[Cluster-devel] [PATCH dlm/next 1/3] fs: dlm: add notes for recovery and membership handling

[Alexander Aring <aahringo@redhat.com>]

This patch adds some comment sections to make aware that the ls_recover()
function should never fail before membership handling. Membership
handling means to add/remove nodes from the lockspace ls_nodes
attribute in dlm_recover_members().

This is because there are functionality like dlm_midcomms_add_member(),
dlm_midcomms_remove_member() or dlm_lsop_recover_slot() which should
always get aware of any join or leave of lockspace members. If we add a
e.g. dlm_locking_stopped() before dlm_recover_members() to check if the
recovery was interrupted and abort it we might skip to call
dlm_midcomms_add_member(), dlm_midcomms_remove_member() or
dlm_lsop_recover_slot().

A reason because the recovery is interrupted could be that the cluster
manager notified about a new configuration .e.g. members joined or
leaved. It is fine to interrupt or fail the recovery handling after
the mentioned handling of dlm_recover_members() but never before.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/member.c   | 6 +++++-
 fs/dlm/recoverd.c | 4 ++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/dlm/member.c b/fs/dlm/member.c
index 731d489aa323..5f5b07bdbcc3 100644
--- a/fs/dlm/member.c
+++ b/fs/dlm/member.c
@@ -540,7 +540,11 @@ int dlm_recover_members(struct dlm_ls *ls, struct dlm_recover *rv, int *neg_out)
 	int i, error, neg = 0, low = -1;
 
 	/* previously removed members that we've not finished removing need to
-	   count as a negative change so the "neg" recovery steps will happen */
+	 * count as a negative change so the "neg" recovery steps will happen
+	 *
+	 * This functionality must report all member changes to lsops or
+	 * midcomms layer and must never return before.
+	 */
 
 	list_for_each_entry(memb, &ls->ls_nodes_gone, list) {
 		log_rinfo(ls, "prev removed member %d", memb->nodeid);
diff --git a/fs/dlm/recoverd.c b/fs/dlm/recoverd.c
index 97d052cea5a9..208b69f46baf 100644
--- a/fs/dlm/recoverd.c
+++ b/fs/dlm/recoverd.c
@@ -70,6 +70,10 @@ static int ls_recover(struct dlm_ls *ls, struct dlm_recover *rv)
 
 	/*
 	 * Add or remove nodes from the lockspace's ls_nodes list.
+	 *
+	 * Due the fact we must report all membership changes to lsops or
+	 * midcomms layer it is not permitted to abort ls_recover() until
+	 * this is done.
 	 */
 
 	error = dlm_recover_members(ls, rv, &neg);
-- 
2.27.0