stable inclusion
from stable-5.10.19
commit 225d207da2e1169aee30faaa71bd7cf70c7277a3
bugzilla: 50607

--------------------------------

commit 8ecfca68 upstream.

Lift the ibdev_to_node from rds to common code and document it.

Link: https://lore.kernel.org/r/20201106181941.1878556-4-hch@lst.deSigned-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>
Cc: Krishnamraju Eraparaju <krishna2@chelsio.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>