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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 25 Sep 2020 10:17:36 -0700
Message-ID: <CAHk-=whAe_n6JDyu40A15vnWs5PTU0QYX6t6-TbNeefanau6MA@mail.gmail.com>
Subject: Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling
 into blk_mq_get_driver_tag
To:     Ming Lei <ming.lei@redhat.com>
Cc:     "Theodore Y. Ts'o" <tytso@mit.edu>, Jens Axboe <axboe@kernel.dk>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-block <linux-block@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, Roman Gushchin <guro@fb.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Shakeel Butt <shakeelb@google.com>
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On Fri, Sep 25, 2020 at 9:19 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> git bisect shows the first bad commit:
>
>         [10befea91b61c4e2c2d1df06a2e978d182fcf792] mm: memcg/slab: use a single set of
>                 kmem_caches for all allocations
>
> And I have double checked that the above commit is really the first bad
> commit for the list corruption issue of 'list_del corruption, ffffe1c241b00408->next
> is LIST_POISON1 (dead000000000100)',

Thet commit doesn't revert cleanly, but I think that's purely because
we'd also need to revert

  849504809f86 ("mm: memcg/slab: remove unused argument by charge_slab_page()")
  74d555bed5d0 ("mm: slab: rename (un)charge_slab_page() to
(un)account_slab_page()")

too.

Can you verify that a

    git revert 74d555bed5d0 849504809f86 10befea91b61

on top of current -git makes things work for you again?

I'm going to do an rc8 this release simply because we have another VM
issue that I hope to get fixed - but there we know what the problem
and the fix _is_, it just needs some care.

So if Roman (or somebody else) can see what's wrong and we can fix
this quickly, we don't need to go down the revert path, but ..

                  Linus