[Ocfs2-devel] [PATCH 2/6] Add DLM recovery callbacks

[Goldwyn Rodrigues]

On 11/03/2013 04:16 PM, Mark Fasheh wrote:
> This also looks good in that I don't see anything wrong with the way the
> actual code functions. The extra description you put about the callbacks
> helps in understanding this too. Question - can you explain why oc_this_node
> is an atomic? That is to say I'd like to understand that race that you're
> protecting against :)
> 	--Mark

Ok, we may not require this to be atomic. The dlm thread sets up 
oc_this_node via .recover_done(), but it should not matter because 
this_node() functions are called after .cluster_connect().

>
> On Fri, Oct 18, 2013 at 09:45:25AM -0500, Goldwyn Rodrigues wrote:
>> These are the callbacks called by the fs/dlm code in case the membership
>> changes. If there is a failure while/during calling any of these, the
>> DLM creates a new membership and relays to the rest of the nodes.
>>
>> recover_prep() is called when DLM understands a node is down.
>> recover_slot() is called once all nodes have acknowledged recover_prep
>> and recovery can begin.
>> recover_done() is called once the recovery is complete. It returns the
>> new membership.
>>
>> Signed-off-by: Goldwyn Rodrigues <rgoldwyn at suse.com>
>> ---
>>   fs/ocfs2/stack_user.c | 38 ++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>
>> diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
>> index 286edf1..4111855 100644
>> --- a/fs/ocfs2/stack_user.c
>> +++ b/fs/ocfs2/stack_user.c
>> @@ -110,6 +110,8 @@
>>   struct ocfs2_live_connection {
>>   	struct list_head		oc_list;
>>   	struct ocfs2_cluster_connection	*oc_conn;
>> +	atomic_t                        oc_this_node;
>> +	int                             oc_our_slot;
>>   };
>>
>>   struct ocfs2_control_private {
>> @@ -799,6 +801,42 @@ static int fs_protocol_compare(struct ocfs2_protocol_version *existing,
>>   	return 0;
>>   }
>>
>> +static void user_recover_prep(void *arg)
>> +{
>> +}
>> +
>> +static void user_recover_slot(void *arg, struct dlm_slot *slot)
>> +{
>> +	struct ocfs2_cluster_connection *conn = arg;
>> +	printk(KERN_INFO "ocfs2: Node %d/%d down. Initiating recovery.\n",
>> +			slot->nodeid, slot->slot);
>> +	conn->cc_recovery_handler(slot->nodeid, conn->cc_recovery_data);
>> +
>> +}
>> +
>> +static void user_recover_done(void *arg, struct dlm_slot *slots,
>> +		int num_slots, int our_slot,
>> +		uint32_t generation)
>> +{
>> +	struct ocfs2_cluster_connection *conn = arg;
>> +	struct ocfs2_live_connection *lc = conn->cc_private;
>> +	int i;
>> +
>> +	for (i = 0; i < num_slots; i++)
>> +		if (slots[i].slot == our_slot) {
>> +			atomic_set(&lc->oc_this_node, slots[i].nodeid);
>> +			break;
>> +		}
>> +
>> +	lc->oc_our_slot = our_slot;
>> +}
>> +
>> +const struct dlm_lockspace_ops ocfs2_ls_ops = {
>> +	.recover_prep = user_recover_prep,
>> +	.recover_slot = user_recover_slot,
>> +	.recover_done = user_recover_done,
>> +};
>> +
>>   static int user_cluster_connect(struct ocfs2_cluster_connection *conn)
>>   {
>>   	dlm_lockspace_t *fsdlm;
>> --
>> 1.8.1.4
>>
>>
>> --
>> Goldwyn
> --
> Mark Fasheh
>


-- 
Goldwyn