Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:53576 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595AbaGBVOa (ORCPT ); Wed, 2 Jul 2014 17:14:30 -0400 Date: Wed, 2 Jul 2014 17:14:24 -0400 From: "J. Bruce Fields" To: Jeff Layton Cc: linux-nfs@vger.kernel.org Subject: Re: [PATCH v3 004/114] nfsd: Avoid taking state_lock while holding inode lock in nfsd_break_one_deleg Message-ID: <20140702211424.GD11510@fieldses.org> References: <1404143423-24381-1-git-send-email-jlayton@primarydata.com> <1404143423-24381-5-git-send-email-jlayton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1404143423-24381-5-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Jun 30, 2014 at 11:48:33AM -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. The code tends to assume that the callback thread only works with the delegation struct itself and puts it when done but doesn't otherwise touch other state. I wonder how this interacts with state shutdown.... E.g. in nfs4_state_shutdown_net() we walk the dl_recall_lru and destroy everything we find, but this callback workqueue is still running so I think another delegation could get added to that list after this? Does that cause bugs? And it'd also be worth checking delegreturn and destroy_client. Maybe there's no bug, or they just need to flush the workqueue at the appropriate point. There's also a preexisting expire_client/laundromat vs break race: - expire_client/laundromat adds a delegation to its local reaplist using the same dl_recall_lru field that a delegation uses to track its position on the recall lru and drops the state lock. - a concurrent break_lease adds the delegation to the lru. - expire/client/laundromat then walks it reaplist and sees the lru head as just another delegation on the list.... Possibly unrelated, but it might be good to fix that first. --b. > > Signed-off-by: Trond Myklebust > Signed-off-by: Jeff Layton > Reviewed-by: Christoph Hellwig > --- > fs/nfsd/nfs4callback.c | 28 +++++++++++++++++++++------- > fs/nfsd/nfs4state.c | 43 ++++++++++++++++++++++++++++--------------- > fs/nfsd/state.h | 2 ++ > 3 files changed, 51 insertions(+), 22 deletions(-) > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > index 00cb9b7a75f6..cba4ca375f5e 100644 > --- a/fs/nfsd/nfs4callback.c > +++ b/fs/nfsd/nfs4callback.c > @@ -43,7 +43,7 @@ > #define NFSDDBG_FACILITY NFSDDBG_PROC > > static void nfsd4_mark_cb_fault(struct nfs4_client *, int reason); > -static void nfsd4_do_callback_rpc(struct work_struct *w); > +static void nfsd4_run_cb_null(struct work_struct *w); > > #define NFSPROC4_CB_NULL 0 > #define NFSPROC4_CB_COMPOUND 1 > @@ -764,7 +764,7 @@ static void do_probe_callback(struct nfs4_client *clp) > > cb->cb_ops = &nfsd4_cb_probe_ops; > > - INIT_WORK(&cb->cb_work, nfsd4_do_callback_rpc); > + INIT_WORK(&cb->cb_work, nfsd4_run_cb_null); > > run_nfsd4_cb(cb); > } > @@ -936,7 +936,7 @@ 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); > @@ -1014,9 +1014,8 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb) > run_nfsd4_cb(cb); > } > > -static 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; > > @@ -1034,6 +1033,22 @@ static void nfsd4_do_callback_rpc(struct work_struct *w) > cb->cb_ops, cb); > } > > +static 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); > +} > + > +static 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; > @@ -1050,8 +1065,7 @@ void nfsd4_cb_recall(struct nfs4_delegation *dp) > > INIT_LIST_HEAD(&cb->cb_per_client); > cb->cb_done = true; > - > - INIT_WORK(&cb->cb_work, nfsd4_do_callback_rpc); > + INIT_WORK(&cb->cb_work, nfsd4_run_cb_recall); > > run_nfsd4_cb(&dp->dl_recall); > } > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index b49b46b0ce23..461229a01963 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -513,7 +513,9 @@ 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); > } > > @@ -521,14 +523,18 @@ 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; > } > } > @@ -2612,6 +2618,7 @@ static void nfsd4_init_file(struct nfs4_file *fp, struct inode *ino) > lockdep_assert_held(&state_lock); > > atomic_set(&fp->fi_ref, 1); > + spin_lock_init(&fp->fi_lock); > INIT_LIST_HEAD(&fp->fi_stateids); > INIT_LIST_HEAD(&fp->fi_delegations); > ihold(ino); > @@ -2857,26 +2864,32 @@ out: > 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 can't do this in nfsd_break_deleg_cb because it is > + * already holding inode->i_lock > + */ > + spin_lock(&state_lock); > + if (list_empty(&dp->dl_recall_lru)) { > + dp->dl_time = get_seconds(); > + list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); > + } > + spin_unlock(&state_lock); > +} > + > +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); > - > - list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); > - > - /* Only place dl_time is set; protected by i_lock: */ > - dp->dl_time = get_seconds(); > - > block_delegations(&dp->dl_fh); > - > nfsd4_cb_recall(dp); > } > > @@ -2901,11 +2914,11 @@ 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 9447f86f2778..7d6ba06c1abe 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -382,6 +382,7 @@ static inline struct nfs4_lockowner * lockowner(struct nfs4_stateowner *so) > /* nfs4_file: a file opened by some number of (open) nfs4_stateowners. */ > struct nfs4_file { > atomic_t fi_ref; > + spinlock_t fi_lock; > struct hlist_node fi_hash; /* hash by "struct inode *" */ > struct list_head fi_stateids; > struct list_head fi_delegations; > @@ -471,6 +472,7 @@ 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 >