afs: Trace afs_server usage

Add a tracepoint (afs_server) to track the afs_server object usage count.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/callback.c

@@ -48,7 +48,7 @@ static struct afs_cb_interest *afs_create_interest(struct afs_server *server,
 	refcount_set(&new->usage, 1);
 	new->sb = vnode->vfs_inode.i_sb;
 	new->vid = vnode->volume->vid;
-	new->server = afs_get_server(server);
+	new->server = afs_get_server(server, afs_server_trace_get_new_cbi);
 	INIT_HLIST_NODE(&new->cb_vlink);
 
 	write_lock(&server->cb_break_lock);
@@ -195,7 +195,7 @@ void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
 			write_unlock(&cbi->server->cb_break_lock);
 			if (vi)
 				kfree_rcu(vi, rcu);
-			afs_put_server(net, cbi->server);
+			afs_put_server(net, cbi->server, afs_server_trace_put_cbi);
 		}
 		kfree_rcu(cbi, rcu);
 	}

fs/afs/cmservice.c

@@ -260,8 +260,11 @@ static void SRXAFSCB_CallBack(struct work_struct *work)
 	 * server holds up change visibility till it receives our reply so as
 	 * to maintain cache coherency.
 	 */
-	if (call->server)
+	if (call->server) {
+		trace_afs_server(call->server, atomic_read(&call->server->usage),
+				 afs_server_trace_callback);
 		afs_break_callbacks(call->server, call->count, call->request);
+	}
 
 	afs_send_empty_reply(call);
 	afs_put_call(call);

fs/afs/fsclient.c

@@ -1915,7 +1915,7 @@ struct afs_call *afs_fs_get_capabilities(struct afs_net *net,
 		return ERR_PTR(-ENOMEM);
 
 	call->key = key;
-	call->server = afs_get_server(server);
+	call->server = afs_get_server(server, afs_server_trace_get_caps);
 	call->server_index = server_index;
 	call->upgrade = true;
 	call->async = true;

fs/afs/internal.h

@@ -518,6 +518,7 @@ struct afs_server {
 	atomic_t		usage;
 	u32			addr_version;	/* Address list version */
 	u32			cm_epoch;	/* Server RxRPC epoch */
+	unsigned int		debug_id;	/* Debugging ID for traces */
 
 	/* file service access */
 	rwlock_t		fs_lock;	/* access lock */
@@ -1244,17 +1245,12 @@ extern void __exit afs_clean_up_permit_cache(void);
  */
 extern spinlock_t afs_server_peer_lock;
 
-static inline struct afs_server *afs_get_server(struct afs_server *server)
-{
-	atomic_inc(&server->usage);
-	return server;
-}
-
 extern struct afs_server *afs_find_server(struct afs_net *,
 					  const struct sockaddr_rxrpc *);
 extern struct afs_server *afs_find_server_by_uuid(struct afs_net *, const uuid_t *);
 extern struct afs_server *afs_lookup_server(struct afs_cell *, struct key *, const uuid_t *);
-extern void afs_put_server(struct afs_net *, struct afs_server *);
+extern struct afs_server *afs_get_server(struct afs_server *, enum afs_server_trace);
+extern void afs_put_server(struct afs_net *, struct afs_server *, enum afs_server_trace);
 extern void afs_manage_servers(struct work_struct *);
 extern void afs_servers_timer(struct timer_list *);
 extern void __net_exit afs_purge_servers(struct afs_net *);

fs/afs/rxrpc.c

@@ -188,7 +188,7 @@ void afs_put_call(struct afs_call *call)
 		if (call->type->destructor)
 			call->type->destructor(call);
 
-		afs_put_server(call->net, call->server);
+		afs_put_server(call->net, call->server, afs_server_trace_put_call);
 		afs_put_cb_interest(call->net, call->cbi);
 		afs_put_addrlist(call->alist);
 		kfree(call->request);

fs/afs/server.c

@@ -17,6 +17,7 @@
 
 static unsigned afs_server_gc_delay = 10;	/* Server record timeout in seconds */
 static unsigned afs_server_update_delay = 30;	/* Time till VLDB recheck in secs */
+static atomic_t afs_server_debug_id;
 
 static void afs_inc_servers_outstanding(struct afs_net *net)
 {
@@ -51,7 +52,7 @@ struct afs_server *afs_find_server(struct afs_net *net,
 
 	do {
 		if (server)
-			afs_put_server(net, server);
+			afs_put_server(net, server, afs_server_trace_put_find_rsq);
 		server = NULL;
 		read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
 
@@ -116,7 +117,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu
 		 * changes.
 		 */
 		if (server)
-			afs_put_server(net, server);
+			afs_put_server(net, server, afs_server_trace_put_uuid_rsq);
 		server = NULL;
 
 		read_seqbegin_or_lock(&net->fs_lock, &seq);
@@ -131,7 +132,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu
 			} else if (diff > 0) {
 				p = p->rb_right;
 			} else {
-				afs_get_server(server);
+				afs_get_server(server, afs_server_trace_get_by_uuid);
 				break;
 			}
 
@@ -202,7 +203,7 @@ static struct afs_server *afs_install_server(struct afs_net *net,
 	ret = 0;
 
 exists:
-	afs_get_server(server);
+	afs_get_server(server, afs_server_trace_get_install);
 	write_sequnlock(&net->fs_lock);
 	return server;
 }
@@ -223,6 +224,7 @@ static struct afs_server *afs_alloc_server(struct afs_net *net,
 		goto enomem;
 
 	atomic_set(&server->usage, 1);
+	server->debug_id = atomic_inc_return(&afs_server_debug_id);
 	RCU_INIT_POINTER(server->addresses, alist);
 	server->addr_version = alist->version;
 	server->uuid = *uuid;
@@ -234,6 +236,7 @@ static struct afs_server *afs_alloc_server(struct afs_net *net,
 	spin_lock_init(&server->probe_lock);
 
 	afs_inc_servers_outstanding(net);
+	trace_afs_server(server, 1, afs_server_trace_alloc);
 	_leave(" = %p", server);
 	return server;
 
@@ -328,10 +331,23 @@ void afs_servers_timer(struct timer_list *timer)
 		afs_dec_servers_outstanding(net);
 }
 
+/*
+ * Get a reference on a server object.
+ */
+struct afs_server *afs_get_server(struct afs_server *server,
+				  enum afs_server_trace reason)
+{
+	unsigned int u = atomic_inc_return(&server->usage);
+
+	trace_afs_server(server, u, reason);
+	return server;
+}
+
 /*
  * Release a reference on a server record.
  */
-void afs_put_server(struct afs_net *net, struct afs_server *server)
+void afs_put_server(struct afs_net *net, struct afs_server *server,
+		    enum afs_server_trace reason)
 {
 	unsigned int usage;
 
@@ -342,7 +358,7 @@ void afs_put_server(struct afs_net *net, struct afs_server *server)
 
 	usage = atomic_dec_return(&server->usage);
 
-	_enter("{%u}", usage);
+	trace_afs_server(server, usage, reason);
 
 	if (likely(usage > 0))
 		return;
@@ -354,6 +370,8 @@ 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->usage),
+			 afs_server_trace_free);
 	afs_put_addrlist(rcu_access_pointer(server->addresses));
 	kfree(server);
 }
@@ -369,7 +387,9 @@ static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 		.index	= alist->preferred,
 		.error	= 0,
 	};
-	_enter("%p", server);
+
+	trace_afs_server(server, atomic_read(&server->usage),
+			 afs_server_trace_give_up_cb);
 
 	if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 		afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
@@ -377,6 +397,8 @@ static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 	wait_var_event(&server->probe_outstanding,
 		       atomic_read(&server->probe_outstanding) == 0);
 
+	trace_afs_server(server, atomic_read(&server->usage),
+			 afs_server_trace_destroy);
 	call_rcu(&server->rcu, afs_server_rcu);
 	afs_dec_servers_outstanding(net);
 }
@@ -396,6 +418,7 @@ static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 		write_seqlock(&net->fs_lock);
 		usage = 1;
 		deleted = atomic_try_cmpxchg(&server->usage, &usage, 0);
+		trace_afs_server(server, usage, afs_server_trace_gc);
 		if (deleted) {
 			rb_erase(&server->uuid_rb, &net->fs_servers);
 			hlist_del_rcu(&server->proc_link);
@@ -518,6 +541,8 @@ static noinline bool afs_update_server_record(struct afs_fs_cursor *fc, struct a
 
 	_enter("");
 
+	trace_afs_server(server, atomic_read(&server->usage), afs_server_trace_update);
+
 	alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
 				    &server->uuid);
 	if (IS_ERR(alist)) {

fs/afs/server_list.c

@@ -20,7 +20,8 @@ void afs_put_serverlist(struct afs_net *net, struct afs_server_list *slist)
 	if (slist && refcount_dec_and_test(&slist->usage)) {
 		for (i = 0; i < slist->nr_servers; i++) {
 			afs_put_cb_interest(net, slist->servers[i].cb_interest);
-			afs_put_server(net, slist->servers[i].server);
+			afs_put_server(net, slist->servers[i].server,
+				       afs_server_trace_put_slist);
 		}
 		kfree(slist);
 	}
@@ -71,7 +72,8 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
 				break;
 		if (j < slist->nr_servers) {
 			if (slist->servers[j].server == server) {
-				afs_put_server(cell->net, server);
+				afs_put_server(cell->net, server,
+					       afs_server_trace_put_slist_isort);
 				continue;
 			}
 

include/trace/events/afs.h

@@ -31,6 +31,26 @@ enum afs_call_trace {
 	afs_call_trace_work,
 };
 
+enum afs_server_trace {
+	afs_server_trace_alloc,
+	afs_server_trace_callback,
+	afs_server_trace_destroy,
+	afs_server_trace_free,
+	afs_server_trace_gc,
+	afs_server_trace_get_by_uuid,
+	afs_server_trace_get_caps,
+	afs_server_trace_get_install,
+	afs_server_trace_get_new_cbi,
+	afs_server_trace_give_up_cb,
+	afs_server_trace_put_call,
+	afs_server_trace_put_cbi,
+	afs_server_trace_put_find_rsq,
+	afs_server_trace_put_slist,
+	afs_server_trace_put_slist_isort,
+	afs_server_trace_put_uuid_rsq,
+	afs_server_trace_update,
+};
+
 enum afs_fs_operation {
 	afs_FS_FetchData		= 130,	/* AFS Fetch file data */
 	afs_FS_FetchACL			= 131,	/* AFS Fetch file ACL */
@@ -219,6 +239,25 @@ enum afs_cb_break_reason {
 	EM(afs_call_trace_wake,			"WAKE ") \
 	E_(afs_call_trace_work,			"WORK ")
 
+#define afs_server_traces \
+	EM(afs_server_trace_alloc,		"ALLOC    ") \
+	EM(afs_server_trace_callback,		"CALLBACK ") \
+	EM(afs_server_trace_destroy,		"DESTROY  ") \
+	EM(afs_server_trace_free,		"FREE     ") \
+	EM(afs_server_trace_gc,			"GC       ") \
+	EM(afs_server_trace_get_by_uuid,	"GET uuid ") \
+	EM(afs_server_trace_get_caps,		"GET caps ") \
+	EM(afs_server_trace_get_install,	"GET inst ") \
+	EM(afs_server_trace_get_new_cbi,	"GET cbi  ") \
+	EM(afs_server_trace_give_up_cb,		"giveup-cb") \
+	EM(afs_server_trace_put_call,		"PUT call ") \
+	EM(afs_server_trace_put_cbi,		"PUT cbi  ") \
+	EM(afs_server_trace_put_find_rsq,	"PUT f-rsq") \
+	EM(afs_server_trace_put_slist,		"PUT slist") \
+	EM(afs_server_trace_put_slist_isort,	"PUT isort") \
+	EM(afs_server_trace_put_uuid_rsq,	"PUT u-req") \
+	E_(afs_server_trace_update,		"UPDATE")
+
 #define afs_fs_operations \
 	EM(afs_FS_FetchData,			"FS.FetchData") \
 	EM(afs_FS_FetchStatus,			"FS.FetchStatus") \
@@ -404,6 +443,7 @@ enum afs_cb_break_reason {
 #define E_(a, b) TRACE_DEFINE_ENUM(a);
 
 afs_call_traces;
+afs_server_traces;
 afs_fs_operations;
 afs_vl_operations;
 afs_edit_dir_ops;
@@ -1240,6 +1280,29 @@ TRACE_EVENT(afs_cb_miss,
 		      __print_symbolic(__entry->reason, afs_cb_break_reasons))
 	    );
 
+TRACE_EVENT(afs_server,
+	    TP_PROTO(struct afs_server *server, int usage, enum afs_server_trace reason),
+
+	    TP_ARGS(server, usage, reason),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		server		)
+		    __field(int,			usage		)
+		    __field(int,			reason		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->server = server->debug_id;
+		    __entry->usage = usage;
+		    __entry->reason = reason;
+			   ),
+
+	    TP_printk("s=%08x %s u=%d",
+		      __entry->server,
+		      __print_symbolic(__entry->reason, afs_server_traces),
+		      __entry->usage)
+	    );
+
 #endif /* _TRACE_AFS_H */
 
 /* This part must be outside protection */