[PATCH v12 02/11] drm/shmem-helper: Factor out pages alloc/release from drm_gem_shmem_get/put_pages()

[Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>]

Factor out pages allocation from drm_gem_shmem_get_pages() into
drm_gem_shmem_acquire_pages() function and similar for the put_pages()
in a preparation for addition of shrinker support to drm-shmem.

Once shrinker will be added, the pages_use_count>0 will no longer determine
whether pages are pinned because pages could be swapped out by the shrinker
and then pages_use_count will be greater than 0 in this case. We will add
new pages_pin_count in a later patch.

The new common drm_gem_shmem_acquire/release_pages() will be used by
shrinker code for performing the page swapping.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 67 +++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 651ca7f380a2..a62c41336a7f 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -165,19 +165,26 @@ 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(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)
-		return 0;
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (shmem->madv < 0) {
+		drm_WARN_ON(obj->dev, shmem->pages);
+		return -ENOMEM;
+	}
+
+	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 +203,48 @@ 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)
+		return 0;
+
+	err = drm_gem_shmem_acquire_pages(shmem);
+	if (err)
+		goto err_zero_use;
+
+	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;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+#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
@@ -214,15 +263,7 @@ 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_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(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
 
-- 
2.39.2