linux-kernel - [PATCH v19 14/30] drm/shmem-helper: Add drm_gem_shmem_put

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Date: Fri,  5 Jan 2024 21:46:08 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: David Airlie <airlied@...il.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Christian König <christian.koenig@....com>,
	Qiang Yu <yuq825@...il.com>,
	Steven Price <steven.price@....com>,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Emma Anholt <emma@...olt.net>,
	Melissa Wen <mwen@...lia.com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	kernel@...labora.com,
	virtualization@...ts.linux-foundation.org
Subject: [PATCH v19 14/30] drm/shmem-helper: Add drm_gem_shmem_put_pages()

We're going to move away from having implicit get_pages() done by
get_pages_sgt() to ease simplify refcnt handling. Drivers will manage
get/put_pages() by themselves. Add drm_gem_shmem_put_pages().

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 20 ++++++++++++++++++++
 include/drm/drm_gem_shmem_helper.h     |  1 +
 2 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index dc416a4bce1b..f5ed64f78648 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -218,6 +218,7 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
  * @shmem: shmem GEM object
  *
  * This function decreases the use count and puts the backing pages when use drops to zero.
+ * Caller must hold GEM's reservation lock.
  */
 void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 {
@@ -228,6 +229,25 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
+/*
+ * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function decreases the use count and puts the backing pages when use drops to zero.
+ * It's unlocked version of drm_gem_shmem_put_pages_locked(), caller must not hold
+ * GEM's reservation lock.
+ */
+void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
+{
+	if (refcount_dec_not_one(&shmem->pages_use_count))
+		return;
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	drm_gem_shmem_put_pages_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages);
+
 /*
  * drm_gem_shmem_get_pages - Increase use count on the backing pages for a shmem GEM object
  * @shmem: shmem GEM object
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 6dedc0739fbc..525480488451 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -111,6 +111,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem);
 
 int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem);
+void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem);
 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem);
-- 
2.43.0