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. 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
