linux-kernel - Re: [PATCH v4 10/10] scsi: ufs: Apply more limitations to user access

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Date:   Thu, 24 Jun 2021 15:25:44 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...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>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bean Huo <beanhuo@...ron.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Keoseong Park <keosung.park@...sung.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 10/10] scsi: ufs: Apply more limitations to user access

On 6/23/21 7:23 PM, Can Guo wrote:
> On 2021-06-24 05:51, Bart Van Assche wrote:
>> On 6/23/21 12:35 AM, Can Guo wrote:
>> - During system suspend, user space software is paused before the device
>>   driver freeze callbacks are invoked. Hence, the hba->is_sys_suspended
>>   check can be left out.
> 
> is_sys_suspended indicates that system resume failed (power/clk is OFF).
> 
>> - If a LUN is runtime suspended, it should be resumed if accessed from
>>   user space instead of failing user space accesses. In other words, the
>>   hba->is_wlu_sys_suspended check seems inappropriate to me.
> 
> hba->is_wlu_sys_suspended indicates that wl system resume failed, device
> is not operational.

Hi Can,

Thanks for the clarification. How about converting the above two answers
into comments inside ufshcd_is_user_access_allowed()?

Should ufshcd_is_user_access_allowed() perhaps be called after
ufshcd_rpm_get_sync() instead of before to prevent that the value of
hba->is_sys_suspended or hba->is_wlu_sys_suspended changes after having
been checked and before the UFS device is accessed?

Thanks,

Bart.