Commit ed0e0ae0 authored by Beau Belgrave's avatar Beau Belgrave Committed by Steven Rostedt (Google)
Browse files

tracing/user_events: Remove user_ns walk for groups 

During discussions it was suggested that user_ns is not a good place to
try to attach a tracing namespace. The current code has stubs to enable
that work that are very likely to change and incur a performance cost.

Remove the user_ns walk when creating a group and determining the system
name to use, since it's unlikely user_ns will be used in the future.

Link: https://lore.kernel.org/all/20230601-urenkel-holzofen-cd9403b9cadd@brauner/
Link: https://lore.kernel.org/linux-trace-kernel/20230601224928.301-1-beaub@linux.microsoft.com



Suggested-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarBeau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 42187bdc

kernel/trace/trace_events_user.c

+5 −37
Original line number Diff line number Diff line
@@ -182,21 +182,11 @@ static void user_event_group_destroy(struct user_event_group *group) 
	kfree(group);

}



static char *user_event_group_system_name(struct user_namespace *user_ns)

static char *user_event_group_system_name(void)

{

	char *system_name;

	int len = sizeof(USER_EVENTS_SYSTEM) + 1;



	if (user_ns != &init_user_ns) {

		/*

		 * Unexpected at this point:

		 * We only currently support init_user_ns.

		 * When we enable more, this will trigger a failure so log.

		 */

		pr_warn("user_events: Namespace other than init_user_ns!\n");

		return NULL;

	}



	system_name = kmalloc(len, GFP_KERNEL);



	if (!system_name)
@@ -207,34 +197,12 @@ static char *user_event_group_system_name(struct user_namespace *user_ns) 
	return system_name;

}



static inline struct user_event_group

*user_event_group_from_user_ns(struct user_namespace *user_ns)

{

	if (user_ns == &init_user_ns)

		return init_group;



	return NULL;

}



static struct user_event_group *current_user_event_group(void)

{

	struct user_namespace *user_ns = current_user_ns();

	struct user_event_group *group = NULL;



	while (user_ns) {

		group = user_event_group_from_user_ns(user_ns);



		if (group)

			break;



		user_ns = user_ns->parent;

	}



	return group;

	return init_group;

}



static struct user_event_group

*user_event_group_create(struct user_namespace *user_ns)

static struct user_event_group *user_event_group_create(void)

{

	struct user_event_group *group;
@@ -243,7 +211,7 @@ static struct user_event_group 
	if (!group)

		return NULL;



	group->system_name = user_event_group_system_name(user_ns);

	group->system_name = user_event_group_system_name();



	if (!group->system_name)

		goto error;
@@ -2603,7 +2571,7 @@ static int __init trace_events_user_init(void) 
	if (!fault_cache)

		return -ENOMEM;



	init_group = user_event_group_create(&init_user_ns);

	init_group = user_event_group_create();



	if (!init_group) {

		kmem_cache_destroy(fault_cache);