From: Hideki EIRAKU <hdk1983@gmail.com>
To: linux-nilfs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_co
Date: Thu, 30 Apr 2020 21:38:42 +0900 (JST) [thread overview]
Message-ID: <20200430.213842.00392641.hdk1983@gmail.com> (raw)
In-Reply-To: <20200328.182640.1933740379722138264.hermes@ceres.dti.ne.jp>
> In Msg <874kuapb2s.fsf@logand.com>;
> Subject "Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct":
>
>> Tomas Hlavaty <tom@logand.com> writes:
>>>>> 2) Can you mount the corrupted(?) partition from a recent version of
>>>>> kernel ?
>>
>> I tried the following Linux kernel versions:
>>
>> - v4.19
>> - v5.4
>> - v5.5.11
>>
>> and still get the crash
I found conditions to reproduce this issue with Linux 5.7-rc3:
- CONFIG_MEMCG=y *and* CONFIG_BLK_CGROUP=y
- When the NILFS2 file system writes to a device, the device file has
never written by other programs since boot
The following is an example with CONFIG_MEMCG=y and
CONFIG_BLK_CGROUP=y kernel. If you do mkfs and mount it, it works
because the mkfs command has written data to the device file before
mounting:
# mkfs -t nilfs2 /dev/sda1
mkfs.nilfs2 (nilfs-utils 2.2.7)
Start writing file system initial data to the device
Blocksize:4096 Device:/dev/sda1 Device Size:267386880
File system initialization succeeded !!
# mount /dev/sda1 /mnt
# touch /mnt
# sync
#
Loopback mount seems to be the same - if you do losetup, mkfs and
mount on a loopback device, it works:
# losetup /dev/loop0 foo
# mkfs -t nilfs2 /dev/loop0
mkfs.nilfs2 (nilfs-utils 2.2.7)
Start writing file system initial data to the device
Blocksize:4096 Device:/dev/loop0 Device Size:267386880
File system initialization succeeded !!
# mount /dev/sda1 /mnt
# touch /mnt
# sync
#
But if you do mkfs on a file and use mount -o loop, it may fail,
depending on whether the loopback device assigned by the mount command
was used or not before mounting:
# /sbin/mkfs.nilfs2 ./foo
mkfs.nilfs2 (nilfs-utils 2.2.7)
Start writing file system initial data to the device
Blocksize:4096 Device:./foo Device Size:268435456
File system initialization succeeded !!
# mount -o loop ./foo /mnt
[ 36.371331] NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
# touch /mnt
# sync
[ 40.252869] BUG: kernel NULL pointer dereference, address: 00000000000000a8
(snip)
After reboot, it fails:
# mount /dev/sda1 /mnt
[ 14.021188] NILFS (sda1): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
# touch /mnt
# sync
[ 20.576309] BUG: kernel NULL pointer dereference, address: 00000000000000a8
(snip)
But if you do dummy write to the device file before mounting, it
works:
# dd if=/dev/sda1 of=/dev/sda1 count=1
1+0 records in
1+0 records out
512 bytes copied, 0.0135982 s, 37.7 kB/s
# mount /dev/sda1 /mnt
[ 52.604560] NILFS (sda1): mounting unchecked fs
[ 52.613335] NILFS (sda1): recovery complete
[ 52.613877] NILFS (sda1): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
# touch /mnt
# sync
#
# losetup /dev/loop0 foo
# dd if=/dev/loop0 of=/dev/loop0 count=1
1+0 records in
1+0 records out
512 bytes copied, 0.0243797 s, 21.0 kB/s
# mount /dev/loop0 /mnt
[ 271.915595] NILFS (loop0): mounting unchecked fs
[ 272.049603] NILFS (loop0): recovery complete
[ 272.049724] NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
# touch /mnt
# sync
#
I think the dummy write is a simple workaround for now, unless
mounting NILFS2 at boot time. But I have been using NILFS2 /home for
years, I would like to know better workarounds.
next prev parent reply other threads:[~2020-04-30 12:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-17 17:34 BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct Tomas Hlavaty
2019-11-18 16:51 ` Ryusuke Konishi
2019-11-19 6:04 ` Viacheslav Dubeyko
2020-01-23 13:00 ` Tomas Hlavaty
2019-12-19 21:02 ` Tomas Hlavaty
2020-01-23 12:31 ` Tomas Hlavaty
2020-03-27 6:26 ` Tomas Hlavaty
[not found] ` <CAKFNMomjWkNvHvHkEp=Jv_BiGPNj=oLEChyoXX1yCj5xctAkMA@mail.gmail.com>
2020-03-28 9:26 ` ARAI Shun-ichi
2020-04-30 12:38 ` Hideki EIRAKU [this message]
2020-04-30 15:27 ` BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_co Tom
2020-05-31 17:49 ` Ryusuke Konishi
[not found] ` <20200601024013.1296-1-hdanton@sina.com>
2020-06-01 11:46 ` Ryusuke Konishi
2020-01-23 13:58 ` BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct ARAI Shun-ichi
2020-01-23 14:30 ` ARAI Shun-ichi
2020-02-10 13:46 ` ARAI Shun-ichi
2020-02-16 2:10 ` ARAI Shun-ichi
2020-02-16 2:24 ` Brian G.
2020-02-16 3:59 ` Ryusuke Konishi
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