Re: [PATCH RFC v21 3/7] NFSD: move create/destroy of laundry_wq to init_nfsd and exit_nfsd

[dai.ngo@oracle.com]

On 4/25/22 12:35 PM, J. Bruce Fields wrote:
> On Mon, Apr 25, 2022 at 08:27:22AM -0700, dai.ngo@oracle.com wrote:
>> This patch has problem to build with this error:
>>
>>>> nfsctl.c:(.exit.text+0x0): undefined reference to `laundry_wq'
>>>> mipsel-linux-ld: nfsctl.c:(.exit.text+0x4): undefined reference to `laundry_wq'
>> This happens when CONFIG_NFSD is defined but CONFIG_NFSD_V4
>> is not. I think to fix this we need to also move the declaration
>> of laundry_wq from nfs4state.c to nfsctl.c. However this seems
>> odd since the laundry_wq is only used for v4, unless you have
>> any other suggestion.
> I'd just leave laundry_wq private to nfs4state.c.  Define
> create_laundromat() and destroy_laundromat() in nfs4state.c too.  And in
> nfsd.h, do the usual trick of defining no-op versions of those functions
> in the non-v4 case.  (See e.g. what we do with nfsd4_init/free_slabs().)

ok, thanks.

-Dai

>
> --b.
>
>> -Dai
>>
>> On 4/23/22 11:44 AM, Dai Ngo wrote:
>>> This patch moves create/destroy of laundry_wq from nfs4_state_start
>>> and nfs4_state_shutdown_net to init_nfsd and exit_nfsd to prevent
>>> the laundromat from being freed while a thread is processing a
>>> conflicting lock.
>>>
>>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>>> ---
>>>   fs/nfsd/nfs4state.c | 15 ++-------------
>>>   fs/nfsd/nfsctl.c    |  6 ++++++
>>>   fs/nfsd/nfsd.h      |  1 +
>>>   3 files changed, 9 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index b08c132648b9..b70ba2eb5665 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -125,7 +125,7 @@ static void free_session(struct nfsd4_session *);
>>>   static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
>>>   static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>>> -static struct workqueue_struct *laundry_wq;
>>> +struct workqueue_struct *laundry_wq;
>>>   static bool is_session_dead(struct nfsd4_session *ses)
>>>   {
>>> @@ -7798,22 +7798,12 @@ nfs4_state_start(void)
>>>   {
>>>   	int ret;
>>> -	laundry_wq = alloc_workqueue("%s", WQ_UNBOUND, 0, "nfsd4");
>>> -	if (laundry_wq == NULL) {
>>> -		ret = -ENOMEM;
>>> -		goto out;
>>> -	}
>>>   	ret = nfsd4_create_callback_queue();
>>>   	if (ret)
>>> -		goto out_free_laundry;
>>> +		return ret;
>>>   	set_max_delegations();
>>>   	return 0;
>>> -
>>> -out_free_laundry:
>>> -	destroy_workqueue(laundry_wq);
>>> -out:
>>> -	return ret;
>>>   }
>>>   void
>>> @@ -7850,7 +7840,6 @@ nfs4_state_shutdown_net(struct net *net)
>>>   void
>>>   nfs4_state_shutdown(void)
>>>   {
>>> -	destroy_workqueue(laundry_wq);
>>>   	nfsd4_destroy_callback_queue();
>>>   }
>>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>>> index 16920e4512bd..884e873b46ad 100644
>>> --- a/fs/nfsd/nfsctl.c
>>> +++ b/fs/nfsd/nfsctl.c
>>> @@ -1544,6 +1544,11 @@ static int __init init_nfsd(void)
>>>   	retval = register_cld_notifier();
>>>   	if (retval)
>>>   		goto out_free_all;
>>> +	laundry_wq = alloc_workqueue("%s", WQ_UNBOUND, 0, "nfsd4");
>>> +	if (laundry_wq == NULL) {
>>> +		retval = -ENOMEM;
>>> +		goto out_free_all;
>>> +	}
>>>   	return 0;
>>>   out_free_all:
>>>   	unregister_pernet_subsys(&nfsd_net_ops);
>>> @@ -1566,6 +1571,7 @@ static int __init init_nfsd(void)
>>>   static void __exit exit_nfsd(void)
>>>   {
>>> +	destroy_workqueue(laundry_wq);
>>>   	unregister_cld_notifier();
>>>   	unregister_pernet_subsys(&nfsd_net_ops);
>>>   	nfsd_drc_slab_free();
>>> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
>>> index 23996c6ca75e..d41dcf1c4312 100644
>>> --- a/fs/nfsd/nfsd.h
>>> +++ b/fs/nfsd/nfsd.h
>>> @@ -72,6 +72,7 @@ extern unsigned long		nfsd_drc_max_mem;
>>>   extern unsigned long		nfsd_drc_mem_used;
>>>   extern const struct seq_operations nfs_exports_op;
>>> +extern struct workqueue_struct *laundry_wq;
>>>   /*
>>>    * Common void argument and result helpers