Virtualization - Jun 2022 - [PATCH v6 17/22] drm/shmem-helper: Add generic memory shrinker

On Fri, 27 May 2022 at 01:55, Dmitry Osipenko
<dmitry.osipenko at collabora.com> wrote:
>
> Introduce a common DRM SHMEM shrinker framework that allows to reduce
> code duplication among DRM drivers by replacing theirs custom shrinker
> implementations with the generic shrinker.
>
> In order to start using DRM SHMEM shrinker drivers should:
>
> 1. Implement new evict() shmem object callback.
> 2. Register shrinker using drm_gem_shmem_shrinker_register(drm_device).
> 3. Use drm_gem_shmem_set_purgeable(shmem) and alike API functions to
>    activate shrinking of shmem GEMs.
>
> This patch is based on a ideas borrowed from Rob's Clark MSM shrinker,
> Thomas' Zimmermann variant of SHMEM shrinker and Intel's i915
shrinker.
>
> Signed-off-by: Daniel Almeida <daniel.almeida at collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko at collabora.com>
So I guess I get a price for being blind since forever, because this
thing existed since at least 2013. I just stumbled over
llist_lru.[hc], a purpose built list helper for shrinkers. I think we
should try to adopt that so that our gpu shrinkers look more like
shrinkers for everything else.

Apologies for this, since I fear this might cause a bit of churn.
Hopefully it's all contained to the list manipulation code in shmem
helpers, I don't think this should leak any further.
-Daniel
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c        | 540 ++++++++++++++++--
>  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
>  drivers/gpu/drm/virtio/virtgpu_drv.h          |   3 +
>  include/drm/drm_device.h                      |   4 +
>  include/drm/drm_gem_shmem_helper.h            |  87 ++-
>  5 files changed, 594 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 555fe212bd98..4cd0b5913492 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -126,6 +126,42 @@ struct drm_gem_shmem_object
*drm_gem_shmem_create(struct drm_device *dev, size_t
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>
> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +       return (shmem->madv >= 0) && shmem->evict
&&
> +               shmem->eviction_enabled &&
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_shrinker *gem_shrinker =
obj->dev->shmem_shrinker;
> +
> +       dma_resv_assert_held(shmem->base.resv);
> +
> +       if (!gem_shrinker || obj->import_attach)
> +               return;
> +
> +       mutex_lock(&gem_shrinker->lock);
> +
> +       if (drm_gem_shmem_is_evictable(shmem) ||
> +           drm_gem_shmem_is_purgeable(shmem))
> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evictable);
> +       else if (shmem->madv < 0)
> +               list_del_init(&shmem->madv_list);
> +       else if (shmem->evicted)
> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evicted);
> +       else if (!shmem->pages)
> +               list_del_init(&shmem->madv_list);
> +       else
> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_pinned);
> +
> +       mutex_unlock(&gem_shrinker->lock);
> +}
> +
>  /**
>   * drm_gem_shmem_free - Free resources associated with a shmem GEM object
>   * @shmem: shmem GEM object to free
> @@ -142,6 +178,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object
*shmem)
>         } else {
>                 dma_resv_lock(shmem->base.resv, NULL);
>
> +               /* take out shmem GEM object from the memory shrinker */
> +               drm_gem_shmem_madvise(shmem, -1);
> +
>                 WARN_ON(shmem->vmap_use_count);
>
>                 if (shmem->sgt) {
> @@ -150,7 +189,7 @@ 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);
>
>                 WARN_ON(shmem->pages_use_count);
> @@ -163,18 +202,82 @@ 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(struct drm_gem_shmem_object *shmem)
> +/**
> + * drm_gem_shmem_set_evictable() - Make GEM evictable by memory shrinker
> + * @shmem: shmem GEM object
> + *
> + * Tell memory shrinker that this GEM can be evicted. Initially eviction
is
> + * disabled for all GEMs. If GEM was purged, then -ENOMEM is returned.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_set_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +       dma_resv_lock(shmem->base.resv, NULL);
> +
> +       if (shmem->madv < 0)
> +               return -ENOMEM;
> +
> +       shmem->eviction_enabled = true;
> +
> +       dma_resv_unlock(shmem->base.resv);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_evictable);
> +
> +/**
> + * 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. 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)
> +{
> +       dma_resv_lock(shmem->base.resv, NULL);
> +
> +       if (shmem->madv < 0)
> +               return -ENOMEM;
> +
> +       shmem->purge_enabled = true;
> +
> +       drm_gem_shmem_update_pages_state(shmem);
> +
> +       dma_resv_unlock(shmem->base.resv);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable);
> +
> +static int
> +drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem)
>  {
>         struct drm_gem_object *obj = &shmem->base;
>         struct page **pages;
>
> -       if (shmem->pages_use_count++ > 0)
> +       dma_resv_assert_held(shmem->base.resv);
> +
> +       if (shmem->madv < 0) {
> +               WARN_ON(shmem->pages);
> +               return -ENOMEM;
> +       }
> +
> +       if (shmem->pages) {
> +               WARN_ON(!shmem->evicted);
>                 return 0;
> +       }
> +
> +       if (WARN_ON(!shmem->pages_use_count))
> +               return -EINVAL;
>
>         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);
>         }
>
> @@ -193,6 +296,58 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
>         return 0;
>  }
>
> +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
> +{
> +       int err;
> +
> +       dma_resv_assert_held(shmem->base.resv);
> +
> +       if (shmem->madv < 0)
> +               return -ENOMEM;
> +
> +       if (shmem->pages_use_count++ > 0) {
> +               err = drm_gem_shmem_swap_in(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:
> +       shmem->pages_use_count = 0;
> +
> +       return err;
> +}
> +
> +static void
> +drm_gem_shmem_release_pages(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)
> +               set_pages_array_wb(shmem->pages, obj->size >>
PAGE_SHIFT);
> +#endif
> +
> +       drm_gem_put_pages(obj, shmem->pages,
> +                         shmem->pages_mark_dirty_on_put,
> +                         shmem->pages_mark_accessed_on_put);
> +       shmem->pages = NULL;
> +}
> +
>  /*
>   * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a
shmem GEM object
>   * @shmem: shmem GEM object
> @@ -201,8 +356,6 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
>   */
>  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);
>
>         if (WARN_ON_ONCE(!shmem->pages_use_count))
> @@ -211,15 +364,9 @@ void drm_gem_shmem_put_pages(struct
drm_gem_shmem_object *shmem)
>         if (--shmem->pages_use_count > 0)
>                 return;
>
> -#ifdef CONFIG_X86
> -       if (shmem->map_wc)
> -               set_pages_array_wb(shmem->pages, obj->size >>
PAGE_SHIFT);
> -#endif
> +       drm_gem_shmem_release_pages(shmem);
>
> -       drm_gem_put_pages(obj, shmem->pages,
> -                         shmem->pages_mark_dirty_on_put,
> -                         shmem->pages_mark_accessed_on_put);
> -       shmem->pages = NULL;
> +       drm_gem_shmem_update_pages_state(shmem);
>  }
>  EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>
> @@ -235,11 +382,17 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>   */
>  int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>  {
> +       int ret;
> +
>         dma_resv_assert_held(shmem->base.resv);
>
>         WARN_ON(shmem->base.import_attach);
>
> -       return drm_gem_shmem_get_pages(shmem);
> +       ret = drm_gem_shmem_get_pages(shmem);
> +       if (!ret)
> +               shmem->pages_pin_count++;
> +
> +       return ret;
>  }
>  EXPORT_SYMBOL(drm_gem_shmem_pin);
>
> @@ -257,6 +410,8 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object
*shmem)
>         WARN_ON(shmem->base.import_attach);
>
>         drm_gem_shmem_put_pages(shmem);
> +
> +       shmem->pages_pin_count--;
>  }
>  EXPORT_SYMBOL(drm_gem_shmem_unpin);
>
> @@ -299,7 +454,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
>                         return 0;
>                 }
>
> -               ret = drm_gem_shmem_get_pages(shmem);
> +               ret = drm_gem_shmem_pin(shmem);
>                 if (ret)
>                         goto err_zero_use;
>
> @@ -322,7 +477,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
>
>  err_put_pages:
>         if (!obj->import_attach)
> -               drm_gem_shmem_put_pages(shmem);
> +               drm_gem_shmem_unpin(shmem);
>  err_zero_use:
>         shmem->vmap_use_count = 0;
>
> @@ -359,7 +514,7 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object
*shmem,
>                         return;
>
>                 vunmap(shmem->vaddr);
> -               drm_gem_shmem_put_pages(shmem);
> +               drm_gem_shmem_unpin(shmem);
>         }
>
>         shmem->vaddr = NULL;
> @@ -403,41 +558,77 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object
*shmem, int madv)
>
>         madv = shmem->madv;
>
> +       drm_gem_shmem_update_pages_state(shmem);
> +
>         return (madv >= 0);
>  }
>  EXPORT_SYMBOL(drm_gem_shmem_madvise);
>
> -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
> +/**
> + * drm_gem_shmem_swap_in() - 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_swap_in(struct drm_gem_shmem_object *shmem)
>  {
>         struct drm_gem_object *obj = &shmem->base;
> -       struct drm_device *dev = obj->dev;
> +       struct sg_table *sgt;
> +       int err;
>
>         dma_resv_assert_held(shmem->base.resv);
>
> -       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> +       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;
> +               }
>
> -       dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL,
0);
> -       sg_free_table(shmem->sgt);
> -       kfree(shmem->sgt);
> -       shmem->sgt = NULL;
> +               shmem->sgt = sgt;
> +               shmem->evicted = false;
>
> -       drm_gem_shmem_put_pages(shmem);
> +               drm_gem_shmem_update_pages_state(shmem);
> +       }
>
> -       shmem->madv = -1;
> +       if (!shmem->pages)
> +               return -ENOMEM;
>
> -       drm_vma_node_unmap(&obj->vma_node,
dev->anon_inode->i_mapping);
> -       drm_gem_free_mmap_offset(obj);
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in);
>
> -       /* Our goal here is to return as much of the memory as
> -        * is possible back to the system as we are called from OOM.
> -        * To do this we must instruct the shmfs to drop all of its
> -        * backing pages, *now*.
> -        */
> -       shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
> +static void drm_gem_shmem_unpin_pages(struct drm_gem_shmem_object *shmem)
> +{
> +       struct drm_gem_object *obj = &shmem->base;
> +       struct drm_device *dev = obj->dev;
>
> -       invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0,
(loff_t)-1);
> +       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);
> +
> +       sg_free_table(shmem->sgt);
> +       kfree(shmem->sgt);
> +       shmem->sgt = NULL;
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_purge);
>
>  /**
>   * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
> @@ -488,22 +679,33 @@ 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 ||
> -           WARN_ON_ONCE(!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);
> +       WARN_ON_ONCE(!shmem->pages ^ pages_unpinned);
> +
> +       if (page_offset >= num_pages || (!shmem->pages &&
!shmem->evicted)) {
>                 ret = VM_FAULT_SIGBUS;
>         } else {
> +               err = drm_gem_shmem_swap_in(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;
> @@ -513,13 +715,15 @@ 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);
>
>         dma_resv_lock(shmem->base.resv, NULL);
> -       ret = drm_gem_shmem_get_pages(shmem);
> -       WARN_ON_ONCE(ret != 0);
> +
> +       if (drm_gem_shmem_get_pages(shmem))
> +               shmem->pages_use_count++;
> +
> +       drm_gem_shmem_update_pages_state(shmem);
>         dma_resv_unlock(shmem->base.resv);
>
>         drm_gem_vm_open(vma);
> @@ -583,6 +787,8 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
>  void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>                               struct drm_printer *p, unsigned int indent)
>  {
> +       drm_printf_indent(p, indent, "eviction_enabled=%d\n",
shmem->eviction_enabled);
> +       drm_printf_indent(p, indent, "purge_enabled=%d\n",
shmem->purge_enabled);
>         drm_printf_indent(p, indent, "pages_use_count=%u\n",
shmem->pages_use_count);
>
>         if (shmem->base.import_attach)
> @@ -592,7 +798,9 @@ void drm_gem_shmem_print_info(const struct
drm_gem_shmem_object *shmem,
>                 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);
>
> @@ -667,6 +875,8 @@ 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);
> +
>         dma_resv_unlock(shmem->base.resv);
>
>         return sgt;
> @@ -717,6 +927,250 @@ 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);
> +       struct drm_gem_shmem_object *shmem;
> +       unsigned long count = 0;
> +
> +       if (!mutex_trylock(&gem_shrinker->lock))
> +               return 0;
> +
> +       list_for_each_entry(shmem, &gem_shrinker->lru_evictable,
madv_list) {
> +               count += shmem->base.size;
> +
> +               if (count >= SHRINK_EMPTY)
> +                       break;
> +       }
> +
> +       mutex_unlock(&gem_shrinker->lock);
> +
> +       if (count >= SHRINK_EMPTY)
> +               return SHRINK_EMPTY - 1;
> +
> +       return count ?: SHRINK_EMPTY;
> +}
> +
> +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem)
> +{
> +       WARN_ON(!drm_gem_shmem_is_evictable(shmem));
> +       WARN_ON(shmem->evicted);
> +
> +       drm_gem_shmem_unpin_pages(shmem);
> +
> +       shmem->evicted = true;
> +       drm_gem_shmem_update_pages_state(shmem);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict);
> +
> +int drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
> +{
> +       struct drm_gem_object *obj = &shmem->base;
> +
> +       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> +
> +       drm_gem_shmem_unpin_pages(shmem);
> +       drm_gem_free_mmap_offset(obj);
> +
> +       /* Our goal here is to return as much of the memory as
> +        * is possible back to the system as we are called from OOM.
> +        * To do this we must instruct the shmfs to drop all of its
> +        * backing pages, *now*.
> +        */
> +       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;
> +       shmem->evicted = false;
> +       drm_gem_shmem_update_pages_state(shmem);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
> +
> +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;
> +       size_t page_count;
> +       int err;
> +
> +       INIT_LIST_HEAD(&still_in_list);
> +
> +       mutex_lock(&gem_shrinker->lock);
> +
> +       while (freed < nr_to_scan) {
> +               shmem =
list_first_entry_or_null(&gem_shrinker->lru_evictable,
> +                                                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) {
> +                       if (!drm_gem_shmem_is_evictable(shmem) ||
> +                           get_nr_swap_pages() < page_count)
> +                               continue;
> +               } else {
> +                       if (!drm_gem_shmem_is_purgeable(shmem))
> +                               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 importing/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,
DMA_RESV_USAGE_WRITE))
> +                       goto object_name_unlock;
> +
> +               /* re-check whether eviction status hasn't changed */
> +               if (!drm_gem_shmem_is_evictable(shmem) &&
> +                   !drm_gem_shmem_is_purgeable(shmem))
> +                       goto object_name_unlock;
> +
> +               err = shmem->evict(shmem);
> +               if (!err)
> +                       freed += obj->size >> PAGE_SHIFT;
> +
> +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,
&gem_shrinker->lru_evictable);
> +
> +       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);
> +
> +       /* evict as many objects as we can */
> +       if (freed < nr_to_scan)
> +               freed += drm_gem_shmem_shrinker_run_objects_scan(shrinker,
> +                                                                nr_to_scan
- freed,
> +                                                               
&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_evictable);
> +       INIT_LIST_HEAD(&gem_shrinker->lru_evicted);
> +       INIT_LIST_HEAD(&gem_shrinker->lru_pinned);
> +       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_evictable));
> +               WARN_ON(!list_empty(&gem_shrinker->lru_evicted));
> +               WARN_ON(!list_empty(&gem_shrinker->lru_pinned));
> +               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/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> index a4bedfeb2ec4..7cc32556f908 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/drivers/gpu/drm/virtio/virtgpu_drv.h
b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index b2d93cb12ebf..81bacc7e1873 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -89,6 +89,7 @@ struct virtio_gpu_object {
>         uint32_t hw_res_handle;
>         bool dumb;
>         bool created;
> +       bool detached;
>         bool host3d_blob, guest_blob;
>         uint32_t blob_mem, blob_flags;
>
> @@ -453,6 +454,8 @@ int virtio_gpu_object_create(struct virtio_gpu_device
*vgdev,
>
>  bool virtio_gpu_is_shmem(struct virtio_gpu_object *bo);
>
> +int virtio_gpu_reattach_shmem_object(struct virtio_gpu_object *bo);
> +
>  int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
>                                uint32_t *resid);
>  /* virtgpu_prime.c */
> 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_shmem_helper.h
b/include/drm/drm_gem_shmem_helper.h
> index 9a8983ee8abe..62c640678a91 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>
> @@ -15,6 +16,7 @@
>  struct dma_buf_attachment;
>  struct drm_mode_create_dumb;
>  struct drm_printer;
> +struct drm_device;
>  struct sg_table;
>
>  /**
> @@ -39,12 +41,21 @@ struct drm_gem_shmem_object {
>          */
>         unsigned int pages_use_count;
>
> +       /**
> +        * @pages_pin_count:
> +        *
> +        * Reference count on the pinned pages table.
> +        * The pages can be evicted by memory shrinker
> +        * when the count reaches zero.
> +        */
> +       unsigned int pages_pin_count;
> +
>         /**
>          * @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 +102,39 @@ struct drm_gem_shmem_object {
>          * @map_wc: map object write-combined (instead of using shmem
defaults).
>          */
>         bool map_wc;
> +
> +       /**
> +        * @eviction_enabled:
> +        *
> +        * The shmem pages can be evicted only if @eviction_enabled is set
to true.
> +        * Used internally by memory shrinker.
> +        */
> +       bool eviction_enabled;
> +
> +       /**
> +        * @purge_enabled:
> +        *
> +        * The shmem pages can be purged only if @purge_enabled is set to
true.
> +        * Used internally by memory shrinker.
> +        */
> +       bool purge_enabled;
> +
> +       /**
> +        * @evicted: True if shmem pages are evicted by the memory
shrinker.
> +        * Used internally by memory shrinker.
> +        */
> +       bool evicted;
> +
> +       /**
> +        * @evict:
> +        *
> +        * Invoked by shmem shrinker before evicting shmem GEM from memory.
> +        * GEM's DMA reservation is kept locked by the shrinker. This
is
> +        * optional callback that should be specified by drivers.
> +        *
> +        * Returns 0 on success, or -errno on error.
> +        */
> +       int (*evict)(struct drm_gem_shmem_object *shmem);
>  };
>
>  #define to_drm_gem_shmem_obj(obj) \
> @@ -110,14 +154,21 @@ 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_evictable(struct drm_gem_shmem_object *shmem);
> +
>  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->evict
&&
> +               shmem->purge_enabled &&
shmem->pages_use_count &&
> +               !shmem->pages_pin_count &&
!shmem->base.dma_buf &&
> +               !shmem->base.import_attach && (shmem->sgt ||
shmem->evicted);
>  }
>
> -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_swap_in(struct drm_gem_shmem_object *shmem);
> +
> +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem);
> +int 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);
>  struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object
*shmem);
> @@ -260,6 +311,32 @@ 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_pinned: List of pinned shmem GEM objects */
> +       struct list_head lru_pinned;
> +
> +       /** @lru_evictable: List of shmem GEM objects to 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;
> +};
> +
> +int drm_gem_shmem_shrinker_register(struct drm_device *dev);
> +void drm_gem_shmem_shrinker_unregister(struct drm_device *dev);
> +
>  /*
>   * Driver ops
>   */
> --
> 2.35.3
>

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

On Sun, Jun 5, 2022 at 9:47 AM Daniel Vetter <daniel at ffwll.ch>
wrote:
>
> On Fri, 27 May 2022 at 01:55, Dmitry Osipenko
> <dmitry.osipenko at collabora.com> wrote:
> >
> > Introduce a common DRM SHMEM shrinker framework that allows to reduce
> > code duplication among DRM drivers by replacing theirs custom shrinker
> > implementations with the generic shrinker.
> >
> > In order to start using DRM SHMEM shrinker drivers should:
> >
> > 1. Implement new evict() shmem object callback.
> > 2. Register shrinker using
drm_gem_shmem_shrinker_register(drm_device).
> > 3. Use drm_gem_shmem_set_purgeable(shmem) and alike API functions to
> >    activate shrinking of shmem GEMs.
> >
> > This patch is based on a ideas borrowed from Rob's Clark MSM
shrinker,
> > Thomas' Zimmermann variant of SHMEM shrinker and Intel's i915
shrinker.
> >
> > Signed-off-by: Daniel Almeida <daniel.almeida at collabora.com>
> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko at
collabora.com>
>
> So I guess I get a price for being blind since forever, because this
> thing existed since at least 2013. I just stumbled over
> llist_lru.[hc], a purpose built list helper for shrinkers. I think we
> should try to adopt that so that our gpu shrinkers look more like
> shrinkers for everything else.
followup from a bit of irc discussion w/ danvet about list_lru:

* It seems to be missing a way to bail out of iteration before
  nr_to_scan is hit.. which is going to be inconvenient if you
  want to allow active bos on the LRU but bail scanning once
  you encounter the first one.

* Not sure if the numa node awareness is super useful for GEM
  bos

First issue is perhaps not too hard to fix.  But maybe a better
idea is a drm_gem_lru helper type thing which is more tailored
to GEM buffers?

BR,
-R
> Apologies for this, since I fear this might cause a bit of churn.
> Hopefully it's all contained to the list manipulation code in shmem
> helpers, I don't think this should leak any further.
> -Daniel
>
> > ---
> >  drivers/gpu/drm/drm_gem_shmem_helper.c        | 540
++++++++++++++++--
> >  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
> >  drivers/gpu/drm/virtio/virtgpu_drv.h          |   3 +
> >  include/drm/drm_device.h                      |   4 +
> >  include/drm/drm_gem_shmem_helper.h            |  87 ++-
> >  5 files changed, 594 insertions(+), 49 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
> > index 555fe212bd98..4cd0b5913492 100644
> > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> > @@ -126,6 +126,42 @@ struct drm_gem_shmem_object
*drm_gem_shmem_create(struct drm_device *dev, size_t
> >  }
> >  EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
> >
> > +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object
*shmem)
> > +{
> > +       return (shmem->madv >= 0) && shmem->evict
&&
> > +               shmem->eviction_enabled &&
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_shrinker *gem_shrinker =
obj->dev->shmem_shrinker;
> > +
> > +       dma_resv_assert_held(shmem->base.resv);
> > +
> > +       if (!gem_shrinker || obj->import_attach)
> > +               return;
> > +
> > +       mutex_lock(&gem_shrinker->lock);
> > +
> > +       if (drm_gem_shmem_is_evictable(shmem) ||
> > +           drm_gem_shmem_is_purgeable(shmem))
> > +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evictable);
> > +       else if (shmem->madv < 0)
> > +               list_del_init(&shmem->madv_list);
> > +       else if (shmem->evicted)
> > +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evicted);
> > +       else if (!shmem->pages)
> > +               list_del_init(&shmem->madv_list);
> > +       else
> > +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_pinned);
> > +
> > +       mutex_unlock(&gem_shrinker->lock);
> > +}
> > +
> >  /**
> >   * drm_gem_shmem_free - Free resources associated with a shmem GEM
object
> >   * @shmem: shmem GEM object to free
> > @@ -142,6 +178,9 @@ void drm_gem_shmem_free(struct
drm_gem_shmem_object *shmem)
> >         } else {
> >                 dma_resv_lock(shmem->base.resv, NULL);
> >
> > +               /* take out shmem GEM object from the memory shrinker
*/
> > +               drm_gem_shmem_madvise(shmem, -1);
> > +
> >                 WARN_ON(shmem->vmap_use_count);
> >
> >                 if (shmem->sgt) {
> > @@ -150,7 +189,7 @@ 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);
> >
> >                 WARN_ON(shmem->pages_use_count);
> > @@ -163,18 +202,82 @@ 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(struct drm_gem_shmem_object
*shmem)
> > +/**
> > + * drm_gem_shmem_set_evictable() - Make GEM evictable by memory
shrinker
> > + * @shmem: shmem GEM object
> > + *
> > + * Tell memory shrinker that this GEM can be evicted. Initially
eviction is
> > + * disabled for all GEMs. If GEM was purged, then -ENOMEM is
returned.
> > + *
> > + * Returns:
> > + * 0 on success or a negative error code on failure.
> > + */
> > +int drm_gem_shmem_set_evictable(struct drm_gem_shmem_object *shmem)
> > +{
> > +       dma_resv_lock(shmem->base.resv, NULL);
> > +
> > +       if (shmem->madv < 0)
> > +               return -ENOMEM;
> > +
> > +       shmem->eviction_enabled = true;
> > +
> > +       dma_resv_unlock(shmem->base.resv);
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_evictable);
> > +
> > +/**
> > + * 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. 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)
> > +{
> > +       dma_resv_lock(shmem->base.resv, NULL);
> > +
> > +       if (shmem->madv < 0)
> > +               return -ENOMEM;
> > +
> > +       shmem->purge_enabled = true;
> > +
> > +       drm_gem_shmem_update_pages_state(shmem);
> > +
> > +       dma_resv_unlock(shmem->base.resv);
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable);
> > +
> > +static int
> > +drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem)
> >  {
> >         struct drm_gem_object *obj = &shmem->base;
> >         struct page **pages;
> >
> > -       if (shmem->pages_use_count++ > 0)
> > +       dma_resv_assert_held(shmem->base.resv);
> > +
> > +       if (shmem->madv < 0) {
> > +               WARN_ON(shmem->pages);
> > +               return -ENOMEM;
> > +       }
> > +
> > +       if (shmem->pages) {
> > +               WARN_ON(!shmem->evicted);
> >                 return 0;
> > +       }
> > +
> > +       if (WARN_ON(!shmem->pages_use_count))
> > +               return -EINVAL;
> >
> >         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);
> >         }
> >
> > @@ -193,6 +296,58 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
> >         return 0;
> >  }
> >
> > +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object
*shmem)
> > +{
> > +       int err;
> > +
> > +       dma_resv_assert_held(shmem->base.resv);
> > +
> > +       if (shmem->madv < 0)
> > +               return -ENOMEM;
> > +
> > +       if (shmem->pages_use_count++ > 0) {
> > +               err = drm_gem_shmem_swap_in(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:
> > +       shmem->pages_use_count = 0;
> > +
> > +       return err;
> > +}
> > +
> > +static void
> > +drm_gem_shmem_release_pages(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)
> > +               set_pages_array_wb(shmem->pages, obj->size
>> PAGE_SHIFT);
> > +#endif
> > +
> > +       drm_gem_put_pages(obj, shmem->pages,
> > +                         shmem->pages_mark_dirty_on_put,
> > +                         shmem->pages_mark_accessed_on_put);
> > +       shmem->pages = NULL;
> > +}
> > +
> >  /*
> >   * drm_gem_shmem_put_pages - Decrease use count on the backing pages
for a shmem GEM object
> >   * @shmem: shmem GEM object
> > @@ -201,8 +356,6 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
> >   */
> >  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);
> >
> >         if (WARN_ON_ONCE(!shmem->pages_use_count))
> > @@ -211,15 +364,9 @@ void drm_gem_shmem_put_pages(struct
drm_gem_shmem_object *shmem)
> >         if (--shmem->pages_use_count > 0)
> >                 return;
> >
> > -#ifdef CONFIG_X86
> > -       if (shmem->map_wc)
> > -               set_pages_array_wb(shmem->pages, obj->size
>> PAGE_SHIFT);
> > -#endif
> > +       drm_gem_shmem_release_pages(shmem);
> >
> > -       drm_gem_put_pages(obj, shmem->pages,
> > -                         shmem->pages_mark_dirty_on_put,
> > -                         shmem->pages_mark_accessed_on_put);
> > -       shmem->pages = NULL;
> > +       drm_gem_shmem_update_pages_state(shmem);
> >  }
> >  EXPORT_SYMBOL(drm_gem_shmem_put_pages);
> >
> > @@ -235,11 +382,17 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
> >   */
> >  int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
> >  {
> > +       int ret;
> > +
> >         dma_resv_assert_held(shmem->base.resv);
> >
> >         WARN_ON(shmem->base.import_attach);
> >
> > -       return drm_gem_shmem_get_pages(shmem);
> > +       ret = drm_gem_shmem_get_pages(shmem);
> > +       if (!ret)
> > +               shmem->pages_pin_count++;
> > +
> > +       return ret;
> >  }
> >  EXPORT_SYMBOL(drm_gem_shmem_pin);
> >
> > @@ -257,6 +410,8 @@ void drm_gem_shmem_unpin(struct
drm_gem_shmem_object *shmem)
> >         WARN_ON(shmem->base.import_attach);
> >
> >         drm_gem_shmem_put_pages(shmem);
> > +
> > +       shmem->pages_pin_count--;
> >  }
> >  EXPORT_SYMBOL(drm_gem_shmem_unpin);
> >
> > @@ -299,7 +454,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
> >                         return 0;
> >                 }
> >
> > -               ret = drm_gem_shmem_get_pages(shmem);
> > +               ret = drm_gem_shmem_pin(shmem);
> >                 if (ret)
> >                         goto err_zero_use;
> >
> > @@ -322,7 +477,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
> >
> >  err_put_pages:
> >         if (!obj->import_attach)
> > -               drm_gem_shmem_put_pages(shmem);
> > +               drm_gem_shmem_unpin(shmem);
> >  err_zero_use:
> >         shmem->vmap_use_count = 0;
> >
> > @@ -359,7 +514,7 @@ void drm_gem_shmem_vunmap(struct
drm_gem_shmem_object *shmem,
> >                         return;
> >
> >                 vunmap(shmem->vaddr);
> > -               drm_gem_shmem_put_pages(shmem);
> > +               drm_gem_shmem_unpin(shmem);
> >         }
> >
> >         shmem->vaddr = NULL;
> > @@ -403,41 +558,77 @@ int drm_gem_shmem_madvise(struct
drm_gem_shmem_object *shmem, int madv)
> >
> >         madv = shmem->madv;
> >
> > +       drm_gem_shmem_update_pages_state(shmem);
> > +
> >         return (madv >= 0);
> >  }
> >  EXPORT_SYMBOL(drm_gem_shmem_madvise);
> >
> > -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
> > +/**
> > + * drm_gem_shmem_swap_in() - 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_swap_in(struct drm_gem_shmem_object *shmem)
> >  {
> >         struct drm_gem_object *obj = &shmem->base;
> > -       struct drm_device *dev = obj->dev;
> > +       struct sg_table *sgt;
> > +       int err;
> >
> >         dma_resv_assert_held(shmem->base.resv);
> >
> > -       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> > +       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;
> > +               }
> >
> > -       dma_unmap_sgtable(dev->dev, shmem->sgt,
DMA_BIDIRECTIONAL, 0);
> > -       sg_free_table(shmem->sgt);
> > -       kfree(shmem->sgt);
> > -       shmem->sgt = NULL;
> > +               shmem->sgt = sgt;
> > +               shmem->evicted = false;
> >
> > -       drm_gem_shmem_put_pages(shmem);
> > +               drm_gem_shmem_update_pages_state(shmem);
> > +       }
> >
> > -       shmem->madv = -1;
> > +       if (!shmem->pages)
> > +               return -ENOMEM;
> >
> > -       drm_vma_node_unmap(&obj->vma_node,
dev->anon_inode->i_mapping);
> > -       drm_gem_free_mmap_offset(obj);
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in);
> >
> > -       /* Our goal here is to return as much of the memory as
> > -        * is possible back to the system as we are called from OOM.
> > -        * To do this we must instruct the shmfs to drop all of its
> > -        * backing pages, *now*.
> > -        */
> > -       shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
> > +static void drm_gem_shmem_unpin_pages(struct drm_gem_shmem_object
*shmem)
> > +{
> > +       struct drm_gem_object *obj = &shmem->base;
> > +       struct drm_device *dev = obj->dev;
> >
> > -      
invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
> > +       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);
> > +
> > +       sg_free_table(shmem->sgt);
> > +       kfree(shmem->sgt);
> > +       shmem->sgt = NULL;
> >  }
> > -EXPORT_SYMBOL(drm_gem_shmem_purge);
> >
> >  /**
> >   * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
> > @@ -488,22 +679,33 @@ 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 ||
> > -           WARN_ON_ONCE(!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);
> > +       WARN_ON_ONCE(!shmem->pages ^ pages_unpinned);
> > +
> > +       if (page_offset >= num_pages || (!shmem->pages
&& !shmem->evicted)) {
> >                 ret = VM_FAULT_SIGBUS;
> >         } else {
> > +               err = drm_gem_shmem_swap_in(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;
> > @@ -513,13 +715,15 @@ 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);
> >
> >         dma_resv_lock(shmem->base.resv, NULL);
> > -       ret = drm_gem_shmem_get_pages(shmem);
> > -       WARN_ON_ONCE(ret != 0);
> > +
> > +       if (drm_gem_shmem_get_pages(shmem))
> > +               shmem->pages_use_count++;
> > +
> > +       drm_gem_shmem_update_pages_state(shmem);
> >         dma_resv_unlock(shmem->base.resv);
> >
> >         drm_gem_vm_open(vma);
> > @@ -583,6 +787,8 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
> >  void drm_gem_shmem_print_info(const struct drm_gem_shmem_object
*shmem,
> >                               struct drm_printer *p, unsigned int
indent)
> >  {
> > +       drm_printf_indent(p, indent,
"eviction_enabled=%d\n", shmem->eviction_enabled);
> > +       drm_printf_indent(p, indent, "purge_enabled=%d\n",
shmem->purge_enabled);
> >         drm_printf_indent(p, indent, "pages_use_count=%u\n",
shmem->pages_use_count);
> >
> >         if (shmem->base.import_attach)
> > @@ -592,7 +798,9 @@ void drm_gem_shmem_print_info(const struct
drm_gem_shmem_object *shmem,
> >                 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);
> >
> > @@ -667,6 +875,8 @@ 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);
> > +
> >         dma_resv_unlock(shmem->base.resv);
> >
> >         return sgt;
> > @@ -717,6 +927,250 @@ 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);
> > +       struct drm_gem_shmem_object *shmem;
> > +       unsigned long count = 0;
> > +
> > +       if (!mutex_trylock(&gem_shrinker->lock))
> > +               return 0;
> > +
> > +       list_for_each_entry(shmem,
&gem_shrinker->lru_evictable, madv_list) {
> > +               count += shmem->base.size;
> > +
> > +               if (count >= SHRINK_EMPTY)
> > +                       break;
> > +       }
> > +
> > +       mutex_unlock(&gem_shrinker->lock);
> > +
> > +       if (count >= SHRINK_EMPTY)
> > +               return SHRINK_EMPTY - 1;
> > +
> > +       return count ?: SHRINK_EMPTY;
> > +}
> > +
> > +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem)
> > +{
> > +       WARN_ON(!drm_gem_shmem_is_evictable(shmem));
> > +       WARN_ON(shmem->evicted);
> > +
> > +       drm_gem_shmem_unpin_pages(shmem);
> > +
> > +       shmem->evicted = true;
> > +       drm_gem_shmem_update_pages_state(shmem);
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict);
> > +
> > +int drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
> > +{
> > +       struct drm_gem_object *obj = &shmem->base;
> > +
> > +       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> > +
> > +       drm_gem_shmem_unpin_pages(shmem);
> > +       drm_gem_free_mmap_offset(obj);
> > +
> > +       /* Our goal here is to return as much of the memory as
> > +        * is possible back to the system as we are called from OOM.
> > +        * To do this we must instruct the shmfs to drop all of its
> > +        * backing pages, *now*.
> > +        */
> > +       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;
> > +       shmem->evicted = false;
> > +       drm_gem_shmem_update_pages_state(shmem);
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
> > +
> > +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;
> > +       size_t page_count;
> > +       int err;
> > +
> > +       INIT_LIST_HEAD(&still_in_list);
> > +
> > +       mutex_lock(&gem_shrinker->lock);
> > +
> > +       while (freed < nr_to_scan) {
> > +               shmem =
list_first_entry_or_null(&gem_shrinker->lru_evictable,
> > +                                                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) {
> > +                       if (!drm_gem_shmem_is_evictable(shmem) ||
> > +                           get_nr_swap_pages() < page_count)
> > +                               continue;
> > +               } else {
> > +                       if (!drm_gem_shmem_is_purgeable(shmem))
> > +                               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 importing/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,
DMA_RESV_USAGE_WRITE))
> > +                       goto object_name_unlock;
> > +
> > +               /* re-check whether eviction status hasn't changed
*/
> > +               if (!drm_gem_shmem_is_evictable(shmem) &&
> > +                   !drm_gem_shmem_is_purgeable(shmem))
> > +                       goto object_name_unlock;
> > +
> > +               err = shmem->evict(shmem);
> > +               if (!err)
> > +                       freed += obj->size >> PAGE_SHIFT;
> > +
> > +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,
&gem_shrinker->lru_evictable);
> > +
> > +       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);
> > +
> > +       /* evict as many objects as we can */
> > +       if (freed < nr_to_scan)
> > +               freed +=
drm_gem_shmem_shrinker_run_objects_scan(shrinker,
> > +                                                               
nr_to_scan - freed,
> > +                                                               
&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_evictable);
> > +       INIT_LIST_HEAD(&gem_shrinker->lru_evicted);
> > +       INIT_LIST_HEAD(&gem_shrinker->lru_pinned);
> > +       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_evictable));
> > +              
WARN_ON(!list_empty(&gem_shrinker->lru_evicted));
> > +              
WARN_ON(!list_empty(&gem_shrinker->lru_pinned));
> > +               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/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > index a4bedfeb2ec4..7cc32556f908 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/drivers/gpu/drm/virtio/virtgpu_drv.h
b/drivers/gpu/drm/virtio/virtgpu_drv.h
> > index b2d93cb12ebf..81bacc7e1873 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> > @@ -89,6 +89,7 @@ struct virtio_gpu_object {
> >         uint32_t hw_res_handle;
> >         bool dumb;
> >         bool created;
> > +       bool detached;
> >         bool host3d_blob, guest_blob;
> >         uint32_t blob_mem, blob_flags;
> >
> > @@ -453,6 +454,8 @@ int virtio_gpu_object_create(struct
virtio_gpu_device *vgdev,
> >
> >  bool virtio_gpu_is_shmem(struct virtio_gpu_object *bo);
> >
> > +int virtio_gpu_reattach_shmem_object(struct virtio_gpu_object *bo);
> > +
> >  int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
> >                                uint32_t *resid);
> >  /* virtgpu_prime.c */
> > 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_shmem_helper.h
b/include/drm/drm_gem_shmem_helper.h
> > index 9a8983ee8abe..62c640678a91 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>
> > @@ -15,6 +16,7 @@
> >  struct dma_buf_attachment;
> >  struct drm_mode_create_dumb;
> >  struct drm_printer;
> > +struct drm_device;
> >  struct sg_table;
> >
> >  /**
> > @@ -39,12 +41,21 @@ struct drm_gem_shmem_object {
> >          */
> >         unsigned int pages_use_count;
> >
> > +       /**
> > +        * @pages_pin_count:
> > +        *
> > +        * Reference count on the pinned pages table.
> > +        * The pages can be evicted by memory shrinker
> > +        * when the count reaches zero.
> > +        */
> > +       unsigned int pages_pin_count;
> > +
> >         /**
> >          * @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 +102,39 @@ struct drm_gem_shmem_object {
> >          * @map_wc: map object write-combined (instead of using shmem
defaults).
> >          */
> >         bool map_wc;
> > +
> > +       /**
> > +        * @eviction_enabled:
> > +        *
> > +        * The shmem pages can be evicted only if @eviction_enabled is
set to true.
> > +        * Used internally by memory shrinker.
> > +        */
> > +       bool eviction_enabled;
> > +
> > +       /**
> > +        * @purge_enabled:
> > +        *
> > +        * The shmem pages can be purged only if @purge_enabled is set
to true.
> > +        * Used internally by memory shrinker.
> > +        */
> > +       bool purge_enabled;
> > +
> > +       /**
> > +        * @evicted: True if shmem pages are evicted by the memory
shrinker.
> > +        * Used internally by memory shrinker.
> > +        */
> > +       bool evicted;
> > +
> > +       /**
> > +        * @evict:
> > +        *
> > +        * Invoked by shmem shrinker before evicting shmem GEM from
memory.
> > +        * GEM's DMA reservation is kept locked by the shrinker.
This is
> > +        * optional callback that should be specified by drivers.
> > +        *
> > +        * Returns 0 on success, or -errno on error.
> > +        */
> > +       int (*evict)(struct drm_gem_shmem_object *shmem);
> >  };
> >
> >  #define to_drm_gem_shmem_obj(obj) \
> > @@ -110,14 +154,21 @@ 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_evictable(struct drm_gem_shmem_object *shmem);
> > +
> >  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->evict
&&
> > +               shmem->purge_enabled &&
shmem->pages_use_count &&
> > +               !shmem->pages_pin_count &&
!shmem->base.dma_buf &&
> > +               !shmem->base.import_attach &&
(shmem->sgt || shmem->evicted);
> >  }
> >
> > -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
> > +int drm_gem_shmem_swap_in(struct drm_gem_shmem_object *shmem);
> > +
> > +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem);
> > +int 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);
> >  struct sg_table *drm_gem_shmem_get_pages_sgt(struct
drm_gem_shmem_object *shmem);
> > @@ -260,6 +311,32 @@ 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_pinned: List of pinned shmem GEM objects */
> > +       struct list_head lru_pinned;
> > +
> > +       /** @lru_evictable: List of shmem GEM objects to 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;
> > +};
> > +
> > +int drm_gem_shmem_shrinker_register(struct drm_device *dev);
> > +void drm_gem_shmem_shrinker_unregister(struct drm_device *dev);
> > +
> >  /*
> >   * Driver ops
> >   */
> > --
> > 2.35.3
> >
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Am 05.06.22 um 18:47 schrieb Daniel Vetter:
> On Fri, 27 May 2022 at 01:55, Dmitry Osipenko
> <dmitry.osipenko at collabora.com> wrote:
>> Introduce a common DRM SHMEM shrinker framework that allows to reduce
>> code duplication among DRM drivers by replacing theirs custom shrinker
>> implementations with the generic shrinker.
>>
>> In order to start using DRM SHMEM shrinker drivers should:
>>
>> 1. Implement new evict() shmem object callback.
>> 2. Register shrinker using drm_gem_shmem_shrinker_register(drm_device).
>> 3. Use drm_gem_shmem_set_purgeable(shmem) and alike API functions to
>>     activate shrinking of shmem GEMs.
>>
>> This patch is based on a ideas borrowed from Rob's Clark MSM
shrinker,
>> Thomas' Zimmermann variant of SHMEM shrinker and Intel's i915
shrinker.
>>
>> Signed-off-by: Daniel Almeida <daniel.almeida at collabora.com>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko at collabora.com>
> So I guess I get a price for being blind since forever, because this
> thing existed since at least 2013. I just stumbled over
> llist_lru.[hc], a purpose built list helper for shrinkers. I think we
> should try to adopt that so that our gpu shrinkers look more like
> shrinkers for everything else.
What the heck are you talking about?

I can't find any llist_lru.[hc] in the linux kernel sources.

Christian.
>
> Apologies for this, since I fear this might cause a bit of churn.
> Hopefully it's all contained to the list manipulation code in shmem
> helpers, I don't think this should leak any further.
> -Daniel
>
>> ---
>>   drivers/gpu/drm/drm_gem_shmem_helper.c        | 540
++++++++++++++++--
>>   .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
>>   drivers/gpu/drm/virtio/virtgpu_drv.h          |   3 +
>>   include/drm/drm_device.h                      |   4 +
>>   include/drm/drm_gem_shmem_helper.h            |  87 ++-
>>   5 files changed, 594 insertions(+), 49 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index 555fe212bd98..4cd0b5913492 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -126,6 +126,42 @@ struct drm_gem_shmem_object
*drm_gem_shmem_create(struct drm_device *dev, size_t
>>   }
>>   EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>>
>> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object
*shmem)
>> +{
>> +       return (shmem->madv >= 0) && shmem->evict
&&
>> +               shmem->eviction_enabled &&
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_shrinker *gem_shrinker =
obj->dev->shmem_shrinker;
>> +
>> +       dma_resv_assert_held(shmem->base.resv);
>> +
>> +       if (!gem_shrinker || obj->import_attach)
>> +               return;
>> +
>> +       mutex_lock(&gem_shrinker->lock);
>> +
>> +       if (drm_gem_shmem_is_evictable(shmem) ||
>> +           drm_gem_shmem_is_purgeable(shmem))
>> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evictable);
>> +       else if (shmem->madv < 0)
>> +               list_del_init(&shmem->madv_list);
>> +       else if (shmem->evicted)
>> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_evicted);
>> +       else if (!shmem->pages)
>> +               list_del_init(&shmem->madv_list);
>> +       else
>> +               list_move_tail(&shmem->madv_list,
&gem_shrinker->lru_pinned);
>> +
>> +       mutex_unlock(&gem_shrinker->lock);
>> +}
>> +
>>   /**
>>    * drm_gem_shmem_free - Free resources associated with a shmem GEM
object
>>    * @shmem: shmem GEM object to free
>> @@ -142,6 +178,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object
*shmem)
>>          } else {
>>                  dma_resv_lock(shmem->base.resv, NULL);
>>
>> +               /* take out shmem GEM object from the memory shrinker
*/
>> +               drm_gem_shmem_madvise(shmem, -1);
>> +
>>                  WARN_ON(shmem->vmap_use_count);
>>
>>                  if (shmem->sgt) {
>> @@ -150,7 +189,7 @@ 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);
>>
>>                  WARN_ON(shmem->pages_use_count);
>> @@ -163,18 +202,82 @@ 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(struct drm_gem_shmem_object *shmem)
>> +/**
>> + * drm_gem_shmem_set_evictable() - Make GEM evictable by memory
shrinker
>> + * @shmem: shmem GEM object
>> + *
>> + * Tell memory shrinker that this GEM can be evicted. Initially
eviction is
>> + * disabled for all GEMs. If GEM was purged, then -ENOMEM is returned.
>> + *
>> + * Returns:
>> + * 0 on success or a negative error code on failure.
>> + */
>> +int drm_gem_shmem_set_evictable(struct drm_gem_shmem_object *shmem)
>> +{
>> +       dma_resv_lock(shmem->base.resv, NULL);
>> +
>> +       if (shmem->madv < 0)
>> +               return -ENOMEM;
>> +
>> +       shmem->eviction_enabled = true;
>> +
>> +       dma_resv_unlock(shmem->base.resv);
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_evictable);
>> +
>> +/**
>> + * 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. 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)
>> +{
>> +       dma_resv_lock(shmem->base.resv, NULL);
>> +
>> +       if (shmem->madv < 0)
>> +               return -ENOMEM;
>> +
>> +       shmem->purge_enabled = true;
>> +
>> +       drm_gem_shmem_update_pages_state(shmem);
>> +
>> +       dma_resv_unlock(shmem->base.resv);
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable);
>> +
>> +static int
>> +drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem)
>>   {
>>          struct drm_gem_object *obj = &shmem->base;
>>          struct page **pages;
>>
>> -       if (shmem->pages_use_count++ > 0)
>> +       dma_resv_assert_held(shmem->base.resv);
>> +
>> +       if (shmem->madv < 0) {
>> +               WARN_ON(shmem->pages);
>> +               return -ENOMEM;
>> +       }
>> +
>> +       if (shmem->pages) {
>> +               WARN_ON(!shmem->evicted);
>>                  return 0;
>> +       }
>> +
>> +       if (WARN_ON(!shmem->pages_use_count))
>> +               return -EINVAL;
>>
>>          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);
>>          }
>>
>> @@ -193,6 +296,58 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
>>          return 0;
>>   }
>>
>> +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
>> +{
>> +       int err;
>> +
>> +       dma_resv_assert_held(shmem->base.resv);
>> +
>> +       if (shmem->madv < 0)
>> +               return -ENOMEM;
>> +
>> +       if (shmem->pages_use_count++ > 0) {
>> +               err = drm_gem_shmem_swap_in(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:
>> +       shmem->pages_use_count = 0;
>> +
>> +       return err;
>> +}
>> +
>> +static void
>> +drm_gem_shmem_release_pages(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)
>> +               set_pages_array_wb(shmem->pages, obj->size
>> PAGE_SHIFT);
>> +#endif
>> +
>> +       drm_gem_put_pages(obj, shmem->pages,
>> +                         shmem->pages_mark_dirty_on_put,
>> +                         shmem->pages_mark_accessed_on_put);
>> +       shmem->pages = NULL;
>> +}
>> +
>>   /*
>>    * drm_gem_shmem_put_pages - Decrease use count on the backing pages
for a shmem GEM object
>>    * @shmem: shmem GEM object
>> @@ -201,8 +356,6 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
>>    */
>>   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);
>>
>>          if (WARN_ON_ONCE(!shmem->pages_use_count))
>> @@ -211,15 +364,9 @@ void drm_gem_shmem_put_pages(struct
drm_gem_shmem_object *shmem)
>>          if (--shmem->pages_use_count > 0)
>>                  return;
>>
>> -#ifdef CONFIG_X86
>> -       if (shmem->map_wc)
>> -               set_pages_array_wb(shmem->pages, obj->size
>> PAGE_SHIFT);
>> -#endif
>> +       drm_gem_shmem_release_pages(shmem);
>>
>> -       drm_gem_put_pages(obj, shmem->pages,
>> -                         shmem->pages_mark_dirty_on_put,
>> -                         shmem->pages_mark_accessed_on_put);
>> -       shmem->pages = NULL;
>> +       drm_gem_shmem_update_pages_state(shmem);
>>   }
>>   EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>>
>> @@ -235,11 +382,17 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>>    */
>>   int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>>   {
>> +       int ret;
>> +
>>          dma_resv_assert_held(shmem->base.resv);
>>
>>          WARN_ON(shmem->base.import_attach);
>>
>> -       return drm_gem_shmem_get_pages(shmem);
>> +       ret = drm_gem_shmem_get_pages(shmem);
>> +       if (!ret)
>> +               shmem->pages_pin_count++;
>> +
>> +       return ret;
>>   }
>>   EXPORT_SYMBOL(drm_gem_shmem_pin);
>>
>> @@ -257,6 +410,8 @@ void drm_gem_shmem_unpin(struct
drm_gem_shmem_object *shmem)
>>          WARN_ON(shmem->base.import_attach);
>>
>>          drm_gem_shmem_put_pages(shmem);
>> +
>> +       shmem->pages_pin_count--;
>>   }
>>   EXPORT_SYMBOL(drm_gem_shmem_unpin);
>>
>> @@ -299,7 +454,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
>>                          return 0;
>>                  }
>>
>> -               ret = drm_gem_shmem_get_pages(shmem);
>> +               ret = drm_gem_shmem_pin(shmem);
>>                  if (ret)
>>                          goto err_zero_use;
>>
>> @@ -322,7 +477,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object
*shmem,
>>
>>   err_put_pages:
>>          if (!obj->import_attach)
>> -               drm_gem_shmem_put_pages(shmem);
>> +               drm_gem_shmem_unpin(shmem);
>>   err_zero_use:
>>          shmem->vmap_use_count = 0;
>>
>> @@ -359,7 +514,7 @@ void drm_gem_shmem_vunmap(struct
drm_gem_shmem_object *shmem,
>>                          return;
>>
>>                  vunmap(shmem->vaddr);
>> -               drm_gem_shmem_put_pages(shmem);
>> +               drm_gem_shmem_unpin(shmem);
>>          }
>>
>>          shmem->vaddr = NULL;
>> @@ -403,41 +558,77 @@ int drm_gem_shmem_madvise(struct
drm_gem_shmem_object *shmem, int madv)
>>
>>          madv = shmem->madv;
>>
>> +       drm_gem_shmem_update_pages_state(shmem);
>> +
>>          return (madv >= 0);
>>   }
>>   EXPORT_SYMBOL(drm_gem_shmem_madvise);
>>
>> -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
>> +/**
>> + * drm_gem_shmem_swap_in() - 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_swap_in(struct drm_gem_shmem_object *shmem)
>>   {
>>          struct drm_gem_object *obj = &shmem->base;
>> -       struct drm_device *dev = obj->dev;
>> +       struct sg_table *sgt;
>> +       int err;
>>
>>          dma_resv_assert_held(shmem->base.resv);
>>
>> -       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
>> +       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;
>> +               }
>>
>> -       dma_unmap_sgtable(dev->dev, shmem->sgt,
DMA_BIDIRECTIONAL, 0);
>> -       sg_free_table(shmem->sgt);
>> -       kfree(shmem->sgt);
>> -       shmem->sgt = NULL;
>> +               shmem->sgt = sgt;
>> +               shmem->evicted = false;
>>
>> -       drm_gem_shmem_put_pages(shmem);
>> +               drm_gem_shmem_update_pages_state(shmem);
>> +       }
>>
>> -       shmem->madv = -1;
>> +       if (!shmem->pages)
>> +               return -ENOMEM;
>>
>> -       drm_vma_node_unmap(&obj->vma_node,
dev->anon_inode->i_mapping);
>> -       drm_gem_free_mmap_offset(obj);
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in);
>>
>> -       /* Our goal here is to return as much of the memory as
>> -        * is possible back to the system as we are called from OOM.
>> -        * To do this we must instruct the shmfs to drop all of its
>> -        * backing pages, *now*.
>> -        */
>> -       shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
>> +static void drm_gem_shmem_unpin_pages(struct drm_gem_shmem_object
*shmem)
>> +{
>> +       struct drm_gem_object *obj = &shmem->base;
>> +       struct drm_device *dev = obj->dev;
>>
>> -      
invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
>> +       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);
>> +
>> +       sg_free_table(shmem->sgt);
>> +       kfree(shmem->sgt);
>> +       shmem->sgt = NULL;
>>   }
>> -EXPORT_SYMBOL(drm_gem_shmem_purge);
>>
>>   /**
>>    * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
>> @@ -488,22 +679,33 @@ 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 ||
>> -           WARN_ON_ONCE(!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);
>> +       WARN_ON_ONCE(!shmem->pages ^ pages_unpinned);
>> +
>> +       if (page_offset >= num_pages || (!shmem->pages &&
!shmem->evicted)) {
>>                  ret = VM_FAULT_SIGBUS;
>>          } else {
>> +               err = drm_gem_shmem_swap_in(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;
>> @@ -513,13 +715,15 @@ 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);
>>
>>          dma_resv_lock(shmem->base.resv, NULL);
>> -       ret = drm_gem_shmem_get_pages(shmem);
>> -       WARN_ON_ONCE(ret != 0);
>> +
>> +       if (drm_gem_shmem_get_pages(shmem))
>> +               shmem->pages_use_count++;
>> +
>> +       drm_gem_shmem_update_pages_state(shmem);
>>          dma_resv_unlock(shmem->base.resv);
>>
>>          drm_gem_vm_open(vma);
>> @@ -583,6 +787,8 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
>>   void drm_gem_shmem_print_info(const struct drm_gem_shmem_object
*shmem,
>>                                struct drm_printer *p, unsigned int
indent)
>>   {
>> +       drm_printf_indent(p, indent, "eviction_enabled=%d\n",
shmem->eviction_enabled);
>> +       drm_printf_indent(p, indent, "purge_enabled=%d\n",
shmem->purge_enabled);
>>          drm_printf_indent(p, indent, "pages_use_count=%u\n",
shmem->pages_use_count);
>>
>>          if (shmem->base.import_attach)
>> @@ -592,7 +798,9 @@ void drm_gem_shmem_print_info(const struct
drm_gem_shmem_object *shmem,
>>                  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);
>>
>> @@ -667,6 +875,8 @@ 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);
>> +
>>          dma_resv_unlock(shmem->base.resv);
>>
>>          return sgt;
>> @@ -717,6 +927,250 @@ 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);
>> +       struct drm_gem_shmem_object *shmem;
>> +       unsigned long count = 0;
>> +
>> +       if (!mutex_trylock(&gem_shrinker->lock))
>> +               return 0;
>> +
>> +       list_for_each_entry(shmem, &gem_shrinker->lru_evictable,
madv_list) {
>> +               count += shmem->base.size;
>> +
>> +               if (count >= SHRINK_EMPTY)
>> +                       break;
>> +       }
>> +
>> +       mutex_unlock(&gem_shrinker->lock);
>> +
>> +       if (count >= SHRINK_EMPTY)
>> +               return SHRINK_EMPTY - 1;
>> +
>> +       return count ?: SHRINK_EMPTY;
>> +}
>> +
>> +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem)
>> +{
>> +       WARN_ON(!drm_gem_shmem_is_evictable(shmem));
>> +       WARN_ON(shmem->evicted);
>> +
>> +       drm_gem_shmem_unpin_pages(shmem);
>> +
>> +       shmem->evicted = true;
>> +       drm_gem_shmem_update_pages_state(shmem);
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict);
>> +
>> +int drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
>> +{
>> +       struct drm_gem_object *obj = &shmem->base;
>> +
>> +       WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
>> +
>> +       drm_gem_shmem_unpin_pages(shmem);
>> +       drm_gem_free_mmap_offset(obj);
>> +
>> +       /* Our goal here is to return as much of the memory as
>> +        * is possible back to the system as we are called from OOM.
>> +        * To do this we must instruct the shmfs to drop all of its
>> +        * backing pages, *now*.
>> +        */
>> +       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;
>> +       shmem->evicted = false;
>> +       drm_gem_shmem_update_pages_state(shmem);
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
>> +
>> +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;
>> +       size_t page_count;
>> +       int err;
>> +
>> +       INIT_LIST_HEAD(&still_in_list);
>> +
>> +       mutex_lock(&gem_shrinker->lock);
>> +
>> +       while (freed < nr_to_scan) {
>> +               shmem =
list_first_entry_or_null(&gem_shrinker->lru_evictable,
>> +                                                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) {
>> +                       if (!drm_gem_shmem_is_evictable(shmem) ||
>> +                           get_nr_swap_pages() < page_count)
>> +                               continue;
>> +               } else {
>> +                       if (!drm_gem_shmem_is_purgeable(shmem))
>> +                               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 importing/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,
DMA_RESV_USAGE_WRITE))
>> +                       goto object_name_unlock;
>> +
>> +               /* re-check whether eviction status hasn't changed
*/
>> +               if (!drm_gem_shmem_is_evictable(shmem) &&
>> +                   !drm_gem_shmem_is_purgeable(shmem))
>> +                       goto object_name_unlock;
>> +
>> +               err = shmem->evict(shmem);
>> +               if (!err)
>> +                       freed += obj->size >> PAGE_SHIFT;
>> +
>> +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,
&gem_shrinker->lru_evictable);
>> +
>> +       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);
>> +
>> +       /* evict as many objects as we can */
>> +       if (freed < nr_to_scan)
>> +               freed +=
drm_gem_shmem_shrinker_run_objects_scan(shrinker,
>> +                                                               
nr_to_scan - freed,
>> +                                                               
&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_evictable);
>> +       INIT_LIST_HEAD(&gem_shrinker->lru_evicted);
>> +       INIT_LIST_HEAD(&gem_shrinker->lru_pinned);
>> +       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_evictable));
>> +              
WARN_ON(!list_empty(&gem_shrinker->lru_evicted));
>> +               WARN_ON(!list_empty(&gem_shrinker->lru_pinned));
>> +               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/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
>> index a4bedfeb2ec4..7cc32556f908 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/drivers/gpu/drm/virtio/virtgpu_drv.h
b/drivers/gpu/drm/virtio/virtgpu_drv.h
>> index b2d93cb12ebf..81bacc7e1873 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
>> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
>> @@ -89,6 +89,7 @@ struct virtio_gpu_object {
>>          uint32_t hw_res_handle;
>>          bool dumb;
>>          bool created;
>> +       bool detached;
>>          bool host3d_blob, guest_blob;
>>          uint32_t blob_mem, blob_flags;
>>
>> @@ -453,6 +454,8 @@ int virtio_gpu_object_create(struct
virtio_gpu_device *vgdev,
>>
>>   bool virtio_gpu_is_shmem(struct virtio_gpu_object *bo);
>>
>> +int virtio_gpu_reattach_shmem_object(struct virtio_gpu_object *bo);
>> +
>>   int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
>>                                 uint32_t *resid);
>>   /* virtgpu_prime.c */
>> 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_shmem_helper.h
b/include/drm/drm_gem_shmem_helper.h
>> index 9a8983ee8abe..62c640678a91 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>
>> @@ -15,6 +16,7 @@
>>   struct dma_buf_attachment;
>>   struct drm_mode_create_dumb;
>>   struct drm_printer;
>> +struct drm_device;
>>   struct sg_table;
>>
>>   /**
>> @@ -39,12 +41,21 @@ struct drm_gem_shmem_object {
>>           */
>>          unsigned int pages_use_count;
>>
>> +       /**
>> +        * @pages_pin_count:
>> +        *
>> +        * Reference count on the pinned pages table.
>> +        * The pages can be evicted by memory shrinker
>> +        * when the count reaches zero.
>> +        */
>> +       unsigned int pages_pin_count;
>> +
>>          /**
>>           * @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 +102,39 @@ struct drm_gem_shmem_object {
>>           * @map_wc: map object write-combined (instead of using shmem
defaults).
>>           */
>>          bool map_wc;
>> +
>> +       /**
>> +        * @eviction_enabled:
>> +        *
>> +        * The shmem pages can be evicted only if @eviction_enabled is
set to true.
>> +        * Used internally by memory shrinker.
>> +        */
>> +       bool eviction_enabled;
>> +
>> +       /**
>> +        * @purge_enabled:
>> +        *
>> +        * The shmem pages can be purged only if @purge_enabled is set
to true.
>> +        * Used internally by memory shrinker.
>> +        */
>> +       bool purge_enabled;
>> +
>> +       /**
>> +        * @evicted: True if shmem pages are evicted by the memory
shrinker.
>> +        * Used internally by memory shrinker.
>> +        */
>> +       bool evicted;
>> +
>> +       /**
>> +        * @evict:
>> +        *
>> +        * Invoked by shmem shrinker before evicting shmem GEM from
memory.
>> +        * GEM's DMA reservation is kept locked by the shrinker.
This is
>> +        * optional callback that should be specified by drivers.
>> +        *
>> +        * Returns 0 on success, or -errno on error.
>> +        */
>> +       int (*evict)(struct drm_gem_shmem_object *shmem);
>>   };
>>
>>   #define to_drm_gem_shmem_obj(obj) \
>> @@ -110,14 +154,21 @@ 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_evictable(struct drm_gem_shmem_object *shmem);
>> +
>>   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->evict
&&
>> +               shmem->purge_enabled &&
shmem->pages_use_count &&
>> +               !shmem->pages_pin_count &&
!shmem->base.dma_buf &&
>> +               !shmem->base.import_attach && (shmem->sgt
|| shmem->evicted);
>>   }
>>
>> -void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
>> +int drm_gem_shmem_swap_in(struct drm_gem_shmem_object *shmem);
>> +
>> +int drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem);
>> +int 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);
>>   struct sg_table *drm_gem_shmem_get_pages_sgt(struct
drm_gem_shmem_object *shmem);
>> @@ -260,6 +311,32 @@ 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_pinned: List of pinned shmem GEM objects */
>> +       struct list_head lru_pinned;
>> +
>> +       /** @lru_evictable: List of shmem GEM objects to 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;
>> +};
>> +
>> +int drm_gem_shmem_shrinker_register(struct drm_device *dev);
>> +void drm_gem_shmem_shrinker_unregister(struct drm_device *dev);
>> +
>>   /*
>>    * Driver ops
>>    */
>> --
>> 2.35.3
>>
>