We found a race between purge and migration when doing code review. Node
A put lockres to purgelist before receiving the migrate message from node
B which is the master. Node A call dlm_mig_lockres_handler to handle
this message.
dlm_mig_lockres_handler
dlm_lookup_lockres
>>>>>> race window, dlm_run_purge_list may run and send
deref message to master, waiting the response
spin_lock(&res->spinlock);
res->state |= DLM_LOCK_RES_MIGRATING;
spin_unlock(&res->spinlock);
dlm_mig_lockres_handler returns
>>>>>> dlm_thread receives the response from master for the deref
message and triggers the BUG because the lockres has the state
DLM_LOCK_RES_MIGRATING with the following message:
dlm_purge_lockres:209 ERROR: 6633EB681FA7474A9C280A4E1A836F0F:
res M0000000000000000030c0300000000 in use after deref
Signed-off-by: Jiufei Xue <xuejiu...@huawei.com>
Reviewed-by: Joseph Qi <joseph...@huawei.com>
---
fs/ocfs2/dlm/dlmrecovery.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index 58eaa5c..4055909 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1373,6 +1373,7 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32
len, void *data,
char *buf = NULL;
struct dlm_work_item *item = NULL;
struct dlm_lock_resource *res = NULL;
+ unsigned int hash;
if (!dlm_grab(dlm))
return -EINVAL;
@@ -1400,7 +1401,10 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32
len, void *data,
/* lookup the lock to see if we have a secondary queue for this
* already... just add the locks in and this will have its owner
* and RECOVERY flag changed when it completes. */
- res = dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len);
+ hash = dlm_lockid_hash(mres->lockname, mres->lockname_len);
+ spin_lock(&dlm->spinlock);
+ res = __dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len,
+ hash);
if (res) {
/* this will get a ref on res */
/* mark it as recovering/migrating and hash it */
@@ -1421,13 +1425,16 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32
len, void *data,
mres->lockname_len, mres->lockname);
ret = -EFAULT;
spin_unlock(&res->spinlock);
+ spin_unlock(&dlm->spinlock);
dlm_lockres_put(res);
goto leave;
}
res->state |= DLM_LOCK_RES_MIGRATING;
}
spin_unlock(&res->spinlock);
+ spin_unlock(&dlm->spinlock);
} else {
+ spin_unlock(&dlm->spinlock);
/* need to allocate, just like if it was
* mastered here normally */
res = dlm_new_lockres(dlm, mres->lockname, mres->lockname_len);
--
1.8.4.3
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