Albert Lee wrote: > Hi Doug, > > A problem related to SG_IO. > When testing the 2.6.18-rc1 libata, a flood of ALLOW_MEDIUM_REMOVAL is seen > after ejecting a removable disk drive: > > http://bugzilla.kernel.org/show_bug.cgi?id=6799 > > The interaction to trigger the problem is below: > 1. The "eject" utility, using SG_IO, issues ALLOW_MEDIUM_REMOVAL twice to unlock the disk of the device. > 2. The disk of the physical device is now unlocked, however, sdev->locked is still 1, inconsistent with the physical device status. > 3. The "eject" utility ejects the disk by START_STOP_UNIT. > 4. Someone issues TEST_UNIT_READY. The device is not ready since no disk inside. ATAPI check condition returned. > 5. 2.6.18-rc1 libata EH triggered in SCSI EH context to request sense. > 6. scsi_restart_operations(), seeing sdev->locked == 1, tries to lock the door. > 7. Lock failed since no disk inside. ATAPI check condition returned. > 8. 2.6.18 libata EH triggered in SCSI EH context. Goto 5 and loop forever until the disk is inserted again. > > It looks more like eject/scsi problem. (Libata 2.6.17 EH is not affected by the problem > because the request sense is done when qc is completed, not in the SCSI EH context.) > > Maybe adding a filter to the SCSI SG IO layer to > - Check incoming SCSI commands > - Whenever ALLOW_MEDIUM_REMOVAL is seen, update the sdev->locked to make the > kernel data structure consistent with the physical device status > can fix the problem? Albert, Just fix libata. My usb external cd/dvd combo drive has a little switch under it to unlock the door. How could use of that switch be "filtered" by an OS? If an OS wants to maintain a state variable for a device that a user (and perhaps another initiator) can get to then it needs to be able to cope with that state variable being out of sync once in a while. Doug Gilbert - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
