
 * Author: Rob Clark <robdclark@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "msm_drv.h"
#include "msm_gem.h"

static bool mutex_is_locked_by(struct mutex *mutex, struct task_struct *task)
{
	if (!mutex_is_locked(mutex))
		return false;

#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_MUTEXES)
	return mutex->owner == task;
#else
	/* Since UP may be pre-empted, we cannot assume that we own the lock */
	return false;
#endif
}

static bool msm_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
{
	if (!mutex_trylock(&dev->struct_mutex)) {
		if (!mutex_is_locked_by(&dev->struct_mutex, current))
			return false;
		*unlock = false;
	} else {
		*unlock = true;
	}

	return true;
}


static unsigned long
msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
{
	struct msm_drm_private *priv =
		container_of(shrinker, struct msm_drm_private, shrinker);
	struct drm_device *dev = priv->dev;
	struct msm_gem_object *msm_obj;
	unsigned long count = 0;
	bool unlock;

	if (!msm_gem_shrinker_lock(dev, &unlock))
		return 0;

	list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
		if (is_purgeable(msm_obj))
			count += msm_obj->base.size >> PAGE_SHIFT;
	}

	if (unlock)
		mutex_unlock(&dev->struct_mutex);

	return count;
}

static unsigned long
msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
{
	struct msm_drm_private *priv =
		container_of(shrinker, struct msm_drm_private, shrinker);
	struct drm_device *dev = priv->dev;
	struct msm_gem_object *msm_obj;
	unsigned long freed = 0;
	bool unlock;

	if (!msm_gem_shrinker_lock(dev, &unlock))
		return SHRINK_STOP;

	list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
		if (freed >= sc->nr_to_scan)
			break;
		if (is_purgeable(msm_obj)) {
			msm_gem_purge(&msm_obj->base);
			freed += msm_obj->base.size >> PAGE_SHIFT;
		}
	}

	if (unlock)
		mutex_unlock(&dev->struct_mutex);

	if (freed > 0)
		pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);

	return freed;
}

static int
msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
{
	struct msm_drm_private *priv =
		container_of(nb, struct msm_drm_private, vmap_notifier);
	struct drm_device *dev = priv->dev;
	struct msm_gem_object *msm_obj;
	unsigned unmapped = 0;
	bool unlock;

	if (!msm_gem_shrinker_lock(dev, &unlock))
		return NOTIFY_DONE;

	list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
		if (is_vunmapable(msm_obj)) {
			msm_gem_vunmap(&msm_obj->base);
			/* since we don't know any better, lets bail after a few
			 * and if necessary the shrinker will be invoked again.
			 * Seems better than unmapping *everything*
			 */
			if (++unmapped >= 15)
				break;
		}
	}

	if (unlock)
		mutex_unlock(&dev->struct_mutex);

	*(unsigned long *)ptr += unmapped;

	if (unmapped > 0)
		pr_info_ratelimited("Purging %u vmaps\n", unmapped);

	return NOTIFY_DONE;
}

/**
 * msm_gem_shrinker_init - Initialize msm shrinker
 * @dev_priv: msm device
 *
 * This function registers and sets up the msm shrinker.
 */
void msm_gem_shrinker_init(struct drm_device *dev)
{
	struct msm_drm_private *priv = dev->dev_private;
	priv->shrinker.count_objects = msm_gem_shrinker_count;
	priv->shrinker.scan_objects = msm_gem_shrinker_scan;
	priv->shrinker.seeks = DEFAULT_SEEKS;
	WARN_ON(register_shrinker(&priv->shrinker));

	priv->vmap_notifier.notifier_call = msm_gem_shrinker_vmap;
	WARN_ON(register_vmap_purge_notifier(&priv->vmap_notifier));
}

/**
 * msm_gem_shrinker_cleanup - Clean up msm shrinker
 * @dev_priv: msm device
 *
 * This function unregisters the msm shrinker.
 */
void msm_gem_shrinker_cleanup(struct drm_device *dev)
{
	struct msm_drm_private *priv = dev->dev_private;

	if (priv->shrinker.nr_deferred) {
		WARN_ON(unregister_vmap_purge_notifier(&priv->vmap_notifier));
		unregister_shrinker(&priv->shrinker);
	}
}