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From:   Joel Fernandes <joel@joelfernandes.org>
Mime-Version: 1.0 (1.0)
Subject: Re: amusing SLUB compaction bug when CC_OPTIMIZE_FOR_SIZE
Date:   Wed, 28 Sep 2022 15:53:04 -0400
Message-Id: <66C933BF-D5AC-490F-81DC-601BE1DEEE60@joelfernandes.org>
References: <YzSK3LJst80JkP4q@hyeyoo>
Cc:     Hugh Dickins <hughd@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
In-Reply-To: <YzSK3LJst80JkP4q@hyeyoo>
To:     Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>
Precedence: bulk


> On Sep 28, 2022, at 1:56 PM, Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote:
>=20
> =EF=BB=BFOn Wed, Sep 28, 2022 at 06:20:10PM +0200, Vlastimil Babka wrote:
[..]
>>>> Thank you for report!
>>>>=20
>>>> That should be due to commit 65505d1f2338e7
>>>> ("mm/sl[au]b: rearrange struct slab fields to allow larger rcu_head")
>>>> as now rcu_head can use some bits that shares with mapping.
>>>>=20
>>>> Hmm IMO we have two choices...
>>>>=20
>>>> 1. simply drop the commit as it's only for debugging (RCU folks may not=
 like [1])
>>>=20
>>> Yeah definitely don't like this option as patches are out that depend on=

>>> this (not yet merged though). :-)
>>=20
>> But we'll have to do that for now and postpone to 6.2 I'm afraid as merge=

>> window for 6.1 is too close to have confidence in any solution that we ca=
me
>> up this moment.

I am ok with your postponing till then, gives me time to get other patches i=
n, in the mean while :-)

Thanks again for your work on this,

 - Joel