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Subject: Re: [PATCH V4 2/2] scsi: ufshcd: Fix device links when BOOT WLUN
 fails to probe
To:     Avri Altman <Avri.Altman@wdc.com>,
        "Rafael J . Wysocki" <rafael@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Saravana Kannan <saravanak@google.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        Bean Huo <huobean@gmail.com>, Can Guo <cang@codeaurora.org>,
        Asutosh Das <asutoshd@codeaurora.org>,
        Bart Van Assche <bvanassche@acm.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20210716114408.17320-1-adrian.hunter@intel.com>
 <20210716114408.17320-3-adrian.hunter@intel.com>
 <DM6PR04MB65758A834069CC7B56669905FC109@DM6PR04MB6575.namprd04.prod.outlook.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
Message-ID: <2a19830e-47cb-4c2a-ddbc-f2370af01452@intel.com>
Date:   Mon, 2 Aug 2021 08:45:01 +0300
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On 17/07/21 9:02 pm, Avri Altman wrote:
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 708b3b62fc4d..9864a8ee0263 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -5020,15 +5020,34 @@ static int ufshcd_slave_configure(struct scsi_device
>> *sdev)
>>  static void ufshcd_slave_destroy(struct scsi_device *sdev)
>>  {
>>         struct ufs_hba *hba;
>> +       unsigned long flags;
>>
>>         hba = shost_priv(sdev->host);
>>         /* Drop the reference as it won't be needed anymore */
>>         if (ufshcd_scsi_to_upiu_lun(sdev->lun) == UFS_UPIU_UFS_DEVICE_WLUN) {
>> -               unsigned long flags;
>> -
>>                 spin_lock_irqsave(hba->host->host_lock, flags);
>>                 hba->sdev_ufs_device = NULL;
>>                 spin_unlock_irqrestore(hba->host->host_lock, flags);
>> +       } else if (hba->sdev_ufs_device) {
>> +               struct device *supplier = NULL;
>> +
>> +               /* Ensure UFS Device WLUN exists and does not disappear */
>> +               spin_lock_irqsave(hba->host->host_lock, flags);
>> +               if (hba->sdev_ufs_device) {
> Was just checked in the outer clause?

Yes, but need to re-check with the spinlock locked.

> 
> Thanks,
> Avri
> 
>> +                       supplier = &hba->sdev_ufs_device->sdev_gendev;
>> +                       get_device(supplier);
>> +               }
>> +               spin_unlock_irqrestore(hba->host->host_lock, flags);
>> +
>> +               if (supplier) {
>> +                       /*
>> +                        * If a LUN fails to probe (e.g. absent BOOT WLUN), the
>> +                        * device will not have been registered but can still
>> +                        * have a device link holding a reference to the device.
>> +                        */
>> +                       device_link_remove(&sdev->sdev_gendev, supplier);
>> +                       put_device(supplier);
>> +               }
>>         }
>>  }
>>
>> --
>> 2.17.1
>