[PATCH v6 21/21] dma-buf: Remove obsoleted internal lock

From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
To: "David Airlie" <airlied@linux.ie>,
	"Gerd Hoffmann" <kraxel@redhat.com>,
	"Gurchetan Singh" <gurchetansingh@chromium.org>,
	"Chia-I Wu" <olvaffe@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Daniel Almeida" <daniel.almeida@collabora.com>,
	"Gert Wollny" <gert.wollny@collabora.com>,
	"Gustavo Padovan" <gustavo.padovan@collabora.com>,
	"Daniel Stone" <daniel@fooishbar.org>,
	"Tomeu Vizoso" <tomeu.vizoso@collabora.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Rob Clark" <robdclark@gmail.com>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Pan, Xinhui" <Xinhui.Pan@amd.com>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Tomasz Figa" <tfiga@chromium.org>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Tvrtko Ursulin" <tvrtko.ursulin@linux.intel.com>,
	"Thomas Hellström" <thomas_os@shipmail.org>,
	"Qiang Yu" <yuq825@gmail.com>,
	"Srinivas Kandagatla" <srinivas.kandagatla@linaro.org>,
	"Amol Maheshwari" <amahesh@qti.qualcomm.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Leon Romanovsky" <leon@kernel.org>,
	"Juergen Gross" <jgross@suse.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
	"Tomi Valkeinen" <tomba@kernel.org>,
	"Russell King" <linux@armlinux.org.uk>,
	"Lucas Stach" <l.stach@pengutronix.de>,
	"Christian Gmeiner" <christian.gmeiner@gmail.com>,
	"Ruhl Michael J" <michael.j.ruhl@intel.com>
Cc: linux-rdma@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	amd-gfx@lists.freedesktop.org,
	virtualization@lists.linux-foundation.org,
	linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org,
	Dmitry Osipenko <digetx@gmail.com>,
	kernel@collabora.com, linux-media@vger.kernel.org
Subject: [PATCH v6 21/21] dma-buf: Remove obsoleted internal lock
Date: Wed, 28 Sep 2022 22:16:00 +0300	[thread overview]
Message-ID: <20220928191600.5874-22-dmitry.osipenko@collabora.com> (raw)
In-Reply-To: <20220928191600.5874-1-dmitry.osipenko@collabora.com>

The internal dma-buf lock isn't needed anymore because the updated
locking specification claims that dma-buf reservation must be locked
by importers, and thus, the internal data is already protected by the
reservation lock. Remove the obsoleted internal lock.

Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/dma-buf/dma-buf.c | 14 ++++----------
 include/linux/dma-buf.h   |  9 ---------
 2 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index e04d504441a5..82f72b5647f8 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -657,7 +657,6 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 
 	dmabuf->file = file;
 
-	mutex_init(&dmabuf->lock);
 	INIT_LIST_HEAD(&dmabuf->attachments);
 
 	mutex_lock(&db_list.lock);
@@ -1503,7 +1502,7 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
 {
 	struct iosys_map ptr;
-	int ret = 0;
+	int ret;
 
 	iosys_map_clear(map);
 
@@ -1515,28 +1514,25 @@ int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
 	if (!dmabuf->ops->vmap)
 		return -EINVAL;
 
-	mutex_lock(&dmabuf->lock);
 	if (dmabuf->vmapping_counter) {
 		dmabuf->vmapping_counter++;
 		BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
 		*map = dmabuf->vmap_ptr;
-		goto out_unlock;
+		return 0;
 	}
 
 	BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
 
 	ret = dmabuf->ops->vmap(dmabuf, &ptr);
 	if (WARN_ON_ONCE(ret))
-		goto out_unlock;
+		return ret;
 
 	dmabuf->vmap_ptr = ptr;
 	dmabuf->vmapping_counter = 1;
 
 	*map = dmabuf->vmap_ptr;
 
-out_unlock:
-	mutex_unlock(&dmabuf->lock);
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
 
@@ -1581,13 +1577,11 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
 	BUG_ON(dmabuf->vmapping_counter == 0);
 	BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
 
-	mutex_lock(&dmabuf->lock);
 	if (--dmabuf->vmapping_counter == 0) {
 		if (dmabuf->ops->vunmap)
 			dmabuf->ops->vunmap(dmabuf, map);
 		iosys_map_clear(&dmabuf->vmap_ptr);
 	}
-	mutex_unlock(&dmabuf->lock);
 }
 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
 
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index f11b5bbc2f37..6fa8d4e29719 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -326,15 +326,6 @@ struct dma_buf {
 	/** @ops: dma_buf_ops associated with this buffer object. */
 	const struct dma_buf_ops *ops;
 
-	/**
-	 * @lock:
-	 *
-	 * Used internally to serialize list manipulation, attach/detach and
-	 * vmap/unmap. Note that in many cases this is superseeded by
-	 * dma_resv_lock() on @resv.
-	 */
-	struct mutex lock;
-
 	/**
 	 * @vmapping_counter:
 	 *
-- 
2.37.3

