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Date: Fri, 20 May 2011 18:04:22 +0200
From: Christoph Hellwig <hch@lst.de>
Message-ID: <20110520160422.GM4466@lst.de>
References: <1305630067-2119-1-git-send-email-pbonzini@redhat.com>
	<1305630067-2119-14-git-send-email-pbonzini@redhat.com>
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In-Reply-To: <1305630067-2119-14-git-send-email-pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v3 13/21] scsi: do not call
	send_command	directly
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org

> -void scsi_req_enqueue(SCSIRequest *req)
> +int32_t scsi_req_enqueue(SCSIRequest *req, uint8_t *buf)
>  {
> +    int32_t rc;
>      assert(!req->enqueued);
>      scsi_req_ref(req);
>      req->enqueued = true;
>      QTAILQ_INSERT_TAIL(&req->dev->requests, req, next);
> +
> +    /* Make sure the request doesn't disappear under send_command's feet.  */
> +    scsi_req_ref(req);
> +    rc = req->dev->info->send_command(req, buf);
> +    scsi_req_unref(req);
> +    return rc;

How would it disappear given that we grabbed another reference just before?
That probably needs a bit more documentation here.  Also why not move
the two scsi_req_ref calls together?