[PATCH v3 11/15] drm/shmem-helper: Add generic memory shrinker

[Dmitry Osipenko]

Introduce a common DRM SHMEM shrinker. It allows to reduce code
duplication among DRM drivers that implement theirs own shrinkers.
This is initial version of the shrinker that covers basic needs of
GPU drivers, both purging and eviction of shmem objects are supported.

This patch is based on a couple ideas borrowed from Rob's Clark MSM
shrinker and Thomas' Zimmermann variant of SHMEM shrinker.

In order to start using DRM SHMEM shrinker drivers should:

1. Implement new purge(), evict() + swap_in() GEM callbacks.
2. Register shrinker using drm_gem_shmem_shrinker_register(drm_device).
3. Use drm_gem_shmem_set_purgeable_and_evictable(shmem) and alike API
   functions to activate shrinking of GEMs.

Signed-off-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 766 ++++++++++++++++++++++++-
 include/drm/drm_device.h               |   4 +
 include/drm/drm_gem.h                  |  35 ++
 include/drm/drm_gem_shmem_helper.h     | 105 +++-
 4 files changed, 878 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 3ecef571eff3..7e4851363d14 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -88,6 +88,13 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
 
 	INIT_LIST_HEAD(&shmem->madv_list);
 
+	/*
+	 * Eviction and purging are disabled by default, shmem user must enable
+	 * them explicitly using drm_gem_shmem_set_evictable/purgeable().
+	 */
+	shmem->eviction_disable_count = 1;
+	shmem->purging_disable_count = 1;
+
 	if (!private) {
 		/*
 		 * Our buffers are kept pinned, so allocating them
@@ -126,6 +133,107 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
 
+static void
+drm_gem_shmem_add_pages_to_shrinker(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
+	size_t page_count = obj->size >> PAGE_SHIFT;
+
+	if (!shmem->pages_shrinkable) {
+		WARN_ON(gem_shrinker->shrinkable_count + page_count < page_count);
+		gem_shrinker->shrinkable_count += page_count;
+		shmem->pages_shrinkable = true;
+	}
+}
+
+static void
+drm_gem_shmem_remove_pages_from_shrinker(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
+	size_t page_count = obj->size >> PAGE_SHIFT;
+
+	if (shmem->pages_shrinkable) {
+		WARN_ON(gem_shrinker->shrinkable_count < page_count);
+		gem_shrinker->shrinkable_count -= page_count;
+		shmem->pages_shrinkable = false;
+	}
+}
+
+static void
+drm_gem_shmem_set_pages_state_locked(struct drm_gem_shmem_object *shmem,
+				     enum drm_gem_shmem_pages_state new_state)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
+
+	lockdep_assert_held(&gem_shrinker->lock);
+	lockdep_assert_held(&obj->resv->lock.base);
+
+	if (new_state >= DRM_GEM_SHMEM_PAGES_STATE_ACTIVE) {
+		if (drm_gem_shmem_is_evictable(shmem))
+			new_state = DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE;
+
+		if (drm_gem_shmem_is_purgeable(shmem))
+			new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE;
+
+		if (!shmem->pages)
+			new_state = DRM_GEM_SHMEM_PAGES_STATE_INACTIVE;
+
+		if (shmem->evicted)
+			new_state = DRM_GEM_SHMEM_PAGES_STATE_EVICTED;
+	}
+
+	if (shmem->pages_state == new_state)
+		return;
+
+	switch (new_state) {
+	case DRM_GEM_SHMEM_PAGES_STATE_INACTIVE:
+	case DRM_GEM_SHMEM_PAGES_STATE_PURGED:
+		drm_gem_shmem_remove_pages_from_shrinker(shmem);
+		list_del_init(&shmem->madv_list);
+		break;
+
+	case DRM_GEM_SHMEM_PAGES_STATE_ACTIVE:
+		drm_gem_shmem_remove_pages_from_shrinker(shmem);
+		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_active);
+		break;
+
+	case DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE:
+		drm_gem_shmem_add_pages_to_shrinker(shmem);
+		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_purgeable);
+		break;
+
+	case DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE:
+		drm_gem_shmem_add_pages_to_shrinker(shmem);
+		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_evictable);
+		break;
+
+	case DRM_GEM_SHMEM_PAGES_STATE_EVICTED:
+		drm_gem_shmem_remove_pages_from_shrinker(shmem);
+		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_evicted);
+		break;
+	}
+
+	shmem->pages_state = new_state;
+}
+
+static void
+drm_gem_shmem_set_pages_state(struct drm_gem_shmem_object *shmem,
+			      enum drm_gem_shmem_pages_state new_state)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
+
+	if (!gem_shrinker)
+		return;
+
+	mutex_lock(&gem_shrinker->lock);
+	drm_gem_shmem_set_pages_state_locked(shmem, new_state);
+	mutex_unlock(&gem_shrinker->lock);
+}
+
 /**
  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
  * @shmem: shmem GEM object to free
@@ -137,6 +245,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 
+	/* take out shmem GEM object from the memory shrinker */
+	drm_gem_shmem_madvise(shmem, -1);
+
 	WARN_ON(shmem->vmap_use_count);
 
 	if (obj->import_attach) {
@@ -145,10 +256,11 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 		if (shmem->sgt) {
 			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
 					  DMA_BIDIRECTIONAL, 0);
+
 			sg_free_table(shmem->sgt);
 			kfree(shmem->sgt);
 		}
-		if (shmem->pages)
+		if (shmem->pages_use_count)
 			drm_gem_shmem_put_pages(shmem);
 	}
 
@@ -159,18 +271,226 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
 
-static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
+static void drm_gem_shmem_update_pages_state_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
+	enum drm_gem_shmem_pages_state new_state;
+
+	if (!gem_shrinker || obj->import_attach)
+		return;
+
+	mutex_lock(&gem_shrinker->lock);
+
+	if (!shmem->madv)
+		new_state = DRM_GEM_SHMEM_PAGES_STATE_ACTIVE;
+	else if (shmem->madv > 0)
+		new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE;
+	else if (shmem->madv < 0)
+		new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGED;
+
+	drm_gem_shmem_set_pages_state_locked(shmem, new_state);
+
+	mutex_unlock(&gem_shrinker->lock);
+}
+
+static void drm_gem_shmem_update_pages_state(struct drm_gem_shmem_object *shmem)
+{
+	dma_resv_lock(shmem->base.resv, NULL);
+	drm_gem_shmem_update_pages_state_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+}
+
+static int
+drm_gem_shmem_set_evictable_locked(struct drm_gem_shmem_object *shmem)
+{
+	int ret = 0;
+
+	WARN_ON_ONCE(!shmem->eviction_disable_count--);
+
+	if (shmem->madv < 0)
+		ret = -ENOMEM;
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
+	return ret;
+}
+
+static int
+drm_gem_shmem_set_unevictable_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int err;
+
+	if (shmem->madv < 0)
+		return -ENOMEM;
+
+	if (shmem->evicted) {
+		err = obj->funcs->swap_in(obj);
+		if (err)
+			return err;
+	}
+
+	shmem->eviction_disable_count++;
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
+	return 0;
+}
+
+static int
+drm_gem_shmem_set_purgeable_locked(struct drm_gem_shmem_object *shmem)
+{
+	int ret = 0;
+
+	WARN_ON_ONCE(!shmem->purging_disable_count--);
+
+	if (shmem->madv < 0)
+		ret = -ENOMEM;
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
+	return ret;
+}
+
+/**
+ * drm_gem_shmem_set_purgeable() - Make GEM purgeable by memory shrinker
+ * @shmem: shmem GEM object
+ *
+ * Tell memory shrinker that this GEM can be purged. Initially purging is
+ * disabled for all GEMs. Each set_pureable() call must have corresponding
+ * set_unpureable() call. If GEM was purged, then -ENOMEM is returned.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_set_purgeable(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	ret = drm_gem_shmem_set_purgeable_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable);
+
+static int
+drm_gem_shmem_set_unpurgeable_locked(struct drm_gem_shmem_object *shmem)
+{
+	if (shmem->madv < 0)
+		return -ENOMEM;
+
+	shmem->purging_disable_count++;
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
+	return 0;
+}
+
+static int
+drm_gem_shmem_set_purgeable_and_evictable_locked(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	ret = drm_gem_shmem_set_evictable_locked(shmem);
+	if (!ret) {
+		ret = drm_gem_shmem_set_purgeable_locked(shmem);
+		if (ret)
+			drm_gem_shmem_set_unevictable_locked(shmem);
+	}
+
+	return ret;
+}
+
+static int
+drm_gem_shmem_set_unpurgeable_and_unevictable_locked(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	ret = drm_gem_shmem_set_unpurgeable_locked(shmem);
+	if (!ret) {
+		ret = drm_gem_shmem_set_unevictable_locked(shmem);
+		if (ret)
+			drm_gem_shmem_set_purgeable_locked(shmem);
+	}
+
+	return ret;
+}
+
+/**
+ * drm_gem_shmem_set_purgeable_and_evictable() - Make GEM unpurgeable and
+ * 						 unevictable by memory shrinker
+ * @shmem: shmem GEM object
+ *
+ * Tell memory shrinker that this GEM can't be purged and evicted. Each
+ * set_purgeable_and_evictable() call must have corresponding
+ * unpurgeable_and_unevictable() call. If GEM was purged, then -ENOMEM
+ * is returned.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_set_purgeable_and_evictable(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	ret = drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable_and_evictable);
+
+/**
+ * drm_gem_shmem_set_unpurgeable_and_unevictable() - Make GEM purgeable and
+ * 						     evictable by memory shrinker
+ * @shmem: shmem GEM object
+ *
+ * Tell memory shrinker that this GEM can be purged and evicted. Each
+ * unpurgeable_and_unevictable() call must have corresponding
+ * set_purgeable_and_evictable() call. If GEM was purged, then -ENOMEM
+ * is returned.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_set_unpurgeable_and_unevictable(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
+	if (ret)
+		return ret;
+
+	ret = drm_gem_shmem_set_unpurgeable_and_unevictable_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_set_unpurgeable_and_unevictable);
+
+static int
+drm_gem_shmem_acquire_pages_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct page **pages;
 
-	if (shmem->pages_use_count++ > 0)
+	if (shmem->madv < 0) {
+		WARN_ON(shmem->pages);
+		return -ENOMEM;
+	}
+
+	if (shmem->pages) {
+		WARN_ON(!shmem->evicted);
 		return 0;
+	}
 
 	pages = drm_gem_get_pages(obj);
 	if (IS_ERR(pages)) {
 		DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
-		shmem->pages_use_count = 0;
 		return PTR_ERR(pages);
 	}
 
@@ -189,6 +509,25 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 	return 0;
 }
 
+static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	int err;
+
+	if (shmem->madv < 0)
+		return -ENOMEM;
+
+	if (shmem->pages_use_count++ > 0)
+		return 0;
+
+	err = drm_gem_shmem_acquire_pages_locked(shmem);
+	if (err) {
+		shmem->pages_use_count = 0;
+		return err;
+	}
+
+	return 0;
+}
+
 /*
  * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
  * @shmem: shmem GEM object
@@ -209,21 +548,38 @@ int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
 	if (ret)
 		return ret;
 	ret = drm_gem_shmem_get_pages_locked(shmem);
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
 	dma_resv_unlock(shmem->base.resv);
 
 	return ret;
 }
 EXPORT_SYMBOL(drm_gem_shmem_get_pages);
 
-static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
+static void drm_gem_shmem_get_pages_no_fail(struct drm_gem_shmem_object *shmem)
 {
-	struct drm_gem_object *obj = &shmem->base;
+	WARN_ON(shmem->base.import_attach);
 
-	if (WARN_ON_ONCE(!shmem->pages_use_count))
-		return;
+	dma_resv_lock(shmem->base.resv, NULL);
 
-	if (--shmem->pages_use_count > 0)
+	if (drm_gem_shmem_get_pages_locked(shmem))
+		shmem->pages_use_count++;
+
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
+	dma_resv_unlock(shmem->base.resv);
+}
+
+static void
+drm_gem_shmem_release_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	if (!shmem->pages) {
+		WARN_ON(!shmem->evicted && shmem->madv >= 0);
 		return;
+	}
 
 #ifdef CONFIG_X86
 	if (shmem->map_wc)
@@ -236,6 +592,21 @@ static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 	shmem->pages = NULL;
 }
 
+static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	lockdep_assert_held(&obj->resv->lock.base);
+
+	if (WARN_ON(!shmem->pages_use_count))
+		return;
+
+	if (--shmem->pages_use_count > 0)
+		return;
+
+	drm_gem_shmem_release_pages_locked(shmem);
+}
+
 /*
  * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
  * @shmem: shmem GEM object
@@ -246,6 +617,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
 {
 	dma_resv_lock(shmem->base.resv, NULL);
 	drm_gem_shmem_put_pages_locked(shmem);
+	drm_gem_shmem_update_pages_state_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 }
 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
@@ -262,9 +634,21 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
  */
 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
 {
+	int err;
+
 	WARN_ON(shmem->base.import_attach);
 
-	return drm_gem_shmem_get_pages(shmem);
+	err = drm_gem_shmem_set_unpurgeable_and_unevictable(shmem);
+	if (err)
+		return err;
+
+	err = drm_gem_shmem_get_pages(shmem);
+	if (err) {
+		drm_gem_shmem_set_purgeable_and_evictable(shmem);
+		return err;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(drm_gem_shmem_pin);
 
@@ -280,6 +664,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 	WARN_ON(shmem->base.import_attach);
 
 	drm_gem_shmem_put_pages(shmem);
+	drm_gem_shmem_set_purgeable_and_evictable(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_unpin);
 
@@ -359,7 +744,18 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
 	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
 	if (ret)
 		return ret;
+
+	ret = drm_gem_shmem_set_unpurgeable_and_unevictable_locked(shmem);
+	if (ret)
+		goto unlock;
+
 	ret = drm_gem_shmem_vmap_locked(shmem, map);
+	if (ret)
+		drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
+	else
+		drm_gem_shmem_update_pages_state_locked(shmem);
+
+unlock:
 	dma_resv_unlock(shmem->base.resv);
 
 	return ret;
@@ -404,9 +800,9 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
 {
 	dma_resv_lock(shmem->base.resv, NULL);
 	drm_gem_shmem_vunmap_locked(shmem, map);
+	drm_gem_shmem_update_pages_state_locked(shmem);
+	drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
-
-	drm_gem_shmem_update_purgeable_status(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_vunmap);
 
@@ -447,29 +843,140 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
 
 	madv = shmem->madv;
 
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
 	dma_resv_unlock(shmem->base.resv);
 
 	return (madv >= 0);
 }
 EXPORT_SYMBOL(drm_gem_shmem_madvise);
 
-void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
+/**
+ * drm_gem_shmem_swap_in_pages_locked() - Moves shmem pages back to memory
+ * @shmem: shmem GEM object
+ *
+ * This function moves pages back to memory if they were previously evicted
+ * by the memory shrinker.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_swap_in_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct sg_table *sgt;
+	int ret;
+
+	lockdep_assert_held(&obj->resv->lock.base);
+
+	if (shmem->evicted) {
+		ret = drm_gem_shmem_acquire_pages_locked(shmem);
+		if (ret)
+			return ret;
+
+		sgt = drm_gem_shmem_get_sg_table(shmem);
+		if (IS_ERR(sgt))
+			return PTR_ERR(sgt);
+
+		ret = dma_map_sgtable(obj->dev->dev, sgt,
+				      DMA_BIDIRECTIONAL, 0);
+		if (ret) {
+			sg_free_table(sgt);
+			kfree(sgt);
+			return ret;
+		}
+
+		shmem->sgt = sgt;
+		shmem->evicted = false;
+		shmem->pages_state = DRM_GEM_SHMEM_PAGES_STATE_ACTIVE;
+
+		drm_gem_shmem_update_pages_state_locked(shmem);
+	}
+
+	return shmem->pages ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in_pages_locked);
+
+/**
+ * drm_gem_shmem_swap_in_locked() - Moves shmem GEM back to memory
+ * @shmem: shmem GEM object
+ *
+ * This function moves shmem GEM back to memory if it was previously evicted
+ * by the memory shrinker. The GEM is ready to use on success.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_swap_in_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	lockdep_assert_held(&obj->resv->lock.base);
+
+	if (shmem->evicted)
+		return obj->funcs->swap_in(obj);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in_locked);
+
+static void drm_gem_shmem_unpin_pages_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct drm_device *dev = obj->dev;
 
-	WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
+	if (shmem->evicted)
+		return;
 
 	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
+	drm_gem_shmem_release_pages_locked(shmem);
+	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+
 	sg_free_table(shmem->sgt);
 	kfree(shmem->sgt);
 	shmem->sgt = NULL;
+}
 
-	drm_gem_shmem_put_pages_locked(shmem);
+/**
+ * drm_gem_shmem_evict_locked - Evict shmem pages
+ * @shmem: shmem GEM object
+ *
+ * This function unpins shmem pages, allowing them to be swapped out from
+ * memory.
+ */
+void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
 
-	shmem->madv = -1;
+	lockdep_assert_held(&obj->resv->lock.base);
 
-	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+	WARN_ON(!drm_gem_shmem_is_evictable(shmem));
+	WARN_ON(shmem->madv < 0);
+	WARN_ON(shmem->evicted);
+
+	drm_gem_shmem_unpin_pages_locked(shmem);
+
+	shmem->evicted = true;
+	drm_gem_shmem_set_pages_state(shmem, DRM_GEM_SHMEM_PAGES_STATE_EVICTED);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_evict_locked);
+
+/**
+ * drm_gem_shmem_purge_locked - Purge shmem pages
+ * @shmem: shmem GEM object
+ *
+ * This function permanently releases shmem pages.
+ */
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	lockdep_assert_held(&obj->resv->lock.base);
+
+	WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
+	WARN_ON(shmem->madv < 0);
+
+	drm_gem_shmem_unpin_pages_locked(shmem);
 	drm_gem_free_mmap_offset(obj);
 
 	/* Our goal here is to return as much of the memory as
@@ -480,6 +987,9 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
 	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
 
 	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
+
+	shmem->madv = -1;
+	drm_gem_shmem_set_pages_state(shmem, DRM_GEM_SHMEM_PAGES_STATE_PURGED);
 }
 EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
 
@@ -543,22 +1053,31 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 	vm_fault_t ret;
 	struct page *page;
 	pgoff_t page_offset;
+	bool pages_inactive;
+	int err;
 
 	/* We don't use vmf->pgoff since that has the fake offset */
 	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
 
 	dma_resv_lock(shmem->base.resv, NULL);
 
-	if (page_offset >= num_pages ||
-	    WARN_ON_ONCE(!shmem->pages) ||
-	    shmem->madv < 0) {
+	pages_inactive = shmem->pages_state < DRM_GEM_SHMEM_PAGES_STATE_ACTIVE;
+	WARN_ON_ONCE(!shmem->pages ^ pages_inactive);
+
+	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
 		ret = VM_FAULT_SIGBUS;
 	} else {
+		err = drm_gem_shmem_swap_in_locked(shmem);
+		if (err) {
+			ret = VM_FAULT_OOM;
+			goto unlock;
+		}
+
 		page = shmem->pages[page_offset];
 
 		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
 	}
-
+unlock:
 	dma_resv_unlock(shmem->base.resv);
 
 	return ret;
@@ -568,13 +1087,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 {
 	struct drm_gem_object *obj = vma->vm_private_data;
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
-	int ret;
-
-	WARN_ON(shmem->base.import_attach);
-
-	ret = drm_gem_shmem_get_pages(shmem);
-	WARN_ON_ONCE(ret != 0);
 
+	drm_gem_shmem_get_pages_no_fail(shmem);
 	drm_gem_vm_open(vma);
 }
 
@@ -716,6 +1230,8 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
 
 	shmem->sgt = sgt;
 
+	drm_gem_shmem_update_pages_state(shmem);
+
 	return sgt;
 
 err_free_sgt:
@@ -762,6 +1278,202 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
 
+static struct drm_gem_shmem_shrinker *
+to_drm_shrinker(struct shrinker *shrinker)
+{
+	return container_of(shrinker, struct drm_gem_shmem_shrinker, base);
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_count_objects(struct shrinker *shrinker,
+				     struct shrink_control *sc)
+{
+	struct drm_gem_shmem_shrinker *gem_shrinker = to_drm_shrinker(shrinker);
+	u64 count = READ_ONCE(gem_shrinker->shrinkable_count);
+
+	if (count >= SHRINK_EMPTY)
+		return SHRINK_EMPTY - 1;
+
+	return count ?: SHRINK_EMPTY;
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_run_objects_scan(struct shrinker *shrinker,
+					unsigned long nr_to_scan,
+					bool *lock_contention,
+					bool evict)
+{
+	struct drm_gem_shmem_shrinker *gem_shrinker = to_drm_shrinker(shrinker);
+	struct drm_gem_shmem_object *shmem;
+	struct list_head still_in_list;
+	struct drm_gem_object *obj;
+	unsigned long freed = 0;
+	struct list_head *lru;
+	size_t page_count;
+
+	INIT_LIST_HEAD(&still_in_list);
+
+	mutex_lock(&gem_shrinker->lock);
+
+	if (evict)
+		lru = &gem_shrinker->lru_evictable;
+	else
+		lru = &gem_shrinker->lru_purgeable;
+
+	while (freed < nr_to_scan) {
+		shmem = list_first_entry_or_null(lru, typeof(*shmem), madv_list);
+		if (!shmem)
+			break;
+
+		obj = &shmem->base;
+		page_count = obj->size >> PAGE_SHIFT;
+		list_move_tail(&shmem->madv_list, &still_in_list);
+
+		if (evict && get_nr_swap_pages() < page_count)
+			continue;
+
+		/*
+		 * If it's in the process of being freed, gem_object->free()
+		 * may be blocked on lock waiting to remove it.  So just
+		 * skip it.
+		 */
+		if (!kref_get_unless_zero(&obj->refcount))
+			continue;
+
+		mutex_unlock(&gem_shrinker->lock);
+
+		/* prevent racing with job-submission code paths */
+		if (!dma_resv_trylock(obj->resv)) {
+			*lock_contention |= true;
+			goto shrinker_lock;
+		}
+
+		/* prevent racing with the dma-buf exporting */
+		if (!mutex_trylock(&gem_shrinker->dev->object_name_lock)) {
+			*lock_contention |= true;
+			goto resv_unlock;
+		}
+
+		/* check whether h/w uses this object */
+		if (!dma_resv_test_signaled(obj->resv, true))
+			goto object_name_unlock;
+
+		/* GEM may've become unpurgeable while shrinker was unlocked */
+		if (evict) {
+			if (!drm_gem_shmem_is_evictable(shmem))
+				goto object_name_unlock;
+		} else {
+			if (!drm_gem_shmem_is_purgeable(shmem))
+				goto object_name_unlock;
+		}
+
+		if (evict)
+			freed += obj->funcs->evict(obj);
+		else
+			freed += obj->funcs->purge(obj);
+object_name_unlock:
+		mutex_unlock(&gem_shrinker->dev->object_name_lock);
+resv_unlock:
+		dma_resv_unlock(obj->resv);
+shrinker_lock:
+		drm_gem_object_put(&shmem->base);
+		mutex_lock(&gem_shrinker->lock);
+	}
+
+	list_splice_tail(&still_in_list, lru);
+
+	mutex_unlock(&gem_shrinker->lock);
+
+	return freed;
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
+				    struct shrink_control *sc)
+{
+	unsigned long nr_to_scan = sc->nr_to_scan;
+	bool lock_contention = false;
+	unsigned long freed;
+
+	/* purge as many objects as we can */
+	freed = drm_gem_shmem_shrinker_run_objects_scan(shrinker, nr_to_scan,
+							&lock_contention, false);
+	nr_to_scan -= freed;
+
+	/* evict as many objects as we can */
+	if (freed < nr_to_scan)
+		freed += drm_gem_shmem_shrinker_run_objects_scan(shrinker,
+								 nr_to_scan,
+								 &lock_contention,
+								 true);
+
+	return (!freed && !lock_contention) ? SHRINK_STOP : freed;
+}
+
+/**
+ * drm_gem_shmem_shrinker_register() - Register shmem shrinker
+ * @dev: DRM device
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_shrinker_register(struct drm_device *dev)
+{
+	struct drm_gem_shmem_shrinker *gem_shrinker;
+	int err;
+
+	if (WARN_ON(dev->shmem_shrinker))
+		return -EBUSY;
+
+	gem_shrinker = kzalloc(sizeof(*gem_shrinker), GFP_KERNEL);
+	if (!gem_shrinker)
+		return -ENOMEM;
+
+	gem_shrinker->base.count_objects = drm_gem_shmem_shrinker_count_objects;
+	gem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
+	gem_shrinker->base.seeks = DEFAULT_SEEKS;
+	gem_shrinker->dev = dev;
+
+	INIT_LIST_HEAD(&gem_shrinker->lru_purgeable);
+	INIT_LIST_HEAD(&gem_shrinker->lru_evictable);
+	INIT_LIST_HEAD(&gem_shrinker->lru_evicted);
+	INIT_LIST_HEAD(&gem_shrinker->lru_active);
+	mutex_init(&gem_shrinker->lock);
+
+	dev->shmem_shrinker = gem_shrinker;
+
+	err = register_shrinker(&gem_shrinker->base);
+	if (err) {
+		dev->shmem_shrinker = NULL;
+		kfree(gem_shrinker);
+		return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_shrinker_register);
+
+/**
+ * drm_gem_shmem_shrinker_unregister() - Unregister shmem shrinker
+ * @dev: DRM device
+ */
+void drm_gem_shmem_shrinker_unregister(struct drm_device *dev)
+{
+	struct drm_gem_shmem_shrinker *gem_shrinker = dev->shmem_shrinker;
+
+	if (gem_shrinker) {
+		unregister_shrinker(&gem_shrinker->base);
+		WARN_ON(!list_empty(&gem_shrinker->lru_purgeable));
+		WARN_ON(!list_empty(&gem_shrinker->lru_evictable));
+		WARN_ON(!list_empty(&gem_shrinker->lru_evicted));
+		WARN_ON(!list_empty(&gem_shrinker->lru_active));
+		mutex_destroy(&gem_shrinker->lock);
+		dev->shmem_shrinker = NULL;
+		kfree(gem_shrinker);
+	}
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_shrinker_unregister);
+
 MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
 MODULE_IMPORT_NS(DMA_BUF);
 MODULE_LICENSE("GPL v2");
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 9923c7a6885e..929546cad894 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -16,6 +16,7 @@ struct drm_vblank_crtc;
 struct drm_vma_offset_manager;
 struct drm_vram_mm;
 struct drm_fb_helper;
+struct drm_gem_shmem_shrinker;
 
 struct inode;
 
@@ -277,6 +278,9 @@ struct drm_device {
 	/** @vram_mm: VRAM MM memory manager */
 	struct drm_vram_mm *vram_mm;
 
+	/** @shmem_shrinker: SHMEM GEM memory shrinker */
+	struct drm_gem_shmem_shrinker *shmem_shrinker;
+
 	/**
 	 * @switch_power_state:
 	 *
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 9d7c61a122dc..390d1ce08ed3 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -172,6 +172,41 @@ struct drm_gem_object_funcs {
 	 * This is optional but necessary for mmap support.
 	 */
 	const struct vm_operations_struct *vm_ops;
+
+	/**
+	 * @purge:
+	 *
+	 * Releases the GEM object's allocated backing storage to the system.
+	 *
+	 * Returns the number of pages that have been freed by purging the GEM object.
+	 *
+	 * This callback is used by the GEM shrinker.
+	 */
+	unsigned long (*purge)(struct drm_gem_object *obj);
+
+	/**
+	 * @evict:
+	 *
+	 * Unpins the GEM object's allocated backing storage, allowing shmem pages
+	 * to be swapped out.
+	 *
+	 * Returns the number of pages that have been unpinned.
+	 *
+	 * This callback is used by the GEM shrinker.
+	 */
+	unsigned long (*evict)(struct drm_gem_object *obj);
+
+	/**
+	 * @swap_in:
+	 *
+	 * Pins GEM object's allocated backing storage if it was previously evicted,
+	 * moving swapped out pages back to memory.
+	 *
+	 * Returns 0 on success, or -errno on error.
+	 *
+	 * This callback is used by the GEM shrinker.
+	 */
+	int (*swap_in)(struct drm_gem_object *obj);
 };
 
 /**
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 70889533962a..dc1c2db7d095 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -6,6 +6,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
+#include <linux/shrinker.h>
 
 #include <drm/drm_file.h>
 #include <drm/drm_gem.h>
@@ -15,8 +16,18 @@
 struct dma_buf_attachment;
 struct drm_mode_create_dumb;
 struct drm_printer;
+struct drm_device;
 struct sg_table;
 
+enum drm_gem_shmem_pages_state {
+	DRM_GEM_SHMEM_PAGES_STATE_PURGED = -2,
+	DRM_GEM_SHMEM_PAGES_STATE_EVICTED = -1,
+	DRM_GEM_SHMEM_PAGES_STATE_INACTIVE = 0,
+	DRM_GEM_SHMEM_PAGES_STATE_ACTIVE = 1,
+	DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE = 2,
+	DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE = 3,
+};
+
 /**
  * struct drm_gem_shmem_object - GEM object backed by shmem
  */
@@ -43,8 +54,8 @@ struct drm_gem_shmem_object {
 	 * @madv: State for madvise
 	 *
 	 * 0 is active/inuse.
+	 * 1 is not-needed/can-be-purged
 	 * A negative value is the object is purged.
-	 * Positive values are driver specific and not used by the helpers.
 	 */
 	int madv;
 
@@ -91,6 +102,40 @@ struct drm_gem_shmem_object {
 	 * @map_wc: map object write-combined (instead of using shmem defaults).
 	 */
 	bool map_wc;
+
+	/**
+	 * @eviction_disable_count:
+	 *
+	 * The shmem pages are disallowed to be evicted by the memory shrinker
+	 * while count is non-zero. Used internally by memory shrinker.
+	 */
+	unsigned int eviction_disable_count;
+
+	/**
+	 * @purging_disable_count:
+	 *
+	 * The shmem pages are disallowed to be purged by the memory shrinker
+	 * while count is non-zero. Used internally by memory shrinker.
+	 */
+	unsigned int purging_disable_count;
+
+	/**
+	 * @pages_state: Current state of shmem pages. Used internally by
+	 * memory shrinker.
+	 */
+	enum drm_gem_shmem_pages_state pages_state;
+
+	/**
+	 * @evicted: True if shmem pages were evicted by the memory shrinker.
+	 * Used internally by memory shrinker.
+	 */
+	bool evicted;
+
+	/**
+	 * @pages_shrinkable: True if shmem pages can be evicted or purged
+	 * by the memory shrinker. Used internally by memory shrinker.
+	 */
+	bool pages_shrinkable;
 };
 
 #define to_drm_gem_shmem_obj(obj) \
@@ -111,15 +156,33 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 
 int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
 
+int drm_gem_shmem_set_purgeable(struct drm_gem_shmem_object *shmem);
+int drm_gem_shmem_set_purgeable_and_evictable(struct drm_gem_shmem_object *shmem);
+int drm_gem_shmem_set_unpurgeable_and_unevictable(struct drm_gem_shmem_object *shmem);
+
+static inline bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
+{
+	return (shmem->madv >= 0) && !shmem->eviction_disable_count &&
+		shmem->base.funcs->evict && shmem->base.funcs->swap_in &&
+		!shmem->vmap_use_count && !shmem->base.dma_buf &&
+		!shmem->base.import_attach && shmem->sgt;
+}
+
 static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
 {
-	return (shmem->madv > 0) &&
-		!shmem->vmap_use_count && shmem->sgt &&
-		!shmem->base.dma_buf && !shmem->base.import_attach;
+	return (shmem->madv > 0) && !shmem->purging_disable_count &&
+		!shmem->vmap_use_count && shmem->base.funcs->purge &&
+		!shmem->base.dma_buf && !shmem->base.import_attach &&
+		shmem->sgt;
 }
 
-void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
+int drm_gem_shmem_swap_in_pages_locked(struct drm_gem_shmem_object *shmem);
+int drm_gem_shmem_swap_in_locked(struct drm_gem_shmem_object *shmem);
+
+void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem);
+
 bool drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem);
@@ -262,6 +325,38 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
 	return drm_gem_shmem_mmap(shmem, vma);
 }
 
+/**
+ * struct drm_gem_shmem_shrinker - Generic memory shrinker for shmem GEMs
+ */
+struct drm_gem_shmem_shrinker {
+	/** @base: Shrinker for purging shmem GEM objects */
+	struct shrinker base;
+
+	/** @lock: Protects @lru_* */
+	struct mutex lock;
+
+	/** @lru_purgeable: List of shmem GEM objects available for purging */
+	struct list_head lru_purgeable;
+
+	/** @lru_active: List of active shmem GEM objects */
+	struct list_head lru_active;
+
+	/** @lru_evictable: List of shmem GEM objects that can be evicted */
+	struct list_head lru_evictable;
+
+	/** @lru_evicted: List of evicted shmem GEM objects */
+	struct list_head lru_evicted;
+
+	/** @dev: DRM device that uses this shrinker */
+	struct drm_device *dev;
+
+	/** @shrinkable_count: Count of shmem GEM pages to be purged and evicted */
+	u64 shrinkable_count;
+};
+
+int drm_gem_shmem_shrinker_register(struct drm_device *dev);
+void drm_gem_shmem_shrinker_unregister(struct drm_device *dev);
+
 /*
  * Driver ops
  */
-- 
2.35.1