ceph: unlock dangling spinlock in try_flush_caps()

BugLink: http://bugs.launchpad.net/bugs/1731882

commit 6c2838fb upstream.

sparse warns:

  fs/ceph/caps.c:2042:9: warning: context imbalance in 'try_flush_caps' - wrong count at exit

We need to exit this function with the lock unlocked, but a couple of
cases leave it locked.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

fs/ceph/caps.c

@@ -1850,6 +1850,7 @@ static int try_flush_caps(struct inode *inode, u64 *ptid)
 retry:
 	spin_lock(&ci->i_ceph_lock);
 	if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
+		spin_unlock(&ci->i_ceph_lock);
 		dout("try_flush_caps skipping %p I_NOFLUSH set\n", inode);
 		goto out;
 	}
@@ -1867,8 +1868,10 @@ static int try_flush_caps(struct inode *inode, u64 *ptid)
 			mutex_lock(&session->s_mutex);
 			goto retry;
 		}
-		if (cap->session->s_state < CEPH_MDS_SESSION_OPEN)
+		if (cap->session->s_state < CEPH_MDS_SESSION_OPEN) {
+			spin_unlock(&ci->i_ceph_lock);
 			goto out;
+		}
 
 		flushing = __mark_caps_flushing(inode, session, &flush_tid,
 						&oldest_flush_tid);