mm/kmemleak: use object_cache instead of kmemleak_initialized to check in set_track_prepare()

Patch series "mm/kmemleak: use object_cache instead of
kmemleak_initialized", v3.

Use object_cache instead of kmemleak_initialized to check in
set_track_prepare(), so that memory leaks after kmemleak_init() can be
recorded and Rename kmemleak_initialized to kmemleak_late_initialized

unreferenced object 0xc674ca80 (size 64):
 comm "swapper/0", pid 1, jiffies 4294938337 (age 204.880s)
 hex dump (first 32 bytes):
  80 55 75 c6 80 54 75 c6 00 55 75 c6 80 52 75 c6 .Uu..Tu..Uu..Ru.
  00 53 75 c6 00 00 00 00 00 00 00 00 00 00 00 00 .Su..........


This patch (of 2):

kmemleak_initialized is set in kmemleak_late_init(), which also means that
there is no call trace which object's memory leak is before
kmemleak_late_init(), so use object_cache instead of kmemleak_initialized
to check in set_track_prepare() to avoid no call trace records when there
is a memory leak in the code between kmemleak_init() and
kmemleak_late_init().

unreferenced object 0xc674ca80 (size 64):
 comm "swapper/0", pid 1, jiffies 4294938337 (age 204.880s)
 hex dump (first 32 bytes):
  80 55 75 c6 80 54 75 c6 00 55 75 c6 80 52 75 c6 .Uu..Tu..Uu..Ru.
  00 53 75 c6 00 00 00 00 00 00 00 00 00 00 00 00 .Su..........

Link: https://lkml.kernel.org/r/20230815144128.3623103-1-xiaolei.wang@windriver.com
Link: https://lkml.kernel.org/r/20230815144128.3623103-2-xiaolei.wang@windriver.com
Fixes: 56a61617 ("mm: use stack_depot for recording kmemleak's backtrace")
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kmemleak.c

@@ -610,7 +610,12 @@ static noinline depot_stack_handle_t set_track_prepare(void)
 	unsigned long entries[MAX_TRACE];
 	unsigned int nr_entries;
 
-	if (!kmemleak_initialized)
+	/*
+	 * Use object_cache to determine whether kmemleak_init() has
+	 * been invoked. stack_depot_early_init() is called before
+	 * kmemleak_init() in mm_core_init().
+	 */
+	if (!object_cache)
 		return 0;
 	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
 	trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);