On 09/24/2015 12:11 PM, Joseph Qi wrote:
> Hi Junxiao,
>
> On 2015/9/24 11:58, Junxiao Bi wrote:
>> On 09/24/2015 11:14 AM, Joseph Qi wrote:
>>> There is a race window between dlmconvert_remote and
>>> dlm_move_lockres_to_recovery_list, which will cause a lock with
>>> OCFS2_LOCK_BUSY in grant list, thus system hangs.
>>>
>>> dlmconvert_remote
>>> {
>>> spin_lock(&res->spinlock);
>>> list_move_tail(&lock->list, &res->converting);
>>> lock->convert_pending = 1;
>>> spin_unlock(&res->spinlock);
>>>
>>> status = dlm_send_remote_convert_request();
>>> >>>>>> race window, master has queued ast and return DLM_NORMAL,
>>> and then down before sending ast.
>>> this node detects master down and calls
>>> dlm_move_lockres_to_recovery_list, which will revert the
>>> lock to grant list.
>>> Then OCFS2_LOCK_BUSY won't be cleared as new master won't
>>> send ast any more because it thinks already be authorized.
>> How this race windowed fixed?
>> the process have sent convert request to master node successfully(return
>> value DLM_NORMAL) then wait on LOCK_BUSY, then when master node panic
>> before send out ast, dlm_move_lockres_to_recovery_list() move the lock
>> to grant list. Ast never come.
> res->state is now having DLM_LOCK_RES_RECOVERING set.
But what happened if master node panic after
dlm_send_remote_convert_request() return DLM_NORMAL and wait on LOCK_BUSY?
Thanks,
Junxiao.
This patch will
> reset the status to DLM_RECOVERING and then retry convert request. Then
> new master will handle it and send ast.
>
>>
>> Thanks,
>> Junxiao.
>>
>>>
>>> spin_lock(&res->spinlock);
>>> lock->convert_pending = 0;
>>> if (status != DLM_NORMAL)
>>> dlm_revert_pending_convert(res, lock);
>>> spin_unlock(&res->spinlock);
>>> }
>>>
>>> In this case, check if res->state has DLM_LOCK_RES_RECOVERING bit set
>>> (res is still in recovering) or res master changed (new master has
>>> finished recovery), reset the status to DLM_RECOVERING, then it will
>>> retry convert.
>>>
>>> Signed-off-by: Joseph Qi <joseph...@huawei.com>
>>> Reported-by: Yiwen Jiang <jiangyi...@huawei.com>
>>> Cc: <sta...@vger.kernel.org>
>>> ---
>>> fs/ocfs2/dlm/dlmconvert.c | 11 ++++++++++-
>>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
>>> index e36d63f..9e6116e 100644
>>> --- a/fs/ocfs2/dlm/dlmconvert.c
>>> +++ b/fs/ocfs2/dlm/dlmconvert.c
>>> @@ -262,6 +262,7 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm,
>>> struct dlm_lock *lock, int flags, int type)
>>> {
>>> enum dlm_status status;
>>> + u8 old_owner = res->owner;
>>>
>>> mlog(0, "type=%d, convert_type=%d, busy=%d\n", lock->ml.type,
>>> lock->ml.convert_type, res->state & DLM_LOCK_RES_IN_PROGRESS);
>>> @@ -316,11 +317,19 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt
>>> *dlm,
>>> spin_lock(&res->spinlock);
>>> res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
>>> lock->convert_pending = 0;
>>> - /* if it failed, move it back to granted queue */
>>> + /* if it failed, move it back to granted queue.
>>> + * if master returns DLM_NORMAL and then down before sending ast,
>>> + * it may have already been moved to granted queue, reset to
>>> + * DLM_RECOVERING and retry convert */
>>> if (status != DLM_NORMAL) {
>>> if (status != DLM_NOTQUEUED)
>>> dlm_error(status);
>>> dlm_revert_pending_convert(res, lock);
>>> + } else if ((res->state & DLM_LOCK_RES_RECOVERING) ||
>>> + (old_owner != res->owner)) {
>>> + mlog(0, "res %.*s is in recovering or has been recovered.\n",
>>> + res->lockname.len, res->lockname.name);
>>> + status = DLM_RECOVERING;
>>> }
>>> bail:
>>> spin_unlock(&res->spinlock);
>>>
>>
>>
>> .
>>
>
>
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