[Ocfs2-devel] [PATCH] Wakeup down-convert thread just after clearing OCFS2_LOCK_UPCONVERT_FINISHING -v3

[Sunil Mushran]

http://people.redhat.com/~teigland/make_panic

This test has been useful in exposing dlmglue issues.

On 09/15/2011 10:15 AM, Sunil Mushran wrote:
> I am fine with the kick in recover from dlm error. Not so in cluster lock.
> We have to be very very sure before meddling with that function. It is
> a state machine with many hidden gotchas.
>
> So is this patch for a bug encountered or just code audit. Also, what kind
> testing has been done.
>
> On 09/14/2011 08:27 PM, Wengang Wang wrote:
>> When the lockres state UPCONVERT_FINISHING is cleared,
>> we should wake up the downconvert thread incase that lockres
>> is in the blocked queue. Currently we are not doing so and thus
>> are at the mercy of another event waking up the dc thread.
>>
>> Signed-off-by: Wengang Wang<wen.gang.wang at oracle.com>
>> ---
>>    fs/ocfs2/dlmglue.c |    9 ++++++++-
>>    1 files changed, 8 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
>> index 7642d7c..524bd88 100644
>> --- a/fs/ocfs2/dlmglue.c
>> +++ b/fs/ocfs2/dlmglue.c
>> @@ -1195,6 +1195,7 @@ static inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
>>    						int convert)
>>    {
>>    	unsigned long flags;
>> +	int kick_dc;
>>
>>    	spin_lock_irqsave(&lockres->l_lock, flags);
>>    	lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
>> @@ -1203,9 +1204,12 @@ static inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
>>    		lockres->l_action = OCFS2_AST_INVALID;
>>    	else
>>    		lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;
>> +	kick_dc = (lockres->l_flags&   OCFS2_LOCK_QUEUED);
>>    	spin_unlock_irqrestore(&lockres->l_lock, flags);
>>
>>    	wake_up(&lockres->l_event);
>> +	if (kick_dc)
>> +		ocfs2_wake_downconvert_thread(ocfs2_get_lockres_osb(lockres));
>>    }
>>
>>    /* Note: If we detect another process working on the lock (i.e.,
>> @@ -1373,6 +1377,7 @@ static int __ocfs2_cluster_lock(struct ocfs2_super *osb,
>>    	unsigned long flags;
>>    	unsigned int gen;
>>    	int noqueue_attempted = 0;
>> +	int kick_dc;
>>
>>    	ocfs2_init_mask_waiter(&mw);
>>
>> @@ -1500,8 +1505,10 @@ update_holders:
>>    	ret = 0;
>>    unlock:
>>    	lockres_clear_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);
>> -
>> +	kick_dc = (lockres->l_flags&   OCFS2_LOCK_QUEUED);
>>    	spin_unlock_irqrestore(&lockres->l_lock, flags);
>> +	if (kick_dc)
>> +		ocfs2_wake_downconvert_thread(osb);
>>    out:
>>    	/*
>>    	 * This is helping work around a lock inversion between the page lock
>
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