On Sun, 3 Sep 2023 20:07:26 +0300
Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> Add separate pages_pin_count for tracking of whether drm-shmem pages are
> moveable or not. With the addition of memory shrinker support to drm-shmem,
> the pages_use_count will no longer determine whether pages are hard-pinned
> in memory, but whether pages exist and are soft-pinned (and could be swapped
> out). The pages_pin_count > 1 will hard-pin pages in memory.
>
> Suggested-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 24 ++++++++++++++++--------
> include/drm/drm_gem_shmem_helper.h | 10 ++++++++++
> 2 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 25e99468ced2..7e1e674e2c9f 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -236,18 +236,16 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>
> dma_resv_assert_held(shmem->base.resv);
>
> + if (refcount_inc_not_zero(&shmem->pages_pin_count))
> + return 0;
> +
> ret = drm_gem_shmem_get_pages_locked(shmem);
> + if (!ret)
> + refcount_set(&shmem->pages_pin_count, 1);
>
> return ret;
> }
>
> -static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
> -{
> - dma_resv_assert_held(shmem->base.resv);
> -
> - drm_gem_shmem_put_pages_locked(shmem);
> -}
> -
> /**
> * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
> * @shmem: shmem GEM object
> @@ -265,6 +263,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> + if (refcount_inc_not_zero(&shmem->pages_pin_count))
> + return 0;
> +
> ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
> if (ret)
> return ret;
> @@ -288,8 +289,14 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> + if (refcount_dec_not_one(&shmem->pages_pin_count))
> + return;
> +
> dma_resv_lock(shmem->base.resv, NULL);
> - drm_gem_shmem_unpin_locked(shmem);
> +
> + if (refcount_dec_and_test(&shmem->pages_pin_count))
> + drm_gem_shmem_put_pages_locked(shmem);
> +
> dma_resv_unlock(shmem->base.resv);
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
> @@ -634,6 +641,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
> if (shmem->base.import_attach)
> return;
>
> + 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", shmem->pages_use_count);
> drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
> drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 808083279fd5..1cd74ae5761a 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -39,6 +39,16 @@ 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 and purged by memory
> + * shrinker only when the count is zero, otherwise pages
> + * are hard-pinned in memory.
> + */
> + refcount_t pages_pin_count;
> +
> /**
> * @madv: State for madvise
> *
