Re: [PATCH] drdb: Switch to kvfree_rcu() API

[Uladzislau Rezki]

On Wed, Dec 15, 2021 at 12:18:37PM +0100, Uladzislau Rezki (Sony) wrote:
> Instead of invoking a synchronize_rcu() to free a pointer
> after a grace period we can directly make use of new API
> that does the same but in more efficient way.
> 
> TO: Jens Axboe <axboe@xxxxxxxxx>
> TO: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
> TO: Jason Gunthorpe <jgg@xxxxxxxxxx>
> TO: drbd-dev@xxxxxxxxxxxxxxxx
> TO: linux-block@xxxxxxxxxxxxxxx
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---
>  drivers/block/drbd/drbd_nl.c       | 9 +++------
>  drivers/block/drbd/drbd_receiver.c | 6 ++----
>  drivers/block/drbd/drbd_state.c    | 3 +--
>  3 files changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
> index 44ccf8b4f4b2..28f4d84945fd 100644
> --- a/drivers/block/drbd/drbd_nl.c
> +++ b/drivers/block/drbd/drbd_nl.c
> @@ -1679,8 +1679,7 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
>  			drbd_send_sync_param(peer_device);
>  	}
>  
> -	synchronize_rcu();
> -	kfree(old_disk_conf);
> +	kvfree_rcu(old_disk_conf);
>  	kfree(old_plan);
>  	mod_timer(&device->request_timer, jiffies + HZ);
>  	goto success;
> @@ -2511,8 +2510,7 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
>  
>  	mutex_unlock(&connection->resource->conf_update);
>  	mutex_unlock(&connection->data.mutex);
> -	synchronize_rcu();
> -	kfree(old_net_conf);
> +	kvfree_rcu(old_net_conf);
>  
>  	if (connection->cstate >= C_WF_REPORT_PARAMS) {
>  		struct drbd_peer_device *peer_device;
> @@ -2925,8 +2923,7 @@ int drbd_adm_resize(struct sk_buff *skb, struct genl_info *info)
>  		new_disk_conf->disk_size = (sector_t)rs.resize_size;
>  		rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
>  		mutex_unlock(&device->resource->conf_update);
> -		synchronize_rcu();
> -		kfree(old_disk_conf);
> +		kvfree_rcu(old_disk_conf);
>  		new_disk_conf = NULL;
>  	}
>  
> diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
> index 1f740e42e457..d73a53242a75 100644
> --- a/drivers/block/drbd/drbd_receiver.c
> +++ b/drivers/block/drbd/drbd_receiver.c
> @@ -3799,8 +3799,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
>  		drbd_info(connection, "peer data-integrity-alg: %s\n",
>  			  integrity_alg[0] ? integrity_alg : "(none)");
>  
> -	synchronize_rcu();
> -	kfree(old_net_conf);
> +	kvfree_rcu(old_net_conf);
>  	return 0;
>  
>  disconnect_rcu_unlock:
> @@ -4168,8 +4167,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
>  
>  			rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
>  			mutex_unlock(&connection->resource->conf_update);
> -			synchronize_rcu();
> -			kfree(old_disk_conf);
> +			kvfree_rcu(old_disk_conf);
>  
>  			drbd_info(device, "Peer sets u_size to %lu sectors (old: %lu)\n",
>  				 (unsigned long)p_usize, (unsigned long)my_usize);
> diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
> index b8a27818ab3f..826e496821c7 100644
> --- a/drivers/block/drbd/drbd_state.c
> +++ b/drivers/block/drbd/drbd_state.c
> @@ -2071,8 +2071,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
>  		conn_free_crypto(connection);
>  		mutex_unlock(&connection->resource->conf_update);
>  
> -		synchronize_rcu();
> -		kfree(old_conf);
> +		kvfree_rcu(old_conf);
>  	}
>  
>  	if (ns_max.susp_fen) {
> -- 
> 2.30.2
> 
+ Jens Axboe <axboe@xxxxxxxxx>
+ Philipp Reisner <philipp.reisner@xxxxxxxxxx>
+ Jason Gunthorpe <jgg@xxxxxxxxxx>
+ drbd-dev@xxxxxxxxxxxxxxxx
+ linux-block@xxxxxxxxxxxxxxx

--
Vlad Rezki