linux-kernel - RE: scsi_set_medium

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Date:   Tue, 30 Oct 2018 09:24:38 +0000
From:   "Zengtao (B)" <prime.zeng@...ilicon.com>
To:     Oliver Neukum <oneukum@...e.com>,
        "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>
CC:     "usb-storage@...ts.one-eyed-alien.net" 
        <usb-storage@...ts.one-eyed-alien.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: scsi_set_medium_removal timeout issue

Hi:

>-----Original Message-----
>From: Oliver Neukum [mailto:oneukum@...e.com]
>Sent: Tuesday, October 30, 2018 4:56 PM
>To: Zengtao (B) <prime.zeng@...ilicon.com>; jejb@...ux.vnet.ibm.com;
>gregkh@...uxfoundation.org; martin.petersen@...cle.com;
>stern@...land.harvard.edu
>Cc: usb-storage@...ts.one-eyed-alien.net; linux-kernel@...r.kernel.org;
>linux-scsi@...r.kernel.org; linux-usb@...r.kernel.org
>Subject: Re: scsi_set_medium_removal timeout issue
>
>On Di, 2018-10-30 at 08:28 +0000,  Zengtao (B)  wrote:
>> Hi
>
>> For the issue itself, there is my observation:
>> In the step 4, the Host will issue an
>PREVENT_ALLOW_MEDIUM_REMOVAL scsi command.
>> and and timeout happens due to the device 's very slow
>fsg_lun_fsync_sub.
>> I found there are two methods to workaround the issue:
>> 1. Change the timeout value of host scsi command
>> PREVENT_ALLOW_MEDIUM_REMOVAL to to about 60 seconds from 10
>seconds.
>
>That is near useless, because the gadget can be used with other systems.
>

Is it reasonable to keep the current value? Or can we change it to cover
as much systems as possible. 

>> 2. Remove the fsg_lun_fsync_sub in the device's Mass storage gadget
>driver.
>
>It exists for a reason. The blocks have to be on the medium.
>It seems to me that your gadget just allows too many dirty pages in the
>cache.
>
>	Regards
>		Oliver

Regards
Zengtao