Introduce common drm-shmem shrinker for DRM drivers.

To start using drm-shmem shrinker drivers should do the following:

1. Implement evict() callback of GEM object where driver should check
   whether object is purgeable or evictable using drm-shmem helpers and
   perform the shrinking action

2. Initialize drm-shmem internals using drmm_gem_shmem_init(drm_device),
   which will register drm-shmem shrinker

3. Implement madvise IOCTL that will use drm_gem_shmem_madvise()

Signed-off-by: Daniel Almeida <daniel.alme...@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c        | 351 +++++++++++++++++-
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
 include/drm/drm_device.h                      |  10 +-
 include/drm/drm_gem_shmem_helper.h            |  52 ++-
 4 files changed, 402 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 48df4e87da26..a02377a5131b 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -20,6 +20,7 @@
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_prime.h>
 #include <drm/drm_print.h>
 
@@ -88,8 +89,6 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, 
bool private)
        if (ret)
                goto err_release;
 
-       INIT_LIST_HEAD(&shmem->madv_list);
-
        if (!private) {
                /*
                 * Our buffers are kept pinned, so allocating them
@@ -128,6 +127,57 @@ 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_resv_assert_held(struct drm_gem_shmem_object *shmem)
+{
+       /*
+        * Destroying the object is a special case.. drm_gem_shmem_free()
+        * calls many things that WARN_ON if the obj lock is not held.  But
+        * acquiring the obj lock in drm_gem_shmem_free() can cause a locking
+        * order inversion between reservation_ww_class_mutex and fs_reclaim.
+        *
+        * This deadlock is not actually possible, because no one should
+        * be already holding the lock when drm_gem_shmem_free() is called.
+        * Unfortunately lockdep is not aware of this detail.  So when the
+        * refcount drops to zero, we pretend it is already locked.
+        */
+       if (kref_read(&shmem->base.refcount))
+               dma_resv_assert_held(shmem->base.resv);
+}
+
+static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
+{
+       dma_resv_assert_held(shmem->base.resv);
+
+       return (shmem->madv >= 0) && shmem->base.funcs->evict &&
+               shmem->pages_use_count && !shmem->pages_pin_count &&
+               !shmem->base.dma_buf && !shmem->base.import_attach &&
+               shmem->sgt && !shmem->evicted;
+}
+
+static void
+drm_gem_shmem_update_pages_state(struct drm_gem_shmem_object *shmem)
+{
+       struct drm_gem_object *obj = &shmem->base;
+       struct drm_gem_shmem *shmem_mm = obj->dev->shmem_mm;
+       struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+
+       drm_gem_shmem_resv_assert_held(shmem);
+
+       if (!shmem_shrinker || obj->import_attach)
+               return;
+
+       if (shmem->madv < 0)
+               drm_gem_lru_remove(&shmem->base);
+       else if (drm_gem_shmem_is_evictable(shmem) || 
drm_gem_shmem_is_purgeable(shmem))
+               drm_gem_lru_move_tail(&shmem_shrinker->lru_evictable, 
&shmem->base);
+       else if (shmem->evicted)
+               drm_gem_lru_move_tail(&shmem_shrinker->lru_evicted, 
&shmem->base);
+       else if (!shmem->pages)
+               drm_gem_lru_remove(&shmem->base);
+       else
+               drm_gem_lru_move_tail(&shmem_shrinker->lru_pinned, 
&shmem->base);
+}
+
 /**
  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
  * @shmem: shmem GEM object to free
@@ -142,7 +192,8 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
        if (obj->import_attach) {
                drm_prime_gem_destroy(obj, shmem->sgt);
        } else {
-               dma_resv_lock(shmem->base.resv, NULL);
+               /* take out shmem GEM object from the memory shrinker */
+               drm_gem_shmem_madvise(shmem, -1);
 
                drm_WARN_ON(obj->dev, shmem->vmap_use_count);
 
@@ -152,12 +203,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object 
*shmem)
                        sg_free_table(shmem->sgt);
                        kfree(shmem->sgt);
                }
-               if (shmem->pages)
+               if (shmem->pages_use_count)
                        drm_gem_shmem_put_pages(shmem);
 
                drm_WARN_ON(obj->dev, shmem->pages_use_count);
-
-               dma_resv_unlock(shmem->base.resv);
        }
 
        drm_gem_object_release(obj);
@@ -178,6 +227,11 @@ drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object 
*shmem)
                return -ENOMEM;
        }
 
+       if (shmem->pages) {
+               drm_WARN_ON(obj->dev, !shmem->evicted);
+               return 0;
+       }
+
        if (drm_WARN_ON(obj->dev, !shmem->pages_use_count))
                return -EINVAL;
 
@@ -212,13 +266,20 @@ static int drm_gem_shmem_get_pages(struct 
drm_gem_shmem_object *shmem)
        if (shmem->madv < 0)
                return -ENOMEM;
 
-       if (shmem->pages_use_count++ > 0)
+       if (shmem->pages_use_count++ > 0) {
+               err = drm_gem_shmem_swapin(shmem);
+               if (err)
+                       goto err_zero_use;
+
                return 0;
+       }
 
        err = drm_gem_shmem_acquire_pages(shmem);
        if (err)
                goto err_zero_use;
 
+       drm_gem_shmem_update_pages_state(shmem);
+
        return 0;
 
 err_zero_use:
@@ -232,7 +293,12 @@ drm_gem_shmem_release_pages(struct drm_gem_shmem_object 
*shmem)
 {
        struct drm_gem_object *obj = &shmem->base;
 
-       dma_resv_assert_held(shmem->base.resv);
+       drm_gem_shmem_resv_assert_held(shmem);
+
+       if (!shmem->pages) {
+               drm_WARN_ON(obj->dev, !shmem->evicted && shmem->madv >= 0);
+               return;
+       }
 
 #ifdef CONFIG_X86
        if (shmem->map_wc)
@@ -255,7 +321,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object 
*shmem)
 {
        struct drm_gem_object *obj = &shmem->base;
 
-       dma_resv_assert_held(shmem->base.resv);
+       drm_gem_shmem_resv_assert_held(shmem);
 
        if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
                return;
@@ -264,6 +330,8 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object 
*shmem)
                return;
 
        drm_gem_shmem_release_pages(shmem);
+
+       drm_gem_shmem_update_pages_state(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
 
@@ -475,13 +543,15 @@ drm_gem_shmem_create_with_handle(struct drm_file 
*file_priv,
  */
 int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
 {
-       dma_resv_assert_held(shmem->base.resv);
+       drm_gem_shmem_resv_assert_held(shmem);
 
        if (shmem->madv >= 0)
                shmem->madv = madv;
 
        madv = shmem->madv;
 
+       drm_gem_shmem_update_pages_state(shmem);
+
        return (madv >= 0);
 }
 EXPORT_SYMBOL(drm_gem_shmem_madvise);
@@ -493,6 +563,9 @@ static void drm_gem_shmem_unpin_pages(struct 
drm_gem_shmem_object *shmem)
 
        dma_resv_assert_held(shmem->base.resv);
 
+       if (shmem->evicted)
+               return;
+
        dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
        drm_gem_shmem_release_pages(shmem);
        drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
@@ -521,9 +594,60 @@ void drm_gem_shmem_purge(struct drm_gem_shmem_object 
*shmem)
        invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, 
(loff_t)-1);
 
        shmem->madv = -1;
+       shmem->evicted = false;
+       drm_gem_shmem_update_pages_state(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_purge);
 
+/**
+ * drm_gem_shmem_swapin() - Moves shmem GEM back to memory and enables
+ *                          hardware access to the 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_swapin(struct drm_gem_shmem_object *shmem)
+{
+       struct drm_gem_object *obj = &shmem->base;
+       struct sg_table *sgt;
+       int err;
+
+       dma_resv_assert_held(shmem->base.resv);
+
+       if (shmem->evicted) {
+               err = drm_gem_shmem_acquire_pages(shmem);
+               if (err)
+                       return err;
+
+               sgt = drm_gem_shmem_get_sg_table(shmem);
+               if (IS_ERR(sgt))
+                       return PTR_ERR(sgt);
+
+               err = dma_map_sgtable(obj->dev->dev, sgt,
+                                     DMA_BIDIRECTIONAL, 0);
+               if (err) {
+                       sg_free_table(sgt);
+                       kfree(sgt);
+                       return err;
+               }
+
+               shmem->sgt = sgt;
+               shmem->evicted = false;
+
+               drm_gem_shmem_update_pages_state(shmem);
+       }
+
+       if (!shmem->pages)
+               return -ENOMEM;
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_swapin);
+
 /**
  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
  * @file: DRM file structure to create the dumb buffer for
@@ -570,22 +694,33 @@ 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_unpinned;
+       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 ||
-           drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
-           shmem->madv < 0) {
+       /* Sanity-check that we have the pages pointer when it should present */
+       pages_unpinned = (shmem->evicted || shmem->madv < 0 || 
!shmem->pages_use_count);
+       drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
+
+       if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
                ret = VM_FAULT_SIGBUS;
        } else {
+               err = drm_gem_shmem_swapin(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;
@@ -608,6 +743,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct 
*vma)
        if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
                shmem->pages_use_count++;
 
+       drm_gem_shmem_update_pages_state(shmem);
        dma_resv_unlock(shmem->base.resv);
 
        drm_gem_vm_open(vma);
@@ -689,7 +825,9 @@ void drm_gem_shmem_print_info(const struct 
drm_gem_shmem_object *shmem,
 
        drm_printf_indent(p, indent, "pages_use_count=%u\n", 
shmem->pages_use_count);
        drm_printf_indent(p, indent, "vmap_use_count=%u\n", 
shmem->vmap_use_count);
+       drm_printf_indent(p, indent, "evicted=%d\n", shmem->evicted);
        drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
+       drm_printf_indent(p, indent, "madv=%d\n", shmem->madv);
 }
 EXPORT_SYMBOL(drm_gem_shmem_print_info);
 
@@ -744,6 +882,8 @@ static struct sg_table 
*drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 
        shmem->sgt = sgt;
 
+       drm_gem_shmem_update_pages_state(shmem);
+
        return sgt;
 
 err_free_sgt:
@@ -820,6 +960,191 @@ 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_gem_shmem_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 *shmem_shrinker =
+                                       to_drm_gem_shmem_shrinker(shrinker);
+       unsigned long count = shmem_shrinker->lru_evictable.count;
+
+       if (count >= SHRINK_EMPTY)
+               return SHRINK_EMPTY - 1;
+
+       return count ?: SHRINK_EMPTY;
+}
+
+void drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem)
+{
+       struct drm_gem_object *obj = &shmem->base;
+
+       drm_WARN_ON(obj->dev, !drm_gem_shmem_is_evictable(shmem));
+       drm_WARN_ON(obj->dev, shmem->evicted);
+
+       drm_gem_shmem_unpin_pages(shmem);
+
+       shmem->evicted = true;
+       drm_gem_shmem_update_pages_state(shmem);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_evict);
+
+static bool drm_gem_shmem_shrinker_evict(struct drm_gem_object *obj)
+{
+       struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+       int err;
+
+       if (!drm_gem_shmem_is_evictable(shmem) ||
+           get_nr_swap_pages() < obj->size >> PAGE_SHIFT)
+               return false;
+
+       err = drm_gem_evict(obj);
+       if (err)
+               return false;
+
+       return true;
+}
+
+static bool drm_gem_shmem_shrinker_purge(struct drm_gem_object *obj)
+{
+       struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+       int err;
+
+       if (!drm_gem_shmem_is_purgeable(shmem))
+               return false;
+
+       err = drm_gem_evict(obj);
+       if (err)
+               return false;
+
+       return true;
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
+                                   struct shrink_control *sc)
+{
+       struct drm_gem_shmem_shrinker *shmem_shrinker;
+       unsigned long nr_to_scan = sc->nr_to_scan;
+       unsigned long remaining = 0;
+       unsigned long freed = 0;
+
+       shmem_shrinker = to_drm_gem_shmem_shrinker(shrinker);
+
+       /* purge as many objects as we can */
+       freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
+                                 nr_to_scan, &remaining,
+                                 drm_gem_shmem_shrinker_purge);
+
+       /* evict as many objects as we can */
+       if (freed < nr_to_scan)
+               freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
+                                         nr_to_scan - freed, &remaining,
+                                         drm_gem_shmem_shrinker_evict);
+
+       return (freed > 0 && remaining > 0) ? freed : SHRINK_STOP;
+}
+
+static int drm_gem_shmem_shrinker_init(struct drm_gem_shmem *shmem_mm,
+                                      const char *shrinker_name)
+{
+       struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+       int err;
+
+       shmem_shrinker->base.count_objects = 
drm_gem_shmem_shrinker_count_objects;
+       shmem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
+       shmem_shrinker->base.seeks = DEFAULT_SEEKS;
+
+       mutex_init(&shmem_shrinker->lock);
+       drm_gem_lru_init(&shmem_shrinker->lru_evictable, &shmem_shrinker->lock);
+       drm_gem_lru_init(&shmem_shrinker->lru_evicted, &shmem_shrinker->lock);
+       drm_gem_lru_init(&shmem_shrinker->lru_pinned, &shmem_shrinker->lock);
+
+       err = register_shrinker(&shmem_shrinker->base, shrinker_name);
+       if (err) {
+               mutex_destroy(&shmem_shrinker->lock);
+               return err;
+       }
+
+       return 0;
+}
+
+static void drm_gem_shmem_shrinker_release(struct drm_device *dev,
+                                          struct drm_gem_shmem *shmem_mm)
+{
+       struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+
+       unregister_shrinker(&shmem_shrinker->base);
+       drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evictable.list));
+       drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evicted.list));
+       drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_pinned.list));
+       mutex_destroy(&shmem_shrinker->lock);
+}
+
+static int drm_gem_shmem_init(struct drm_device *dev)
+{
+       int err;
+
+       if (drm_WARN_ON(dev, dev->shmem_mm))
+               return -EBUSY;
+
+       dev->shmem_mm = kzalloc(sizeof(*dev->shmem_mm), GFP_KERNEL);
+       if (!dev->shmem_mm)
+               return -ENOMEM;
+
+       err = drm_gem_shmem_shrinker_init(dev->shmem_mm, dev->unique);
+       if (err)
+               goto free_gem_shmem;
+
+       return 0;
+
+free_gem_shmem:
+       kfree(dev->shmem_mm);
+       dev->shmem_mm = NULL;
+
+       return err;
+}
+
+static void drm_gem_shmem_release(struct drm_device *dev, void *ptr)
+{
+       struct drm_gem_shmem *shmem_mm = dev->shmem_mm;
+
+       drm_gem_shmem_shrinker_release(dev, shmem_mm);
+       dev->shmem_mm = NULL;
+       kfree(shmem_mm);
+}
+
+/**
+ * drmm_gem_shmem_init() - Initialize drm-shmem internals
+ * @dev: DRM device
+ *
+ * Cleanup is automatically managed as part of DRM device releasing.
+ * Calling this function multiple times will result in a error.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drmm_gem_shmem_init(struct drm_device *dev)
+{
+       int err;
+
+       err = drm_gem_shmem_init(dev);
+       if (err)
+               return err;
+
+       err = drmm_add_action_or_reset(dev, drm_gem_shmem_release, NULL);
+       if (err)
+               return err;
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(drmm_gem_shmem_init);
+
 MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
 MODULE_IMPORT_NS(DMA_BUF);
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c 
b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index 6a71a2555f85..865a989d67c8 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -15,6 +15,13 @@
 #include "panfrost_gem.h"
 #include "panfrost_mmu.h"
 
+static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
+{
+       return (shmem->madv > 0) &&
+               !shmem->pages_pin_count && shmem->sgt &&
+               !shmem->base.dma_buf && !shmem->base.import_attach;
+}
+
 static unsigned long
 panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control 
*sc)
 {
@@ -27,7 +34,7 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct 
shrink_control *sc
                return 0;
 
        list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
-               if (drm_gem_shmem_is_purgeable(shmem))
+               if (panfrost_gem_shmem_is_purgeable(shmem))
                        count += shmem->base.size >> PAGE_SHIFT;
        }
 
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 7cf4afae2e79..a978f0cb5e84 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;
 
@@ -290,8 +291,13 @@ struct drm_device {
        /** @vma_offset_manager: GEM information */
        struct drm_vma_offset_manager *vma_offset_manager;
 
-       /** @vram_mm: VRAM MM memory manager */
-       struct drm_vram_mm *vram_mm;
+       union {
+               /** @vram_mm: VRAM MM memory manager */
+               struct drm_vram_mm *vram_mm;
+
+               /** @shmem_mm: SHMEM GEM memory manager */
+               struct drm_gem_shmem *shmem_mm;
+       };
 
        /**
         * @switch_power_state:
diff --git a/include/drm/drm_gem_shmem_helper.h 
b/include/drm/drm_gem_shmem_helper.h
index 7d823c9fc480..e99f1715514b 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>
@@ -13,6 +14,7 @@
 #include <drm/drm_prime.h>
 
 struct dma_buf_attachment;
+struct drm_device;
 struct drm_mode_create_dumb;
 struct drm_printer;
 struct sg_table;
@@ -52,8 +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;
 
@@ -100,6 +102,12 @@ struct drm_gem_shmem_object {
         * @map_wc: map object write-combined (instead of using shmem defaults).
         */
        bool map_wc : 1;
+
+       /**
+        * @evicted: True if shmem pages are evicted by the memory shrinker.
+        * Used internally by memory shrinker.
+        */
+       bool evicted : 1;
 };
 
 #define to_drm_gem_shmem_obj(obj) \
@@ -121,11 +129,17 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object 
*shmem, int madv);
 
 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;
+       dma_resv_assert_held(shmem->base.resv);
+
+       return (shmem->madv > 0) && shmem->base.funcs->evict &&
+               shmem->pages_use_count && !shmem->pages_pin_count &&
+               !shmem->base.dma_buf && !shmem->base.import_attach &&
+               (shmem->sgt || shmem->evicted);
 }
 
+int drm_gem_shmem_swapin(struct drm_gem_shmem_object *shmem);
+
+void drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object 
*shmem);
@@ -269,6 +283,36 @@ 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 - Memory shrinker of GEM shmem memory manager
+ */
+struct drm_gem_shmem_shrinker {
+       /** @base: Shrinker for purging shmem GEM objects */
+       struct shrinker base;
+
+       /** @lock: Protects @lru_* */
+       struct mutex lock;
+
+       /** @lru_pinned: List of pinned shmem GEM objects */
+       struct drm_gem_lru lru_pinned;
+
+       /** @lru_evictable: List of shmem GEM objects to be evicted */
+       struct drm_gem_lru lru_evictable;
+
+       /** @lru_evicted: List of evicted shmem GEM objects */
+       struct drm_gem_lru lru_evicted;
+};
+
+/**
+ * struct drm_gem_shmem - GEM shmem memory manager
+ */
+struct drm_gem_shmem {
+       /** @shrinker: GEM shmem shrinker */
+       struct drm_gem_shmem_shrinker shrinker;
+};
+
+int drmm_gem_shmem_init(struct drm_device *dev);
+
 /*
  * Driver ops
  */
-- 
2.39.2

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