ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list
This patch adds a new lock, dlm->tracking_lock, to protect adding/removing
lockres' to/from the dlm->tracking_list. We were previously using dlm->spinlock
for the same, but that proved inadequate as we could be freeing a lockres from
a context that did not hold that lock. As the new lock only protects this list,
we can explicitly take it when removing the lockres from the tracking list.
This bug was exposed when testing multiple processes concurrently flock() the
same file.
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
index d5a86fb..bb53714 100644
--- a/fs/ocfs2/dlm/dlmcommon.h
+++ b/fs/ocfs2/dlm/dlmcommon.h
@@ -140,6 +140,7 @@
unsigned int purge_count;
spinlock_t spinlock;
spinlock_t ast_lock;
+ spinlock_t track_lock;
char *name;
u8 node_num;
u32 key;
@@ -316,6 +317,8 @@
* put on a list for the dlm thread to run. */
unsigned long last_used;
+ struct dlm_ctxt *dlm;
+
unsigned migration_pending:1;
atomic_t asts_reserved;
spinlock_t spinlock;
diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
index 1b81dcb..b32f60a 100644
--- a/fs/ocfs2/dlm/dlmdebug.c
+++ b/fs/ocfs2/dlm/dlmdebug.c
@@ -630,43 +630,38 @@
{
struct debug_lockres *dl = m->private;
struct dlm_ctxt *dlm = dl->dl_ctxt;
+ struct dlm_lock_resource *oldres = dl->dl_res;
struct dlm_lock_resource *res = NULL;
+ struct list_head *track_list;
- spin_lock(&dlm->spinlock);
+ spin_lock(&dlm->track_lock);
+ if (oldres)
+ track_list = &oldres->tracking;
+ else
+ track_list = &dlm->tracking_list;
- if (dl->dl_res) {
- list_for_each_entry(res, &dl->dl_res->tracking, tracking) {
- if (dl->dl_res) {
- dlm_lockres_put(dl->dl_res);
- dl->dl_res = NULL;
- }
- if (&res->tracking == &dlm->tracking_list) {
- mlog(0, "End of list found, %p\n", res);
- dl = NULL;
- break;
- }
+ list_for_each_entry(res, track_list, tracking) {
+ if (&res->tracking == &dlm->tracking_list)
+ res = NULL;
+ else
dlm_lockres_get(res);
- dl->dl_res = res;
- break;
- }
- } else {
- if (!list_empty(&dlm->tracking_list)) {
- list_for_each_entry(res, &dlm->tracking_list, tracking)
- break;
- dlm_lockres_get(res);
- dl->dl_res = res;
- } else
- dl = NULL;
+ break;
}
+ spin_unlock(&dlm->track_lock);
- if (dl) {
- spin_lock(&dl->dl_res->spinlock);
- dump_lockres(dl->dl_res, dl->dl_buf, dl->dl_len - 1);
- spin_unlock(&dl->dl_res->spinlock);
- }
+ if (oldres)
+ dlm_lockres_put(oldres);
- spin_unlock(&dlm->spinlock);
+ dl->dl_res = res;
+ if (res) {
+ spin_lock(&res->spinlock);
+ dump_lockres(res, dl->dl_buf, dl->dl_len - 1);
+ spin_unlock(&res->spinlock);
+ } else
+ dl = NULL;
+
+ /* passed to seq_show */
return dl;
}
diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
index 63f8125..d8d578f 100644
--- a/fs/ocfs2/dlm/dlmdomain.c
+++ b/fs/ocfs2/dlm/dlmdomain.c
@@ -1550,6 +1550,7 @@
spin_lock_init(&dlm->spinlock);
spin_lock_init(&dlm->master_lock);
spin_lock_init(&dlm->ast_lock);
+ spin_lock_init(&dlm->track_lock);
INIT_LIST_HEAD(&dlm->list);
INIT_LIST_HEAD(&dlm->dirty_list);
INIT_LIST_HEAD(&dlm->reco.resources);
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 92fd1d7..cbf3abe 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -505,8 +505,10 @@
static void dlm_lockres_release(struct kref *kref)
{
struct dlm_lock_resource *res;
+ struct dlm_ctxt *dlm;
res = container_of(kref, struct dlm_lock_resource, refs);
+ dlm = res->dlm;
/* This should not happen -- all lockres' have a name
* associated with them at init time. */
@@ -515,6 +517,7 @@
mlog(0, "destroying lockres %.*s\n", res->lockname.len,
res->lockname.name);
+ spin_lock(&dlm->track_lock);
if (!list_empty(&res->tracking))
list_del_init(&res->tracking);
else {
@@ -522,6 +525,9 @@
res->lockname.len, res->lockname.name);
dlm_print_one_lock_resource(res);
}
+ spin_unlock(&dlm->track_lock);
+
+ dlm_put(dlm);
if (!hlist_unhashed(&res->hash_node) ||
!list_empty(&res->granted) ||
@@ -595,6 +601,10 @@
res->migration_pending = 0;
res->inflight_locks = 0;
+ /* put in dlm_lockres_release */
+ dlm_grab(dlm);
+ res->dlm = dlm;
+
kref_init(&res->refs);
/* just for consistency */