drivers/gpu/drm/i915/i915_gem_shrinker.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright © 2008-2015 Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  *
  */

 #include <linux/oom.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/pci.h>
 #include <linux/dma-buf.h>
 #include <linux/vmalloc.h>
 #include <drm/drmP.h>
 #include <drm/i915_drm.h>

 #include "i915_drv.h"
 #include "i915_trace.h"

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

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

 static bool i915_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 bool any_vma_pinned(struct drm_i915_gem_object *obj)
 {
 	struct i915_vma *vma;

 	list_for_each_entry(vma, &obj->vma_list, obj_link)
 		if (i915_vma_is_pinned(vma))
 			return true;

 	return false;
 }

 static bool swap_available(void)
 {
 	return get_nr_swap_pages() > 0;
 }

 static bool can_release_pages(struct drm_i915_gem_object *obj)
 {
 	if (!obj->mm.pages)
 		return false;

 	/* Consider only shrinkable ojects. */
 	if (!i915_gem_object_is_shrinkable(obj))
 		return false;

 	/* Only report true if by unbinding the object and putting its pages
 	 * we can actually make forward progress towards freeing physical
 	 * pages.
 	 *
 	 * If the pages are pinned for any other reason than being bound
 	 * to the GPU, simply unbinding from the GPU is not going to succeed
 	 * in releasing our pin count on the pages themselves.
 	 */
 	if (atomic_read(&obj->mm.pages_pin_count) > obj->bind_count)
 		return false;

 	if (any_vma_pinned(obj))
 		return false;

 	/* We can only return physical pages to the system if we can either
 	 * discard the contents (because the user has marked them as being
 	 * purgeable) or if we can move their contents out to swap.
 	 */
 	return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
 }

 static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
 {
 	if (i915_gem_object_unbind(obj) == 0)
 		__i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
 	return !READ_ONCE(obj->mm.pages);
 }

 /**
  * i915_gem_shrink - Shrink buffer object caches
  * @dev_priv: i915 device
  * @target: amount of memory to make available, in pages
  * @flags: control flags for selecting cache types
  *
  * This function is the main interface to the shrinker. It will try to release
  * up to @target pages of main memory backing storage from buffer objects.
  * Selection of the specific caches can be done with @flags. This is e.g. useful
  * when purgeable objects should be removed from caches preferentially.
  *
  * Note that it's not guaranteed that released amount is actually available as
  * free system memory - the pages might still be in-used to due to other reasons
  * (like cpu mmaps) or the mm core has reused them before we could grab them.
  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
  *
  * Also note that any kind of pinning (both per-vma address space pins and
  * backing storage pins at the buffer object level) result in the shrinker code
  * having to skip the object.
  *
  * Returns:
  * The number of pages of backing storage actually released.
  */
 unsigned long
 i915_gem_shrink(struct drm_i915_private *dev_priv,
 		unsigned long target, unsigned flags)
 {
 	const struct {
 		struct list_head *list;
 		unsigned int bit;
 	} phases[] = {
 		{ &dev_priv->mm.unbound_list, I915_SHRINK_UNBOUND },
 		{ &dev_priv->mm.bound_list, I915_SHRINK_BOUND },
 		{ NULL, 0 },
 	}, *phase;
 	unsigned long count = 0;
 	bool unlock;

 	if (!i915_gem_shrinker_lock(&dev_priv->drm, &unlock))
 		return 0;

 	trace_i915_gem_shrink(dev_priv, target, flags);
 	i915_gem_retire_requests(dev_priv);

 	/*
 	 * Unbinding of objects will require HW access; Let us not wake the
 	 * device just to recover a little memory. If absolutely necessary,
 	 * we will force the wake during oom-notifier.
 	 */
 	if ((flags & I915_SHRINK_BOUND) &&
 	    !intel_runtime_pm_get_if_in_use(dev_priv))
 		flags &= ~I915_SHRINK_BOUND;

 	/*
 	 * As we may completely rewrite the (un)bound list whilst unbinding
 	 * (due to retiring requests) we have to strictly process only
 	 * one element of the list at the time, and recheck the list
 	 * on every iteration.
 	 *
 	 * In particular, we must hold a reference whilst removing the
 	 * object as we may end up waiting for and/or retiring the objects.
 	 * This might release the final reference (held by the active list)
 	 * and result in the object being freed from under us. This is
 	 * similar to the precautions the eviction code must take whilst
 	 * removing objects.
 	 *
 	 * Also note that although these lists do not hold a reference to
 	 * the object we can safely grab one here: The final object
 	 * unreferencing and the bound_list are both protected by the
 	 * dev->struct_mutex and so we won't ever be able to observe an
 	 * object on the bound_list with a reference count equals 0.
 	 */
 	for (phase = phases; phase->list; phase++) {
 		struct list_head still_in_list;
 		struct drm_i915_gem_object *obj;

 		if ((flags & phase->bit) == 0)
 			continue;

 		INIT_LIST_HEAD(&still_in_list);
 		while (count < target &&
 		       (obj = list_first_entry_or_null(phase->list,
 						       typeof(*obj),
 						       global_link))) {
 			list_move_tail(&obj->global_link, &still_in_list);
 			if (!obj->mm.pages) {
 				list_del_init(&obj->global_link);
 				continue;
 			}

 			if (flags & I915_SHRINK_PURGEABLE &&
 			    obj->mm.madv != I915_MADV_DONTNEED)
 				continue;

 			if (flags & I915_SHRINK_VMAPS &&
 			    !is_vmalloc_addr(obj->mm.mapping))
 				continue;

 			if (!(flags & I915_SHRINK_ACTIVE) &&
 			    (i915_gem_object_is_active(obj) ||
 			     obj->framebuffer_references))
 				continue;

 			if (!can_release_pages(obj))
 				continue;

 			if (unsafe_drop_pages(obj)) {
 				/* May arrive from get_pages on another bo */
 				mutex_lock_nested(&obj->mm.lock,
 						  I915_MM_SHRINKER);
 				if (!obj->mm.pages) {
 					__i915_gem_object_invalidate(obj);
 					list_del_init(&obj->global_link);
 					count += obj->base.size >> PAGE_SHIFT;
 				}
 				mutex_unlock(&obj->mm.lock);
 			}
 		}
 		list_splice_tail(&still_in_list, phase->list);
 	}

 	if (flags & I915_SHRINK_BOUND)
 		intel_runtime_pm_put(dev_priv);

 	i915_gem_retire_requests(dev_priv);
 	if (unlock)
 		mutex_unlock(&dev_priv->drm.struct_mutex);

 	/* expedite the RCU grace period to free some request slabs */
 	synchronize_rcu_expedited();

 	return count;
 }

 /**
  * i915_gem_shrink_all - Shrink buffer object caches completely
  * @dev_priv: i915 device
  *
  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
  * caches completely. It also first waits for and retires all outstanding
  * requests to also be able to release backing storage for active objects.
  *
  * This should only be used in code to intentionally quiescent the gpu or as a
  * last-ditch effort when memory seems to have run out.
  *
  * Returns:
  * The number of pages of backing storage actually released.
  */
 unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
 {
 	unsigned long freed;

 	freed = i915_gem_shrink(dev_priv, -1UL,
 				I915_SHRINK_BOUND |
 				I915_SHRINK_UNBOUND |
 				I915_SHRINK_ACTIVE);
 	rcu_barrier(); /* wait until our RCU delayed slab frees are completed */

 	return freed;
 }

 static unsigned long
 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
 	struct drm_i915_private *dev_priv =
 		container_of(shrinker, struct drm_i915_private, mm.shrinker);
 	struct drm_device *dev = &dev_priv->drm;
 	struct drm_i915_gem_object *obj;
 	unsigned long count;
 	bool unlock;

 	if (!i915_gem_shrinker_lock(dev, &unlock))
 		return 0;

 	i915_gem_retire_requests(dev_priv);

 	count = 0;
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_link)
 		if (can_release_pages(obj))
 			count += obj->base.size >> PAGE_SHIFT;

 	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_link) {
 		if (!i915_gem_object_is_active(obj) && can_release_pages(obj))
 			count += obj->base.size >> PAGE_SHIFT;
 	}

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

 	return count;
 }

 static unsigned long
 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 {
 	struct drm_i915_private *dev_priv =
 		container_of(shrinker, struct drm_i915_private, mm.shrinker);
 	struct drm_device *dev = &dev_priv->drm;
 	unsigned long freed;
 	bool unlock;

 	if (!i915_gem_shrinker_lock(dev, &unlock))
 		return SHRINK_STOP;

 	freed = i915_gem_shrink(dev_priv,
 				sc->nr_to_scan,
 				I915_SHRINK_BOUND |
 				I915_SHRINK_UNBOUND |
 				I915_SHRINK_PURGEABLE);
 	if (freed < sc->nr_to_scan)
 		freed += i915_gem_shrink(dev_priv,
 					 sc->nr_to_scan - freed,
 					 I915_SHRINK_BOUND |
 					 I915_SHRINK_UNBOUND);
 	if (unlock)
 		mutex_unlock(&dev->struct_mutex);

 	return freed;
 }

 struct shrinker_lock_uninterruptible {
 	bool was_interruptible;
 	bool unlock;
 };

 static bool
 i915_gem_shrinker_lock_uninterruptible(struct drm_i915_private *dev_priv,
 				       struct shrinker_lock_uninterruptible *slu,
 				       int timeout_ms)
 {
 	unsigned long timeout = jiffies + msecs_to_jiffies_timeout(timeout_ms);

 	do {
 		if (i915_gem_wait_for_idle(dev_priv, 0) == 0 &&
 		    i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock))
 			break;

 		schedule_timeout_killable(1);
 		if (fatal_signal_pending(current))
 			return false;

 		if (time_after(jiffies, timeout)) {
 			pr_err("Unable to lock GPU to purge memory.\n");
 			return false;
 		}
 	} while (1);

 	slu->was_interruptible = dev_priv->mm.interruptible;
 	dev_priv->mm.interruptible = false;
 	return true;
 }

 static void
 i915_gem_shrinker_unlock_uninterruptible(struct drm_i915_private *dev_priv,
 					 struct shrinker_lock_uninterruptible *slu)
 {
 	dev_priv->mm.interruptible = slu->was_interruptible;
 	if (slu->unlock)
 		mutex_unlock(&dev_priv->drm.struct_mutex);
 }

 static int
 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 {
 	struct drm_i915_private *dev_priv =
 		container_of(nb, struct drm_i915_private, mm.oom_notifier);
 	struct shrinker_lock_uninterruptible slu;
 	struct drm_i915_gem_object *obj;
 	unsigned long unevictable, bound, unbound, freed_pages;

 	if (!i915_gem_shrinker_lock_uninterruptible(dev_priv, &slu, 5000))
 		return NOTIFY_DONE;

 	intel_runtime_pm_get(dev_priv);
 	freed_pages = i915_gem_shrink_all(dev_priv);
 	intel_runtime_pm_put(dev_priv);

 	/* Because we may be allocating inside our own driver, we cannot
 	 * assert that there are no objects with pinned pages that are not
 	 * being pointed to by hardware.
 	 */
 	unbound = bound = unevictable = 0;
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_link) {
 		if (!obj->mm.pages)
 			continue;

 		if (!can_release_pages(obj))
 			unevictable += obj->base.size >> PAGE_SHIFT;
 		else
 			unbound += obj->base.size >> PAGE_SHIFT;
 	}
 	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_link) {
 		if (!obj->mm.pages)
 			continue;

 		if (!can_release_pages(obj))
 			unevictable += obj->base.size >> PAGE_SHIFT;
 		else
 			bound += obj->base.size >> PAGE_SHIFT;
 	}

 	i915_gem_shrinker_unlock_uninterruptible(dev_priv, &slu);

 	if (freed_pages || unbound || bound)
 		pr_info("Purging GPU memory, %lu pages freed, "
 			"%lu pages still pinned.\n",
 			freed_pages, unevictable);
 	if (unbound || bound)
 		pr_err("%lu and %lu pages still available in the "
 		       "bound and unbound GPU page lists.\n",
 		       bound, unbound);

 	*(unsigned long *)ptr += freed_pages;
 	return NOTIFY_DONE;
 }

 static int
 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 {
 	struct drm_i915_private *dev_priv =
 		container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 	struct shrinker_lock_uninterruptible slu;
 	struct i915_vma *vma, *next;
 	unsigned long freed_pages = 0;
 	int ret;

 	if (!i915_gem_shrinker_lock_uninterruptible(dev_priv, &slu, 5000))
 		return NOTIFY_DONE;

 	/* Force everything onto the inactive lists */
 	ret = i915_gem_wait_for_idle(dev_priv, I915_WAIT_LOCKED);
 	if (ret)
 		goto out;

 	intel_runtime_pm_get(dev_priv);
 	freed_pages += i915_gem_shrink(dev_priv, -1UL,
 				       I915_SHRINK_BOUND |
 				       I915_SHRINK_UNBOUND |
 				       I915_SHRINK_ACTIVE |
 				       I915_SHRINK_VMAPS);
 	intel_runtime_pm_put(dev_priv);

 	/* We also want to clear any cached iomaps as they wrap vmap */
 	list_for_each_entry_safe(vma, next,
 				 &dev_priv->ggtt.base.inactive_list, vm_link) {
 		unsigned long count = vma->node.size >> PAGE_SHIFT;
 		if (vma->iomap && i915_vma_unbind(vma) == 0)
 			freed_pages += count;
 	}

 out:
 	i915_gem_shrinker_unlock_uninterruptible(dev_priv, &slu);

 	*(unsigned long *)ptr += freed_pages;
 	return NOTIFY_DONE;
 }

 /**
  * i915_gem_shrinker_init - Initialize i915 shrinker
  * @dev_priv: i915 device
  *
  * This function registers and sets up the i915 shrinker and OOM handler.
  */
 void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
 {
 	dev_priv->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 	dev_priv->mm.shrinker.count_objects = i915_gem_shrinker_count;
 	dev_priv->mm.shrinker.seeks = DEFAULT_SEEKS;
 	WARN_ON(register_shrinker(&dev_priv->mm.shrinker));

 	dev_priv->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 	WARN_ON(register_oom_notifier(&dev_priv->mm.oom_notifier));

 	dev_priv->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
 	WARN_ON(register_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
 }

 /**
  * i915_gem_shrinker_cleanup - Clean up i915 shrinker
  * @dev_priv: i915 device
  *
  * This function unregisters the i915 shrinker and OOM handler.
  */
 void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv)
 {
 	WARN_ON(unregister_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
 	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
 	unregister_shrinker(&dev_priv->mm.shrinker);
 }
	/*
	* Copyright © 2008-2015 Intel Corporation
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice (including the next
	* paragraph) shall be included in all copies or substantial portions of the
	* Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	* IN THE SOFTWARE.
	*
	*/

	#include <linux/oom.h>
	#include <linux/shmem_fs.h>
	#include <linux/slab.h>
	#include <linux/swap.h>
	#include <linux/pci.h>
	#include <linux/dma-buf.h>
	#include <linux/vmalloc.h>
	#include <drm/drmP.h>
	#include <drm/i915_drm.h>

	#include "i915_drv.h"
	#include "i915_trace.h"

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

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

	static bool i915_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 bool any_vma_pinned(struct drm_i915_gem_object *obj)
	{
	struct i915_vma *vma;

	list_for_each_entry(vma, &obj->vma_list, obj_link)
	if (i915_vma_is_pinned(vma))
	return true;

	return false;
	}

	static bool swap_available(void)
	{
	return get_nr_swap_pages() > 0;
	}

	static bool can_release_pages(struct drm_i915_gem_object *obj)
	{
	if (!obj->mm.pages)
	return false;

	/* Consider only shrinkable ojects. */
	if (!i915_gem_object_is_shrinkable(obj))
	return false;

	/* Only report true if by unbinding the object and putting its pages
	* we can actually make forward progress towards freeing physical
	* pages.
	*
	* If the pages are pinned for any other reason than being bound
	* to the GPU, simply unbinding from the GPU is not going to succeed
	* in releasing our pin count on the pages themselves.
	*/
	if (atomic_read(&obj->mm.pages_pin_count) > obj->bind_count)
	return false;

	if (any_vma_pinned(obj))
	return false;

	/* We can only return physical pages to the system if we can either
	* discard the contents (because the user has marked them as being
	* purgeable) or if we can move their contents out to swap.
	*/
	return swap_available() \|\| obj->mm.madv == I915_MADV_DONTNEED;
	}

	static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
	{
	if (i915_gem_object_unbind(obj) == 0)
	__i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
	return !READ_ONCE(obj->mm.pages);
	}

	/**
	* i915_gem_shrink - Shrink buffer object caches
	* @dev_priv: i915 device
	* @target: amount of memory to make available, in pages
	* @flags: control flags for selecting cache types
	*
	* This function is the main interface to the shrinker. It will try to release
	* up to @target pages of main memory backing storage from buffer objects.
	* Selection of the specific caches can be done with @flags. This is e.g. useful
	* when purgeable objects should be removed from caches preferentially.
	*
	* Note that it's not guaranteed that released amount is actually available as
	* free system memory - the pages might still be in-used to due to other reasons
	* (like cpu mmaps) or the mm core has reused them before we could grab them.
	* Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
	* avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
	*
	* Also note that any kind of pinning (both per-vma address space pins and
	* backing storage pins at the buffer object level) result in the shrinker code
	* having to skip the object.
	*
	* Returns:
	* The number of pages of backing storage actually released.
	*/
	unsigned long
	i915_gem_shrink(struct drm_i915_private *dev_priv,
	unsigned long target, unsigned flags)
	{
	const struct {
	struct list_head *list;
	unsigned int bit;
	} phases[] = {
	{ &dev_priv->mm.unbound_list, I915_SHRINK_UNBOUND },
	{ &dev_priv->mm.bound_list, I915_SHRINK_BOUND },
	{ NULL, 0 },
	}, *phase;
	unsigned long count = 0;
	bool unlock;

	if (!i915_gem_shrinker_lock(&dev_priv->drm, &unlock))
	return 0;

	trace_i915_gem_shrink(dev_priv, target, flags);
	i915_gem_retire_requests(dev_priv);

	/*
	* Unbinding of objects will require HW access; Let us not wake the
	* device just to recover a little memory. If absolutely necessary,
	* we will force the wake during oom-notifier.
	*/
	if ((flags & I915_SHRINK_BOUND) &&
	!intel_runtime_pm_get_if_in_use(dev_priv))
	flags &= ~I915_SHRINK_BOUND;

	/*
	* As we may completely rewrite the (un)bound list whilst unbinding
	* (due to retiring requests) we have to strictly process only
	* one element of the list at the time, and recheck the list
	* on every iteration.
	*
	* In particular, we must hold a reference whilst removing the
	* object as we may end up waiting for and/or retiring the objects.
	* This might release the final reference (held by the active list)
	* and result in the object being freed from under us. This is
	* similar to the precautions the eviction code must take whilst
	* removing objects.
	*
	* Also note that although these lists do not hold a reference to
	* the object we can safely grab one here: The final object
	* unreferencing and the bound_list are both protected by the
	* dev->struct_mutex and so we won't ever be able to observe an
	* object on the bound_list with a reference count equals 0.
	*/
	for (phase = phases; phase->list; phase++) {
	struct list_head still_in_list;
	struct drm_i915_gem_object *obj;

	if ((flags & phase->bit) == 0)
	continue;

	INIT_LIST_HEAD(&still_in_list);
	while (count < target &&
	(obj = list_first_entry_or_null(phase->list,
	typeof(*obj),
	global_link))) {
	list_move_tail(&obj->global_link, &still_in_list);
	if (!obj->mm.pages) {
	list_del_init(&obj->global_link);
	continue;
	}

	if (flags & I915_SHRINK_PURGEABLE &&
	obj->mm.madv != I915_MADV_DONTNEED)
	continue;

	if (flags & I915_SHRINK_VMAPS &&
	!is_vmalloc_addr(obj->mm.mapping))
	continue;

	if (!(flags & I915_SHRINK_ACTIVE) &&
	(i915_gem_object_is_active(obj) \|\|
	obj->framebuffer_references))
	continue;

	if (!can_release_pages(obj))
	continue;

	if (unsafe_drop_pages(obj)) {
	/* May arrive from get_pages on another bo */
	mutex_lock_nested(&obj->mm.lock,
	I915_MM_SHRINKER);
	if (!obj->mm.pages) {
	__i915_gem_object_invalidate(obj);
	list_del_init(&obj->global_link);
	count += obj->base.size >> PAGE_SHIFT;
	}
	mutex_unlock(&obj->mm.lock);
	}
	}
	list_splice_tail(&still_in_list, phase->list);
	}

	if (flags & I915_SHRINK_BOUND)
	intel_runtime_pm_put(dev_priv);

	i915_gem_retire_requests(dev_priv);
	if (unlock)
	mutex_unlock(&dev_priv->drm.struct_mutex);

	/* expedite the RCU grace period to free some request slabs */
	synchronize_rcu_expedited();

	return count;
	}

	/**
	* i915_gem_shrink_all - Shrink buffer object caches completely
	* @dev_priv: i915 device
	*
	* This is a simple wraper around i915_gem_shrink() to aggressively shrink all
	* caches completely. It also first waits for and retires all outstanding
	* requests to also be able to release backing storage for active objects.
	*
	* This should only be used in code to intentionally quiescent the gpu or as a
	* last-ditch effort when memory seems to have run out.
	*
	* Returns:
	* The number of pages of backing storage actually released.
	*/
	unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
	{
	unsigned long freed;

	freed = i915_gem_shrink(dev_priv, -1UL,
	I915_SHRINK_BOUND \|
	I915_SHRINK_UNBOUND \|
	I915_SHRINK_ACTIVE);
	rcu_barrier(); /* wait until our RCU delayed slab frees are completed */

	return freed;
	}

	static unsigned long
	i915_gem_shrinker_count(struct shrinker shrinker, struct shrink_control sc)
	{
	struct drm_i915_private *dev_priv =
	container_of(shrinker, struct drm_i915_private, mm.shrinker);
	struct drm_device *dev = &dev_priv->drm;
	struct drm_i915_gem_object *obj;
	unsigned long count;
	bool unlock;

	if (!i915_gem_shrinker_lock(dev, &unlock))
	return 0;

	i915_gem_retire_requests(dev_priv);

	count = 0;
	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_link)
	if (can_release_pages(obj))
	count += obj->base.size >> PAGE_SHIFT;

	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_link) {
	if (!i915_gem_object_is_active(obj) && can_release_pages(obj))
	count += obj->base.size >> PAGE_SHIFT;
	}

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

	return count;
	}

	static unsigned long
	i915_gem_shrinker_scan(struct shrinker shrinker, struct shrink_control sc)
	{
	struct drm_i915_private *dev_priv =
	container_of(shrinker, struct drm_i915_private, mm.shrinker);
	struct drm_device *dev = &dev_priv->drm;
	unsigned long freed;
	bool unlock;

	if (!i915_gem_shrinker_lock(dev, &unlock))
	return SHRINK_STOP;

	freed = i915_gem_shrink(dev_priv,
	sc->nr_to_scan,
	I915_SHRINK_BOUND \|
	I915_SHRINK_UNBOUND \|
	I915_SHRINK_PURGEABLE);
	if (freed < sc->nr_to_scan)
	freed += i915_gem_shrink(dev_priv,
	sc->nr_to_scan - freed,
	I915_SHRINK_BOUND \|
	I915_SHRINK_UNBOUND);
	if (unlock)
	mutex_unlock(&dev->struct_mutex);

	return freed;
	}

	struct shrinker_lock_uninterruptible {
	bool was_interruptible;
	bool unlock;
	};

	static bool
	i915_gem_shrinker_lock_uninterruptible(struct drm_i915_private *dev_priv,
	struct shrinker_lock_uninterruptible *slu,
	int timeout_ms)
	{
	unsigned long timeout = jiffies + msecs_to_jiffies_timeout(timeout_ms);

	do {
	if (i915_gem_wait_for_idle(dev_priv, 0) == 0 &&
	i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock))
	break;

	schedule_timeout_killable(1);
	if (fatal_signal_pending(current))
	return false;

	if (time_after(jiffies, timeout)) {
	pr_err("Unable to lock GPU to purge memory.\n");
	return false;
	}
	} while (1);

	slu->was_interruptible = dev_priv->mm.interruptible;
	dev_priv->mm.interruptible = false;
	return true;
	}

	static void
	i915_gem_shrinker_unlock_uninterruptible(struct drm_i915_private *dev_priv,
	struct shrinker_lock_uninterruptible *slu)
	{
	dev_priv->mm.interruptible = slu->was_interruptible;
	if (slu->unlock)
	mutex_unlock(&dev_priv->drm.struct_mutex);
	}

	static int
	i915_gem_shrinker_oom(struct notifier_block nb, unsigned long event, void ptr)
	{
	struct drm_i915_private *dev_priv =
	container_of(nb, struct drm_i915_private, mm.oom_notifier);
	struct shrinker_lock_uninterruptible slu;
	struct drm_i915_gem_object *obj;
	unsigned long unevictable, bound, unbound, freed_pages;

	if (!i915_gem_shrinker_lock_uninterruptible(dev_priv, &slu, 5000))
	return NOTIFY_DONE;

	intel_runtime_pm_get(dev_priv);
	freed_pages = i915_gem_shrink_all(dev_priv);
	intel_runtime_pm_put(dev_priv);

	/* Because we may be allocating inside our own driver, we cannot
	* assert that there are no objects with pinned pages that are not
	* being pointed to by hardware.
	*/
	unbound = bound = unevictable = 0;
	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_link) {
	if (!obj->mm.pages)
	continue;

	if (!can_release_pages(obj))
	unevictable += obj->base.size >> PAGE_SHIFT;
	else
	unbound += obj->base.size >> PAGE_SHIFT;
	}
	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_link) {
	if (!obj->mm.pages)
	continue;

	if (!can_release_pages(obj))
	unevictable += obj->base.size >> PAGE_SHIFT;
	else
	bound += obj->base.size >> PAGE_SHIFT;
	}

	i915_gem_shrinker_unlock_uninterruptible(dev_priv, &slu);

	if (freed_pages \|\| unbound \|\| bound)
	pr_info("Purging GPU memory, %lu pages freed, "
	"%lu pages still pinned.\n",
	freed_pages, unevictable);
	if (unbound \|\| bound)
	pr_err("%lu and %lu pages still available in the "
	"bound and unbound GPU page lists.\n",
	bound, unbound);

	(unsigned long )ptr += freed_pages;
	return NOTIFY_DONE;
	}

	static int
	i915_gem_shrinker_vmap(struct notifier_block nb, unsigned long event, void ptr)
	{
	struct drm_i915_private *dev_priv =
	container_of(nb, struct drm_i915_private, mm.vmap_notifier);
	struct shrinker_lock_uninterruptible slu;
	struct i915_vma vma, next;
	unsigned long freed_pages = 0;
	int ret;

	if (!i915_gem_shrinker_lock_uninterruptible(dev_priv, &slu, 5000))
	return NOTIFY_DONE;

	/* Force everything onto the inactive lists */
	ret = i915_gem_wait_for_idle(dev_priv, I915_WAIT_LOCKED);
	if (ret)
	goto out;

	intel_runtime_pm_get(dev_priv);
	freed_pages += i915_gem_shrink(dev_priv, -1UL,
	I915_SHRINK_BOUND \|
	I915_SHRINK_UNBOUND \|
	I915_SHRINK_ACTIVE \|
	I915_SHRINK_VMAPS);
	intel_runtime_pm_put(dev_priv);

	/* We also want to clear any cached iomaps as they wrap vmap */
	list_for_each_entry_safe(vma, next,
	&dev_priv->ggtt.base.inactive_list, vm_link) {
	unsigned long count = vma->node.size >> PAGE_SHIFT;
	if (vma->iomap && i915_vma_unbind(vma) == 0)
	freed_pages += count;
	}

	out:
	i915_gem_shrinker_unlock_uninterruptible(dev_priv, &slu);

	(unsigned long )ptr += freed_pages;
	return NOTIFY_DONE;
	}

	/**
	* i915_gem_shrinker_init - Initialize i915 shrinker
	* @dev_priv: i915 device
	*
	* This function registers and sets up the i915 shrinker and OOM handler.
	*/
	void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
	{
	dev_priv->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
	dev_priv->mm.shrinker.count_objects = i915_gem_shrinker_count;
	dev_priv->mm.shrinker.seeks = DEFAULT_SEEKS;
	WARN_ON(register_shrinker(&dev_priv->mm.shrinker));

	dev_priv->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
	WARN_ON(register_oom_notifier(&dev_priv->mm.oom_notifier));

	dev_priv->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
	WARN_ON(register_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
	}

	/**
	* i915_gem_shrinker_cleanup - Clean up i915 shrinker
	* @dev_priv: i915 device
	*
	* This function unregisters the i915 shrinker and OOM handler.
	*/
	void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv)
	{
	WARN_ON(unregister_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
	unregister_shrinker(&dev_priv->mm.shrinker);
	}