Return-Path: Received: from fieldses.org ([174.143.236.118]:54935 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005Ab0ELCkb (ORCPT ); Tue, 11 May 2010 22:40:31 -0400 Date: Tue, 11 May 2010 22:40:30 -0400 From: " J. Bruce Fields" To: Benny Halevy Cc: linux-nfs@vger.kernel.org Subject: Re: [PATCH v2 8/9] nfsd4: keep a reference count on client while in use Message-ID: <20100512024030.GA27184@fieldses.org> References: <4BE9C7A2.8030801@panasas.com> <1273612434-13726-1-git-send-email-bhalevy@panasas.com> Content-Type: text/plain; charset=us-ascii In-Reply-To: <1273612434-13726-1-git-send-email-bhalevy@panasas.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 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? --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 > --- > 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 >