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From:   Song Liu <song@kernel.org>
Date:   Sun, 27 Dec 2020 13:57:12 -0800
Message-ID: <CAPhsuW5Fs9Zz+-2ZEZQe3g5jen4SiHNf7sRtYCN0w4TBGZ1Vsw@mail.gmail.com>
Subject: Re: PROBLEM: Recent raid10 block discard patchset causes filesystem
 corruption on fstrim
To:     Xiao Ni <xni@redhat.com>
Cc:     Song Liu <songliubraving@fb.com>,
        Matthew Ruffell <matthew.ruffell@canonical.com>,
        linux-raid <linux-raid@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, Coly Li <colyli@suse.de>,
        Guoqing Jiang <guoqing.jiang@cloud.ionos.com>,
        "khalid.elmously@canonical.com" <khalid.elmously@canonical.com>,
        Jay Vosburgh <jay.vosburgh@canonical.com>
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Hi Xiao,

On Thu, Dec 24, 2020 at 2:18 AM Xiao Ni <xni@redhat.com> wrote:
>
>
>
[...]
>
> [  789.709501] discard bio start : 70968, size : 191176
> [  789.709507] first stripe index 69, start disk index 0, start disk
> offset 70968
> [  789.709509] last stripe index 256, end disk index 0, end disk offset
> 262144
> [  789.709511] disk 0, dev start : 70968, dev end : 262144
> [  789.709515] disk 1, dev start : 70656, dev end : 262144
>
> For example, in this test case, it has 2 near copies. The
> start_disk_offset for the first disk is 70968.
> It should use the same offset address for second disk. But it uses the
> start address of this chunk.
> It discard more region. The patch in the attachment can fix this
> problem. It split the region that
> doesn't align with chunk size.
>
> There is another problem. The stripe size should be calculated
> differently for near layout and far layout.
>
> @Song, do you want me to use a separate patch for this fix, or fix this
> in the original patch?

Please fold in the changes in the original patches and resend the whole
set.

Thanks,
Song

>
> Merry Christmas
> Xiao
>