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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: Christian Brauner <brauner@kernel.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Beau Belgrave 2023-06-01 15:49:28 -07:00 committed by Steven Rostedt (Google)
parent 42187bdc3c
commit ed0e0ae0c9
1 changed files with 5 additions and 37 deletions
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42
kernel/trace/trace_events_user.c
View File

@ -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);