linux-kernel - Re: [PATCH] slub: Fix sysfs duplicate filename creation when slub

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Date:   Fri, 10 Nov 2017 07:51:52 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Christopher Lameter <cl@...ux.com>
CC:     Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <wsd_upstream@...iatek.com>, <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] slub: Fix sysfs duplicate filename creation when
 slub_debug=O

On Thu, 2017-11-09 at 09:49 -0600, Christopher Lameter wrote:
> On Thu, 9 Nov 2017, Miles Chen wrote:
> 
> > In this fix patch, it disables slab merging if SLUB_DEBUG=O and
> > CONFIG_SLUB_DEBUG_ON=y but the debug features are disabled by the
> > disable_higher_order_debug logic and it holds the "slab merging is off
> > if any debug features are enabled" behavior.
> 
> Sounds good. Where is the patch?
> 
> 
Sorry for confusing, I meant the original patch of this thread :-)

By checking disable_higher_order_debug & (slub_debug &
SLAB_NEVER_MERGE), we can detect if a cache is unmergeable but become
mergeable because the disable_higher_order_debug=1 logic. Those kind of
caches should be keep unmergeable.


diff --git a/mm/slub.c b/mm/slub.c
index 1efbb812..8cbf9f7 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5704,6 +5704,10 @@ static int sysfs_slab_add(struct kmem_cache *s)
                return 0;
        }
 
+       if (!unmergeable && disable_higher_order_debug &&
+                       (slub_debug & SLAB_NEVER_MERGE))
+               unmergeable = 1;
+
        if (unmergeable) {
                /*
                 * Slabcache can never be merged so we can use the name
proper.