linux-kernel - [RFC patch 11/41] mm/slub: Remove the ULONG

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Message-Id: <20190410103644.574058244@linutronix.de>
Date:   Wed, 10 Apr 2019 12:28:05 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>, linux-mm@...ck.org,
        David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>
Subject: [RFC patch 11/41] 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@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: linux-mm@...ck.org
Cc: David Rientjes <rientjes@...gle.com>
Cc: Christoph Lameter <cl@...ux.com>
---
 mm/slub.c |   13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -553,7 +553,6 @@ static void set_track(struct kmem_cache
 	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
 		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)