Re: [PATCH] mm, slub: do not add duplicate sysfs

[Christoph Lameter <cl@linux.com>]

Maybe something like this may be a proper fix:

Subject: slub: Disable tracing of mergeable slabs

Tracing of mergeable slabs is confusing since the objects
of multiple slab caches will be traced. Moreover this creates
a situation where a mergeable slab will become unmergeable.

If tracing is desired then it may be best to switch merging
off for starters.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c	2014-08-08 11:52:30.039681592 -0500
+++ linux/mm/slub.c	2014-08-27 10:30:16.508108726 -0500
@@ -4604,6 +4604,14 @@ static ssize_t trace_show(struct kmem_ca
 static ssize_t trace_store(struct kmem_cache *s, const char *buf,
 							size_t length)
 {
+	/*
+	 * Tracing a merged cache is going to give confusing results
+	 * as well as cause other issues like converting a mergeable
+	 * cache into an umergeable one.
+	 */
+	if (s->refcount > 1)
+		return -EINVAL;
+
 	s->flags &= ~SLAB_TRACE;
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;

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