NewDreamNetwork/ceph-client — comment on commit 971d9728082a09868963bbc043bce36947c1d10a
File:  line 0
By liewegas:

Oh right, the mutex will protect for that. Sounds good.

The first part was from the commit message: "Unfortunately,
the lock is held during the call to ceph_mdsc_put_request(req),
which translates to a kref_put(), which can end up sleeping."