This patch fixes two problems in dlm_run_purgelist
1. If a lockres is found to be in use, dlm_run_purgelist keeps trying to purge
the same lockres instead of trying the next lockres.
2. When a lockres is found unused, dlm_run_purgelist releases lockres spinlock
before setting DLM_LOCK_RES_DROPPING_REF and calls dlm_purge_lockres.
spinlock is reacquired but in this window lockres can get reused. This leads
to BUG.
This patch modifies dlm_run_purgelist to skip lockres if it's in use and purge
next lockres. It also sets DLM_LOCK_RES_DROPPING_REF before releasing the
lockres spinlock protecting it from getting reused.
Signed-off-by: Srinivas Eeda srinivas.e...@oracle.com
Acked-by: Sunil Mushran sunil.mush...@oracle.com
---
fs/ocfs2/dlm/dlmthread.c | 80 +++--
1 files changed, 34 insertions(+), 46 deletions(-)
diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
index 11a6d1f..960dc8d 100644
--- a/fs/ocfs2/dlm/dlmthread.c
+++ b/fs/ocfs2/dlm/dlmthread.c
@@ -152,45 +152,25 @@ void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
spin_unlock(dlm-spinlock);
}
-static int dlm_purge_lockres(struct dlm_ctxt *dlm,
+static void dlm_purge_lockres(struct dlm_ctxt *dlm,
struct dlm_lock_resource *res)
{
int master;
int ret = 0;
- spin_lock(res-spinlock);
- if (!__dlm_lockres_unused(res)) {
- mlog(0, %s:%.*s: tried to purge but not unused\n,
-dlm-name, res-lockname.len, res-lockname.name);
- __dlm_print_one_lock_resource(res);
- spin_unlock(res-spinlock);
- BUG();
- }
-
- if (res-state DLM_LOCK_RES_MIGRATING) {
- mlog(0, %s:%.*s: Delay dropref as this lockres is
-being remastered\n, dlm-name, res-lockname.len,
-res-lockname.name);
- /* Re-add the lockres to the end of the purge list */
- if (!list_empty(res-purge)) {
- list_del_init(res-purge);
- list_add_tail(res-purge, dlm-purge_list);
- }
- spin_unlock(res-spinlock);
- return 0;
- }
+ assert_spin_locked(dlm-spinlock);
+ assert_spin_locked(res-spinlock);
master = (res-owner == dlm-node_num);
- if (!master)
- res-state |= DLM_LOCK_RES_DROPPING_REF;
- spin_unlock(res-spinlock);
mlog(0, purging lockres %.*s, master = %d\n, res-lockname.len,
res-lockname.name, master);
if (!master) {
+ res-state |= DLM_LOCK_RES_DROPPING_REF;
/* drop spinlock... retake below */
+ spin_unlock(res-spinlock);
spin_unlock(dlm-spinlock);
spin_lock(res-spinlock);
@@ -208,31 +188,35 @@ static int dlm_purge_lockres(struct dlm_ctxt *dlm,
mlog(0, %s:%.*s: dlm_deref_lockres returned %d\n,
dlm-name, res-lockname.len, res-lockname.name, ret);
spin_lock(dlm-spinlock);
+ spin_lock(res-spinlock);
}
- spin_lock(res-spinlock);
if (!list_empty(res-purge)) {
mlog(0, removing lockres %.*s:%p from purgelist,
master = %d\n, res-lockname.len, res-lockname.name,
res, master);
list_del_init(res-purge);
- spin_unlock(res-spinlock);
dlm_lockres_put(res);
dlm-purge_count--;
- } else
- spin_unlock(res-spinlock);
+ }
+
+ if (!__dlm_lockres_unused(res)) {
+ mlog(ML_ERROR, found lockres %s:%.*s: in use after deref\n,
+dlm-name, res-lockname.len, res-lockname.name);
+ __dlm_print_one_lock_resource(res);
+ BUG();
+ }
__dlm_unhash_lockres(res);
/* lockres is not in the hash now. drop the flag and wake up
* any processes waiting in dlm_get_lock_resource. */
if (!master) {
- spin_lock(res-spinlock);
res-state = ~DLM_LOCK_RES_DROPPING_REF;
spin_unlock(res-spinlock);
wake_up(res-wq);
- }
- return 0;
+ } else
+ spin_unlock(res-spinlock);
}
static void dlm_run_purge_list(struct dlm_ctxt *dlm,
@@ -251,17 +235,7 @@ static void dlm_run_purge_list(struct dlm_ctxt *dlm,
lockres = list_entry(dlm-purge_list.next,
struct dlm_lock_resource, purge);
- /* Status of the lockres *might* change so double
-* check. If the lockres is unused, holding the dlm
-* spinlock will prevent people from getting and more
-* refs on it -- there's no need to keep the lockres
-* spinlock. */
spin_lock(lockres-spinlock);
-
