linux-kernel - Re: [PATCH] mm: slub: remove dead and buggy code from sysfs_slab

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Date:   Sun, 9 Oct 2022 20:54:36 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: slub: remove dead and buggy code from
 sysfs_slab_add()

On Fri, 30 Sep 2022, Rasmus Villemoes wrote:

> The function sysfs_slab_add() has two callers:
> 
> One is slab_sysfs_init(), which first initializes slab_kset, and only
> when that succeeds sets slab_state to FULL, and then proceeds to call
> sysfs_slab_add() for all previously created slabs.
> 
> The other is __kmem_cache_create(), but only after a
> 
> 	if (slab_state <= UP)
> 		return 0;
> 
> check.
> 
> So in other words, sysfs_slab_add() is never called without
> slab_kset (aka the return value of cache_kset()) being non-NULL.
> 
> And this is just as well, because if we ever did take this path and
> called kobject_init(&s->kobj), and then later when called again from
> slab_sysfs_init() would end up calling kobject_init_and_add(), we
> would hit
> 
> 	if (kobj->state_initialized) {
> 		/* do not error out as sometimes we can recover */
> 		pr_err("kobject (%p): tried to init an initialized object, something is seriously wrong.\n",
> 		dump_stack();
> 	}
> 
> in kobject.c.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>

Acked-by: David Rientjes <rientjes@...gle.com>