Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker
From: Boris Brezillon
Date: Tue Sep 05 2023 - 12:42:45 EST
On Sun, 3 Sep 2023 20:07:31 +0300
Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 442 ++++++++++++++++--
> .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 9 +-
> include/drm/drm_device.h | 10 +-
> include/drm/drm_gem_shmem_helper.h | 71 ++-
> 4 files changed, 494 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 4633a418faba..a0a6c7e505c8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -20,6 +20,7 @@
> #include <drm/drm_device.h>
> #include <drm/drm_drv.h>
> #include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_managed.h>
> #include <drm/drm_prime.h>
> #include <drm/drm_print.h>
>
> @@ -88,8 +89,6 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
> if (ret)
> goto err_release;
>
> - INIT_LIST_HEAD(&shmem->madv_list);
> -
> if (!private) {
> /*
> * Our buffers are kept pinned, so allocating them
> @@ -128,6 +127,62 @@ 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)
> +{
> + dma_resv_assert_held(shmem->base.resv);
> +
> + return (shmem->madv >= 0) && shmem->base.funcs->evict &&
> + refcount_read(&shmem->pages_use_count) &&
> + !refcount_read(&shmem->pages_pin_count) &&
> + !shmem->base.dma_buf && !shmem->base.import_attach &&
> + shmem->sgt && !shmem->evicted;
> +}
> +
> +static void
> +drm_gem_shmem_update_pages_state_locked(struct drm_gem_shmem_object *shmem)
> +{
> + struct drm_gem_object *obj = &shmem->base;
> + struct drm_gem_shmem *shmem_mm = obj->dev->shmem_mm;
> + struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> +
> + dma_resv_assert_held(shmem->base.resv);
> +
> + if (!shmem_shrinker || obj->import_attach)
> + return;
> +
> + if (shmem->madv < 0)
> + drm_gem_lru_remove(&shmem->base);
> + else if (drm_gem_shmem_is_evictable(shmem) || drm_gem_shmem_is_purgeable(shmem))
> + drm_gem_lru_move_tail(&shmem_shrinker->lru_evictable, &shmem->base);
> + else if (shmem->evicted)
> + drm_gem_lru_move_tail(&shmem_shrinker->lru_evicted, &shmem->base);
> + else if (!shmem->pages)
> + drm_gem_lru_remove(&shmem->base);
> + else
> + drm_gem_lru_move_tail(&shmem_shrinker->lru_pinned, &shmem->base);
> +}
> +
> +static void
> +drm_gem_shmem_do_release_pages_locked(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_free - Free resources associated with a shmem GEM object
> * @shmem: shmem GEM object to free
> @@ -142,8 +197,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
> if (obj->import_attach) {
> drm_prime_gem_destroy(obj, shmem->sgt);
> } else if (!shmem->imported_sgt) {
> - dma_resv_lock(shmem->base.resv, NULL);
> -
> drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
>
> if (shmem->sgt) {
> @@ -152,14 +205,27 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
> sg_free_table(shmem->sgt);
> kfree(shmem->sgt);
> }
> - if (refcount_read(&shmem->pages_use_count)) {
> - drm_gem_shmem_put_pages_locked(shmem);
It would be preferable to introduce
drm_gem_shmem_do_release_pages_locked() earlier in the series (not a
huge fan of the name BTW, especially since this function can be called
without the lock held in the free path), so we keep things bisectable.
> - drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
> +
> + /*
> + * Destroying the object is a special case.. drm_gem_shmem_free()
> + * calls many things that WARN_ON if the obj lock is not held.
If that's the case, that should be fixed the same way you're fixing the
put_pages_locked() situation here.
> * But
> + * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> + * cause a locking order inversion between reservation_ww_class_mutex
> + * and fs_reclaim.
> + *
> + * This deadlock is not actually possible, because no one should
> + * be already holding the lock when drm_gem_shmem_free() is called.
> + * Unfortunately lockdep is not aware of this detail. So when the
> + * refcount drops to zero, don't touch the reservation lock.
> + */
> + if (shmem->got_pages_sgt &&
> + refcount_dec_and_test(&shmem->pages_use_count)) {
> + drm_gem_shmem_do_release_pages_locked(shmem);
> + shmem->got_pages_sgt = false;
> }
Leaking memory is the right thing to do if pages_use_count > 1 (it's
better to leak than having someone access memory it no longer owns), but
I think it's worth mentioning in the above comment.
>
> drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
> -
> - dma_resv_unlock(shmem->base.resv);
> + drm_WARN_ON(obj->dev, shmem->got_pages_sgt);
> }
>
> drm_gem_object_release(obj);
> @@ -167,15 +233,26 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
>
> -static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +static int
> +drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem, bool init)
> {
> struct drm_gem_object *obj = &shmem->base;
> struct page **pages;
>
> dma_resv_assert_held(shmem->base.resv);
I'd defer this check to the caller (AFAICT, all callers have this
already). This way the function name is consistent with its behavior.
>
> - if (refcount_inc_not_zero(&shmem->pages_use_count))
> + 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, !(init ^ refcount_read(&shmem->pages_use_count))))
> + return -EINVAL;
>
> pages = drm_gem_get_pages(obj);
> if (IS_ERR(pages)) {
> @@ -196,8 +273,36 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>
> shmem->pages = pages;
>
> + return 0;
> +}
> +
> +static void
> +drm_gem_shmem_release_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> + dma_resv_assert_held(shmem->base.resv);
> + drm_gem_shmem_do_release_pages_locked(shmem);
> +}
Do we really need an intermediate helper here. Can't we let the callers
ensure the resv is held (that's already the case BTW). This way, you
simply have drm_gem_shmem_{release,acquire}_pages() helpers, and the
drm_gem_shmem_release_pages() helper can be used in
drm_gem_shmem_free().
> +
> +static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> + int err;
> +
> + dma_resv_assert_held(shmem->base.resv);
> +
> + if (shmem->madv < 0)
> + return -ENOMEM;
> +
> + if (refcount_inc_not_zero(&shmem->pages_use_count))
> + return 0;
> +
> + err = drm_gem_shmem_acquire_pages(shmem, true);
> + if (err)
> + return err;
> +
> refcount_set(&shmem->pages_use_count, 1);
>
> + drm_gem_shmem_update_pages_state_locked(shmem);
> +
> return 0;
> }
>
> @@ -209,20 +314,11 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> */
> void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
> {
> - struct drm_gem_object *obj = &shmem->base;
> -
> dma_resv_assert_held(shmem->base.resv);
>
> if (refcount_dec_and_test(&shmem->pages_use_count)) {
> -#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_release_pages_locked(shmem);
> + drm_gem_shmem_update_pages_state_locked(shmem);
> }
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
> @@ -251,8 +347,15 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
> return 0;
>
> ret = drm_gem_shmem_get_pages_locked(shmem);
> - if (!ret)
> + if (!ret) {
> + ret = drm_gem_shmem_swapin_locked(shmem);
> + if (ret) {
> + drm_gem_shmem_put_pages_locked(shmem);
> + return ret;
> + }
> +
> refcount_set(&shmem->pages_pin_count, 1);
> + }
>
> return ret;
> }
> @@ -448,29 +551,54 @@ int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv)
>
> madv = shmem->madv;
>
> + drm_gem_shmem_update_pages_state_locked(shmem);
> +
> return (madv >= 0);
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise_locked);
>
> -void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
> +{
> + struct drm_gem_object *obj = &shmem->base;
> + int ret;
> +
> + ret = dma_resv_lock_interruptible(obj->resv, NULL);
> + if (ret)
> + return ret;
> +
> + ret = drm_gem_shmem_madvise_locked(shmem, madv);
> + dma_resv_unlock(obj->resv);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
> +
> +static void drm_gem_shmem_unpin_pages_locked(struct drm_gem_shmem_object *shmem)
> {
> struct drm_gem_object *obj = &shmem->base;
> struct drm_device *dev = obj->dev;
>
> dma_resv_assert_held(shmem->base.resv);
>
> - drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
> + if (shmem->evicted)
> + return;
>
> dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
> + drm_gem_shmem_release_pages_locked(shmem);
> + drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> +
> sg_free_table(shmem->sgt);
> kfree(shmem->sgt);
> shmem->sgt = NULL;
> +}
>
> - drm_gem_shmem_put_pages_locked(shmem);
> +void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +{
> + struct drm_gem_object *obj = &shmem->base;
>
> - shmem->madv = -1;
> + drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
>
> - drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> + drm_gem_shmem_unpin_pages_locked(shmem);
> drm_gem_free_mmap_offset(obj);
>
> /* Our goal here is to return as much of the memory as
> @@ -481,9 +609,59 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
>
> invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
> +
> + shmem->madv = -1;
> + shmem->evicted = false;
> + drm_gem_shmem_update_pages_state_locked(shmem);
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_purge_locked);
>
> +/**
> + * drm_gem_shmem_swapin_locked() - Moves shmem GEM back to memory and enables
> + * hardware access to the memory.
> + * @shmem: shmem GEM object
> + *
> + * This function moves shmem GEM back to memory if it was previously evicted
> + * by the memory shrinker. The GEM is ready to use on success.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem)
> +{
> + struct drm_gem_object *obj = &shmem->base;
> + struct sg_table *sgt;
> + int err;
> +
> + dma_resv_assert_held(shmem->base.resv);
> +
> + if (shmem->evicted) {
> + err = drm_gem_shmem_acquire_pages(shmem, false);
> + if (err)
> + return err;
> +
> + sgt = drm_gem_shmem_get_sg_table(shmem);
> + if (IS_ERR(sgt))
> + return PTR_ERR(sgt);
> +
> + err = dma_map_sgtable(obj->dev->dev, sgt,
> + DMA_BIDIRECTIONAL, 0);
> + if (err) {
> + sg_free_table(sgt);
> + kfree(sgt);
> + return err;
> + }
> +
> + shmem->sgt = sgt;
> + shmem->evicted = false;
> +
> + drm_gem_shmem_update_pages_state_locked(shmem);
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swapin_locked);
> +
> /**
> * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
> * @file: DRM file structure to create the dumb buffer for
> @@ -530,22 +708,34 @@ 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 ||
> + !refcount_read(&shmem->pages_use_count));
> + drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
> +
> + if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
> ret = VM_FAULT_SIGBUS;
> } else {
> + err = drm_gem_shmem_swapin_locked(shmem);
> + if (err) {
> + ret = VM_FAULT_OOM;
> + goto unlock;
> + }
> +
> page = shmem->pages[page_offset];
>
> ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
> }
>
> +unlock:
> dma_resv_unlock(shmem->base.resv);
>
> return ret;
> @@ -568,6 +758,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
> drm_WARN_ON_ONCE(obj->dev,
> !refcount_inc_not_zero(&shmem->pages_use_count));
>
> + drm_gem_shmem_update_pages_state_locked(shmem);
> dma_resv_unlock(shmem->base.resv);
>
> drm_gem_vm_open(vma);
> @@ -653,7 +844,9 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
> drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
> drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
> drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&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_GPL(drm_gem_shmem_print_info);
>
> @@ -715,6 +908,8 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
>
> shmem->sgt = sgt;
>
> + drm_gem_shmem_update_pages_state_locked(shmem);
> +
> return sgt;
>
> err_free_sgt:
> @@ -802,6 +997,191 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
>
> +static struct drm_gem_shmem_shrinker *
> +to_drm_gem_shmem_shrinker(struct shrinker *shrinker)
> +{
> + return container_of(shrinker, struct drm_gem_shmem_shrinker, base);
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_count_objects(struct shrinker *shrinker,
> + struct shrink_control *sc)
> +{
> + struct drm_gem_shmem_shrinker *shmem_shrinker =
> + to_drm_gem_shmem_shrinker(shrinker);
> + unsigned long count = shmem_shrinker->lru_evictable.count;
> +
> + if (count >= SHRINK_EMPTY)
> + return SHRINK_EMPTY - 1;
> +
> + return count ?: SHRINK_EMPTY;
> +}
> +
> +void drm_gem_shmem_evict_locked(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_locked(shmem);
> +
> + shmem->evicted = true;
> + drm_gem_shmem_update_pages_state_locked(shmem);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict_locked);
> +
> +static bool drm_gem_shmem_shrinker_evict_locked(struct drm_gem_object *obj)
> +{
> + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> + int err;
> +
> + if (!drm_gem_shmem_is_evictable(shmem) ||
> + get_nr_swap_pages() < obj->size >> PAGE_SHIFT)
> + return false;
> +
> + err = drm_gem_evict_locked(obj);
> + if (err)
> + return false;
> +
> + return true;
> +}
> +
> +static bool drm_gem_shmem_shrinker_purge_locked(struct drm_gem_object *obj)
> +{
> + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> + int err;
> +
> + if (!drm_gem_shmem_is_purgeable(shmem))
> + return false;
> +
> + err = drm_gem_evict_locked(obj);
> + if (err)
> + return false;
> +
> + return true;
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
> + struct shrink_control *sc)
> +{
> + struct drm_gem_shmem_shrinker *shmem_shrinker;
> + unsigned long nr_to_scan = sc->nr_to_scan;
> + unsigned long remaining = 0;
> + unsigned long freed = 0;
> +
> + shmem_shrinker = to_drm_gem_shmem_shrinker(shrinker);
> +
> + /* purge as many objects as we can */
> + freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
> + nr_to_scan, &remaining,
> + drm_gem_shmem_shrinker_purge_locked);
> +
> + /* evict as many objects as we can */
> + if (freed < nr_to_scan)
> + freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
> + nr_to_scan - freed, &remaining,
> + drm_gem_shmem_shrinker_evict_locked);
> +
> + return (freed > 0 && remaining > 0) ? freed : SHRINK_STOP;
> +}
> +
> +static int drm_gem_shmem_shrinker_init(struct drm_gem_shmem *shmem_mm,
> + const char *shrinker_name)
> +{
> + struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> + int err;
> +
> + shmem_shrinker->base.count_objects = drm_gem_shmem_shrinker_count_objects;
> + shmem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
> + shmem_shrinker->base.seeks = DEFAULT_SEEKS;
> +
> + mutex_init(&shmem_shrinker->lock);
> + drm_gem_lru_init(&shmem_shrinker->lru_evictable, &shmem_shrinker->lock);
> + drm_gem_lru_init(&shmem_shrinker->lru_evicted, &shmem_shrinker->lock);
> + drm_gem_lru_init(&shmem_shrinker->lru_pinned, &shmem_shrinker->lock);
> +
> + err = register_shrinker(&shmem_shrinker->base, shrinker_name);
> + if (err) {
> + mutex_destroy(&shmem_shrinker->lock);
> + return err;
> + }
> +
> + return 0;
> +}
> +
> +static void drm_gem_shmem_shrinker_release(struct drm_device *dev,
> + struct drm_gem_shmem *shmem_mm)
> +{
> + struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> +
> + unregister_shrinker(&shmem_shrinker->base);
> + drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evictable.list));
> + drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evicted.list));
> + drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_pinned.list));
> + mutex_destroy(&shmem_shrinker->lock);
> +}
> +
> +static int drm_gem_shmem_init(struct drm_device *dev)
> +{
> + int err;
> +
> + if (drm_WARN_ON(dev, dev->shmem_mm))
> + return -EBUSY;
> +
> + dev->shmem_mm = kzalloc(sizeof(*dev->shmem_mm), GFP_KERNEL);
> + if (!dev->shmem_mm)
> + return -ENOMEM;
> +
> + err = drm_gem_shmem_shrinker_init(dev->shmem_mm, dev->unique);
> + if (err)
> + goto free_gem_shmem;
> +
> + return 0;
> +
> +free_gem_shmem:
> + kfree(dev->shmem_mm);
> + dev->shmem_mm = NULL;
> +
> + return err;
> +}
> +
> +static void drm_gem_shmem_release(struct drm_device *dev, void *ptr)
> +{
> + struct drm_gem_shmem *shmem_mm = dev->shmem_mm;
> +
> + drm_gem_shmem_shrinker_release(dev, shmem_mm);
> + dev->shmem_mm = NULL;
> + kfree(shmem_mm);
> +}
> +
> +/**
> + * drmm_gem_shmem_init() - Initialize drm-shmem internals
> + * @dev: DRM device
> + *
> + * Cleanup is automatically managed as part of DRM device releasing.
> + * Calling this function multiple times will result in a error.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drmm_gem_shmem_init(struct drm_device *dev)
> +{
> + int err;
> +
> + err = drm_gem_shmem_init(dev);
> + if (err)
> + return err;
> +
> + err = drmm_add_action_or_reset(dev, drm_gem_shmem_release, NULL);
> + if (err)
> + return err;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(drmm_gem_shmem_init);
> +
> MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
> MODULE_IMPORT_NS(DMA_BUF);
> MODULE_LICENSE("GPL v2");
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> index 72193bd734e1..1aa94fff7072 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) &&
> + !refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
> + !shmem->base.dma_buf && !shmem->base.import_attach;
> +}
> +
> static unsigned long
> panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> {
> @@ -27,7 +34,7 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
> return 0;
>
> list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> - if (drm_gem_shmem_is_purgeable(shmem))
> + if (panfrost_gem_shmem_is_purgeable(shmem))
> count += shmem->base.size >> PAGE_SHIFT;
> }
>
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 7cf4afae2e79..a978f0cb5e84 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -16,6 +16,7 @@ struct drm_vblank_crtc;
> struct drm_vma_offset_manager;
> struct drm_vram_mm;
> struct drm_fb_helper;
> +struct drm_gem_shmem_shrinker;
>
> struct inode;
>
> @@ -290,8 +291,13 @@ struct drm_device {
> /** @vma_offset_manager: GEM information */
> struct drm_vma_offset_manager *vma_offset_manager;
>
> - /** @vram_mm: VRAM MM memory manager */
> - struct drm_vram_mm *vram_mm;
> + union {
> + /** @vram_mm: VRAM MM memory manager */
> + struct drm_vram_mm *vram_mm;
> +
> + /** @shmem_mm: SHMEM GEM memory manager */
> + struct drm_gem_shmem *shmem_mm;
> + };
>
> /**
> * @switch_power_state:
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 63e91e8f2d5c..65c99da25048 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -6,6 +6,7 @@
> #include <linux/fs.h>
> #include <linux/mm.h>
> #include <linux/mutex.h>
> +#include <linux/shrinker.h>
>
> #include <drm/drm_file.h>
> #include <drm/drm_gem.h>
> @@ -13,6 +14,7 @@
> #include <drm/drm_prime.h>
>
> struct dma_buf_attachment;
> +struct drm_device;
> struct drm_mode_create_dumb;
> struct drm_printer;
> struct sg_table;
> @@ -53,8 +55,8 @@ struct drm_gem_shmem_object {
> * @madv: State for madvise
> *
> * 0 is active/inuse.
> + * 1 is not-needed/can-be-purged
> * A negative value is the object is purged.
> - * Positive values are driver specific and not used by the helpers.
> */
> int madv;
>
> @@ -115,6 +117,12 @@ 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) \
> @@ -133,14 +141,22 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
> int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma);
>
> int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
> +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) &&
> - !refcount_read(&shmem->pages_pin_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 &&
> + refcount_read(&shmem->pages_use_count) &&
> + !refcount_read(&shmem->pages_pin_count) &&
> + !shmem->base.dma_buf && !shmem->base.import_attach &&
> + (shmem->sgt || shmem->evicted);
> }
>
> +int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem);
> +
> +void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem);
> void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
>
> struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
> @@ -284,6 +300,53 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
> return drm_gem_shmem_mmap(shmem, vma);
> }
>
> +/**
> + * drm_gem_shmem_object_madvise - unlocked GEM object function for drm_gem_shmem_madvise_locked()
> + * @obj: GEM object
> + * @madv: Madvise value
> + *
> + * This function wraps drm_gem_shmem_madvise_locked(), providing unlocked variant.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +static inline int drm_gem_shmem_object_madvise(struct drm_gem_object *obj, int madv)
> +{
> + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> + return drm_gem_shmem_madvise(shmem, madv);
> +}
> +
> +/**
> + * 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
> */