bug with umounting loop devices in busybox 1.10.2

Denys Vlasenko vda.linux at googlemail.com
Thu May 22 15:56:34 UTC 2008


On Thursday 22 May 2008 17:48, Natanael Copa wrote:
> hi,
> 
> I have noticed a problem with mount or umount in busybox-1.10.2
> 
> # /dev/sda1 is ext3
> mount /dev/sda1 on /mnt
> 
> # mount a loop back device
> mkdir /1
> mount -o loop /mnt/loopback /1
> 
> umount /1
> umount /mnt
> 
> The result is:
> umount: cannot umount /mnt: Device or resource busy
> 
> Doing exactly the same works in busybox-1.9.2.

Yes. This was an incompatible change, to make our umount match
util-linux. It has -d "free loop device", we were using -D
with an inverted meaning:

# /app/busybox-1.9.0.svn/busybox umount --help
BusyBox v1.9.0.svn (2007-12-20 23:47:50 GMT) multi-call binary

Usage: umount [flags] FILESYSTEM|DIRECTORY

Unmount file systems

Options:

        -a      Unmount all file systems
        -r      Try to remount devices as read-only if mount is busy
        -l      Lazy umount (detach filesystem)
        -f      Force umount (i.e., unreachable NFS server)
        -D      Do not free loop device (if a loop device has been used)

# umount --help
BusyBox v1.10.0 (2008-03-22 15:35:10 CET) multi-call binary

Usage: umount [flags] FILESYSTEM|DIRECTORY

Unmount file systems

Options:
        -a      Unmount all file systems
        -r      Try to remount devices as read-only if mount is busy
        -l      Lazy umount (detach filesystem)
        -f      Force umount (i.e., unreachable NFS server)
        -d      Free loop device if it has been used


man umount:

NAME
       umount - unmount file systems
SYNOPSIS
       umount [-hV]
       umount -a [-dflnrv] [-t vfstype] [-O options]
       umount [-dflnrv] dir | device [...]
DESCRIPTION
...
       -d     In case the unmounted device was a loop device, also free this loop device.

Sorry for inconvenience...
--
vda



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