Comment 5 for bug 1566468

ok, so it is /lib/modules-load.d/open-iscsi.conf that has 'ib_iser' in it.

ib_iser per modinfo "iSER (iSCSI Extensions for RDMA) Datamover".

per depmod on full linux-image-extra system:
 kernel/drivers/infiniband/ulp/iser/ib_iser.ko: kernel/drivers/infiniband/core/rdma_cm.ko kernel/drivers/infiniband/core/iw_cm.ko kernel/drivers/infiniband/core/ib_cm.ko kernel/drivers/infiniband/core/ib_sa.ko kernel/drivers/infiniband/core/ib_mad.ko kernel/drivers/infiniband/core/ib_core.ko kernel/drivers/infiniband/core/ib_addr.ko kernel/drivers/scsi/libiscsi.ko kernel/drivers/scsi/scsi_transport_iscsi.ko

$ ls -l /lib/modules/4.4.0-17-generic/kernel/drivers/infiniband/ulp/iser/ib_iser.ko
-rw-r--r-- 1 root root 81382 Mar 29 15:15 /lib/modules/4.4.0-17-generic/kernel/drivers/infiniband/ulp/iser/ib_iser.ko

So the easiest fix for this, at a cost of 81kb is to just move ib_iser from linux-image-extra to linux-image.

There might be some way to say "load if present, do not complain" but I dont see it immediately. Possibly something with modprobe.d. It would seem that such function would be needed to avoid warning failure if a driver was simply built into the kernel. Ie, a custom kernel built ib_iser into the kernel, then we'd not want to warn.