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From:   Tomas Hlavaty <tom@logand.com>
To:     Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc:     linux-nilfs <linux-nilfs@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct
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Date:   Thu, 23 Jan 2020 13:31:38 +0100
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Hi Ryusuke,

>> 2) Can you mount the corrupted(?) partition from a recent version of
>> kernel ?

this will take me some time to figure out

>> 3) Does read-only mount option (-r) work to avoid the crash ?

ro mount doesn't seem to crash

at least after mounting the partition read-only
- running lscp
- running sudo find . -type f inside the mounted partition
- cat <some random file on the nilfs partition>
does not crash

the crash i was seeing was during rsync (writing i guess)

Other info that might be relevant:

- the nilfs partition was on top of luks
- the corruption happened probably during shutdown
  the shutdown hanged for a long time waiting for nilfs
  disk (iirc it waits for 1m30s) and even after that it did
  not finish so i turned the computer off without waiting
  further.  after new start, i got the crash
- i got the same problem on another disk recently

Regards,

Tomas