drm/shmem-helper: Use refcount_t for pages_use_count

Use atomic refcount_t helper for pages_use_count to optimize pin/unpin
functions by skipping reservation locking while GEM's pin refcount > 1.

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.d>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250322212608.40511-9-dmitry.osipenko@collabora.com

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index d338b36f4eaa4c3585edb2f8aa454b7ddcd0f9d4..6fb96e790abd24c4a37a36cfb64eee395de822be 100644 (file)
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -176,7 +176,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
                if (shmem->pages)
                        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_use_count));
                drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count));
 
                dma_resv_unlock(shmem->base.resv);
@@ -194,14 +194,13 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 
        dma_resv_assert_held(shmem->base.resv);
 
-       if (shmem->pages_use_count++ > 0)
+       if (refcount_inc_not_zero(&shmem->pages_use_count))
                return 0;
 
        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);
        }
 
@@ -217,6 +216,8 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 
        shmem->pages = pages;
 
+       refcount_set(&shmem->pages_use_count, 1);
+
        return 0;
 }
 
@@ -232,21 +233,17 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 
        dma_resv_assert_held(shmem->base.resv);
 
-       if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
-               return;
-
-       if (--shmem->pages_use_count > 0)
-               return;
-
+       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);
+               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_put_pages(obj, shmem->pages,
+                                 shmem->pages_mark_dirty_on_put,
+                                 shmem->pages_mark_accessed_on_put);
+               shmem->pages = NULL;
+       }
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
@@ -582,8 +579,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
         * mmap'd, vm_open() just grabs an additional reference for the new
         * mm the vma is getting copied into (ie. on fork()).
         */
-       if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
-               shmem->pages_use_count++;
+       drm_WARN_ON_ONCE(obj->dev,
+                        !refcount_inc_not_zero(&shmem->pages_use_count));
 
        dma_resv_unlock(shmem->base.resv);
 
@@ -674,7 +671,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
                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, "pages_use_count=%u\n", refcount_read(&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/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 609221351cdeb21b0d68ea55781df57d37153537..5deec673c11eddfb0099496e44b8c406e1dd884a 100644 (file)
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -47,7 +47,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
                }
 
                bo->base.pages = pages;
-               bo->base.pages_use_count = 1;
+               refcount_set(&bo->base.pages_use_count, 1);
 
                mapping_set_unevictable(mapping);
        }

diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index b91019cd5acb191a560b7217ff792cf4222004fa..4a0b4bf03f1a1675588e400ce8cdfd00ec8b6ffc 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -489,7 +489,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
                        goto err_unlock;
                }
                bo->base.pages = pages;
-               bo->base.pages_use_count = 1;
+               refcount_set(&bo->base.pages_use_count, 1);
        } else {
                pages = bo->base.pages;
                if (pages[page_offset]) {

diff --git a/drivers/gpu/drm/tests/drm_gem_shmem_test.c b/drivers/gpu/drm/tests/drm_gem_shmem_test.c
index 98884966bb9279557ab5093f565f875c1f5edd28..1459cdb0c41331ab10ee52f16f5f71d9d3d0540c 100644 (file)
--- a/drivers/gpu/drm/tests/drm_gem_shmem_test.c
+++ b/drivers/gpu/drm/tests/drm_gem_shmem_test.c
@@ -134,7 +134,7 @@ static void drm_gem_shmem_test_pin_pages(struct kunit *test)
        shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
        KUNIT_EXPECT_NULL(test, shmem->pages);
-       KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 0);
+       KUNIT_EXPECT_EQ(test, refcount_read(&shmem->pages_use_count), 0);
 
        ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
        KUNIT_ASSERT_EQ(test, ret, 0);
@@ -142,14 +142,14 @@ static void drm_gem_shmem_test_pin_pages(struct kunit *test)
        ret = drm_gem_shmem_pin(shmem);
        KUNIT_ASSERT_EQ(test, ret, 0);
        KUNIT_ASSERT_NOT_NULL(test, shmem->pages);
-       KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 1);
+       KUNIT_EXPECT_EQ(test, refcount_read(&shmem->pages_use_count), 1);
 
        for (i = 0; i < (shmem->base.size >> PAGE_SHIFT); i++)
                KUNIT_ASSERT_NOT_NULL(test, shmem->pages[i]);
 
        drm_gem_shmem_unpin(shmem);
        KUNIT_EXPECT_NULL(test, shmem->pages);
-       KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 0);
+       KUNIT_EXPECT_EQ(test, refcount_read(&shmem->pages_use_count), 0);
 }
 
 /*
@@ -251,7 +251,7 @@ static void drm_gem_shmem_test_get_sg_table(struct kunit *test)
        sgt = drm_gem_shmem_get_pages_sgt(shmem);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, sgt);
        KUNIT_ASSERT_NOT_NULL(test, shmem->pages);
-       KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 1);
+       KUNIT_EXPECT_EQ(test, refcount_read(&shmem->pages_use_count), 1);
        KUNIT_EXPECT_PTR_EQ(test, sgt, shmem->sgt);
 
        for_each_sgtable_sg(sgt, sg, si) {

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index d411215fe49403ad906bb6b616a7c9085d826980..3a4be433d5f0cf55712b76e32641a7773cea3b0a 100644 (file)
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -37,7 +37,7 @@ struct drm_gem_shmem_object {
         * Reference count on the pages table.
         * The pages are put when the count reaches zero.
         */
-       unsigned int pages_use_count;
+       refcount_t pages_use_count;
 
        /**
         * @pages_pin_count: