[v18,06/26] drm/shmem-helper: Add and use pages_pin_count

Commit Message

Dmitry Osipenko Oct. 29, 2023, 11:01 p.m. UTC

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.

Reviewed-by: Boris Brezillon <[e-mail]>
Suggested-by: Boris Brezillon <[e-mail]>
Signed-off-by: Dmitry Osipenko <[e-mail]>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 25 +++++++++++++++++--------
 include/drm/drm_gem_shmem_helper.h     | 11 +++++++++++
 2 files changed, 28 insertions(+), 8 deletions(-)

Comments

Maxime Ripard Nov. 24, 2023, 10:41 a.m. UTC | #1

On Mon, 30 Oct 2023 02:01:45 +0300, Dmitry Osipenko 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.
> 
> [ ... ]

Acked-by: Maxime Ripard <[e-mail]>

Thanks!
Maxime

Patch

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 2cc0601865f6..b9b71a1a563a 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -156,6 +156,7 @@  void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			drm_gem_shmem_put_pages_locked(shmem);
 
 		drm_WARN_ON(obj->dev, shmem->pages_use_count);
+		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count));
 
 		dma_resv_unlock(shmem->base.resv);
 	}
@@ -234,18 +235,16 @@  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
@@ -263,6 +262,9 @@  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;
@@ -286,8 +288,14 @@  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);
@@ -632,6 +640,7 @@  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 6ee4a4046980..5088bd623518 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -39,6 +39,17 @@  struct drm_gem_shmem_object {
 	 */
 	unsigned int pages_use_count;
 
+	/**
+	 * @pages_pin_count:
+	 *
+	 * Reference count on the pinned pages table.
+	 *
+	 * Pages are hard-pinned and reside in memory if count
+	 * greater than zero. Otherwise, when count is zero, the pages are
+	 * allowed to be evicted and purged by memory shrinker.
+	 */
+	refcount_t pages_pin_count;
+
 	/**
 	 * @madv: State for madvise
 	 *