Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct

[ARAI Shun-ichi]

And,

In <20200210.224609.499887311281343618.hermes@xxxxxxxxxxxxxxx>;
   ARAI Shun-ichi <hermes@xxxxxxxxxxxxxxx> wrote
   as Subject "Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct":

> Hi,
> 
> FYI, reporting additional test results.
> 
> I reproduced this problem with clean NILFS2 fs in previous mail.
> "clean" means that "make filesystem before every tests."
> In this mail, I tried to reproduct with/without VG/LV, LUKS, loopback.
> 
> * Not reproduced
>  USB stick - primary partition - NILFS2
>  USB stick - primary partition - VG/LV - NILFS2
>  USB stick - primary partition - VG/LV - LUKS - NILFS2
>  USB stick - primary partition - LUKS - VG/LV - NILFS2
>  USB stick - primary partition - LUKS - VG/LV - LUKS - NILFS2
>  /tmp (tmpfs) - regular file - NILFS2 (loopback mount, kernel 4.19.82)
>  USB stick - primary partition(512MiB) - NILFS2
> 
> * Reproduced (always, immediately)
>  /tmp (tmpfs) - regular file - NILFS2 (loopback mount)
>  USB stick - primary partition - ext4 - regular file - NILFS2 (loopback mount)

this loopback problem is seen in Kernel 5.5.4.

> Test conditions:
>  kernel 4.19.86 (same as previous test)
>  NILFS2/ext4 filesystem, VG/LV, LUKS were made with default parameters
>  size of "primary partition" in USB stick is approx. 14GiB
>  size of "regular file" is approx. 512MiB
>  "reproduce": mount NILFS2, touch file, sync