Hi Karel
Thanks for your detailed explanation. Good to hear I did hit a real
(although already known) issue. Too bad there is no easy fix.
Anyway, one last minor comment:
Ubuntu 13.04 64bit does not yet support option -P for losetup. So
this must be an older version of util-linux. But then: how do I
determine the version of util-linux installed? The binaries have
no --version option and 'strings /sbin/losetup | egrep '[0-9]' does
not reveal anything useful either. Maybe there is a general version
for util-linux available in another binary? The man page does not
tell. I failed to identify the version number!
Regards
BB.
On 07.10.2013 13:38, Karel Zak wrote:
> On Tue, Sep 24, 2013 at 06:22:11PM +0200, butter@xxxxxxxxxx wrote:
>> get deleted when you call "losetup -d DEVICE". This causes other programs
>> (like lvmdiskscan -l) to report Input/output errors.
>>
>> Here is how to reproduce the problem:
>>
>> LOOPDEV=/dev/loop3
>> IMAGEFILE=`pwd`/mydisk.img
>> MOUNTPOINT=`pwd`/mnt
>>
>> # 1. Create and mount an ext4 partition from a file-based disk image
>> dd if=/dev/zero of=$IMAGEFILE bs=1M count=80
>> sudo losetup $LOOPDEV $IMAGEFILE
>
> kernel uses partitions on loop devices conditionally, and here you said
> "I don't care about partitions...". You have to use
>
> sudo losetup -P $LOOPDEV $IMAGEFILE
>
> if you want to force kernel loopdev driver to use partitions.
>
>> sudo parted $LOOPDEV mklabel msdos
>> sudo parted $LOOPDEV mkpart primary 2048s 43007s
>> sudo mkfs -t ext4 ${LOOPDEV}p1
>> mkdir $MOUNTPOINT
>> sudo mount ${LOOPDEV}p1 $MOUNTPOINT
>>
>> # 2. Unmount again => ERROR: the partition device files are not deleted
>> sudo umount $MOUNTPOINT
>
> mount/umount is completely irrelevant for this issue. The simple way
> to reproduce the problem is:
>
> dd if=/dev/zero of=img bs=1M count=80
> losetup -f img --show
> parted /dev/loop0 mklabel msdos
> parted /dev/loop0 mklabel msdos
> losetup -d /dev/loop0
>
> cat /sys/block/loop0/size
> cat /sys/block/loop0/loop0p1/size
>
> Anyway, the problem is that parted uses BLKPG_ADD_PARTITION ioctl to create
> /dev/loop0p1, but the loop0 device has been created without PARTSCAN flag
> (see /sys/block/loop0/loop/partscan). It means that loopdev kernel driver
> does not call BLKRRPART during loop0 cleanup (loop_clr_fd() in kernel code).
>
> You can remove the partition manually by BLKPG_DEL_PARTITION ioctl:
>
> # partx -d /dev/loop0p1
>
>
> ... but this all is known issue, Phillip Susi tried to fix this
> disadvantage, but his solution has been reverted (see kernel commit
> c2fccc1c9f7c81700cbac2120a4ad5441dd37004).
>
>
> Karel
>
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