Re: [BUG] Big fiability issue?

[Edward Shishkin <edward.shishkin@gmail.com>]

On 04/06/2016 04:25 PM, Mathieu Belanger wrote:
> Well, I did boot systemrescuecd to fsck my /dev/sda2 and mount it ro to
> do the backup and I was able to get all the data back but with a bonus :
> I can mount the fscked /dev/sda2 in rw on systemrescuecd, the corruption
> don't come back. SystemrescueCD is based on Gentoo I think. But the one
> I got got a 3.18 kernel.


Please, mount it with "no_write_barrier" option on all kernels older
than 4.5.1 (not yet released). Horrible name, of course: this should
sound like "no_block_write_barrier", or something like this, but it is
too late to fix...

Thanks,
Edward.


>   I did manually compile the latest tools to be
> sure and a got an error because 3.18 support format40 4.0.0, not 4.0.1
> but that error did not affect me.
>
> I will do more test with that "corrupt" partition before restorating
> the backup.
>
> On Tue, 5 Apr 2016 17:43:45 +0200
> Edward Shishkin <edward.shishkin@gmail.com> wrote:
>
>> Hello Mathieu,
>>
>> I found that by default reiser4 still relies on a block layer feature,
>> which is not longer supported. This is so-called "barriers". And yes,
>> on the power outage bad things are bound to happen. However, it
>> is up to bad luck.
>>
>> The attached patch removes the rest of block barriers support in
>> reiser4. So, now we honestly wait for IO completion of wandered
>> blocks (overwrite set) before submitting a journal header (journal
>> footer).
>>
>> Not sure if it will address your problem though. Also, data corruption
>> after rw-mounting of checked (rebuild-fs) partition is still a concern.
>>
>> Thanks,
>> Edward.
>