[v10,08/11] drm/shmem-helper: Add memory shrinker

  Introduce common drm-shmem shrinker for DRM drivers.

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

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

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

3. Implement madvise IOCTL that will use drm_gem_shmem_madvise()

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c        | 460 ++++++++++++++++--
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
 include/drm/drm_device.h                      |  10 +-
 include/drm/drm_gem_shmem_helper.h            |  61 ++-
 4 files changed, 490 insertions(+), 50 deletions(-)
  

Hi

Am 08.01.23 um 22:04 schrieb Dmitry Osipenko:
> Introduce common drm-shmem shrinker for DRM drivers.
> 
> To start using drm-shmem shrinker drivers should do the following:
> 
> 1. Implement evict() callback of GEM object where driver should check
>     whether object is purgeable or evictable using drm-shmem helpers and
>     perform the shrinking action
> 
> 2. Initialize drm-shmem internals using drmm_gem_shmem_init(drm_device),
>     which will register drm-shmem shrinker
> 
> 3. Implement madvise IOCTL that will use drm_gem_shmem_madvise()

I left commenets beloew, but it's complicated code and a fairly large 
change. It there any chance of splitting this up in a meaningful way?

> 
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>   drivers/gpu/drm/drm_gem_shmem_helper.c        | 460 ++++++++++++++++--
>   .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
>   include/drm/drm_device.h                      |  10 +-
>   include/drm/drm_gem_shmem_helper.h            |  61 ++-
>   4 files changed, 490 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index a1f2f2158c50..3ab5ec325ddb 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -20,6 +20,7 @@
>   #include <drm/drm_device.h>
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_managed.h>
>   #include <drm/drm_prime.h>
>   #include <drm/drm_print.h>
>   
> @@ -128,6 +129,57 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
>   }
>   EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>   
> +static void drm_gem_shmem_resv_assert_held(struct drm_gem_shmem_object *shmem)
> +{
> +	/*
> +	 * Destroying the object is a special case.. drm_gem_shmem_free()
> +	 * calls many things that WARN_ON if the obj lock is not held.  But
> +	 * acquiring the obj lock in drm_gem_shmem_free() can cause a locking
> +	 * order inversion between reservation_ww_class_mutex and fs_reclaim.
> +	 *
> +	 * This deadlock is not actually possible, because no one should
> +	 * be already holding the lock when msm_gem_free_object() is called.
> +	 * Unfortunately lockdep is not aware of this detail.  So when the
> +	 * refcount drops to zero, we pretend it is already locked.
> +	 */
> +	if (kref_read(&shmem->base.refcount))
> +		dma_resv_assert_held(shmem->base.resv);
> +}
> +
> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	return (shmem->madv >= 0) && shmem->base.funcs->evict &&
> +		shmem->pages_use_count && !shmem->pages_pin_count &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
> +		shmem->sgt && !shmem->evicted;
> +}
> +
> +static void
> +drm_gem_shmem_update_pages_state(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem *shmem_mm = obj->dev->shmem_mm;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = &shmem_mm->shrinker;
> +
> +	drm_gem_shmem_resv_assert_held(shmem);
> +
> +	if (!gem_shrinker || obj->import_attach)
> +		return;
> +
> +	if (shmem->madv < 0)
> +		drm_gem_lru_remove(&shmem->base);
> +	else if (drm_gem_shmem_is_evictable(shmem) || drm_gem_shmem_is_purgeable(shmem))
> +		drm_gem_lru_move_tail(&gem_shrinker->lru_evictable, &shmem->base);
> +	else if (shmem->evicted)
> +		drm_gem_lru_move_tail(&gem_shrinker->lru_evicted, &shmem->base);
> +	else if (!shmem->pages)
> +		drm_gem_lru_remove(&shmem->base);
> +	else
> +		drm_gem_lru_move_tail(&gem_shrinker->lru_pinned, &shmem->base);
> +}
> +
>   /**
>    * drm_gem_shmem_free - Free resources associated with a shmem GEM object
>    * @shmem: shmem GEM object to free
> @@ -142,7 +194,8 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>   	if (obj->import_attach) {
>   		drm_prime_gem_destroy(obj, shmem->sgt);
>   	} else {
> -		dma_resv_lock(shmem->base.resv, NULL);
> +		/* take out shmem GEM object from the memory shrinker */
> +		drm_gem_shmem_madvise(shmem, -1);
>   
>   		drm_WARN_ON(obj->dev, shmem->vmap_use_count);
>   
> @@ -152,12 +205,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>   			sg_free_table(shmem->sgt);
>   			kfree(shmem->sgt);
>   		}
> -		if (shmem->pages)
> +		if (shmem->pages_use_count)
>   			drm_gem_shmem_put_pages(shmem);
>   
>   		drm_WARN_ON(obj->dev, shmem->pages_use_count);
> -
> -		dma_resv_unlock(shmem->base.resv);
>   	}
>   
>   	drm_gem_object_release(obj);
> @@ -165,19 +216,31 @@ 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)
> +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) {
> +		drm_WARN_ON(obj->dev, shmem->pages);
> +		return -ENOMEM;
> +	}
> +
> +	if (shmem->pages) {
> +		drm_WARN_ON(obj->dev, !shmem->evicted);
>   		return 0;
> +	}
> +
> +	if (drm_WARN_ON(obj->dev, !shmem->pages_use_count))
> +		return -EINVAL;
>   
>   	pages = drm_gem_get_pages(obj);
>   	if (IS_ERR(pages)) {
>   		drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
>   			    PTR_ERR(pages));
> -		shmem->pages_use_count = 0;
>   		return PTR_ERR(pages);
>   	}
>   
> @@ -196,6 +259,58 @@ 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) {
> +		drm_WARN_ON(obj->dev, !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
> @@ -206,7 +321,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
>   {
>   	struct drm_gem_object *obj = &shmem->base;
>   
> -	dma_resv_assert_held(shmem->base.resv);
> +	drm_gem_shmem_resv_assert_held(shmem);
>   
>   	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
>   		return;
> @@ -214,15 +329,9 @@ 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);
>   
> @@ -239,12 +348,17 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>   int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>   {
>   	struct drm_gem_object *obj = &shmem->base;
> +	int ret;
>   
>   	dma_resv_assert_held(shmem->base.resv);
>   
>   	drm_WARN_ON(obj->dev, obj->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);
>   
> @@ -263,7 +377,12 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>   
>   	drm_WARN_ON(obj->dev, obj->import_attach);
>   
> +	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_pin_count))
> +		return;
> +
>   	drm_gem_shmem_put_pages(shmem);
> +
> +	shmem->pages_pin_count--;
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_unpin);
>   
> @@ -306,7 +425,7 @@ 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;
>   
> @@ -329,7 +448,7 @@ 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;
>   
> @@ -366,7 +485,7 @@ 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;
> @@ -403,48 +522,84 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
>    */
>   int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
>   {
> -	dma_resv_assert_held(shmem->base.resv);
> +	drm_gem_shmem_resv_assert_held(shmem);
>   
>   	if (shmem->madv >= 0)
>   		shmem->madv = madv;
>   
>   	madv = shmem->madv;
>   
> +	drm_gem_shmem_update_pages_state(shmem);
> +
>   	return (madv >= 0);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_madvise);
>   
> -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.

Do we have a better name than _swap_in()? I suggest 
drm_gem_shmem_unevict(), which suggest that it's the inverse to _evict().

> + * @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);
>   
> -	drm_WARN_ON(obj->dev, !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
> @@ -495,22 +650,33 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
>   	vm_fault_t ret;
>   	struct page *page;
>   	pgoff_t page_offset;
> +	bool pages_unpinned;
> +	int err;
>   
>   	/* We don't use vmf->pgoff since that has the fake offset */
>   	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
>   
>   	dma_resv_lock(shmem->base.resv, NULL);
>   
> -	if (page_offset >= num_pages ||
> -	    drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
> -	    shmem->madv < 0) {
> +	/* Sanity-check that we have the pages pointer when it should present */
> +	pages_unpinned = (shmem->evicted || shmem->madv < 0 || !shmem->pages_use_count);
> +	drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
> +
> +	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
>   		ret = VM_FAULT_SIGBUS;
>   	} else {
> +		err = drm_gem_shmem_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;
> @@ -533,6 +699,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>   	if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
>   		shmem->pages_use_count++;
>   
> +	drm_gem_shmem_update_pages_state(shmem);
>   	dma_resv_unlock(shmem->base.resv);
>   
>   	drm_gem_vm_open(vma);
> @@ -615,7 +782,9 @@ 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);
>   
> @@ -688,6 +857,8 @@ 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;
> @@ -738,6 +909,209 @@ 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)

to_drm_gem_shmem_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);
> +	unsigned long count = gem_shrinker->lru_evictable.count;
> +
> +	if (count >= SHRINK_EMPTY)
> +		return SHRINK_EMPTY - 1;
> +
> +	return count ?: SHRINK_EMPTY;
> +}
> +
> +void drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_evictable(shmem));
> +	drm_WARN_ON(obj->dev, shmem->evicted);
> +
> +	drm_gem_shmem_unpin_pages(shmem);
> +
> +	shmem->evicted = true;
> +	drm_gem_shmem_update_pages_state(shmem);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict);
> +
> +void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	drm_WARN_ON(obj->dev, !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);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
> +
> +static bool drm_gem_is_busy(struct drm_gem_object *obj)
> +{
> +	return !dma_resv_test_signaled(obj->resv, DMA_RESV_USAGE_READ);
> +}

This is a generic GEM function. But do we need it?

> +
> +static bool drm_gem_shmem_shrinker_evict(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	if (!drm_gem_shmem_is_evictable(shmem) ||
> +	    get_nr_swap_pages() < obj->size >> PAGE_SHIFT ||
> +	    drm_gem_is_busy(obj))

Because here and below, we call drm_gem_is_busy(). Could we test 
dma_resv_test_signaled() directly in drm_gem_shmem_evict() once and for all?

> +		return false;
> +
> +	return drm_gem_object_evict(obj);

I complaint about the use of booleans before. Here is should be

   int ret = _evcit();
   if (ret)
	return false;
    return true

and the shrink callback for drm_gem_lru_scan() should be changed to use 
errno codes as well. That's for a later patchset.

> +}
> +
> +static bool drm_gem_shmem_shrinker_purge(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	if (!drm_gem_shmem_is_purgeable(shmem) ||
> +	    drm_gem_is_busy(obj))
> +		return false;
> +
> +	return drm_gem_object_evict(obj);
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
> +				    struct shrink_control *sc)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = to_drm_shrinker(shrinker);
> +	unsigned long nr_to_scan = sc->nr_to_scan;
> +	unsigned long remaining = 0;
> +	unsigned long freed = 0;
> +
> +	/* purge as many objects as we can */
> +	freed += drm_gem_lru_scan(&gem_shrinker->lru_evictable,
> +				  nr_to_scan, &remaining,
> +				  drm_gem_shmem_shrinker_purge);
> +
> +	/* evict as many objects as we can */
> +	if (freed < nr_to_scan)
> +		freed += drm_gem_lru_scan(&gem_shrinker->lru_evictable,
> +					  nr_to_scan - freed, &remaining,
> +					  drm_gem_shmem_shrinker_evict);
> +
> +	return (freed > 0 && remaining > 0) ? freed : SHRINK_STOP;
> +}
> +
> +static int drm_gem_shmem_shrinker_init(struct drm_gem_shmem *shmem_mm,
> +				       const char *shrinker_name)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = &shmem_mm->shrinker;
> +	int err;
> +
> +	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;
> +
> +	mutex_init(&gem_shrinker->lock);
> +	drm_gem_lru_init(&gem_shrinker->lru_evictable, &gem_shrinker->lock);
> +	drm_gem_lru_init(&gem_shrinker->lru_evicted, &gem_shrinker->lock);
> +	drm_gem_lru_init(&gem_shrinker->lru_pinned, &gem_shrinker->lock);
> +
> +	err = register_shrinker(&gem_shrinker->base, shrinker_name);
> +	if (err) {
> +		mutex_destroy(&gem_shrinker->lock);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static void drm_gem_shmem_shrinker_release(struct drm_device *dev,
> +					   struct drm_gem_shmem *shmem_mm)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = &shmem_mm->shrinker;
> +
> +	unregister_shrinker(&gem_shrinker->base);
> +	drm_WARN_ON(dev, !list_empty(&gem_shrinker->lru_evictable.list));
> +	drm_WARN_ON(dev, !list_empty(&gem_shrinker->lru_evicted.list));
> +	drm_WARN_ON(dev, !list_empty(&gem_shrinker->lru_pinned.list));
> +	mutex_destroy(&gem_shrinker->lock);
> +}
> +
> +static int drm_gem_shmem_init(struct drm_device *dev)
> +{
> +	int err;
> +
> +	if (WARN_ON(dev->shmem_mm))

drm_WARN_ON()

> +		return -EBUSY;
> +
> +	dev->shmem_mm = kzalloc(sizeof(*dev->shmem_mm), GFP_KERNEL);
> +	if (!dev->shmem_mm)
> +		return -ENOMEM;
> +
> +	err = drm_gem_shmem_shrinker_init(dev->shmem_mm, dev->unique);
> +	if (err)
> +		goto free_gem_shmem;
> +
> +	return 0;
> +
> +free_gem_shmem:
> +	kfree(dev->shmem_mm);
> +	dev->shmem_mm = NULL;
> +
> +	return err;
> +}
> +
> +static void drm_gem_shmem_release(struct drm_device *dev, void *ptr)
> +{
> +	struct drm_gem_shmem *shmem_mm = dev->shmem_mm;
> +
> +	drm_gem_shmem_shrinker_release(dev, shmem_mm);
> +	dev->shmem_mm = NULL;
> +	kfree(shmem_mm);
> +}
> +
> +/**
> + * drmm_gem_shmem_init() - Initialize drm-shmem internals
> + * @dev: DRM device
> + *
> + * Cleanup is automatically managed as part of DRM device releasing.
> + * Calling this function multiple times will result in a error.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drmm_gem_shmem_init(struct drm_device *dev)
> +{
> +	int err;
> +
> +	err = drm_gem_shmem_init(dev);
> +	if (err)
> +		return err;
> +
> +	err = drmm_add_action_or_reset(dev, drm_gem_shmem_release, NULL);
> +	if (err)
> +		return err;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drmm_gem_shmem_init);
> +
>   MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
>   MODULE_IMPORT_NS(DMA_BUF);
>   MODULE_LICENSE("GPL v2");
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> index 6a71a2555f85..865a989d67c8 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> @@ -15,6 +15,13 @@
>   #include "panfrost_gem.h"
>   #include "panfrost_mmu.h"
>   
> +static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
> +{
> +	return (shmem->madv > 0) &&
> +		!shmem->pages_pin_count && shmem->sgt &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach;
> +}
> +
>   static unsigned long
>   panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
>   {
> @@ -27,7 +34,7 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
>   		return 0;
>   
>   	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> -		if (drm_gem_shmem_is_purgeable(shmem))
> +		if (panfrost_gem_shmem_is_purgeable(shmem))
>   			count += shmem->base.size >> PAGE_SHIFT;
>   	}
>   
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index a68c6a312b46..8acd455fc156 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;
>   
> @@ -277,8 +278,13 @@ struct drm_device {
>   	/** @vma_offset_manager: GEM information */
>   	struct drm_vma_offset_manager *vma_offset_manager;
>   
> -	/** @vram_mm: VRAM MM memory manager */
> -	struct drm_vram_mm *vram_mm;
> +	union {
> +		/** @vram_mm: VRAM MM memory manager */
> +		struct drm_vram_mm *vram_mm;
> +
> +		/** @shmem_mm: SHMEM GEM memory manager */
> +		struct drm_gem_shmem *shmem_mm;
> +	};
>   
>   	/**
>   	 * @switch_power_state:
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 20ddcd799df9..c264caf6c83b 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;

Alphabetically, please.

>   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 allowed to be evicted by memory shrinker
> +	 * only when the count is 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 +102,12 @@ struct drm_gem_shmem_object {
>   	 * @map_wc: map object write-combined (instead of using shmem defaults).
>   	 */
>   	bool map_wc : 1;
> +
> +	/**
> +	 * @evicted: True if shmem pages are evicted by the memory shrinker.
> +	 * Used internally by memory shrinker.
> +	 */
> +	bool evicted : 1;
>   };
>   
>   #define to_drm_gem_shmem_obj(obj) \
> @@ -112,11 +129,17 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
>   
>   static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
>   {
> -	return (shmem->madv > 0) &&
> -		!shmem->vmap_use_count && shmem->sgt &&
> -		!shmem->base.dma_buf && !shmem->base.import_attach;
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	return (shmem->madv > 0) && shmem->base.funcs->evict &&
> +		shmem->pages_use_count && !shmem->pages_pin_count &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
> +		(shmem->sgt || shmem->evicted);
>   }
>   
> +int drm_gem_shmem_swap_in(struct drm_gem_shmem_object *shmem);
> +
> +void drm_gem_shmem_evict(struct drm_gem_shmem_object *shmem);
>   void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
>   
>   struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
> @@ -260,6 +283,36 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
>   	return drm_gem_shmem_mmap(shmem, vma);
>   }
>   
> +/**
> + * struct drm_gem_shmem_shrinker - Memory shrinker of GEM shmem memory manager
> + */
> +struct drm_gem_shmem_shrinker {
> +	/** @base: Shrinker for purging shmem GEM objects */
> +	struct shrinker base;
> +
> +	/** @lock: Protects @lru_* */
> +	struct mutex lock;
> +
> +	/** @lru_pinned: List of pinned shmem GEM objects */
> +	struct drm_gem_lru lru_pinned;
> +
> +	/** @lru_evictable: List of shmem GEM objects to be evicted */
> +	struct drm_gem_lru lru_evictable;
> +
> +	/** @lru_evicted: List of evicted shmem GEM objects */
> +	struct drm_gem_lru lru_evicted;
> +};
> +
> +/**
> + * struct drm_gem_shmem - GEM shmem memory manager
> + */
> +struct drm_gem_shmem {
> +	/** @shrinker: GEM shmem shrinker */
> +	struct drm_gem_shmem_shrinker shrinker;
> +};
> +
> +int drmm_gem_shmem_init(struct drm_device *dev);
> +
>   /*
>    * Driver ops
>    */

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
  

On 2/17/23 16:19, Thomas Zimmermann wrote:
>> +/**
>> + * drm_gem_shmem_swap_in() - Moves shmem GEM back to memory and enables
>> + *                           hardware access to the memory.
> 
> Do we have a better name than _swap_in()? I suggest
> drm_gem_shmem_unevict(), which suggest that it's the inverse to _evict().

The canonical naming scheme used by TTM and other DRM drivers is
_swapin(), without the underscore. I'll use that variant in v11 for the
naming consistency with the rest of DRM code.