afs: Add a tracepoint to track the lifetime of the afs_volume struct

Add a tracepoint to track the lifetime of the afs_volume struct.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/cell.c

@@ -482,7 +482,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 
 	ASSERTCMP(atomic_read(&cell->usage), ==, 0);
 
-	afs_put_volume(cell->net, cell->root_volume);
+	afs_put_volume(cell->net, cell->root_volume, afs_volume_trace_put_cell_root);
 	afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers));
 	afs_put_cell(cell->net, cell->alias_of);
 	key_put(cell->anonymous_key);

fs/afs/fs_operation.c

@@ -36,7 +36,7 @@ struct afs_operation *afs_alloc_operation(struct key *key, struct afs_volume *vo
 	}
 
 	op->key		= key;
-	op->volume	= afs_get_volume(volume);
+	op->volume	= afs_get_volume(volume, afs_volume_trace_get_new_op);
 	op->net		= volume->cell->net;
 	op->cb_v_break	= volume->cb_v_break;
 	op->debug_id	= atomic_inc_return(&afs_operation_debug_counter);
@@ -233,7 +233,7 @@ int afs_put_operation(struct afs_operation *op)
 	afs_end_cursor(&op->ac);
 	afs_put_cb_interest(op->net, op->cbi);
 	afs_put_serverlist(op->net, op->server_list);
-	afs_put_volume(op->net, op->volume);
+	afs_put_volume(op->net, op->volume, afs_volume_trace_put_put_op);
 	kfree(op);
 	return ret;
 }

fs/afs/internal.h

@@ -1429,17 +1429,11 @@ extern struct afs_vlserver_list *afs_extract_vlserver_list(struct afs_cell *,
 /*
  * volume.c
  */
-static inline struct afs_volume *afs_get_volume(struct afs_volume *volume)
-{
-	if (volume)
-		atomic_inc(&volume->usage);
-	return volume;
-}
-
 extern struct afs_volume *afs_create_volume(struct afs_fs_context *);
 extern void afs_activate_volume(struct afs_volume *);
 extern void afs_deactivate_volume(struct afs_volume *);
-extern void afs_put_volume(struct afs_net *, struct afs_volume *);
+extern struct afs_volume *afs_get_volume(struct afs_volume *, enum afs_volume_trace);
+extern void afs_put_volume(struct afs_net *, struct afs_volume *, enum afs_volume_trace);
 extern int afs_check_volume_status(struct afs_volume *, struct afs_operation *);
 
 /*

fs/afs/super.c

@@ -376,7 +376,8 @@ static int afs_validate_fc(struct fs_context *fc)
 		ctx->key = key;
 
 		if (ctx->volume) {
-			afs_put_volume(ctx->net, ctx->volume);
+			afs_put_volume(ctx->net, ctx->volume,
+				       afs_volume_trace_put_validate_fc);
 			ctx->volume = NULL;
 		}
 
@@ -507,7 +508,8 @@ static struct afs_super_info *afs_alloc_sbi(struct fs_context *fc)
 			as->dyn_root = true;
 		} else {
 			as->cell = afs_get_cell(ctx->cell);
-			as->volume = afs_get_volume(ctx->volume);
+			as->volume = afs_get_volume(ctx->volume,
+						    afs_volume_trace_get_alloc_sbi);
 		}
 	}
 	return as;
@@ -517,7 +519,7 @@ static void afs_destroy_sbi(struct afs_super_info *as)
 {
 	if (as) {
 		struct afs_net *net = afs_net(as->net_ns);
-		afs_put_volume(net, as->volume);
+		afs_put_volume(net, as->volume, afs_volume_trace_put_destroy_sbi);
 		afs_put_cell(net, as->cell);
 		put_net(as->net_ns);
 		kfree(as);
@@ -605,7 +607,7 @@ static void afs_free_fc(struct fs_context *fc)
 	struct afs_fs_context *ctx = fc->fs_private;
 
 	afs_destroy_sbi(fc->s_fs_info);
-	afs_put_volume(ctx->net, ctx->volume);
+	afs_put_volume(ctx->net, ctx->volume, afs_volume_trace_put_free_fc);
 	afs_put_cell(ctx->net, ctx->cell);
 	key_put(ctx->key);
 	kfree(ctx);

fs/afs/vl_alias.c

@@ -193,7 +193,8 @@ static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
 	read_lock(&p->proc_lock);
 	if (!list_empty(&p->proc_volumes))
 		pvol = afs_get_volume(list_first_entry(&p->proc_volumes,
-						       struct afs_volume, proc_link));
+						       struct afs_volume, proc_link),
+				      afs_volume_trace_get_query_alias);
 	read_unlock(&p->proc_lock);
 	if (!pvol)
 		return 0;
@@ -203,7 +204,7 @@ static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
 	/* And see if it's in the new cell. */
 	volume = afs_sample_volume(cell, key, pvol->name, pvol->name_len);
 	if (IS_ERR(volume)) {
-		afs_put_volume(cell->net, pvol);
+		afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
 		if (PTR_ERR(volume) != -ENOMEDIUM)
 			return PTR_ERR(volume);
 		/* That volume is not in the new cell, so not an alias */
@@ -221,8 +222,8 @@ static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
 		rcu_read_unlock();
 	}
 
-	afs_put_volume(cell->net, volume);
-	afs_put_volume(cell->net, pvol);
+	afs_put_volume(cell->net, volume, afs_volume_trace_put_query_alias);
+	afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
 	return ret;
 }
 

fs/afs/volume.c

@@ -52,6 +52,7 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 
 	refcount_set(&slist->usage, 1);
 	rcu_assign_pointer(volume->servers, slist);
+	trace_afs_volume(volume->vid, 1, afs_volume_trace_alloc);
 	return volume;
 
 error_1:
@@ -158,20 +159,38 @@ static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
 
 	afs_put_serverlist(net, rcu_access_pointer(volume->servers));
 	afs_put_cell(net, volume->cell);
+	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
+			 afs_volume_trace_free);
 	kfree(volume);
 
 	_leave(" [destroyed]");
 }
 
 /*
- * Drop a reference on a volume record.
+ * Get a reference on a volume record.
  */
-void afs_put_volume(struct afs_net *net, struct afs_volume *volume)
+struct afs_volume *afs_get_volume(struct afs_volume *volume,
+				  enum afs_volume_trace reason)
 {
 	if (volume) {
-		_enter("%s", volume->name);
+		int u = atomic_inc_return(&volume->usage);
+		trace_afs_volume(volume->vid, u, reason);
+	}
+	return volume;
+}
+
 
-		if (atomic_dec_and_test(&volume->usage))
+/*
+ * Drop a reference on a volume record.
+ */
+void afs_put_volume(struct afs_net *net, struct afs_volume *volume,
+		    enum afs_volume_trace reason)
+{
+	if (volume) {
+		afs_volid_t vid = volume->vid;
+		int u = atomic_dec_return(&volume->usage);
+		trace_afs_volume(vid, u, reason);
+		if (u == 0)
 			afs_destroy_volume(net, volume);
 	}
 }

include/trace/events/afs.h

@@ -50,6 +50,23 @@ enum afs_server_trace {
 	afs_server_trace_update,
 };
 
+enum afs_volume_trace {
+	afs_volume_trace_alloc,
+	afs_volume_trace_free,
+	afs_volume_trace_get_alloc_sbi,
+	afs_volume_trace_get_cell_insert,
+	afs_volume_trace_get_new_op,
+	afs_volume_trace_get_query_alias,
+	afs_volume_trace_put_cell_dup,
+	afs_volume_trace_put_cell_root,
+	afs_volume_trace_put_destroy_sbi,
+	afs_volume_trace_put_free_fc,
+	afs_volume_trace_put_put_op,
+	afs_volume_trace_put_query_alias,
+	afs_volume_trace_put_validate_fc,
+	afs_volume_trace_remove,
+};
+
 enum afs_fs_operation {
 	afs_FS_FetchData		= 130,	/* AFS Fetch file data */
 	afs_FS_FetchACL			= 131,	/* AFS Fetch file ACL */
@@ -262,6 +279,22 @@ enum afs_cb_break_reason {
 	EM(afs_server_trace_put_uuid_rsq,	"PUT u-req") \
 	E_(afs_server_trace_update,		"UPDATE")
 
+#define afs_volume_traces \
+	EM(afs_volume_trace_alloc,		"ALLOC         ") \
+	EM(afs_volume_trace_free,		"FREE          ") \
+	EM(afs_volume_trace_get_alloc_sbi,	"GET sbi-alloc ") \
+	EM(afs_volume_trace_get_cell_insert,	"GET cell-insrt") \
+	EM(afs_volume_trace_get_new_op,		"GET op-new    ") \
+	EM(afs_volume_trace_get_query_alias,	"GET cell-alias") \
+	EM(afs_volume_trace_put_cell_dup,	"PUT cell-dup  ") \
+	EM(afs_volume_trace_put_cell_root,	"PUT cell-root ") \
+	EM(afs_volume_trace_put_destroy_sbi,	"PUT sbi-destry") \
+	EM(afs_volume_trace_put_free_fc,	"PUT fc-free   ") \
+	EM(afs_volume_trace_put_put_op,		"PUT op-put    ") \
+	EM(afs_volume_trace_put_query_alias,	"PUT cell-alias") \
+	EM(afs_volume_trace_put_validate_fc,	"PUT fc-validat") \
+	E_(afs_volume_trace_remove,		"REMOVE        ")
+
 #define afs_fs_operations \
 	EM(afs_FS_FetchData,			"FS.FetchData") \
 	EM(afs_FS_FetchStatus,			"FS.FetchStatus") \
@@ -1302,6 +1335,29 @@ TRACE_EVENT(afs_server,
 		      __entry->active)
 	    );
 
+TRACE_EVENT(afs_volume,
+	    TP_PROTO(afs_volid_t vid, int ref, enum afs_volume_trace reason),
+
+	    TP_ARGS(vid, ref, reason),
+
+	    TP_STRUCT__entry(
+		    __field(afs_volid_t,		vid		)
+		    __field(int,			ref		)
+		    __field(enum afs_volume_trace,	reason		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->vid = vid;
+		    __entry->ref = ref;
+		    __entry->reason = reason;
+			   ),
+
+	    TP_printk("V=%llx %s u=%d",
+		      __entry->vid,
+		      __print_symbolic(__entry->reason, afs_volume_traces),
+		      __entry->ref)
+	    );
+
 #endif /* _TRACE_AFS_H */
 
 /* This part must be outside protection */