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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH] mm: slub: remove dead and buggy code from sysfs_slab_add() Content-Language: en-US To: Rasmus Villemoes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220930084742.771804-1-linux@rasmusvillemoes.dk> From: Vlastimil Babka In-Reply-To: <20220930084742.771804-1-linux@rasmusvillemoes.dk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=e5jz93ek; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=GvYODW4J; spf=pass (imf25.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665735329; a=rsa-sha256; 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spf=pass (imf25.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspamd-Server: rspam07 X-HE-Tag: 1665735328-73250 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/30/22 10:47, 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 Thanks, added to slab.git for-6.2/slub-sysfs > --- > mm/slub.c | 5 ----- > 1 file changed, 5 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 4b98dff9be8e..04a7f75a7b1f 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5937,11 +5937,6 @@ static int sysfs_slab_add(struct kmem_cache *s) > struct kset *kset = cache_kset(s); > int unmergeable = slab_unmergeable(s); > > - if (!kset) { > - kobject_init(&s->kobj, &slab_ktype); > - return 0; > - } > - > if (!unmergeable && disable_higher_order_debug && > (slub_debug & DEBUG_METADATA_FLAGS)) > unmergeable = 1;