Re: [PATCH 15/29] NFSD: dynamically allocate the nfsd-client shrinker

[Qi Zheng <zhengqi.arch@bytedance.com>]

Hi Chuck,

On 2023/6/24 05:49, Chuck Lever wrote:
> On Thu, Jun 22, 2023 at 04:53:21PM +0800, Qi Zheng wrote:
>> In preparation for implementing lockless slab shrink,
>> we need to dynamically allocate the nfsd-client shrinker,
>> so that it can be freed asynchronously using kfree_rcu().
>> Then it doesn't need to wait for RCU read-side critical
>> section when releasing the struct nfsd_net.
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> 
> For 15/29 and 16/29 of this series:
> 
> Acked-by: Chuck Lever <chuck.lever@oracle.com>

Thanks for your review! :)

And I will implement the APIs suggested by Dave in 02/29 in
the v2, so there will be some changes here, but it should
not be much. So I will keep your Acked-bys in the v2.

Thanks,
Qi

> 
> 
>> ---
>>   fs/nfsd/netns.h     |  2 +-
>>   fs/nfsd/nfs4state.c | 20 ++++++++++++--------
>>   2 files changed, 13 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
>> index ec49b200b797..f669444d5336 100644
>> --- a/fs/nfsd/netns.h
>> +++ b/fs/nfsd/netns.h
>> @@ -195,7 +195,7 @@ struct nfsd_net {
>>   	int			nfs4_max_clients;
>>   
>>   	atomic_t		nfsd_courtesy_clients;
>> -	struct shrinker		nfsd_client_shrinker;
>> +	struct shrinker		*nfsd_client_shrinker;
>>   	struct work_struct	nfsd_shrinker_work;
>>   };
>>   
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index 6e61fa3acaf1..a06184270548 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -4388,8 +4388,7 @@ static unsigned long
>>   nfsd4_state_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
>>   {
>>   	int count;
>> -	struct nfsd_net *nn = container_of(shrink,
>> -			struct nfsd_net, nfsd_client_shrinker);
>> +	struct nfsd_net *nn = shrink->private_data;
>>   
>>   	count = atomic_read(&nn->nfsd_courtesy_clients);
>>   	if (!count)
>> @@ -8094,14 +8093,19 @@ static int nfs4_state_create_net(struct net *net)
>>   	INIT_WORK(&nn->nfsd_shrinker_work, nfsd4_state_shrinker_worker);
>>   	get_net(net);
>>   
>> -	nn->nfsd_client_shrinker.scan_objects = nfsd4_state_shrinker_scan;
>> -	nn->nfsd_client_shrinker.count_objects = nfsd4_state_shrinker_count;
>> -	nn->nfsd_client_shrinker.seeks = DEFAULT_SEEKS;
>> -
>> -	if (register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client"))
>> +	nn->nfsd_client_shrinker = shrinker_alloc_and_init(nfsd4_state_shrinker_count,
>> +							   nfsd4_state_shrinker_scan,
>> +							   0, DEFAULT_SEEKS, 0,
>> +							   nn);
>> +	if (!nn->nfsd_client_shrinker)
>>   		goto err_shrinker;
>> +
>> +	if (register_shrinker(nn->nfsd_client_shrinker, "nfsd-client"))
>> +		goto err_register;
>>   	return 0;
>>   
>> +err_register:
>> +	shrinker_free(nn->nfsd_client_shrinker);
>>   err_shrinker:
>>   	put_net(net);
>>   	kfree(nn->sessionid_hashtbl);
>> @@ -8197,7 +8201,7 @@ nfs4_state_shutdown_net(struct net *net)
>>   	struct list_head *pos, *next, reaplist;
>>   	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
>>   
>> -	unregister_shrinker(&nn->nfsd_client_shrinker);
>> +	unregister_and_free_shrinker(nn->nfsd_client_shrinker);
>>   	cancel_work(&nn->nfsd_shrinker_work);
>>   	cancel_delayed_work_sync(&nn->laundromat_work);
>>   	locks_end_grace(&nn->nfsd4_manager);
>> -- 
>> 2.30.2
>>