Hi: >-----Original Message----- >From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] >Sent: Tuesday, October 30, 2018 10:08 PM >To: Zengtao (B) <prime.zeng@xxxxxxxxxxxxx> >Cc: jejb@xxxxxxxxxxxxxxxxxx; martin.petersen@xxxxxxxxxx; >gregkh@xxxxxxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; >linux-kernel@xxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; >usb-storage@xxxxxxxxxxxxxxxxxxxxxxxx >Subject: Re: scsi_set_medium_removal timeout issue > >On Tue, 30 Oct 2018, Zengtao (B) wrote: > >> Hi >> >> I have recently met a scsi_set_medium_removal timeout issue, and it's >> related to both SCSI and USB MASS storage. >> Since i am not an expert in either scsi or usb mass storage, i am >> writing to report the issue and ask for a solution from you guys. >> >> My test scenario is as follow: >> 1.Linux HOST-----Linux mass storage gadget(the back store is a flash >partition). >> 2.Host mount the device. >> 3.Host writes some data to the Mass storage device. >> 4.Host Unmount the device. >> Both Linux kernels(Host and Device) are Linux 4.9. >> Some has reported the same issue a long time ago, but it remains there. >> https://www.spinics.net/lists/linux-usb/msg53739.html >> >> 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. > >Something is wrong here. Before sending PREVENT-ALLOW MEDIUM >REMOVAL, the host should issue SYNCHRONIZE CACHE. This will force >fsg_lun_fsync_sub to run, and the host should allow a long timeout for >this command. Then when PREVENT-ALLOW MEDIUM REMOVAL is sent, >nothing will need to be flushed. > Definitely, I haven't seen the SYNCHRONIZE CACHE from the host, it directly issued the PREVENT-ALLOW MEDIUM REMOVAL, so maybe something wrong with the scsi layer or something wrong with the mass storage class driver? Zengtao >Alan Stern > >> 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. >> 2. Remove the fsg_lun_fsync_sub in the device's Mass storage gadget >driver. >> >> Thanks >> >> Regards >> zentao
