net/vdpa: Use readers/writers semaphore instead of cf_mutex

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>
Message-Id: <20220518133804.1075129-5-elic@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 2ff7de5..9d3534a 100644 (file)
--- 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 2ae8443..2cb1484 100644 (file)
--- 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;
 }