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From: Maurizio Lombardi <mlombard@redhat.com>
To: Mike Christie <michael.christie@oracle.com>,
	martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
	target-devel@vger.kernel.org, mst@redhat.com,
	jasowang@redhat.com, pbonzini@redhat.com, stefanha@redhat.com,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 09/17] vhost scsi: fix cmd completion race
Date: Tue, 27 Oct 2020 13:07:13 +0000
Message-ID: <8662eb42-7632-a05f-cb55-5dc80b444612@redhat.com> (raw)
In-Reply-To: <1603326903-27052-10-git-send-email-michael.christie@oracle.com>



Dne 22. 10. 20 v 2:34 Mike Christie napsal(a):
> We might not do the final se_cmd put from vhost_scsi_complete_cmd_work.
> When the last put happens a little later then we could race where
> vhost_scsi_complete_cmd_work does vhost_signal, the guest runs and sends
> more IO, and vhost_scsi_handle_vq runs but does not find any free cmds.
> 
> This patch has us delay completing the cmd until the last lio core ref
> is dropped. We then know that once we signal to the guest that the cmd
> is completed that if it queues a new command it will find a free cmd.
> 
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>  drivers/vhost/scsi.c | 42 +++++++++++++++---------------------------
>  1 file changed, 15 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index f6b9010..2fa48dd 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -322,7 +322,7 @@ static u32 vhost_scsi_tpg_get_inst_index(struct se_portal_group *se_tpg)
>  	return 1;
>  }
>  
> -static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
> +static void vhost_scsi_release_cmd_res(struct se_cmd *se_cmd)
>  {
>  	struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
>  				struct vhost_scsi_cmd, tvc_se_cmd);
> @@ -344,6 +344,16 @@ static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
>  	vhost_scsi_put_inflight(inflight);
>  }
>  
> +static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
> +{
> +	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
> +					struct vhost_scsi_cmd, tvc_se_cmd);
> +	struct vhost_scsi *vs = cmd->tvc_vhost;
> +
> +	llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);
> +	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
> +}
> +
>  static u32 vhost_scsi_sess_get_index(struct se_session *se_sess)
>  {
>  	return 0;
> @@ -366,28 +376,15 @@ static int vhost_scsi_get_cmd_state(struct se_cmd *se_cmd)
>  	return 0;
>  }
>  
> -static void vhost_scsi_complete_cmd(struct vhost_scsi_cmd *cmd)
> -{
> -	struct vhost_scsi *vs = cmd->tvc_vhost;
> -
> -	llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);
> -
> -	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
> -}
> -
>  static int vhost_scsi_queue_data_in(struct se_cmd *se_cmd)
>  {
> -	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
> -				struct vhost_scsi_cmd, tvc_se_cmd);
> -	vhost_scsi_complete_cmd(cmd);
> +	transport_generic_free_cmd(se_cmd, 0);
>  	return 0;
>  }
>  
>  static int vhost_scsi_queue_status(struct se_cmd *se_cmd)
>  {
> -	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
> -				struct vhost_scsi_cmd, tvc_se_cmd);
> -	vhost_scsi_complete_cmd(cmd);
> +	transport_generic_free_cmd(se_cmd, 0);
>  	return 0;
>  }
>  
> @@ -433,15 +430,6 @@ static void vhost_scsi_free_evt(struct vhost_scsi *vs, struct vhost_scsi_evt *ev
>  	return evt;
>  }
>  
> -static void vhost_scsi_free_cmd(struct vhost_scsi_cmd *cmd)
> -{
> -	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;
> -
> -	/* TODO locking against target/backend threads? */
> -	transport_generic_free_cmd(se_cmd, 0);
> -
> -}
> -
>  static int vhost_scsi_check_stop_free(struct se_cmd *se_cmd)
>  {
>  	return target_put_sess_cmd(se_cmd);
> @@ -560,7 +548,7 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
>  		} else
>  			pr_err("Faulted on virtio_scsi_cmd_resp\n");
>  
> -		vhost_scsi_free_cmd(cmd);
> +		vhost_scsi_release_cmd_res(se_cmd);
>  	}
>  
>  	vq = -1;
> @@ -1096,7 +1084,7 @@ static u16 vhost_buf_to_lun(u8 *lun_buf)
>  						      &prot_iter, exp_data_len,
>  						      &data_iter))) {
>  				vq_err(vq, "Failed to map iov to sgl\n");
> -				vhost_scsi_release_cmd(&cmd->tvc_se_cmd);
> +				vhost_scsi_release_cmd_res(&cmd->tvc_se_cmd);
>  				goto err;
>  			}
>  		}
> 

Looks ok to me.

Reviewed-by: Maurizio Lombardi <mlombard@redhat.com>

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-22  0:34 [PATCH 00/17 V3] vhost: fix scsi cmd handling and cgroup support Mike Christie
2020-10-22  0:34 ` [PATCH 01/17] vhost scsi: add lun parser helper Mike Christie
2020-10-26  3:33   ` Jason Wang
2020-10-22  0:34 ` [PATCH 02/17] vhost: remove work arg from vhost_work_flush Mike Christie
2020-10-22  0:51   ` Chaitanya Kulkarni
2020-10-22  0:34 ` [PATCH 03/17] vhost net: use goto error handling in open Mike Christie
2020-10-22  0:45   ` Chaitanya Kulkarni
2020-10-26  3:34   ` Jason Wang
2020-10-22  0:34 ` [PATCH 04/17] vhost: prep vhost_dev_init users to handle failures Mike Christie
2020-10-22  5:22   ` kernel test robot
2020-10-23 16:15   ` Mike Christie
2020-11-02  5:57   ` Jason Wang
2020-11-03 10:04   ` Dan Carpenter
2020-10-22  0:34 ` [PATCH 05/17] vhost: move vq iovec allocation to dev init time Mike Christie
2020-10-22  0:34 ` [PATCH 06/17] vhost: support delayed vq creation Mike Christie
2020-10-22  0:34 ` [PATCH 07/17] vhost scsi: support delayed IO " Mike Christie
2020-10-26  3:51   ` Jason Wang
2020-10-27  5:47     ` Mike Christie
2020-10-28  1:55       ` Jason Wang
2020-10-30  8:47       ` Michael S. Tsirkin
2020-10-30 16:30         ` Mike Christie
2020-10-30 17:26           ` Mike Christie
2020-11-01 22:06         ` Mike Christie
2020-11-02  6:36         ` Jason Wang
2020-11-02  6:49           ` Jason Wang
2020-11-02 16:19             ` Mike Christie
2020-10-22  0:34 ` [PATCH 08/17] vhost scsi: alloc cmds per vq instead of session Mike Christie
2020-10-22  0:34 ` [PATCH 09/17] vhost scsi: fix cmd completion race Mike Christie
2020-10-27 13:07   ` Maurizio Lombardi [this message]
2020-10-30  8:51   ` Michael S. Tsirkin
2020-10-30 16:04     ` Paolo Bonzini
2020-10-22  0:34 ` [PATCH 10/17] vhost scsi: Add support for LUN resets Mike Christie
2020-10-22  0:34 ` [PATCH 11/17] vhost scsi: remove extra flushes Mike Christie
2020-10-22  0:34 ` [PATCH 12/17] vhost poll: fix coding style Mike Christie
2020-10-22  0:39   ` Chaitanya Kulkarni
2020-10-22  0:34 ` [PATCH 13/17] vhost: support multiple worker threads Mike Christie
2020-10-22  0:35 ` [PATCH 14/17] vhost: poll support support multiple workers Mike Christie
2020-10-22  0:35 ` [PATCH 15/17] host: support delayed vq creation Mike Christie
2020-10-22  0:50   ` Mike Christie
2020-10-22  0:35 ` [PATCH 16/17] vhost scsi: multiple worker support Mike Christie
2020-10-22  0:35 ` [PATCH 17/17] vhost scsi: drop submission workqueue Mike Christie
2020-10-29 21:47 ` [PATCH 00/17 V3] vhost: fix scsi cmd handling and cgroup support Michael S. Tsirkin
2020-10-29 22:19   ` Mike Christie

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