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Subject: [PATCH 1/2] afs: Use refcount_t rather than atomic_t
From:   David Howells <dhowells@redhat.com>
To:     linux-afs@lists.infradead.org
Cc:     Marc Dionne <marc.dionne@auristor.com>, dhowells@redhat.com,
        Marc Dionne <marc.dionne@auristor.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Fri, 29 Jul 2022 17:39:37 +0100
Message-ID: <165911277768.3745403.423349776836296452.stgit@warthog.procyon.org.uk>
In-Reply-To: <165911277121.3745403.18238096564862303683.stgit@warthog.procyon.org.uk>
References: <165911277121.3745403.18238096564862303683.stgit@warthog.procyon.org.uk>
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Use refcount_t rather than atomic_t in afs to make use of the count
checking facilities provided.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
---

 fs/afs/cell.c              |   61 +++++++++++++++++++++-----------------------
 fs/afs/cmservice.c         |    2 +
 fs/afs/internal.h          |   16 ++++++------
 fs/afs/proc.c              |    6 ++--
 fs/afs/rxrpc.c             |   26 ++++++++++---------
 fs/afs/server.c            |   40 +++++++++++++++++------------
 fs/afs/vl_list.c           |   19 ++++----------
 fs/afs/volume.c            |   21 +++++++++------
 include/trace/events/afs.h |   26 +++++++++----------
 9 files changed, 110 insertions(+), 107 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 07ad744eef77..988c2ac7cece 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -158,7 +158,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 		cell->name[i] = tolower(name[i]);
 	cell->name[i] = 0;
 
-	atomic_set(&cell->ref, 1);
+	refcount_set(&cell->ref, 1);
 	atomic_set(&cell->active, 0);
 	INIT_WORK(&cell->manager, afs_manage_cell_work);
 	cell->volumes = RB_ROOT;
@@ -287,7 +287,7 @@ struct afs_cell *afs_lookup_cell(struct afs_net *net,
 	cell = candidate;
 	candidate = NULL;
 	atomic_set(&cell->active, 2);
-	trace_afs_cell(cell->debug_id, atomic_read(&cell->ref), 2, afs_cell_trace_insert);
+	trace_afs_cell(cell->debug_id, refcount_read(&cell->ref), 2, afs_cell_trace_insert);
 	rb_link_node_rcu(&cell->net_node, parent, pp);
 	rb_insert_color(&cell->net_node, &net->cells);
 	up_write(&net->cells_lock);
@@ -295,7 +295,7 @@ struct afs_cell *afs_lookup_cell(struct afs_net *net,
 	afs_queue_cell(cell, afs_cell_trace_get_queue_new);
 
 wait_for_cell:
-	trace_afs_cell(cell->debug_id, atomic_read(&cell->ref), atomic_read(&cell->active),
+	trace_afs_cell(cell->debug_id, refcount_read(&cell->ref), atomic_read(&cell->active),
 		       afs_cell_trace_wait);
 	_debug("wait_for_cell");
 	wait_var_event(&cell->state,
@@ -490,13 +490,13 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 {
 	struct afs_cell *cell = container_of(rcu, struct afs_cell, rcu);
 	struct afs_net *net = cell->net;
-	int u;
+	int r;
 
 	_enter("%p{%s}", cell, cell->name);
 
-	u = atomic_read(&cell->ref);
-	ASSERTCMP(u, ==, 0);
-	trace_afs_cell(cell->debug_id, u, atomic_read(&cell->active), afs_cell_trace_free);
+	r = refcount_read(&cell->ref);
+	ASSERTCMP(r, ==, 0);
+	trace_afs_cell(cell->debug_id, r, atomic_read(&cell->active), afs_cell_trace_free);
 
 	afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
 	afs_unuse_cell(net, cell->alias_of, afs_cell_trace_unuse_alias);
@@ -539,13 +539,10 @@ void afs_cells_timer(struct timer_list *timer)
  */
 struct afs_cell *afs_get_cell(struct afs_cell *cell, enum afs_cell_trace reason)
 {
-	int u;
+	int r;
 
-	if (atomic_read(&cell->ref) <= 0)
-		BUG();
-
-	u = atomic_inc_return(&cell->ref);
-	trace_afs_cell(cell->debug_id, u, atomic_read(&cell->active), reason);
+	__refcount_inc(&cell->ref, &r);
+	trace_afs_cell(cell->debug_id, r + 1, atomic_read(&cell->active), reason);
 	return cell;
 }
 
@@ -556,12 +553,14 @@ void afs_put_cell(struct afs_cell *cell, enum afs_cell_trace reason)
 {
 	if (cell) {
 		unsigned int debug_id = cell->debug_id;
-		unsigned int u, a;
+		unsigned int a;
+		bool zero;
+		int r;
 
 		a = atomic_read(&cell->active);
-		u = atomic_dec_return(&cell->ref);
-		trace_afs_cell(debug_id, u, a, reason);
-		if (u == 0) {
+		zero = __refcount_dec_and_test(&cell->ref, &r);
+		trace_afs_cell(debug_id, r - 1, a, reason);
+		if (zero) {
 			a = atomic_read(&cell->active);
 			WARN(a != 0, "Cell active count %u > 0\n", a);
 			call_rcu(&cell->rcu, afs_cell_destroy);
@@ -574,14 +573,12 @@ void afs_put_cell(struct afs_cell *cell, enum afs_cell_trace reason)
  */
 struct afs_cell *afs_use_cell(struct afs_cell *cell, enum afs_cell_trace reason)
 {
-	int u, a;
-
-	if (atomic_read(&cell->ref) <= 0)
-		BUG();
+	int r, a;
 
-	u = atomic_read(&cell->ref);
+	r = refcount_read(&cell->ref);
+	WARN_ON(r == 0);
 	a = atomic_inc_return(&cell->active);
-	trace_afs_cell(cell->debug_id, u, a, reason);
+	trace_afs_cell(cell->debug_id, r, a, reason);
 	return cell;
 }
 
@@ -593,7 +590,7 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr
 {
 	unsigned int debug_id;
 	time64_t now, expire_delay;
-	int u, a;
+	int r, a;
 
 	if (!cell)
 		return;
@@ -607,9 +604,9 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr
 		expire_delay = afs_cell_gc_delay;
 
 	debug_id = cell->debug_id;
-	u = atomic_read(&cell->ref);
+	r = refcount_read(&cell->ref);
 	a = atomic_dec_return(&cell->active);
-	trace_afs_cell(debug_id, u, a, reason);
+	trace_afs_cell(debug_id, r, a, reason);
 	WARN_ON(a == 0);
 	if (a == 1)
 		/* 'cell' may now be garbage collected. */
@@ -621,11 +618,11 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr
  */
 void afs_see_cell(struct afs_cell *cell, enum afs_cell_trace reason)
 {
-	int u, a;
+	int r, a;
 
-	u = atomic_read(&cell->ref);
+	r = refcount_read(&cell->ref);
 	a = atomic_read(&cell->active);
-	trace_afs_cell(cell->debug_id, u, a, reason);
+	trace_afs_cell(cell->debug_id, r, a, reason);
 }
 
 /*
@@ -739,7 +736,7 @@ static void afs_manage_cell(struct afs_cell *cell)
 		active = 1;
 		if (atomic_try_cmpxchg_relaxed(&cell->active, &active, 0)) {
 			rb_erase(&cell->net_node, &net->cells);
-			trace_afs_cell(cell->debug_id, atomic_read(&cell->ref), 0,
+			trace_afs_cell(cell->debug_id, refcount_read(&cell->ref), 0,
 				       afs_cell_trace_unuse_delete);
 			smp_store_release(&cell->state, AFS_CELL_REMOVED);
 		}
@@ -866,7 +863,7 @@ void afs_manage_cells(struct work_struct *work)
 		bool sched_cell = false;
 
 		active = atomic_read(&cell->active);
-		trace_afs_cell(cell->debug_id, atomic_read(&cell->ref),
+		trace_afs_cell(cell->debug_id, refcount_read(&cell->ref),
 			       active, afs_cell_trace_manage);
 
 		ASSERTCMP(active, >=, 1);
@@ -874,7 +871,7 @@ void afs_manage_cells(struct work_struct *work)
 		if (purging) {
 			if (test_and_clear_bit(AFS_CELL_FL_NO_GC, &cell->flags)) {
 				active = atomic_dec_return(&cell->active);
-				trace_afs_cell(cell->debug_id, atomic_read(&cell->ref),
+				trace_afs_cell(cell->debug_id, refcount_read(&cell->ref),
 					       active, afs_cell_trace_unuse_pin);
 			}
 		}
diff --git a/fs/afs/cmservice.c b/fs/afs/cmservice.c
index a3f5de28be79..cedd627e1fae 100644
--- a/fs/afs/cmservice.c
+++ b/fs/afs/cmservice.c
@@ -213,7 +213,7 @@ static void SRXAFSCB_CallBack(struct work_struct *work)
 	 */
 	if (call->server) {
 		trace_afs_server(call->server,
-				 atomic_read(&call->server->ref),
+				 refcount_read(&call->server->ref),
 				 atomic_read(&call->server->active),
 				 afs_server_trace_callback);
 		afs_break_callbacks(call->server, call->count, call->request);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index a6f25d9e75b5..64ad55494349 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -122,7 +122,7 @@ struct afs_call {
 	};
 	struct afs_operation	*op;
 	unsigned int		server_index;
-	atomic_t		usage;
+	refcount_t		ref;
 	enum afs_call_state	state;
 	spinlock_t		state_lock;
 	int			error;		/* error code */
@@ -365,7 +365,7 @@ struct afs_cell {
 	struct hlist_node	proc_link;	/* /proc cell list link */
 	time64_t		dns_expiry;	/* Time AFSDB/SRV record expires */
 	time64_t		last_inactive;	/* Time of last drop of usage count */
-	atomic_t		ref;		/* Struct refcount */
+	refcount_t		ref;		/* Struct refcount */
 	atomic_t		active;		/* Active usage counter */
 	unsigned long		flags;
 #define AFS_CELL_FL_NO_GC	0		/* The cell was added manually, don't auto-gc */
@@ -410,7 +410,7 @@ struct afs_vlserver {
 #define AFS_VLSERVER_FL_IS_YFS	2		/* Server is YFS not AFS */
 #define AFS_VLSERVER_FL_RESPONDING 3		/* VL server is responding */
 	rwlock_t		lock;		/* Lock on addresses */
-	atomic_t		usage;
+	refcount_t		ref;
 	unsigned int		rtt;		/* Server's current RTT in uS */
 
 	/* Probe state */
@@ -446,7 +446,7 @@ struct afs_vlserver_entry {
 
 struct afs_vlserver_list {
 	struct rcu_head		rcu;
-	atomic_t		usage;
+	refcount_t		ref;
 	u8			nr_servers;
 	u8			index;		/* Server currently in use */
 	u8			preferred;	/* Preferred server */
@@ -517,7 +517,7 @@ struct afs_server {
 #define AFS_SERVER_FL_NO_IBULK	17		/* Fileserver doesn't support FS.InlineBulkStatus */
 #define AFS_SERVER_FL_NO_RM2	18		/* Fileserver doesn't support YFS.RemoveFile2 */
 #define AFS_SERVER_FL_HAS_FS64	19		/* Fileserver supports FS.{Fetch,Store}Data64 */
-	atomic_t		ref;		/* Object refcount */
+	refcount_t		ref;		/* Object refcount */
 	atomic_t		active;		/* Active user count */
 	u32			addr_version;	/* Address list version */
 	unsigned int		rtt;		/* Server's current RTT in uS */
@@ -571,7 +571,7 @@ struct afs_volume {
 		struct rcu_head	rcu;
 		afs_volid_t	vid;		/* volume ID */
 	};
-	atomic_t		usage;
+	refcount_t		ref;
 	time64_t		update_at;	/* Time at which to next update */
 	struct afs_cell		*cell;		/* Cell to which belongs (pins ref) */
 	struct rb_node		cell_node;	/* Link in cell->volumes */
@@ -1493,14 +1493,14 @@ extern int afs_end_vlserver_operation(struct afs_vl_cursor *);
  */
 static inline struct afs_vlserver *afs_get_vlserver(struct afs_vlserver *vlserver)
 {
-	atomic_inc(&vlserver->usage);
+	refcount_inc(&vlserver->ref);
 	return vlserver;
 }
 
 static inline struct afs_vlserver_list *afs_get_vlserverlist(struct afs_vlserver_list *vllist)
 {
 	if (vllist)
-		atomic_inc(&vllist->usage);
+		refcount_inc(&vllist->ref);
 	return vllist;
 }
 
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index e1b863449296..2a0c83d71565 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -47,7 +47,7 @@ static int afs_proc_cells_show(struct seq_file *m, void *v)
 
 	/* display one cell per line on subsequent lines */
 	seq_printf(m, "%3u %3u %6lld %2u %2u %s\n",
-		   atomic_read(&cell->ref),
+		   refcount_read(&cell->ref),
 		   atomic_read(&cell->active),
 		   cell->dns_expiry - ktime_get_real_seconds(),
 		   vllist ? vllist->nr_servers : 0,
@@ -217,7 +217,7 @@ static int afs_proc_cell_volumes_show(struct seq_file *m, void *v)
 	}
 
 	seq_printf(m, "%3d %08llx %s %s\n",
-		   atomic_read(&vol->usage), vol->vid,
+		   refcount_read(&vol->ref), vol->vid,
 		   afs_vol_types[vol->type],
 		   vol->name);
 
@@ -388,7 +388,7 @@ static int afs_proc_servers_show(struct seq_file *m, void *v)
 	alist = rcu_dereference(server->addresses);
 	seq_printf(m, "%pU %3d %3d\n",
 		   &server->uuid,
-		   atomic_read(&server->ref),
+		   refcount_read(&server->ref),
 		   atomic_read(&server->active));
 	seq_printf(m, "  - info: fl=%lx rtt=%u brk=%x\n",
 		   server->flags, server->rtt, server->cb_s_break);
diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index a5434f3e57c6..d9acc43cb6f0 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -145,7 +145,7 @@ static struct afs_call *afs_alloc_call(struct afs_net *net,
 	call->type = type;
 	call->net = net;
 	call->debug_id = atomic_inc_return(&rxrpc_debug_id);
-	atomic_set(&call->usage, 1);
+	refcount_set(&call->ref, 1);
 	INIT_WORK(&call->async_work, afs_process_async_call);
 	init_waitqueue_head(&call->waitq);
 	spin_lock_init(&call->state_lock);
@@ -163,14 +163,15 @@ static struct afs_call *afs_alloc_call(struct afs_net *net,
 void afs_put_call(struct afs_call *call)
 {
 	struct afs_net *net = call->net;
-	int n = atomic_dec_return(&call->usage);
-	int o = atomic_read(&net->nr_outstanding_calls);
+	bool zero;
+	int r, o;
 
-	trace_afs_call(call, afs_call_trace_put, n, o,
+	zero = __refcount_dec_and_test(&call->ref, &r);
+	o = atomic_read(&net->nr_outstanding_calls);
+	trace_afs_call(call, afs_call_trace_put, r - 1, o,
 		       __builtin_return_address(0));
 
-	ASSERTCMP(n, >=, 0);
-	if (n == 0) {
+	if (zero) {
 		ASSERT(!work_pending(&call->async_work));
 		ASSERT(call->type->name != NULL);
 
@@ -198,9 +199,11 @@ void afs_put_call(struct afs_call *call)
 static struct afs_call *afs_get_call(struct afs_call *call,
 				     enum afs_call_trace why)
 {
-	int u = atomic_inc_return(&call->usage);
+	int r;
 
-	trace_afs_call(call, why, u,
+	__refcount_inc(&call->ref, &r);
+
+	trace_afs_call(call, why, r + 1,
 		       atomic_read(&call->net->nr_outstanding_calls),
 		       __builtin_return_address(0));
 	return call;
@@ -668,14 +671,13 @@ static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall,
 				   unsigned long call_user_ID)
 {
 	struct afs_call *call = (struct afs_call *)call_user_ID;
-	int u;
+	int r;
 
 	trace_afs_notify_call(rxcall, call);
 	call->need_attention = true;
 
-	u = atomic_fetch_add_unless(&call->usage, 1, 0);
-	if (u != 0) {
-		trace_afs_call(call, afs_call_trace_wake, u + 1,
+	if (__refcount_inc_not_zero(&call->ref, &r)) {
+		trace_afs_call(call, afs_call_trace_wake, r + 1,
 			       atomic_read(&call->net->nr_outstanding_calls),
 			       __builtin_return_address(0));
 
diff --git a/fs/afs/server.c b/fs/afs/server.c
index 6e5b9a19b234..ffed828622b6 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -228,7 +228,7 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
 	if (!server)
 		goto enomem;
 
-	atomic_set(&server->ref, 1);
+	refcount_set(&server->ref, 1);
 	atomic_set(&server->active, 1);
 	server->debug_id = atomic_inc_return(&afs_server_debug_id);
 	RCU_INIT_POINTER(server->addresses, alist);
@@ -352,9 +352,10 @@ void afs_servers_timer(struct timer_list *timer)
 struct afs_server *afs_get_server(struct afs_server *server,
 				  enum afs_server_trace reason)
 {
-	unsigned int u = atomic_inc_return(&server->ref);
+	int r;
 
-	trace_afs_server(server, u, atomic_read(&server->active), reason);
+	__refcount_inc(&server->ref, &r);
+	trace_afs_server(server, r + 1, atomic_read(&server->active), reason);
 	return server;
 }
 
@@ -364,14 +365,14 @@ struct afs_server *afs_get_server(struct afs_server *server,
 static struct afs_server *afs_maybe_use_server(struct afs_server *server,
 					       enum afs_server_trace reason)
 {
-	unsigned int r = atomic_fetch_add_unless(&server->ref, 1, 0);
 	unsigned int a;
+	int r;
 
-	if (r == 0)
+	if (!__refcount_inc_not_zero(&server->ref, &r))
 		return NULL;
 
 	a = atomic_inc_return(&server->active);
-	trace_afs_server(server, r, a, reason);
+	trace_afs_server(server, r + 1, a, reason);
 	return server;
 }
 
@@ -380,10 +381,13 @@ static struct afs_server *afs_maybe_use_server(struct afs_server *server,
  */
 struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
 {
-	unsigned int r = atomic_inc_return(&server->ref);
-	unsigned int a = atomic_inc_return(&server->active);
+	unsigned int a;
+	int r;
+
+	__refcount_inc(&server->ref, &r);
+	a = atomic_inc_return(&server->active);
 
-	trace_afs_server(server, r, a, reason);
+	trace_afs_server(server, r + 1, a, reason);
 	return server;
 }
 
@@ -393,14 +397,15 @@ struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_tra
 void afs_put_server(struct afs_net *net, struct afs_server *server,
 		    enum afs_server_trace reason)
 {
-	unsigned int usage;
+	bool zero;
+	int r;
 
 	if (!server)
 		return;
 
-	usage = atomic_dec_return(&server->ref);
-	trace_afs_server(server, usage, atomic_read(&server->active), reason);
-	if (unlikely(usage == 0))
+	zero = __refcount_dec_and_test(&server->ref, &r);
+	trace_afs_server(server, r - 1, atomic_read(&server->active), reason);
+	if (unlikely(zero))
 		__afs_put_server(net, server);
 }
 
@@ -436,7 +441,7 @@ static void afs_server_rcu(struct rcu_head *rcu)
 {
 	struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 
-	trace_afs_server(server, atomic_read(&server->ref),
+	trace_afs_server(server, refcount_read(&server->ref),
 			 atomic_read(&server->active), afs_server_trace_free);
 	afs_put_addrlist(rcu_access_pointer(server->addresses));
 	kfree(server);
@@ -487,7 +492,7 @@ static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 
 		active = atomic_read(&server->active);
 		if (active == 0) {
-			trace_afs_server(server, atomic_read(&server->ref),
+			trace_afs_server(server, refcount_read(&server->ref),
 					 active, afs_server_trace_gc);
 			next = rcu_dereference_protected(
 				server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
@@ -553,7 +558,7 @@ void afs_manage_servers(struct work_struct *work)
 		_debug("manage %pU %u", &server->uuid, active);
 
 		if (purging) {
-			trace_afs_server(server, atomic_read(&server->ref),
+			trace_afs_server(server, refcount_read(&server->ref),
 					 active, afs_server_trace_purging);
 			if (active != 0)
 				pr_notice("Can't purge s=%08x\n", server->debug_id);
@@ -633,7 +638,8 @@ static noinline bool afs_update_server_record(struct afs_operation *op,
 
 	_enter("");
 
-	trace_afs_server(server, atomic_read(&server->ref), atomic_read(&server->active),
+	trace_afs_server(server, refcount_read(&server->ref),
+			 atomic_read(&server->active),
 			 afs_server_trace_update);
 
 	alist = afs_vl_lookup_addrs(op->volume->cell, op->key, &server->uuid);
diff --git a/fs/afs/vl_list.c b/fs/afs/vl_list.c
index 38b2ba1d9ec0..acc48216136a 100644
--- a/fs/afs/vl_list.c
+++ b/fs/afs/vl_list.c
@@ -17,7 +17,7 @@ struct afs_vlserver *afs_alloc_vlserver(const char *name, size_t name_len,
 	vlserver = kzalloc(struct_size(vlserver, name, name_len + 1),
 			   GFP_KERNEL);
 	if (vlserver) {
-		atomic_set(&vlserver->usage, 1);
+		refcount_set(&vlserver->ref, 1);
 		rwlock_init(&vlserver->lock);
 		init_waitqueue_head(&vlserver->probe_wq);
 		spin_lock_init(&vlserver->probe_lock);
@@ -39,13 +39,9 @@ static void afs_vlserver_rcu(struct rcu_head *rcu)
 
 void afs_put_vlserver(struct afs_net *net, struct afs_vlserver *vlserver)
 {
-	if (vlserver) {
-		unsigned int u = atomic_dec_return(&vlserver->usage);
-		//_debug("VL PUT %p{%u}", vlserver, u);
-
-		if (u == 0)
-			call_rcu(&vlserver->rcu, afs_vlserver_rcu);
-	}
+	if (vlserver &&
+	    refcount_dec_and_test(&vlserver->ref))
+		call_rcu(&vlserver->rcu, afs_vlserver_rcu);
 }
 
 struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int nr_servers)
@@ -54,7 +50,7 @@ struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int nr_servers)
 
 	vllist = kzalloc(struct_size(vllist, servers, nr_servers), GFP_KERNEL);
 	if (vllist) {
-		atomic_set(&vllist->usage, 1);
+		refcount_set(&vllist->ref, 1);
 		rwlock_init(&vllist->lock);
 	}
 
@@ -64,10 +60,7 @@ struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int nr_servers)
 void afs_put_vlserverlist(struct afs_net *net, struct afs_vlserver_list *vllist)
 {
 	if (vllist) {
-		unsigned int u = atomic_dec_return(&vllist->usage);
-
-		//_debug("VLLS PUT %p{%u}", vllist, u);
-		if (u == 0) {
+		if (refcount_dec_and_test(&vllist->ref)) {
 			int i;
 
 			for (i = 0; i < vllist->nr_servers; i++) {
diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index cc665cef0abe..f4937029dcd7 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -52,7 +52,7 @@ static void afs_remove_volume_from_cell(struct afs_volume *volume)
 	struct afs_cell *cell = volume->cell;
 
 	if (!hlist_unhashed(&volume->proc_link)) {
-		trace_afs_volume(volume->vid, atomic_read(&volume->usage),
+		trace_afs_volume(volume->vid, refcount_read(&cell->ref),
 				 afs_volume_trace_remove);
 		write_seqlock(&cell->volume_lock);
 		hlist_del_rcu(&volume->proc_link);
@@ -87,7 +87,7 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 	volume->type_force	= params->force;
 	volume->name_len	= vldb->name_len;
 
-	atomic_set(&volume->usage, 1);
+	refcount_set(&volume->ref, 1);
 	INIT_HLIST_NODE(&volume->proc_link);
 	rwlock_init(&volume->servers_lock);
 	rwlock_init(&volume->cb_v_break_lock);
@@ -228,7 +228,7 @@ static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
 	afs_remove_volume_from_cell(volume);
 	afs_put_serverlist(net, rcu_access_pointer(volume->servers));
 	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
-	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
+	trace_afs_volume(volume->vid, refcount_read(&volume->ref),
 			 afs_volume_trace_free);
 	kfree_rcu(volume, rcu);
 
@@ -242,8 +242,10 @@ struct afs_volume *afs_get_volume(struct afs_volume *volume,
 				  enum afs_volume_trace reason)
 {
 	if (volume) {
-		int u = atomic_inc_return(&volume->usage);
-		trace_afs_volume(volume->vid, u, reason);
+		int r;
+
+		__refcount_inc(&volume->ref, &r);
+		trace_afs_volume(volume->vid, r + 1, reason);
 	}
 	return volume;
 }
@@ -257,9 +259,12 @@ void afs_put_volume(struct afs_net *net, struct afs_volume *volume,
 {
 	if (volume) {
 		afs_volid_t vid = volume->vid;
-		int u = atomic_dec_return(&volume->usage);
-		trace_afs_volume(vid, u, reason);
-		if (u == 0)
+		bool zero;
+		int r;
+
+		zero = __refcount_dec_and_test(&volume->ref, &r);
+		trace_afs_volume(vid, r - 1, reason);
+		if (zero)
 			afs_destroy_volume(net, volume);
 	}
 }
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index 499f5fabd20f..aa60f42a9763 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -728,14 +728,14 @@ TRACE_EVENT(afs_cb_call,
 
 TRACE_EVENT(afs_call,
 	    TP_PROTO(struct afs_call *call, enum afs_call_trace op,
-		     int usage, int outstanding, const void *where),
+		     int ref, int outstanding, const void *where),
 
-	    TP_ARGS(call, op, usage, outstanding, where),
+	    TP_ARGS(call, op, ref, outstanding, where),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
 		    __field(int,			op		)
-		    __field(int,			usage		)
+		    __field(int,			ref		)
 		    __field(int,			outstanding	)
 		    __field(const void *,		where		)
 			     ),
@@ -743,15 +743,15 @@ TRACE_EVENT(afs_call,
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
 		    __entry->op = op;
-		    __entry->usage = usage;
+		    __entry->ref = ref;
 		    __entry->outstanding = outstanding;
 		    __entry->where = where;
 			   ),
 
-	    TP_printk("c=%08x %s u=%d o=%d sp=%pSR",
+	    TP_printk("c=%08x %s r=%d o=%d sp=%pSR",
 		      __entry->call,
 		      __print_symbolic(__entry->op, afs_call_traces),
-		      __entry->usage,
+		      __entry->ref,
 		      __entry->outstanding,
 		      __entry->where)
 	    );
@@ -1476,36 +1476,36 @@ TRACE_EVENT(afs_volume,
 		    __entry->reason = reason;
 			   ),
 
-	    TP_printk("V=%llx %s u=%d",
+	    TP_printk("V=%llx %s ur=%d",
 		      __entry->vid,
 		      __print_symbolic(__entry->reason, afs_volume_traces),
 		      __entry->ref)
 	    );
 
 TRACE_EVENT(afs_cell,
-	    TP_PROTO(unsigned int cell_debug_id, int usage, int active,
+	    TP_PROTO(unsigned int cell_debug_id, int ref, int active,
 		     enum afs_cell_trace reason),
 
-	    TP_ARGS(cell_debug_id, usage, active, reason),
+	    TP_ARGS(cell_debug_id, ref, active, reason),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		cell		)
-		    __field(int,			usage		)
+		    __field(int,			ref		)
 		    __field(int,			active		)
 		    __field(int,			reason		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->cell = cell_debug_id;
-		    __entry->usage = usage;
+		    __entry->ref = ref;
 		    __entry->active = active;
 		    __entry->reason = reason;
 			   ),
 
-	    TP_printk("L=%08x %s u=%d a=%d",
+	    TP_printk("L=%08x %s r=%d a=%d",
 		      __entry->cell,
 		      __print_symbolic(__entry->reason, afs_cell_traces),
-		      __entry->usage,
+		      __entry->ref,
 		      __entry->active)
 	    );