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Date:   Tue, 15 Mar 2022 09:26:46 -0700
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Subject: Re: [PATCH RFC v16 03/11] NFSD: Add lm_lock_expired call out
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To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     chuck.lever@oracle.com, jlayton@redhat.com,
        viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org,
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On 3/15/22 8:02 AM, J. Bruce Fields wrote:
> On Fri, Mar 11, 2022 at 06:13:27PM -0800, Dai Ngo wrote:
>> Add callout function nfsd4_lm_lock_expired for lm_lock_expired.
>> If lock request has conflict with courtesy client then expire the
>> courtesy client and return no conflict to caller.
>>
>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>> ---
>>   fs/nfsd/nfs4state.c | 37 +++++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index a65d59510681..583ac807e98d 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -6578,10 +6578,47 @@ nfsd4_lm_notify(struct file_lock *fl)
>>   	}
>>   }
>>   
>> +/**
>> + * nfsd4_lm_lock_expired - check if lock conflict can be resolved.
>> + *
>> + * @fl: pointer to file_lock with a potential conflict
>> + * Return values:
>> + *   %false: real conflict, lock conflict can not be resolved.
>> + *   %true: no conflict, lock conflict was resolved.
>> + *
>> + * Note that this function is called while the flc_lock is held.
>> + */
>> +static bool
>> +nfsd4_lm_lock_expired(struct file_lock *fl)
>> +{
>> +	struct nfs4_lockowner *lo;
>> +	struct nfs4_client *clp;
>> +	bool rc = false;
>> +
>> +	if (!fl)
>> +		return false;
>> +	lo = (struct nfs4_lockowner *)fl->fl_owner;
>> +	clp = lo->lo_owner.so_client;
>> +
>> +	/* need to sync with courtesy client trying to reconnect */
>> +	spin_lock(&clp->cl_cs_lock);
>> +	if (test_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags))
>> +		rc = true;
>> +	else {
>> +		if (test_bit(NFSD4_CLIENT_COURTESY, &clp->cl_flags)) {
>> +			set_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags);
>> +			rc =  true;
>> +		}
>> +	}
> I'd prefer:
>
> 	if (test_bit(NFSD4_CLIENT_COURTESY, &clp->cl_flags))
> 		set_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags);

we also need to set rc to true here.

> 	if (test_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags))
> 		rc = true;

With v16 we need to check for NFSD4_CLIENT_EXPIRED first then
NFSD4_CLIENT_COURTESY because both flags can be set. In the
next patch version, we will clear NFSD4_CLIENT_COURTESY when
setting NFSD4_CLIENT_EXPIRED so the order of check does not
matter.

>
> Same result, but more compact and straightforward, I think.

Chuck wants to replace the bits used for courtesy client in
cl_flags with a  separate u8 field so it does not have to use
bit operation to set/test.

-Dai

>
> --b.
>
>> +	spin_unlock(&clp->cl_cs_lock);
>> +	return rc;
>> +}
>> +
>>   static const struct lock_manager_operations nfsd_posix_mng_ops  = {
>>   	.lm_notify = nfsd4_lm_notify,
>>   	.lm_get_owner = nfsd4_lm_get_owner,
>>   	.lm_put_owner = nfsd4_lm_put_owner,
>> +	.lm_lock_expired = nfsd4_lm_lock_expired,
>>   };
>>   
>>   static inline void
>> -- 
>> 2.9.5