[dm-devel] "dm io" slab cache object not released in snapshot test

[Yue Xu]

I can reproduce a bug by running a lvm2 snapshot test
script on my machine. When it happens, the kernel BUG
is triggered and I got the followings in system log:

kmem_cache_destroy: Can't free all objects a7f14914
kernel BUG at slab.c:817!
invalid operand: 0000 

I found out that somehow one of the "dm io" slab cache
objects is not released when the snapshot volume is
removed.  And when dm module is unloaded, the warning
message from kmem_cache_destroy shows up. By the time
that dm module is reloaded, the kernel BUG is
triggered.
  
The kernel is 2.4.26 vanilla + device mapper
2.4.26-rc1 patch + VFS lock patch, the LVMv2 version
is 2.00.25, and the file system is XFS. My machine is
dell PE2650 (Intel Xeon 2CPUS). 

The script is like this:
#!/bin/sh
for i in `seq 1 1000`; do
        modprobe dm-mod
        lvchange -a y /dev/myvg/lvol0
        mount /dev/myvg/lvol0 /vol1
        xfs_freeze -f /vol1
        lvcreate -L50G -s -c 512 -n lvmbackup
/dev/myvg/lvol0
        xfs_freeze -u /vol1
        mount /dev/myvg/lvmbackup /mnt/lvmbackup
-onouuid,ro,norecovery
        umount /mnt/lvmbackup 
        lvremove -f /dev/myvg/lvmbackup
        umount /vol1
        lvchange -a n /dev/myvg/lvol0
        rmmod dm-mod
done

Any ideas or suggestions? 

Thanks. 


		
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