Re: [PATCH 4/5] NFSD: Document and rename the NFSv4.1 session slot shrinker callbacks

On 6/10/26 8:33 PM, NeilBrown wrote:
> On Thu, 11 Jun 2026, Chuck Lever wrote:
>> Clean up: To prevent their reuse by generic code, rename the NFSv4.1
>> session slot shrinker's callback functions to make it clear they are
>> for use only by the shrinker.
>>
>> Though they are static, callbacks are invoked from outside nfsd.ko,
>> so they need appropriate kdoc comments that document their API
>> contracts.
>>
>> Signed-off-by: Chuck Lever <[email protected]>
>> ---
>>  fs/nfsd/nfs4state.c | 36 ++++++++++++++++++++++++++++++++----
>>  1 file changed, 32 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index 9735e9a59f0e..7ce8462e3697 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -2196,22 +2196,50 @@ static void free_session(struct nfsd4_session *ses)
>>  	__free_session(ses);
>>  }
>>  
>> +/**
>> + * nfsd_slot_shrinker_count - report reclaimable DRC slots
>> + * @s: shrinker descriptor (unused)
>> + * @sc: shrink control (unused)
>> + *
>> + * Return: a positive count of reclaimable slots, or SHRINK_EMPTY when
>> + * there is nothing to reclaim.
> 
> I would add to this comment and note that slot zero is not reclaimable,
> so that the subtraction of nfsd_total_sessions is explained.
> 
> But either way:
> 
> Reviewed-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>
> 
> and you can add that to all patches in series.  A definite improvement!

Thanks for the look. I'll address your specific comments before
applying these to nfsd-testing.


> Thanks,
> NeilBrown
> 
> 
>> + */
>>  static unsigned long
>> -nfsd_slot_count(struct shrinker *s, struct shrink_control *sc)
>> +nfsd_slot_shrinker_count(struct shrinker *s, struct shrink_control *sc)
>>  {
>>  	int cnt = atomic_read(&nfsd_total_target_slots) -
>>  		  atomic_read(&nfsd_total_sessions);
>>  
>> +	/*
>> +	 * To prevent deadlock, one slot of each session (slot 0) is
>> +	 * not reclaimable while the session is active. Thus the
>> +	 * number of sessions is subtracted from the total number of
>> +	 * target slots.
>> +	 */
>>  	return cnt > 0 ? cnt : SHRINK_EMPTY;
>>  }
>>  
>> +/**
>> + * nfsd_slot_shrinker_scan - reclaim DRC slots under memory pressure
>> + * @s: shrinker descriptor (unused)
>> + * @sc: shrink control; @sc->nr_to_scan bounds the sessions visited,
>> + *      @sc->nr_scanned reports how many were visited
>> + *
>> + * Return: the number of session slots NFSD will release.
>> + */
>>  static unsigned long
>> -nfsd_slot_scan(struct shrinker *s, struct shrink_control *sc)
>> +nfsd_slot_shrinker_scan(struct shrinker *s, struct shrink_control *sc)
>>  {
>>  	struct nfsd4_session *ses;
>>  	unsigned long scanned = 0;
>>  	unsigned long freed = 0;
>>  
>> +	/*
>> +	 * Each visited session releases at most one slot. After
>> +	 * nr_to_scan sessions have been visited, the list head is
>> +	 * rotated past the last visited session so the next scan
>> +	 * resumes from there.
>> +	 */
>>  	spin_lock(&nfsd_session_list_lock);
>>  	list_for_each_entry(ses, &nfsd_session_list, se_all_sessions) {
>>  		freed += reduce_session_slots(ses, 1);
>> @@ -9120,8 +9148,8 @@ nfs4_state_start(void)
>>  		rhltable_destroy(&nfs4_file_rhltable);
>>  		return -ENOMEM;
>>  	}
>> -	nfsd_slot_shrinker->count_objects = nfsd_slot_count;
>> -	nfsd_slot_shrinker->scan_objects = nfsd_slot_scan;
>> +	nfsd_slot_shrinker->count_objects = nfsd_slot_shrinker_count;
>> +	nfsd_slot_shrinker->scan_objects = nfsd_slot_shrinker_scan;
>>  	shrinker_register(nfsd_slot_shrinker);
>>  
>>  	set_max_delegations();
>>
>> -- 
>> 2.54.0
>>
>>
>>
> 


-- 
Chuck Lever