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 <20210921195632.GR9286@twin.jikos.cz>
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From:   Su Yue <l@damenly.su>
To:     dsterba@suse.cz
Cc:     Chris Murphy <lists@colorremedies.com>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: 5.15.0-rc1 armv7hl Workqueue: btrfs-delalloc btrfs_work_helper
 PC is at mmiocpy LR is at ZSTD_compressStream
Date:   Mon, 04 Oct 2021 19:57:25 +0800
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On Tue 21 Sep 2021 at 21:56, David Sterba <dsterba@suse.cz> wrote:

> On Mon, Sep 20, 2021 at 06:13:07PM -0600, Chris Murphy wrote:
>> https://kojipkgs.fedoraproject.org//work/tasks/8820/75928820/oz-armhfp.log
>
>> 00:09:50,679 EMERG kernel:[<c08bd768>] (mmiocpy) from 
>> [<c089c314>]
>> (ZSTD_compressStream+0x184/0x294)
>
> The last function to fail is inside ZSTD implementation in 
> kernel.
> If btrfs passes wrong data to zstd we'd see that also on non-arm 
> builds,
> so guessing by mmiocpy as a copy-something function it could be 
> some
> sort of alignment problem that works on x86_64 but throws an 
> exception
> on arm as it's stricter about alignment.

It's about 32bits platforms. There is another report about x86 
cpu.
And it's reproduciable by running btrfs/004 (lzo and zstd)in x86 
VM.
In my arm64, all things are fine.
And the bisection result is the highmem related patchset
'[PATCH 0/6] Remove highmem allocations, kmap/kunmap'.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=214565

--
Su