linux-kernel - Re: [RESEND PATCH v3] scsi: Bypass certain SCSI commands on disks with "use_192_bytes_for

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Message-ID: <ad1ba59a-3a67-4b3c-a05d-c4e56405cc19@acm.org>
Date: Mon, 24 Feb 2025 10:11:58 -0800
From: Bart Van Assche <bvanassche@....org>
To: WangYuli <wangyuli@...ontech.com>, James.Bottomley@...senPartnership.com,
 martin.petersen@...cle.com
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
 stern@...land.harvard.edu, zhanjun@...ontech.com, niecheng1@...ontech.com,
 guanwentao@...ontech.com, chenlinxuan@...ontech.com,
 Xinwei Zhou <zhouxinwei@...ontech.com>, Xu Rao <raoxu@...ontech.com>,
 Yujing Ming <mingyujing@...ontech.com>
Subject: Re: [RESEND PATCH v3] scsi: Bypass certain SCSI commands on disks
 with "use_192_bytes_for_3f" attribute

On 2/23/25 7:48 PM, WangYuli wrote:
> However, "lshw" disregards the "use_192_bytes_for_3f" attribute and
> transmits data with a length of 0xff bytes via ioctl, which can cause
> some hard drives to hang and become unusable.

lshw is a user space utility. use_192_bytes_for_3f is not exposed to
user space as far as I know. So how can the above statement be correct?

> @@ -1613,6 +1614,17 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
> +	/*
> +	 * Before we queue this command, check attribute use_192_bytes_for_3f.
> +	 * Because transmits data with a length of 0xff bytes via ioctl may
> +	 * cause some hard drives to hang and become unusable.
> +	 */
> +	if (cmd->cmnd[0] == MODE_SENSE && sdev->use_192_bytes_for_3f &&
> +		cmd->cmnd[2] == 0x3f && cmd->cmnd[4] != 192) {
> +		cmd->result = DID_ABORT << 16;
> +		goto done;
> +	}

 From include/scsi/scsi_device.h:

unsigned use_192_bytes_for_3f:1; /* ask for 192 bytes from page 0x3f */

The above code uses use_192_bytes_for_3f for another purpose. Please 
respect the purpose of the use_192_bytes_for_3f bitfield.

Thanks,

Bart.