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

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Date:   Sun, 31 Jan 2021 18:39:19 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.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 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?

Thanks,

Bart.