[tip:core/stacktrace] mm/slub: Remove the ULONG_MAX stack trace hackery

[tip-bot for Thomas Gleixner]

Commit-ID:  b8ca7ff7731f57b256fcc13a9b7d4913f5282e5c
Gitweb:     https://git.kernel.org/tip/b8ca7ff7731f57b256fcc13a9b7d4913f5282e5c
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 10 Apr 2019 12:28:05 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Sun, 14 Apr 2019 19:58:30 +0200

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@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20190410103644.574058244@xxxxxxxxxxxxx

---
 mm/slub.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index d30ede89f4a6..e2ccd12b6faa 100644
--- 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)