On May. 12, 2010, 7:26 +0300, Benny Halevy <bhalevy@xxxxxxxxxxx> wrote:
> On May. 12, 2010, 5:40 +0300, " J. Bruce Fields" <bfields@xxxxxxxxxxxxxx> wrote:
>> Something still doesn't look quite right: a sequence operation
>> increments cl_count from 1 to 2; then, say, an exchangeid in another
>> thread expires the client, dropping cl_count from 2 to 1; then the
>> laundromat runs, sees cl_count 1, and decides it can expire the
>> client. Meanwhile, the original compound is still running.
>>
>> Am I missing something?
>
> Yeah. exchange_id doesn't touch cl_refcount. It may call expire_client
> explicitly which will unhash the client but will not destroy it if cl_refcount > 0
> the laundromat won't the client either after that since it's not on the lru list
> any more (and even if it would, it's refcount is still great than zero so it would
> have been ignored)
Sorry, I misspoken. exchange_id may decrement cl_refcount via expire_client()
but still the laundromat won't see it as expire_client will have already removed the
client from client_lru.
Benny
>
> Benny
>
>>
>> --b.
>>
>> On Wed, May 12, 2010 at 12:13:54AM +0300, Benny Halevy wrote:
>>> Get a refcount on the client on SEQUENCE,
>>> Release the refcount and renew the client when all respective compounds completed.
>>> Do not expire the client by the laundromat while in use.
>>> If the client was expired via another path, free it when the compounds
>>> complete and the refcount reaches 0.
>>>
>>> Note that unhash_client_locked must call list_del_init on cl_lru as
>>> it may be called twice for the same client (once from nfs4_laundromat
>>> and then from expire_client)
>>>
>>> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
>>> ---
>>> fs/nfsd/nfs4state.c | 27 ++++++++++++++++++++++++---
>>> fs/nfsd/nfs4xdr.c | 3 ++-
>>> fs/nfsd/state.h | 1 +
>>> 3 files changed, 27 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index 378ee86..1a8fb39 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -701,6 +701,22 @@ free_client(struct nfs4_client *clp)
>>> kfree(clp);
>>> }
>>>
>>> +void
>>> +release_session_client(struct nfsd4_session *session)
>>> +{
>>> + struct nfs4_client *clp = session->se_client;
>>> +
>>> + spin_lock(&client_lock);
>>> + BUG_ON(clp->cl_refcount <= 0);
>>> + if (--clp->cl_refcount <= 0) {
>>> + free_client(clp);
>>> + session->se_client = NULL;
>>> + } else if (clp->cl_refcount == 1)
>>> + renew_client_locked(clp);
>>> + spin_unlock(&client_lock);
>>> + nfsd4_put_session(session);
>>> +}
>>> +
>>> /* must be called under the client_lock */
>>> static inline void
>>> unhash_client_locked(struct nfs4_client *clp)
>>> @@ -1477,8 +1493,7 @@ out:
>>> /* Hold a session reference until done processing the compound. */
>>> if (cstate->session) {
>>> nfsd4_get_session(cstate->session);
>>> - /* Renew the clientid on success and on replay */
>>> - renew_client_locked(session->se_client);
>>> + session->se_client->cl_refcount++;
>>> }
>>> spin_unlock(&client_lock);
>>> dprintk("%s: return %d\n", __func__, ntohl(status));
>>> @@ -2599,7 +2614,13 @@ nfs4_laundromat(void)
>>> clientid_val = t;
>>> break;
>>> }
>>> - list_move(&clp->cl_lru, &reaplist);
>>> + if (clp->cl_refcount > 1) {
>>> + dprintk("NFSD: client in use (clientid %08x)\n",
>>> + clp->cl_clientid.cl_id);
>>> + continue;
>>> + }
>>> + unhash_client_locked(clp);
>>> + list_add(&clp->cl_lru, &reaplist);
>>> }
>>> spin_unlock(&client_lock);
>>> list_for_each_safe(pos, next, &reaplist) {
>>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>>> index 5c2de47..126d0ca 100644
>>> --- a/fs/nfsd/nfs4xdr.c
>>> +++ b/fs/nfsd/nfs4xdr.c
>>> @@ -3313,7 +3313,8 @@ nfs4svc_encode_compoundres(struct svc_rqst *rqstp, __be32 *p, struct nfsd4_compo
>>> dprintk("%s: SET SLOT STATE TO AVAILABLE\n", __func__);
>>> cs->slot->sl_inuse = false;
>>> }
>>> - nfsd4_put_session(cs->session);
>>> + /* Renew the clientid on success and on replay */
>>> + release_session_client(cs->session);
>>> }
>>> return 1;
>>> }
>>> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
>>> index 37e1dff..f263174 100644
>>> --- a/fs/nfsd/state.h
>>> +++ b/fs/nfsd/state.h
>>> @@ -419,6 +419,7 @@ extern int nfs4_has_reclaimed_state(const char *name, bool use_exchange_id);
>>> extern void nfsd4_recdir_purge_old(void);
>>> extern int nfsd4_create_clid_dir(struct nfs4_client *clp);
>>> extern void nfsd4_remove_clid_dir(struct nfs4_client *clp);
>>> +extern void release_session_client(struct nfsd4_session *);
>>>
>>> static inline void
>>> nfs4_put_stateowner(struct nfs4_stateowner *so)
>>> --
>>> 1.6.5.1
>>>
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