ceph: make sure mdsc->mutex is nested in s->s_mutex to fix dead lock (ea8412b2) · Commits · 戴 / test

send_mds_reconnect takes the s_mutex while the mdsc->mutex is already held. That inverts the locking order documented in mds_client.h. Drop the mdsc->mutex, acquire the s_mutex and then reacquire the mdsc->mutex to prevent a deadlock. URL: https://tracker.ceph.com/issues/45609 Signed-off-by:

Xiubo Li <xiubli@redhat.com> Reviewed-by:

Jeff Layton <jlayton@kernel.org> Signed-off-by:

Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3769,8 +3769,6 @@ fail:
		* recovering MDS might have.
		*
		* This is a relatively heavyweight operation, but it's rare.
		*
		* called with mdsc->mutex held.
		*/
		static void send_mds_reconnect(struct ceph_mds_client *mdsc,
		struct ceph_mds_session *session)
		@@ -4024,7 +4022,9 @@ static void check_new_map(struct ceph_mds_client *mdsc,
		oldstate != CEPH_MDS_STATE_STARTING)
		pr_info("mds%d recovery completed\n", s->s_mds);
		kick_requests(mdsc, i);
		mutex_unlock(&mdsc->mutex);
		mutex_lock(&s->s_mutex);
		mutex_lock(&mdsc->mutex);
		ceph_kick_flushing_caps(mdsc, s);
		mutex_unlock(&s->s_mutex);
		wake_up_session_caps(s, RECONNECT);

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