[dm-devel] Module reference count problem when using multipath

Ishai Rabinovitz ishai at mellanox.co.il
Wed Jul 12 12:08:00 UTC 2006


Hi All,
 
I take part in the development of SRP (Scsi RDMA Protocol). and I'm
trying to work with dm to support failover.
I downloaded multipath 0.4.7 and I'm working with linux-2.6.18-rc1
kernel over RHAS4.OU3 distribution.
 
I have connected to the SRP target (That has a lot of disks), and they
can be accessed through /dev/sdb /dev/sdc and so on. I run multipath and
got the mapping as it should be.
 
The problem is that the reference count of ib_srp module is equal to the
number of disks that were mapped using multipath. Because of that I can
not remove the ib_srp module.
This does not occur without multipath.
 
There is also reference count of 1 on dm_round_robin.
 
I tried to look at "ps aux" and "lsof" but found no process or file that
should hold reference to ib_srp. I tried to google it without any
success.
 
Can someone answer any of the following questions:
1) Why does every disk that is mapped through multipath hold a reference
to the ib_srp module?  Is this the correct behavior, or is it a bug?
2) Can I remove a mapping from the multipath ?
3) Any ideas how I can debug this.
 
I will appreciate any help.
 
Thanks
Ishai
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