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Date:   Thu, 17 Feb 2022 11:15:11 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Guixin Liu <kanie@linux.alibaba.com>
Cc:     bostroesser@gmail.com, martin.petersen@oracle.com,
        linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
        linux-kernel@vger.kernel.org, xiaoguang.wang@linux.alibaba.com,
        xlpang@linux.alibaba.com
Subject: Re: [PATCH 2/2] scsi:target:tcmu: reduce once copy by using uio ioctl
Message-ID: <Yg4gL1tL7yJELNL2@kroah.com>
References: <1645064962-94123-1-git-send-email-kanie@linux.alibaba.com>
 <1645064962-94123-2-git-send-email-kanie@linux.alibaba.com>
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On Thu, Feb 17, 2022 at 10:29:22AM +0800, Guixin Liu wrote:
> --- a/include/uapi/linux/target_core_user.h
> +++ b/include/uapi/linux/target_core_user.h
> @@ -185,4 +185,13 @@ enum tcmu_genl_attr {
>  };
>  #define TCMU_ATTR_MAX (__TCMU_ATTR_MAX - 1)
>  
> +struct tcmu_data_xfer {
> +	unsigned short cmd_id;
> +	unsigned long iov_cnt;
> +	struct iovec __user *iovec;
> +};

That is no way to define a structure that crosses the user/kernel
boundry, it just will not work at all, even if we wanted it to :(

sorry,

greg k-h