diff mbox series

[v6,2/2] NFSD: add shrinker to reap courtesy clients on low memory condition

Message ID 1663085170-23136-3-git-send-email-dai.ngo@oracle.com (mailing list archive)
State New, archived
Headers show
Series NFSD: memory shrinker for NFSv4 clients | expand

Commit Message

Dai Ngo Sept. 13, 2022, 4:06 p.m. UTC 
Add courtesy_client_reaper to react to low memory condition triggered
by the system memory shrinker.

The delayed_work for the courtesy_client_reaper is scheduled on
the shrinker's count callback using the laundry_wq.

The shrinker's scan callback is not used for expiring the courtesy
clients due to potential deadlocks.

The courtesy_client_reaper rechedules itself to run if low memory
condition persits and there are more courtesy clients in the system.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 fs/nfsd/netns.h     |   3 ++
 fs/nfsd/nfs4state.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++-----
 fs/nfsd/nfsctl.c    |   6 ++--
 fs/nfsd/nfsd.h      |   7 ++--
 4 files changed, 106 insertions(+), 12 deletions(-)

Comments

Chuck Lever III Sept. 13, 2022, 11:57 p.m. UTC | #1 
> On Sep 13, 2022, at 9:06 AM, Dai Ngo <dai.ngo@oracle.com> wrote:
> 
> Add courtesy_client_reaper to react to low memory condition triggered
> by the system memory shrinker.
> 
> The delayed_work for the courtesy_client_reaper is scheduled on
> the shrinker's count callback using the laundry_wq.
> 
> The shrinker's scan callback is not used for expiring the courtesy
> clients due to potential deadlocks.
> 
> The courtesy_client_reaper rechedules itself to run if low memory
> condition persits and there are more courtesy clients in the system.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
> fs/nfsd/netns.h     |   3 ++
> fs/nfsd/nfs4state.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++-----
> fs/nfsd/nfsctl.c    |   6 ++--
> fs/nfsd/nfsd.h      |   7 ++--
> 4 files changed, 106 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> index 55c7006d6109..37457b104eee 100644
> --- a/fs/nfsd/netns.h
> +++ b/fs/nfsd/netns.h
> @@ -194,6 +194,9 @@ struct nfsd_net {
> 	int			nfs4_max_clients;
> 
> 	atomic_t		nfsd_courtesy_clients;
> +	atomic_t		nfsd_client_shrinker_cb_count;

Now that you have a separate function to handle courtesy
client reaping, please get rid of nfsd_client_shrinker_cb_count.


> +	struct shrinker		nfsd_client_shrinker;
> +	struct delayed_work	nfsd_shrinker_work;
> };
> 
> /* Simple check to find out if a given net was properly initialized */
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 3af4fc5241b2..fed4ca3fb581 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -4347,7 +4347,28 @@ nfsd4_init_slabs(void)
> 	return -ENOMEM;
> }
> 
> -void nfsd4_init_leases_net(struct nfsd_net *nn)
> +static unsigned long
> +nfsd_courtesy_client_count(struct shrinker *shrink, struct shrink_control *sc)
> +{
> +	int cnt;
> +	struct nfsd_net *nn = container_of(shrink,
> +			struct nfsd_net, nfsd_client_shrinker);
> +
> +	atomic_inc(&nn->nfsd_client_shrinker_cb_count);
> +	cnt = atomic_read(&nn->nfsd_courtesy_clients);
> +	if (cnt > 0)
> +		mod_delayed_work(laundry_wq, &nn->nfsd_shrinker_work, 0);
> +	return (unsigned long)cnt;
> +}
> +
> +static unsigned long
> +nfsd_courtesy_client_scan(struct shrinker *shrink, struct shrink_control *sc)
> +{
> +	return SHRINK_STOP;
> +}
> +
> +int
> +nfsd4_init_leases_net(struct nfsd_net *nn)
> {
> 	struct sysinfo si;
> 	u64 max_clients;
> @@ -4368,6 +4389,17 @@ void nfsd4_init_leases_net(struct nfsd_net *nn)
> 	nn->nfs4_max_clients = max_t(int, max_clients, NFS4_CLIENTS_PER_GB);
> 
> 	atomic_set(&nn->nfsd_courtesy_clients, 0);
> +	atomic_set(&nn->nfsd_client_shrinker_cb_count, 0);
> +	nn->nfsd_client_shrinker.scan_objects = nfsd_courtesy_client_scan;
> +	nn->nfsd_client_shrinker.count_objects = nfsd_courtesy_client_count;
> +	nn->nfsd_client_shrinker.seeks = DEFAULT_SEEKS;
> +	return register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
> +}
> +
> +void
> +nfsd4_leases_net_shutdown(struct nfsd_net *nn)
> +{
> +	unregister_shrinker(&nn->nfsd_client_shrinker);
> }
> 
> static void init_nfs4_replay(struct nfs4_replay *rp)
> @@ -5909,10 +5941,50 @@ nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
> 	spin_unlock(&nn->client_lock);
> }
> 
> +static void
> +nfs4_get_courtesy_client_reaplist(struct nfsd_net *nn,
> +				struct list_head *reaplist)
> +{
> +	unsigned int maxreap = 0, reapcnt = 0;
> +	struct list_head *pos, *next;
> +	struct nfs4_client *clp;
> +
> +	maxreap = NFSD_CLIENT_MAX_TRIM_PER_RUN;
> +	atomic_set(&nn->nfsd_client_shrinker_cb_count, 0);
> +	INIT_LIST_HEAD(reaplist);
> +
> +	spin_lock(&nn->client_lock);
> +	list_for_each_safe(pos, next, &nn->client_lru) {
> +		clp = list_entry(pos, struct nfs4_client, cl_lru);
> +		if (clp->cl_state == NFSD4_ACTIVE)
> +			break;
> +		if (reapcnt >= maxreap)
> +			break;
> +		if (!mark_client_expired_locked(clp)) {
> +			list_add(&clp->cl_lru, reaplist);
> +			reapcnt++;
> +		}
> +	}
> +	spin_unlock(&nn->client_lock);
> +}
> +
> +static inline void
> +nfs4_process_client_reaplist(struct list_head *reaplist)
> +{
> +	struct list_head *pos, *next;
> +	struct nfs4_client *clp;
> +
> +	list_for_each_safe(pos, next, reaplist) {
> +		clp = list_entry(pos, struct nfs4_client, cl_lru);
> +		trace_nfsd_clid_purged(&clp->cl_clientid);
> +		list_del_init(&clp->cl_lru);
> +		expire_client(clp);
> +	}
> +}
> +
> static time64_t
> nfs4_laundromat(struct nfsd_net *nn)
> {
> -	struct nfs4_client *clp;
> 	struct nfs4_openowner *oo;
> 	struct nfs4_delegation *dp;
> 	struct nfs4_ol_stateid *stp;
> @@ -5941,12 +6013,8 @@ nfs4_laundromat(struct nfsd_net *nn)
> 	}
> 	spin_unlock(&nn->s2s_cp_lock);
> 	nfs4_get_client_reaplist(nn, &reaplist, &lt);
> -	list_for_each_safe(pos, next, &reaplist) {
> -		clp = list_entry(pos, struct nfs4_client, cl_lru);
> -		trace_nfsd_clid_purged(&clp->cl_clientid);
> -		list_del_init(&clp->cl_lru);
> -		expire_client(clp);
> -	}
> +	nfs4_process_client_reaplist(&reaplist);
> +
> 	spin_lock(&state_lock);
> 	list_for_each_safe(pos, next, &nn->del_recall_lru) {
> 		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
> @@ -6029,6 +6097,23 @@ laundromat_main(struct work_struct *laundry)
> 	queue_delayed_work(laundry_wq, &nn->laundromat_work, t*HZ);
> }
> 
> +static void
> +courtesy_client_reaper(struct work_struct *reaper)
> +{
> +	struct list_head reaplist;
> +	struct delayed_work *dwork = to_delayed_work(reaper);
> +	struct nfsd_net *nn = container_of(dwork, struct nfsd_net,
> +					nfsd_shrinker_work);
> +
> +	nfs4_get_courtesy_client_reaplist(nn, &reaplist);
> +	nfs4_process_client_reaplist(&reaplist);
> +	if (atomic_read(&nn->nfsd_client_shrinker_cb_count) > 0 &&
> +			atomic_read(&nn->nfsd_courtesy_clients) > 0) {
> +		queue_delayed_work(laundry_wq, &nn->nfsd_shrinker_work,
> +				NFSD_CLIENT_SHRINKER_MINTIMEOUT * HZ);

IIUC, the count_objects callback will schedule reaping again if
it should be necessary. In fact, I wonder if it's possible for
count_objects to schedule this nn just as we're calling
queue_delayed_work() here -- that would corrupt the list of
work queue items, I would think.

I don't think we want a recursive invocation here -- you can get
rid of this queue_delayed_work and CLIENT_SHRINKER_MINTIMEOUT.


> +	}
> +}
> +
> static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_stid *stp)
> {
> 	if (!fh_match(&fhp->fh_handle, &stp->sc_file->fi_fhandle))
> @@ -7845,6 +7930,7 @@ static int nfs4_state_create_net(struct net *net)
> 	INIT_LIST_HEAD(&nn->blocked_locks_lru);
> 
> 	INIT_DELAYED_WORK(&nn->laundromat_work, laundromat_main);
> +	INIT_DELAYED_WORK(&nn->nfsd_shrinker_work, courtesy_client_reaper);
> 	get_net(net);
> 
> 	return 0;
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 917fa1892fd2..597a26ad4183 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1481,11 +1481,12 @@ static __net_init int nfsd_init_net(struct net *net)
> 		goto out_idmap_error;
> 	nn->nfsd_versions = NULL;
> 	nn->nfsd4_minorversions = NULL;
> +	retval = nfsd4_init_leases_net(nn);
> +	if (retval)
> +		goto out_drc_error;
> 	retval = nfsd_reply_cache_init(nn);
> 	if (retval)
> 		goto out_drc_error;
> -	nfsd4_init_leases_net(nn);
> -
> 	get_random_bytes(&nn->siphash_key, sizeof(nn->siphash_key));
> 	seqlock_init(&nn->writeverf_lock);
> 
> @@ -1507,6 +1508,7 @@ static __net_exit void nfsd_exit_net(struct net *net)
> 	nfsd_idmap_shutdown(net);
> 	nfsd_export_shutdown(net);
> 	nfsd_netns_free_versions(net_generic(net, nfsd_net_id));
> +	nfsd4_leases_net_shutdown(nn);
> }
> 
> static struct pernet_operations nfsd_net_ops = {
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 57a468ed85c3..cd92f615faa3 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -343,6 +343,7 @@ void		nfsd_lockd_shutdown(void);
> #define	NFSD_COURTESY_CLIENT_TIMEOUT	(24 * 60 * 60)	/* seconds */
> #define	NFSD_CLIENT_MAX_TRIM_PER_RUN	128
> #define	NFS4_CLIENTS_PER_GB		1024
> +#define	NFSD_CLIENT_SHRINKER_MINTIMEOUT	1   /* seconds */
> 
> /*
>  * The following attributes are currently not supported by the NFSv4 server:
> @@ -498,7 +499,8 @@ extern void unregister_cld_notifier(void);
> extern void nfsd4_ssc_init_umount_work(struct nfsd_net *nn);
> #endif
> 
> -extern void nfsd4_init_leases_net(struct nfsd_net *nn);
> +extern int nfsd4_init_leases_net(struct nfsd_net *nn);
> +extern void nfsd4_leases_net_shutdown(struct nfsd_net *nn);
> 
> #else /* CONFIG_NFSD_V4 */
> static inline int nfsd4_is_junction(struct dentry *dentry)
> @@ -506,7 +508,8 @@ static inline int nfsd4_is_junction(struct dentry *dentry)
> 	return 0;
> }
> 
> -static inline void nfsd4_init_leases_net(struct nfsd_net *nn) {};
> +static inline int nfsd4_init_leases_net(struct nfsd_net *nn) { return 0; };
> +static inline void nfsd4_leases_net_shutdown(struct nfsd_net *nn) {};
> 
> #define register_cld_notifier() 0
> #define unregister_cld_notifier() do { } while(0)
> -- 
> 2.9.5
> 

--
Chuck Lever
diff mbox series

Patch

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 55c7006d6109..37457b104eee 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -194,6 +194,9 @@  struct nfsd_net {
 	int			nfs4_max_clients;
 
 	atomic_t		nfsd_courtesy_clients;
+	atomic_t		nfsd_client_shrinker_cb_count;
+	struct shrinker		nfsd_client_shrinker;
+	struct delayed_work	nfsd_shrinker_work;
 };
 
 /* Simple check to find out if a given net was properly initialized */
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 3af4fc5241b2..fed4ca3fb581 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4347,7 +4347,28 @@  nfsd4_init_slabs(void)
 	return -ENOMEM;
 }
 
-void nfsd4_init_leases_net(struct nfsd_net *nn)
+static unsigned long
+nfsd_courtesy_client_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	int cnt;
+	struct nfsd_net *nn = container_of(shrink,
+			struct nfsd_net, nfsd_client_shrinker);
+
+	atomic_inc(&nn->nfsd_client_shrinker_cb_count);
+	cnt = atomic_read(&nn->nfsd_courtesy_clients);
+	if (cnt > 0)
+		mod_delayed_work(laundry_wq, &nn->nfsd_shrinker_work, 0);
+	return (unsigned long)cnt;
+}
+
+static unsigned long
+nfsd_courtesy_client_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+	return SHRINK_STOP;
+}
+
+int
+nfsd4_init_leases_net(struct nfsd_net *nn)
 {
 	struct sysinfo si;
 	u64 max_clients;
@@ -4368,6 +4389,17 @@  void nfsd4_init_leases_net(struct nfsd_net *nn)
 	nn->nfs4_max_clients = max_t(int, max_clients, NFS4_CLIENTS_PER_GB);
 
 	atomic_set(&nn->nfsd_courtesy_clients, 0);
+	atomic_set(&nn->nfsd_client_shrinker_cb_count, 0);
+	nn->nfsd_client_shrinker.scan_objects = nfsd_courtesy_client_scan;
+	nn->nfsd_client_shrinker.count_objects = nfsd_courtesy_client_count;
+	nn->nfsd_client_shrinker.seeks = DEFAULT_SEEKS;
+	return register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
+}
+
+void
+nfsd4_leases_net_shutdown(struct nfsd_net *nn)
+{
+	unregister_shrinker(&nn->nfsd_client_shrinker);
 }
 
 static void init_nfs4_replay(struct nfs4_replay *rp)
@@ -5909,10 +5941,50 @@  nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
 	spin_unlock(&nn->client_lock);
 }
 
+static void
+nfs4_get_courtesy_client_reaplist(struct nfsd_net *nn,
+				struct list_head *reaplist)
+{
+	unsigned int maxreap = 0, reapcnt = 0;
+	struct list_head *pos, *next;
+	struct nfs4_client *clp;
+
+	maxreap = NFSD_CLIENT_MAX_TRIM_PER_RUN;
+	atomic_set(&nn->nfsd_client_shrinker_cb_count, 0);
+	INIT_LIST_HEAD(reaplist);
+
+	spin_lock(&nn->client_lock);
+	list_for_each_safe(pos, next, &nn->client_lru) {
+		clp = list_entry(pos, struct nfs4_client, cl_lru);
+		if (clp->cl_state == NFSD4_ACTIVE)
+			break;
+		if (reapcnt >= maxreap)
+			break;
+		if (!mark_client_expired_locked(clp)) {
+			list_add(&clp->cl_lru, reaplist);
+			reapcnt++;
+		}
+	}
+	spin_unlock(&nn->client_lock);
+}
+
+static inline void
+nfs4_process_client_reaplist(struct list_head *reaplist)
+{
+	struct list_head *pos, *next;
+	struct nfs4_client *clp;
+
+	list_for_each_safe(pos, next, reaplist) {
+		clp = list_entry(pos, struct nfs4_client, cl_lru);
+		trace_nfsd_clid_purged(&clp->cl_clientid);
+		list_del_init(&clp->cl_lru);
+		expire_client(clp);
+	}
+}
+
 static time64_t
 nfs4_laundromat(struct nfsd_net *nn)
 {
-	struct nfs4_client *clp;
 	struct nfs4_openowner *oo;
 	struct nfs4_delegation *dp;
 	struct nfs4_ol_stateid *stp;
@@ -5941,12 +6013,8 @@  nfs4_laundromat(struct nfsd_net *nn)
 	}
 	spin_unlock(&nn->s2s_cp_lock);
 	nfs4_get_client_reaplist(nn, &reaplist, &lt);
-	list_for_each_safe(pos, next, &reaplist) {
-		clp = list_entry(pos, struct nfs4_client, cl_lru);
-		trace_nfsd_clid_purged(&clp->cl_clientid);
-		list_del_init(&clp->cl_lru);
-		expire_client(clp);
-	}
+	nfs4_process_client_reaplist(&reaplist);
+
 	spin_lock(&state_lock);
 	list_for_each_safe(pos, next, &nn->del_recall_lru) {
 		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
@@ -6029,6 +6097,23 @@  laundromat_main(struct work_struct *laundry)
 	queue_delayed_work(laundry_wq, &nn->laundromat_work, t*HZ);
 }
 
+static void
+courtesy_client_reaper(struct work_struct *reaper)
+{
+	struct list_head reaplist;
+	struct delayed_work *dwork = to_delayed_work(reaper);
+	struct nfsd_net *nn = container_of(dwork, struct nfsd_net,
+					nfsd_shrinker_work);
+
+	nfs4_get_courtesy_client_reaplist(nn, &reaplist);
+	nfs4_process_client_reaplist(&reaplist);
+	if (atomic_read(&nn->nfsd_client_shrinker_cb_count) > 0 &&
+			atomic_read(&nn->nfsd_courtesy_clients) > 0) {
+		queue_delayed_work(laundry_wq, &nn->nfsd_shrinker_work,
+				NFSD_CLIENT_SHRINKER_MINTIMEOUT * HZ);
+	}
+}
+
 static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_stid *stp)
 {
 	if (!fh_match(&fhp->fh_handle, &stp->sc_file->fi_fhandle))
@@ -7845,6 +7930,7 @@  static int nfs4_state_create_net(struct net *net)
 	INIT_LIST_HEAD(&nn->blocked_locks_lru);
 
 	INIT_DELAYED_WORK(&nn->laundromat_work, laundromat_main);
+	INIT_DELAYED_WORK(&nn->nfsd_shrinker_work, courtesy_client_reaper);
 	get_net(net);
 
 	return 0;
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 917fa1892fd2..597a26ad4183 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1481,11 +1481,12 @@  static __net_init int nfsd_init_net(struct net *net)
 		goto out_idmap_error;
 	nn->nfsd_versions = NULL;
 	nn->nfsd4_minorversions = NULL;
+	retval = nfsd4_init_leases_net(nn);
+	if (retval)
+		goto out_drc_error;
 	retval = nfsd_reply_cache_init(nn);
 	if (retval)
 		goto out_drc_error;
-	nfsd4_init_leases_net(nn);
-
 	get_random_bytes(&nn->siphash_key, sizeof(nn->siphash_key));
 	seqlock_init(&nn->writeverf_lock);
 
@@ -1507,6 +1508,7 @@  static __net_exit void nfsd_exit_net(struct net *net)
 	nfsd_idmap_shutdown(net);
 	nfsd_export_shutdown(net);
 	nfsd_netns_free_versions(net_generic(net, nfsd_net_id));
+	nfsd4_leases_net_shutdown(nn);
 }
 
 static struct pernet_operations nfsd_net_ops = {
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 57a468ed85c3..cd92f615faa3 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -343,6 +343,7 @@  void		nfsd_lockd_shutdown(void);
 #define	NFSD_COURTESY_CLIENT_TIMEOUT	(24 * 60 * 60)	/* seconds */
 #define	NFSD_CLIENT_MAX_TRIM_PER_RUN	128
 #define	NFS4_CLIENTS_PER_GB		1024
+#define	NFSD_CLIENT_SHRINKER_MINTIMEOUT	1   /* seconds */
 
 /*
  * The following attributes are currently not supported by the NFSv4 server:
@@ -498,7 +499,8 @@  extern void unregister_cld_notifier(void);
 extern void nfsd4_ssc_init_umount_work(struct nfsd_net *nn);
 #endif
 
-extern void nfsd4_init_leases_net(struct nfsd_net *nn);
+extern int nfsd4_init_leases_net(struct nfsd_net *nn);
+extern void nfsd4_leases_net_shutdown(struct nfsd_net *nn);
 
 #else /* CONFIG_NFSD_V4 */
 static inline int nfsd4_is_junction(struct dentry *dentry)
@@ -506,7 +508,8 @@  static inline int nfsd4_is_junction(struct dentry *dentry)
 	return 0;
 }
 
-static inline void nfsd4_init_leases_net(struct nfsd_net *nn) {};
+static inline int nfsd4_init_leases_net(struct nfsd_net *nn) { return 0; };
+static inline void nfsd4_leases_net_shutdown(struct nfsd_net *nn) {};
 
 #define register_cld_notifier() 0
 #define unregister_cld_notifier() do { } while(0)