mm: mmap_lock: check trace_mmap_lock_$type_enabled() instead of regcount

mm: mmap_lock: check trace_mmap_lock_$type_enabled() instead of regcount

Since 7d6be67cfdd4 ("mm: mmap_lock: replace get_memcg_path_buf() with
on-stack buffer") we use trace_mmap_lock_reg()/unreg() only to maintain an
atomic reg_refcount which is checked to avoid performing
get_mm_memcg_path() in case none of the tracepoints using it is enabled.

This can be achieved directly by putting all the work needed for the
tracepoint behind the trace_mmap_lock_##type##_enabled(), as suggested by
Documentation/trace/tracepoints.rst and with the following advantages:

- uses the tracepoint's static key instead of evaluating a branch

- the check tracepoint specific, not shared by all of them

- we can get rid of trace_mmap_lock_reg()/unreg() completely

Thus use the trace_..._enabled() check and remove unnecessary code.

Link: https://lkml.kernel.org/r/20241105113456.95066-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>