Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 12.22.5.238 as permitted sender) receiver=protection.outlook.com;
 client-ip=12.22.5.238; helo=mail.nvidia.com; pr=C
From:   Eli Cohen <elic@nvidia.com>
To:     <mst@redhat.com>, <jasowang@redhat.com>
CC:     <virtualization@lists.linux-foundation.org>,
        <linux-kernel@vger.kernel.org>, <si-wei.liu@oracle.com>,
        Eli Cohen <elic@nvidia.com>
Subject: [PATCH v8 4/6] net/vdpa: Use readers/writers semaphore instead of cf_mutex
Date:   Wed, 18 May 2022 16:38:02 +0300
Message-ID: <20220518133804.1075129-5-elic@nvidia.com>
In-Reply-To: <20220518133804.1075129-1-elic@nvidia.com>
References: <20220518133804.1075129-1-elic@nvidia.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 May 2022 13:38:18.4377
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 318cd30e-e4f8-4065-4725-08da38d3ab18
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.238];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT046.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR1201MB0262
X-Spam-Status: No, score=-2.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE
	autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Replace cf_mutex with rw_semaphore to reflect the fact that some calls
could be called concurrently but can suffice with read lock.

Suggested-by: Si-Wei Liu <si-wei.liu@oracle.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
---
 drivers/vdpa/vdpa.c  | 25 ++++++++++++-------------
 include/linux/vdpa.h | 12 ++++++------
 2 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 2ff7de5e6b2f..9d3534a0bc5f 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -23,9 +23,9 @@ static DEFINE_IDA(vdpa_index_ida);
 
 void vdpa_set_status(struct vdpa_device *vdev, u8 status)
 {
-	mutex_lock(&vdev->cf_mutex);
+	down_write(&vdev->cf_lock);
 	vdev->config->set_status(vdev, status);
-	mutex_unlock(&vdev->cf_mutex);
+	up_write(&vdev->cf_lock);
 }
 EXPORT_SYMBOL(vdpa_set_status);
 
@@ -148,7 +148,6 @@ static void vdpa_release_dev(struct device *d)
 		ops->free(vdev);
 
 	ida_simple_remove(&vdpa_index_ida, vdev->index);
-	mutex_destroy(&vdev->cf_mutex);
 	kfree(vdev->driver_override);
 	kfree(vdev);
 }
@@ -211,7 +210,7 @@ struct vdpa_device *__vdpa_alloc_device(struct device *parent,
 	if (err)
 		goto err_name;
 
-	mutex_init(&vdev->cf_mutex);
+	init_rwsem(&vdev->cf_lock);
 	device_initialize(&vdev->dev);
 
 	return vdev;
@@ -407,9 +406,9 @@ static void vdpa_get_config_unlocked(struct vdpa_device *vdev,
 void vdpa_get_config(struct vdpa_device *vdev, unsigned int offset,
 		     void *buf, unsigned int len)
 {
-	mutex_lock(&vdev->cf_mutex);
+	down_read(&vdev->cf_lock);
 	vdpa_get_config_unlocked(vdev, offset, buf, len);
-	mutex_unlock(&vdev->cf_mutex);
+	up_read(&vdev->cf_lock);
 }
 EXPORT_SYMBOL_GPL(vdpa_get_config);
 
@@ -423,9 +422,9 @@ EXPORT_SYMBOL_GPL(vdpa_get_config);
 void vdpa_set_config(struct vdpa_device *vdev, unsigned int offset,
 		     const void *buf, unsigned int length)
 {
-	mutex_lock(&vdev->cf_mutex);
+	down_write(&vdev->cf_lock);
 	vdev->config->set_config(vdev, offset, buf, length);
-	mutex_unlock(&vdev->cf_mutex);
+	up_write(&vdev->cf_lock);
 }
 EXPORT_SYMBOL_GPL(vdpa_set_config);
 
@@ -866,7 +865,7 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
 	u8 status;
 	int err;
 
-	mutex_lock(&vdev->cf_mutex);
+	down_read(&vdev->cf_lock);
 	status = vdev->config->get_status(vdev);
 	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
 		NL_SET_ERR_MSG_MOD(extack, "Features negotiation not completed");
@@ -903,14 +902,14 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
 	if (err)
 		goto msg_err;
 
-	mutex_unlock(&vdev->cf_mutex);
+	up_read(&vdev->cf_lock);
 	genlmsg_end(msg, hdr);
 	return 0;
 
 msg_err:
 	genlmsg_cancel(msg, hdr);
 out:
-	mutex_unlock(&vdev->cf_mutex);
+	up_read(&vdev->cf_lock);
 	return err;
 }
 
@@ -954,7 +953,7 @@ static int vendor_stats_fill(struct vdpa_device *vdev, struct sk_buff *msg,
 {
 	int err;
 
-	mutex_lock(&vdev->cf_mutex);
+	down_read(&vdev->cf_lock);
 	if (!vdev->config->get_vendor_vq_stats) {
 		err = -EOPNOTSUPP;
 		goto out;
@@ -962,7 +961,7 @@ static int vendor_stats_fill(struct vdpa_device *vdev, struct sk_buff *msg,
 
 	err = vdpa_fill_stats_rec(vdev, msg, info, index);
 out:
-	mutex_unlock(&vdev->cf_mutex);
+	up_read(&vdev->cf_lock);
 	return err;
 }
 
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 2ae8443331e1..2cb14847831e 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -66,7 +66,7 @@ struct vdpa_mgmt_dev;
  * @dma_dev: the actual device that is performing DMA
  * @driver_override: driver name to force a match
  * @config: the configuration ops for this device.
- * @cf_mutex: Protects get and set access to configuration layout.
+ * @cf_lock: Protects get and set access to configuration layout.
  * @index: device index
  * @features_valid: were features initialized? for legacy guests
  * @use_va: indicate whether virtual address must be used by this device
@@ -79,7 +79,7 @@ struct vdpa_device {
 	struct device *dma_dev;
 	const char *driver_override;
 	const struct vdpa_config_ops *config;
-	struct mutex cf_mutex; /* Protects get/set config */
+	struct rw_semaphore cf_lock; /* Protects get/set config */
 	unsigned int index;
 	bool features_valid;
 	bool use_va;
@@ -398,10 +398,10 @@ static inline int vdpa_reset(struct vdpa_device *vdev)
 	const struct vdpa_config_ops *ops = vdev->config;
 	int ret;
 
-	mutex_lock(&vdev->cf_mutex);
+	down_write(&vdev->cf_lock);
 	vdev->features_valid = false;
 	ret = ops->reset(vdev);
-	mutex_unlock(&vdev->cf_mutex);
+	up_write(&vdev->cf_lock);
 	return ret;
 }
 
@@ -420,9 +420,9 @@ static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features)
 {
 	int ret;
 
-	mutex_lock(&vdev->cf_mutex);
+	down_write(&vdev->cf_lock);
 	ret = vdpa_set_features_unlocked(vdev, features);
-	mutex_unlock(&vdev->cf_mutex);
+	up_write(&vdev->cf_lock);
 
 	return ret;
 }
-- 
2.35.1