Safeguard against writing to an active device of another node

Safeguard against writing to an active device of another node

Modifying an exiting device's superblock or creating a new superblock
on an existing device needs to be checked because the device could be
in use by another node in another array. So, we check this by taking
all superblock locks in userspace so that we don't  step onto an active
device used by another node and safeguard against accidental edits.
After the edit is complete, we release all locks and the lockspace so
that it can be used by the kernel space.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>