mainline inclusion
from mainline-v5.1-rc1
commit 9567da0b
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I47H3V
CVE: NA

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

commit 9567da0b upstream.

In support of multiple device-dax instances per device-dax-region and
allowing the 'kmem' driver to attach to dax-instances instead of the
current device-node access, convert the dax sub-system from a class to a
bus. Recall that the kmem driver takes reserved / special purpose
memories and assigns them to be managed by the core-mm.

Aside from the fact the device-dax instances are registered and probed
on a bus, two other lifetime-management changes are made:

1/ Delay attaching a cdev until driver probe time

2/ A new run_dax() helper is introduced to allow restoring dax-operation
   after a kill_dax() event. So, at driver ->probe() time we run_dax()
   and at ->remove() time we kill_dax() and invalidate all mappings.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NFan Du <fan.du@intel.com>
Signed-off-by: NJackie Liu <liuyun01@kylinos.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>