Re: test file disappeared after -f, -r, --add-journal for write-journal device

[Shaohua Li <shli@kernel.org>]

On Wed, Jul 27, 2016 at 08:07:19AM -0400, Yi Zhang wrote:
> Hello maintainer
> 
> Here is another strange phenomenon I found after do -f, -r, --add-journal for write-journal device.
> 
> Kernel version: 4.7.0-rc7 
> Steps I used:
> mdadm --create --run /dev/md0 --level 4 --metadata 1.2 --raid-devices 7 /dev/loop1 /dev/loop2 /dev/loop3 /dev/loop4 /dev/loop5 /dev/loop6 /dev/loop7 --write-journal /dev/loop0 --bitmap=internal --bitmap-chunk=64M --chunk 512
> mdadm --wait /dev/md0
> mkfs.ext4 /dev/md0
> mount -t ext4 /dev/md0 /mnt/fortest
> cp bigfile /mnt/fortest &
> wait
> md5sum /mnt/fortest/bigfile > md5sum3
> mdadm /dev/md0 -f /dev/loop0

since loop0 is the journal device and it fails, we will mark the md0 readonly
at this point. Filesystem can't do any write. It's possible the fortest/md5sum3
files not hit disk yet, and are lost. I think your test should do a sync before
mark journal disk failure.

> mdadm /dev/md0 -r /dev/loop0
> umount /dev/md0 -l
> mdadm -o /dev/md0
> mdadm /dev/md0 --add-journal /dev/loop0
> mdadm --wait /dev/md0
> mdadm -D /dev/md0
> mount /dev/md0 /mnt/fortest
> md5sum /mnt/fortest/bigfile > md5sum2   #<----this test file disappeared

If a sync is done before journal disk fails and you still see the file
disappeared, it's a bug.

Thanks,
Shaohua