Insert/remove USB disk leaves a permanent folder

carbide · 03-23-2008, 05:34 PM

Hi

I am having some problems when inserting and removing USB disks on a 2.6.12 kernel. This seems to leave a permanent folder in /dev/scsi/ each time. First time its denoted /dev/scsi/host0/bus0/target0/lun0 second time /dev/scsi/host1/bus0/target0/lun0 and so on. If I remove the USB disk before its "officially" registered the next time it will skip a number going from eg. host6 to host8.
Anybody seen this behavior before and is there anything you can do about it?

regards

bigrigdriver · 03-23-2008, 06:19 PM

I suspect something like this is going on:
When you plug in the USB drive, hotplug detects the event and creates the device node.
When you are done with the USB drive, you unplug it and hotplug does not remove the device node. It's probably happening because you didn't umount the USB disk before removing it.

Try a test:
Plug the USB drive in and wait for the new device node to appear.
Manually umount the device, then unplug the USB drive.
Did the device node remain, or did it disappear?

You can also watch /etc/mtab for the appearance and disappearance of the USB device.

Then look in /etc/udev/rules.d/50-udev-rules. You may see something like this:

Code:

BUS="scsi", PROGRAM="/sbin/udev.get_persistent_device_name.sh", NAME="%k" SYMLINK="%c{1+}", MODE="0660", GROUP="disk"
BUS="usb", PROGRAM="/sbin/udev.get_persistent_device_name.sh", NAME="%k" SYMLINK="%c{1+}", MODE="0660", GROUP="disk"
BUS="ide", PROGRAM="/sbin/udev.get_persistent_device_name.sh", NAME="%k" SYMLINK="%c{1+}", MODE="0660", GROUP="disk"
BUS="ccw", PROGRAM="/sbin/udev.get_persistent_device_name.sh", NAME="%k" SYMLINK="%c{1+}", MODE="0660", GROUP="disk"

Or, those lines may refer to "/sbin/get-unique-drive-id.sh"; in which case, change the lines to read as above.

ak_random · 03-24-2008, 12:58 AM

Quote:

Originally Posted by bigrigdriver

I suspect something like this is going on:
When you plug in the USB drive, hotplug detects the event and creates the device node.
When you are done with the USB drive, you unplug it and hotplug does not remove the device node. It's probably happening because you didn't umount the USB disk before removing it.

In other words, hot plugging a USB device is graceful, but hot unplugging is not? That's rather annoying.

carbide · 03-25-2008, 03:42 AM

thanks for your help on the matter.

The problem occurs even though the usb disc is not mounted. If I insert, remove and insert it again the host number in /dev/scsi/host1/bus0/target0/lun0 will be bumped up one value.

If I, as you suggested, mount/unmount the partion and remove the disc the folder scsi/host1/bus0/target0/lun0 is still not removed from the device folder, so I gather its not related to mounting/unmounting but rather a problem with the scsi mass storage driver.

Output when inserting the usb disk:

# usb 1-1: new full speed USB device using at91rm9200-ohci and address 8
# usb 1-1: Product: DataTraveler2.0
# usb 1-1: Manufacturer: Kingston
# usb 1-1: SerialNumber: 0711080251452
# scsi6 : SCSI emulation for USB Mass Storage devices
# Vendor: Kingston Model: DataTraveler2.0 Rev: 1.00
# Type: Direct-Access ANSI SCSI revision: 02
# SCSI device sda: 1956735 512-byte hdwr sectors (1002 MB)
# sda: Write Protect is off
# sda: assuming drive cache: write through
# SCSI device sda: 1956735 512-byte hdwr sectors (1002 MB)
# sda: Write Protect is off
# sda: assuming drive cache: write through
# /dev/scsi/host6/bus0/target0/lun0:<7>usb-storage: queuecommand called
# p1
# Attached scsi removable disk sda at scsi6, channel 0, id 0, lun 0

Here I take a look at the scsi device folder and it is now using host6, also notice that it has jumped from host1 to host5 which has happened because I inserted/removed the disk a couple of times without waiting for the device to be completely registered:

ls /dev/scsi/
host0 host1 host5 host6

And from the last line of logout put I could see it has attached the disk sda at scsi6.

Another funny thing is that I have no device sda in /dev. If I want to mount the disk I have to use /dev/scsi/host6/bus0/target0/lun0/part1.

regards