linux-kernel - Re: [PATCH v3 3/3] scsi: ufs: Fix wrong Task Tag used in task management request UPIUs

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Date:   Fri, 05 Feb 2021 14:09:54 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     jaegeuk@...nel.org, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, hongwus@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Sujit Reddy Thumma <sthumma@...eaurora.org>,
        Vinayak Holikatti <vinholikatti@...il.com>,
        Yaniv Gardi <ygardi@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] scsi: ufs: Fix wrong Task Tag used in task
 management request UPIUs

On 2021-02-01 10:39, Bart Van Assche wrote:
> On 1/28/21 9:57 PM, Can Guo wrote:
>> On 2021-01-29 11:15, Bart Van Assche wrote:
>>> On 1/27/21 8:16 PM, Can Guo wrote:
>>>> In __ufshcd_issue_tm_cmd(), it is not right to use hba->nutrs +
>>>> req->tag as
>>>> the Task Tag in one TMR UPIU. Directly use req->tag as the Task Tag.
>>> 
>>> Why is the current code wrong and why is this patch the proper fix?
>>> Please explain this in the patch description.
>> 
>> req->tag is the tag allocated for one TMR, no?
> 
> Hi Can,
>  Commit e293313262d3 ("scsi: ufs: Fix broken task management command
> implementation") includes the following changes:
> 
> +       task_tag = hba->nutrs + free_slot;
>         task_req_upiup->header.dword_0 =
>                 UPIU_HEADER_DWORD(UPIU_TRANSACTION_TASK_REQ, 0,
> -                                            lrbp->lun, 
> lrbp->task_tag);
> +                                            lun_id, task_tag);
>         task_req_upiup->header.dword_1 =
>                 UPIU_HEADER_DWORD(0, tm_function, 0, 0);
> 
> As one can see the value written in dword_0 starts at hba->nutrs. Was
> that code correct? If that code was correct, does your patch perhaps
> break task management support?

That code is wrong. The Task Tag in Dword_0 should be the real tag we
allocated for TMR. The transfer request Task Tag which we are trying to
abort is given in Dword_5, which is the Input Parameter 3 of the TMR 
UPIU.
I am not sure why the author gave hba->nutrs + req->tag as the Task Tag
of one TMR, the commit msg abot this part is not quite informative....

Table 10.22 — Task Management Request UPIU
TASK MANAGEMENT REQUEST UPIU
----------------------------------
|0         |1      |2   |3       |
----------------------------------
|xx00 0100b| Flags |LUN |Task Tag|
----------------------------------
...
16 (MSB)   |17     |18  |19 (LSB)|
----------------------------------
Input Parameter 2
----------------------------------

Table 10.24 — Task Management Input Parameters
Field Description
Input Parameter 2 LSB: Task Tag of the task/command operated by the task 
management function.

Thanks,

Can Guo.

> 
> Thanks,
> 
> Bart.