[PATCH 3/5] ceph: flush mdlog before umounting

[xiubli@redhat.com]

From: Xiubo Li <xiubli@redhat.com>

Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 fs/ceph/mds_client.c         | 29 +++++++++++++++++++++++++++++
 fs/ceph/mds_client.h         |  1 +
 include/linux/ceph/ceph_fs.h |  1 +
 3 files changed, 31 insertions(+)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 96bef289f58f..2db87a5c68d4 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -4689,6 +4689,34 @@ static void wait_requests(struct ceph_mds_client *mdsc)
 	dout("wait_requests done\n");
 }
 
+static void send_flush_mdlog(struct ceph_mds_session *s)
+{
+	u64 seq = s->s_seq;
+	struct ceph_msg *msg;
+
+	/*
+	 * For the MDS daemons lower than Luminous will crash when it
+	 * saw this unknown session request.
+	 */
+	if (!CEPH_HAVE_FEATURE(s->s_con.peer_features, SERVER_LUMINOUS))
+		return;
+
+	dout("send_flush_mdlog to mds%d (%s)s seq %lld\n",
+	     s->s_mds, ceph_session_state_name(s->s_state), seq);
+	msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_FLUSH_MDLOG, seq);
+	if (!msg) {
+		pr_err("failed to send_flush_mdlog to mds%d (%s)s seq %lld\n",
+		       s->s_mds, ceph_session_state_name(s->s_state), seq);
+	} else {
+		ceph_con_send(&s->s_con, msg);
+	}
+}
+
+void flush_mdlog(struct ceph_mds_client *mdsc)
+{
+	ceph_mdsc_iterate_sessions(mdsc, send_flush_mdlog, true);
+}
+
 /*
  * called before mount is ro, and before dentries are torn down.
  * (hmm, does this still race with new lookups?)
@@ -4698,6 +4726,7 @@ void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
 	dout("pre_umount\n");
 	mdsc->stopping = 1;
 
+	flush_mdlog(mdsc);
 	ceph_mdsc_iterate_sessions(mdsc, lock_unlock_session, false);
 	ceph_flush_dirty_caps(mdsc);
 	wait_requests(mdsc);
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index fca2cf427eaf..79d5b8ed62bf 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -537,6 +537,7 @@ extern int ceph_iterate_session_caps(struct ceph_mds_session *session,
 				     int (*cb)(struct inode *,
 					       struct ceph_cap *, void *),
 				     void *arg);
+extern void flush_mdlog(struct ceph_mds_client *mdsc);
 extern void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc);
 
 static inline void ceph_mdsc_free_path(char *path, int len)
diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index 57e5bd63fb7a..ae60696fe40b 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -300,6 +300,7 @@ enum {
 	CEPH_SESSION_FLUSHMSG_ACK,
 	CEPH_SESSION_FORCE_RO,
 	CEPH_SESSION_REJECT,
+	CEPH_SESSION_REQUEST_FLUSH_MDLOG,
 };
 
 extern const char *ceph_session_op_name(int op);
-- 
2.27.0