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Subject: Re: [PATCH 2/2] virtio_scsi: implement request batching
To:     Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     jejb@linux.ibm.com, martin.petersen@oracle.com,
        linux-scsi@vger.kernel.org, stefanha@redhat.com
References: <20190530112811.3066-1-pbonzini@redhat.com>
 <20190530112811.3066-3-pbonzini@redhat.com>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <79490df1-0145-5b40-027a-7e8fb96854d4@acm.org>
Date:   Thu, 30 May 2019 10:28:32 -0700
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On 5/30/19 4:28 AM, Paolo Bonzini wrote:
> @@ -531,7 +547,8 @@ static int virtscsi_queuecommand(struct Scsi_Host *shost,
>   		req_size = sizeof(cmd->req.cmd);
>   	}
>   
> -	ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd));
> +	kick = (sc->flags & SCMD_LAST) != 0;
> +	ret = virtscsi_add_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd), kick);

Have you considered to have the SCSI core call commit_rqs() if bd->last 
is true? I think that would avoid that we need to introduce the 
SCMD_LAST flag and that would also avoid that every SCSI LLD that 
supports a commit_rqs callback has to introduce code to test the 
SCMD_LAST flag.

Thanks,

Bart.