Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:57373 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbaGQBet (ORCPT ); Wed, 16 Jul 2014 21:34:49 -0400 Date: Wed, 16 Jul 2014 21:34:41 -0400 From: "J. Bruce Fields" To: Jeff Layton Cc: hch@infradead.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH v2 02/10] nfsd: Avoid taking state_lock while holding inode lock in nfsd_break_one_deleg Message-ID: <20140717013441.GI2397@fieldses.org> References: <1405521125-2303-1-git-send-email-jlayton@primarydata.com> <1405521125-2303-3-git-send-email-jlayton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1405521125-2303-3-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, Jul 16, 2014 at 10:31:57AM -0400, Jeff Layton wrote: > state_lock is a heavily contended global lock. We don't want to grab > that while simultaneously holding the inode->i_lock. > > Add a new per-nfs4_file lock that we can use to protect the > per-nfs4_file delegation list. Hold that while walking the list in the > break_deleg callback and queue the workqueue job for each one. > > The workqueue job can then take the state_lock and do the list > manipulations without the i_lock being held prior to starting the > rpc call. Looks fine. As a separate issue: does nfs4_state_shutdown net have the same problem as destroy_client? It seems like there should be a cp->dl_time++ there too. Though I'm not sure what the point of that del_recall_lru loop is at all. nfs4_state_destroy_net() destroys each client and its associated delegations. Maybe that function should just be nfs4_lock_state(); nfs4_client_tracking_exit(net); nfs4_state_destroy_net(net); WARN_ON(!list_empty(&nn->del_recall_lru); nfs4_unlock_state(); --b. > > Signed-off-by: Trond Myklebust > Signed-off-by: Jeff Layton > Reviewed-by: Christoph Hellwig > --- > fs/nfsd/nfs4callback.c | 25 ++++++++++++++++++---- > fs/nfsd/nfs4state.c | 58 +++++++++++++++++++++++++++++++++----------------- > fs/nfsd/state.h | 4 +++- > 3 files changed, 62 insertions(+), 25 deletions(-) > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > index 30a71cb46001..a88a93e09d69 100644 > --- a/fs/nfsd/nfs4callback.c > +++ b/fs/nfsd/nfs4callback.c > @@ -933,7 +933,7 @@ void nfsd4_shutdown_callback(struct nfs4_client *clp) > set_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags); > /* > * Note this won't actually result in a null callback; > - * instead, nfsd4_do_callback_rpc() will detect the killed > + * instead, nfsd4_run_cb_null() will detect the killed > * client, destroy the rpc client, and stop: > */ > do_probe_callback(clp); > @@ -1011,10 +1011,9 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb) > run_nfsd4_cb(cb); > } > > -void > -nfsd4_do_callback_rpc(struct work_struct *w) > +static void > +nfsd4_run_callback_rpc(struct nfsd4_callback *cb) > { > - struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, cb_work); > struct nfs4_client *clp = cb->cb_clp; > struct rpc_clnt *clnt; > > @@ -1032,6 +1031,24 @@ nfsd4_do_callback_rpc(struct work_struct *w) > cb->cb_ops, cb); > } > > +void > +nfsd4_run_cb_null(struct work_struct *w) > +{ > + struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, > + cb_work); > + nfsd4_run_callback_rpc(cb); > +} > + > +void > +nfsd4_run_cb_recall(struct work_struct *w) > +{ > + struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, > + cb_work); > + > + nfsd4_prepare_cb_recall(cb->cb_op); > + nfsd4_run_callback_rpc(cb); > +} > + > void nfsd4_cb_recall(struct nfs4_delegation *dp) > { > struct nfsd4_callback *cb = &dp->dl_recall; > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 56ea4f12803e..bdf8ac3393bd 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -254,6 +254,8 @@ static void nfsd4_free_file(struct nfs4_file *f) > static inline void > put_nfs4_file(struct nfs4_file *fi) > { > + might_lock(&state_lock); > + > if (atomic_dec_and_lock(&fi->fi_ref, &state_lock)) { > hlist_del(&fi->fi_hash); > spin_unlock(&state_lock); > @@ -554,6 +556,8 @@ static void block_delegations(struct knfsd_fh *fh) > u32 hash; > struct bloom_pair *bd = &blocked_delegations; > > + lockdep_assert_held(&state_lock); > + > hash = arch_fast_hash(&fh->fh_base, fh->fh_size, 0); > > __set_bit(hash&255, bd->set[bd->new]); > @@ -592,7 +596,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct sv > fh_copy_shallow(&dp->dl_fh, ¤t_fh->fh_handle); > dp->dl_time = 0; > atomic_set(&dp->dl_count, 1); > - INIT_WORK(&dp->dl_recall.cb_work, nfsd4_do_callback_rpc); > + INIT_WORK(&dp->dl_recall.cb_work, nfsd4_run_cb_recall); > return dp; > } > > @@ -640,7 +644,9 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) > lockdep_assert_held(&state_lock); > > dp->dl_stid.sc_type = NFS4_DELEG_STID; > + spin_lock(&fp->fi_lock); > list_add(&dp->dl_perfile, &fp->fi_delegations); > + spin_unlock(&fp->fi_lock); > list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations); > } > > @@ -648,14 +654,18 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) > static void > unhash_delegation(struct nfs4_delegation *dp) > { > + struct nfs4_file *fp = dp->dl_file; > + > spin_lock(&state_lock); > list_del_init(&dp->dl_perclnt); > - list_del_init(&dp->dl_perfile); > list_del_init(&dp->dl_recall_lru); > + spin_lock(&fp->fi_lock); > + list_del_init(&dp->dl_perfile); > + spin_unlock(&fp->fi_lock); > spin_unlock(&state_lock); > - if (dp->dl_file) { > - nfs4_put_deleg_lease(dp->dl_file); > - put_nfs4_file(dp->dl_file); > + if (fp) { > + nfs4_put_deleg_lease(fp); > + put_nfs4_file(fp); > dp->dl_file = NULL; > } > } > @@ -1677,7 +1687,7 @@ static struct nfs4_client *create_client(struct xdr_netobj name, > spin_unlock(&nn->client_lock); > return NULL; > } > - INIT_WORK(&clp->cl_cb_null.cb_work, nfsd4_do_callback_rpc); > + INIT_WORK(&clp->cl_cb_null.cb_work, nfsd4_run_cb_null); > clp->cl_time = get_seconds(); > clear_bit(0, &clp->cl_cb_slot_busy); > copy_verf(clp, verf); > @@ -3079,30 +3089,38 @@ nfs4_share_conflict(struct svc_fh *current_fh, unsigned int deny_type) > return ret; > } > > -static void nfsd_break_one_deleg(struct nfs4_delegation *dp) > +void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp) > { > struct nfs4_client *clp = dp->dl_stid.sc_client; > struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id); > > - lockdep_assert_held(&state_lock); > - /* We're assuming the state code never drops its reference > - * without first removing the lease. Since we're in this lease > - * callback (and since the lease code is serialized by the kernel > - * lock) we know the server hasn't removed the lease yet, we know > - * it's safe to take a reference: */ > - atomic_inc(&dp->dl_count); > - > + /* > + * We can't do this in nfsd_break_deleg_cb because it is > + * already holding inode->i_lock > + */ > + spin_lock(&state_lock); > + block_delegations(&dp->dl_fh); > /* > * If the dl_time != 0, then we know that it has already been > * queued for a lease break. Don't queue it again. > */ > if (dp->dl_time == 0) { > - list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); > dp->dl_time = get_seconds(); > + list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); > } > + spin_unlock(&state_lock); > +} > > - block_delegations(&dp->dl_fh); > - > +static void nfsd_break_one_deleg(struct nfs4_delegation *dp) > +{ > + /* > + * We're assuming the state code never drops its reference > + * without first removing the lease. Since we're in this lease > + * callback (and since the lease code is serialized by the kernel > + * lock) we know the server hasn't removed the lease yet, we know > + * it's safe to take a reference. > + */ > + atomic_inc(&dp->dl_count); > nfsd4_cb_recall(dp); > } > > @@ -3127,11 +3145,11 @@ static void nfsd_break_deleg_cb(struct file_lock *fl) > */ > fl->fl_break_time = 0; > > - spin_lock(&state_lock); > fp->fi_had_conflict = true; > + spin_lock(&fp->fi_lock); > list_for_each_entry(dp, &fp->fi_delegations, dl_perfile) > nfsd_break_one_deleg(dp); > - spin_unlock(&state_lock); > + spin_unlock(&fp->fi_lock); > } > > static > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > index 20857142773f..81b7522e3f67 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -436,7 +436,8 @@ extern struct nfs4_client_reclaim *nfsd4_find_reclaim_client(const char *recdir, > extern __be32 nfs4_check_open_reclaim(clientid_t *clid, > struct nfsd4_compound_state *cstate, struct nfsd_net *nn); > extern int set_callback_cred(void); > -void nfsd4_do_callback_rpc(struct work_struct *w); > +void nfsd4_run_cb_null(struct work_struct *w); > +void nfsd4_run_cb_recall(struct work_struct *w); > extern void nfsd4_probe_callback(struct nfs4_client *clp); > extern void nfsd4_probe_callback_sync(struct nfs4_client *clp); > extern void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *); > @@ -444,6 +445,7 @@ extern void nfsd4_cb_recall(struct nfs4_delegation *dp); > extern int nfsd4_create_callback_queue(void); > extern void nfsd4_destroy_callback_queue(void); > extern void nfsd4_shutdown_callback(struct nfs4_client *); > +extern void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp); > extern void nfs4_put_delegation(struct nfs4_delegation *dp); > extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(const char *name, > struct nfsd_net *nn); > -- > 1.9.3 >