> On Mar 15, 2022, at 12:26 PM, Dai Ngo <dai.ngo@xxxxxxxxxx> wrote:
>
>
> 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@xxxxxxxxxx>
>>> ---
>>> 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.
Code audit suggested there are really only four unique
combinations of the bit flags that are used.
Plus, taking a spin_lock and using bitops seems like overkill.
The rules for transitioning between the courtesy states are
straightforward, but need to be done in a critical section.
So I suggested storing the courtesy state in a lock-protected
unsigned int instead of using bit flags.
If we hate it, we can go back to bit flags.
>>> + 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
--
Chuck Lever
