Hi,

In blockdevc-check-errors.patch, add_bd_holder() is modified to
return error values when some of its operation failed.
Among them, it returns -EEXIST when a given bd_holder object already
exists in the list.
However, in this case, the function completed its work successfully
and need no action by its caller other than freeing unused bd_holder
object.
So I think it's better to return success after freeing by itself.

Otherwise, bd_claim-ing with same claim pointer will fail.
Typically, lvresize will fails with following message:
  device-mapper: reload ioctl failed: Invalid argument
and you'll see messages like below in kernel log:
  device-mapper: table: 254:13: linear: dm-linear: Device lookup failed
  device-mapper: ioctl: error adding target to table

Similarly, it should not add bd_holder to the list if either one
of symlinking fails. I don't have a test case for this to happen
but it should cause dereference of freed pointer.

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America