ocfs2/dlm: Migrate lockres with no locks if it has a reference
o2dlm was not migrating resources with zero locks because it assumed that that
resource would get purged by dlm_thread. However, some usage patterns involve
creating and dropping locks at a high rate leading to the migrate thread seeing
zero locks but the purge thread seeing an active reference. When this happens,
the dlm_thread cannot purge the resource and the migrate thread sees no reason
to migrate that resource. The spell is broken when the migrate thread catches
the resource with a lock.
The fix is to make the migrate thread also consider the reference map.
This usage pattern can be triggered by userspace on userdlm locks and flocks.
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index f564b0e..59f0f6b 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -2346,7 +2346,8 @@
*/
static int dlm_is_lockres_migrateable(struct dlm_ctxt *dlm,
struct dlm_lock_resource *res,
- int *numlocks)
+ int *numlocks,
+ int *hasrefs)
{
int ret;
int i;
@@ -2356,6 +2357,9 @@
assert_spin_locked(&res->spinlock);
+ *numlocks = 0;
+ *hasrefs = 0;
+
ret = -EINVAL;
if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
mlog(0, "cannot migrate lockres with unknown owner!\n");
@@ -2386,7 +2390,13 @@
}
*numlocks = count;
- mlog(0, "migrateable lockres having %d locks\n", *numlocks);
+
+ count = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
+ if (count < O2NM_MAX_NODES)
+ *hasrefs = 1;
+
+ mlog(0, "%s: res %.*s, Migrateable, locks %d, refs %d\n", dlm->name,
+ res->lockname.len, res->lockname.name, *numlocks, *hasrefs);
leave:
return ret;
@@ -2408,7 +2418,7 @@
const char *name;
unsigned int namelen;
int mle_added = 0;
- int numlocks;
+ int numlocks, hasrefs;
int wake = 0;
if (!dlm_grab(dlm))
@@ -2417,13 +2427,13 @@
name = res->lockname.name;
namelen = res->lockname.len;
- mlog(0, "migrating %.*s to %u\n", namelen, name, target);
+ mlog(0, "%s: Migrating %.*s to %u\n", dlm->name, namelen, name, target);
/*
* ensure this lockres is a proper candidate for migration
*/
spin_lock(&res->spinlock);
- ret = dlm_is_lockres_migrateable(dlm, res, &numlocks);
+ ret = dlm_is_lockres_migrateable(dlm, res, &numlocks, &hasrefs);
if (ret < 0) {
spin_unlock(&res->spinlock);
goto leave;
@@ -2431,10 +2441,8 @@
spin_unlock(&res->spinlock);
/* no work to do */
- if (numlocks == 0) {
- mlog(0, "no locks were found on this lockres! done!\n");
+ if (numlocks == 0 && !hasrefs)
goto leave;
- }
/*
* preallocate up front
@@ -2459,14 +2467,14 @@
* find a node to migrate the lockres to
*/
- mlog(0, "picking a migration node\n");
spin_lock(&dlm->spinlock);
/* pick a new node */
if (!test_bit(target, dlm->domain_map) ||
target >= O2NM_MAX_NODES) {
target = dlm_pick_migration_target(dlm, res);
}
- mlog(0, "node %u chosen for migration\n", target);
+ mlog(0, "%s: res %.*s, Node %u chosen for migration\n", dlm->name,
+ namelen, name, target);
if (target >= O2NM_MAX_NODES ||
!test_bit(target, dlm->domain_map)) {
@@ -2667,7 +2675,7 @@
{
int ret;
int lock_dropped = 0;
- int numlocks;
+ int numlocks, hasrefs;
spin_lock(&res->spinlock);
if (res->owner != dlm->node_num) {
@@ -2681,8 +2689,8 @@
}
/* No need to migrate a lockres having no locks */
- ret = dlm_is_lockres_migrateable(dlm, res, &numlocks);
- if (ret >= 0 && numlocks == 0) {
+ ret = dlm_is_lockres_migrateable(dlm, res, &numlocks, &hasrefs);
+ if (ret >= 0 && numlocks == 0 && !hasrefs) {
spin_unlock(&res->spinlock);
goto leave;
}
@@ -2915,6 +2923,12 @@
}
queue++;
}
+
+ nodenum = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
+ if (nodenum < O2NM_MAX_NODES) {
+ spin_unlock(&res->spinlock);
+ return nodenum;
+ }
spin_unlock(&res->spinlock);
mlog(0, "have not found a suitable target yet! checking domain map\n");