linux-kernel - Re: scsi_set_medium

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Message-ID: <1540889786.12349.9.camel@suse.com>
Date:   Tue, 30 Oct 2018 09:56:26 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     "Zengtao (B)" <prime.zeng@...ilicon.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

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.

> 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