xuejiufei
2016-Jan-12 07:16 UTC
[Ocfs2-devel] ocfs2: A race between refmap setting and clearing
Hi, Junxiao On 2016/1/12 12:03, Junxiao Bi wrote:> Hi Jiufei, > > On 01/11/2016 10:46 AM, xuejiufei wrote: >> Hi all, >> We have found a race between refmap setting and clearing which >> will cause the lock resource on master is freed before other nodes >> purge it. >> >> Node 1 Node 2(master) >> dlm_do_master_request >> dlm_master_request_handler >> -> dlm_lockres_set_refmap_bit >> call dlm_purge_lockres after unlock >> dlm_deref_handler >> -> find lock resource is in >> DLM_LOCK_RES_SETREF_INPROG state, >> so dispatch a deref work >> dlm_purge_lockres succeed. >> >> dlm_do_master_request >> dlm_master_request_handler >> -> dlm_lockres_set_refmap_bit >> >> deref work trigger, call >> dlm_lockres_clear_refmap_bit >> to clear Node 1 from refmap >> >> Now Node 2 can purge the lock resource but the owner of lock resource >> on Node 1 is still Node 2 which may trigger BUG if the lock resource >> is $RECOVERY or other problems. >> >> We have discussed 2 solutions: >> 1)The master return error to Node 1 if the DLM_LOCK_RES_SETREF_INPROG >> is set. Node 1 will not retry and master send another message to Node 1 >> after clearing the refmap. Node 1 can purge the lock resource after the >> refmap on master is cleared. >> 2) The master return error to Node 1 if the DLM_LOCK_RES_SETREF_INPROG >> is set, and Node 1 will retry to deref the lockres. >> >> Does anybody has better ideas? >> > dlm_purge_lockres() will wait to drop ref until > DLM_LOCK_RES_SETREF_INPROG cleared. So if set this flag when find the > master during doing master request. And then this flag was cleared when > receiving assert master message, can this fix the issue? >I don't think this can fix. Before doing master request, the lock resource is already purged. The master should clear the refmap before client purge it. Thanks, Jiufei> Thanks, > Junxiao. >> Thanks, >> --Jiufei >> > > > . >
Junxiao Bi
2016-Jan-13 02:46 UTC
[Ocfs2-devel] ocfs2: A race between refmap setting and clearing
On 01/12/2016 03:16 PM, xuejiufei wrote:> Hi, Junxiao > > On 2016/1/12 12:03, Junxiao Bi wrote: >> Hi Jiufei, >> >> On 01/11/2016 10:46 AM, xuejiufei wrote: >>> Hi all, >>> We have found a race between refmap setting and clearing which >>> will cause the lock resource on master is freed before other nodes >>> purge it. >>> >>> Node 1 Node 2(master) >>> dlm_do_master_request >>> dlm_master_request_handler >>> -> dlm_lockres_set_refmap_bit >>> call dlm_purge_lockres after unlock >>> dlm_deref_handler >>> -> find lock resource is in >>> DLM_LOCK_RES_SETREF_INPROG state, >>> so dispatch a deref work >>> dlm_purge_lockres succeed. >>> >>> dlm_do_master_request >>> dlm_master_request_handler >>> -> dlm_lockres_set_refmap_bit >>> >>> deref work trigger, call >>> dlm_lockres_clear_refmap_bit >>> to clear Node 1 from refmap >>> >>> Now Node 2 can purge the lock resource but the owner of lock resource >>> on Node 1 is still Node 2 which may trigger BUG if the lock resource >>> is $RECOVERY or other problems. >>> >>> We have discussed 2 solutions: >>> 1)The master return error to Node 1 if the DLM_LOCK_RES_SETREF_INPROG >>> is set. Node 1 will not retry and master send another message to Node 1 >>> after clearing the refmap. Node 1 can purge the lock resource after the >>> refmap on master is cleared. >>> 2) The master return error to Node 1 if the DLM_LOCK_RES_SETREF_INPROG >>> is set, and Node 1 will retry to deref the lockres. >>> >>> Does anybody has better ideas? >>> >> dlm_purge_lockres() will wait to drop ref until >> DLM_LOCK_RES_SETREF_INPROG cleared. So if set this flag when find the >> master during doing master request. And then this flag was cleared when >> receiving assert master message, can this fix the issue? >> > I don't think this can fix. Before doing master request, the lock resource is > already purged. The master should clear the refmap before client purge it.inflight_locks is increased in dlm_get_lock_resource() which will stop lockres purged? Set DLM_LOCK_RES_SETREF_INPROG when found lockres owner during master request, then this will stop lockres purged after unlock? Thanks, Junxiao.> > Thanks, > Jiufei > >> Thanks, >> Junxiao. >>> Thanks, >>> --Jiufei >>> >> >> >> . >> >