ocfs2/dlm: do not purge lockres that is queued for assert master

When workqueue is delayed, it may occur that a lockres is purged while it
is still queued for master assert.  it may trigger BUG() as follows.

N1                                         N2
dlm_get_lockres()
->dlm_do_master_requery
                                  is the master of lockres,
                                  so queue assert_master work

                                  dlm_thread() start running
                                  and purge the lockres

                                  dlm_assert_master_worker()
                                  send assert master message
                                  to other nodes
receiving the assert_master
message, set master to N2

dlmlock_remote() send create_lock message to N2, but receive DLM_IVLOCKID,
if it is RECOVERY lockres, it triggers the BUG().

Another BUG() is triggered when N3 become the new master and send
assert_master to N1, N1 will trigger the BUG() because owner doesn't
match.  So we should not purge lockres when it is queued for assert
master.

Signed-off-by: joyce.xue <xuejiufei@huawei.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
index cf53a822f07f..69aac6f088ad 100644
--- a/fs/ocfs2/dlm/dlmthread.c
+++ b/fs/ocfs2/dlm/dlmthread.c
@@ -259,11 +259,14 @@ static void dlm_run_purge_list(struct dlm_ctxt *dlm,
 		 * refs on it. */
 		unused = __dlm_lockres_unused(lockres);
 		if (!unused ||
-		    (lockres->state & DLM_LOCK_RES_MIGRATING)) {
+		    (lockres->state & DLM_LOCK_RES_MIGRATING) ||
+		    (lockres->inflight_assert_workers != 0)) {
 			mlog(0, "%s: res %.*s is in use or being remastered, "
-			     "used %d, state %d\n", dlm->name,
-			     lockres->lockname.len, lockres->lockname.name,
-			     !unused, lockres->state);
+			     "used %d, state %d, assert master workers %u\n",
+			     dlm->name, lockres->lockname.len,
+			     lockres->lockname.name,
+			     !unused, lockres->state,
+			     lockres->inflight_assert_workers);
 			list_move_tail(&lockres->purge, &dlm->purge_list);
 			spin_unlock(&lockres->spinlock);
 			continue;