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    Date
    SubjectRe: [PATCH v6 17/22] drm/shmem-helper: Add generic memory shrinker
    From
    Am 05.06.22 um 18:47 schrieb Daniel Vetter:
    > On Fri, 27 May 2022 at 01:55, Dmitry Osipenko
    > <dmitry.osipenko@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@collabora.com>
    >> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@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
    >>
    >

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