rbd: use rwsem to protect header updates
Updating an image header needs to be protected to ensure it's
done consistently. However distinct headers can be updated
concurrently without a problem. Instead of using the global
control lock to serialize headder updates, just rely on the header
semaphore. (It's already used, this just moves it out to cover
a broader section of the code.)
That leaves the control mutex protecting only the creation of rbd
clients, so rename it.
This resolves:
http://tracker.ceph.com/issues/5222
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
1 file changed