mm/slub: Remove the ULONG_MAX stack trace hackery

No architecture terminates the stack trace with ULONG_MAX anymore. Remove
the cruft.

While at it remove the pointless loop of clearing the stack array
completely. It's sufficient to clear the last entry as the consumers break
out on the first zeroed entry anyway.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Link: https://lkml.kernel.org/r/20190410103644.574058244@linutronix.de

diff --git a/mm/slub.c b/mm/slub.c
index d30ede89f4a6499a07e69baf981b755d0a1b4400..e2ccd12b6faa34c5ba573b64ed15149d89e9b929 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -553,7 +553,6 @@ static void set_track(struct kmem_cache *s, void *object,
        if (addr) {
 #ifdef CONFIG_STACKTRACE
                struct stack_trace trace;
-               int i;
 
                trace.nr_entries = 0;
                trace.max_entries = TRACK_ADDRS_COUNT;
@@ -563,20 +562,16 @@ static void set_track(struct kmem_cache *s, void *object,
                save_stack_trace(&trace);
                metadata_access_disable();
 
-               /* See rant in lockdep.c */
-               if (trace.nr_entries != 0 &&
-                   trace.entries[trace.nr_entries - 1] == ULONG_MAX)
-                       trace.nr_entries--;
-
-               for (i = trace.nr_entries; i < TRACK_ADDRS_COUNT; i++)
-                       p->addrs[i] = 0;
+               if (trace.nr_entries < TRACK_ADDRS_COUNT)
+                       p->addrs[trace.nr_entries] = 0;
 #endif
                p->addr = addr;
                p->cpu = smp_processor_id();
                p->pid = current->pid;
                p->when = jiffies;
-       } else
+       } else {
                memset(p, 0, sizeof(struct track));
+       }
 }
 
 static void init_tracking(struct kmem_cache *s, void *object)