linux-kernel - Re: [PATCH 1/2] f2fs: use crc and cp version to determine roll-forward recovery

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <96deb7ae-d4a7-a34b-bc86-f8569e50350b@huawei.com>
Date:   Fri, 30 Sep 2016 09:04:57 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 1/2] f2fs: use crc and cp version to determine
 roll-forward recovery

On 2016/9/30 8:53, Jaegeuk Kim wrote:
> On Thu, Sep 29, 2016 at 08:01:32PM +0800, Chao Yu wrote:
>> On 2016/9/20 10:55, Jaegeuk Kim wrote:
>>> Previously, we used cp_version only to detect recoverable dnodes.
>>> In order to avoid same garbage cp_version, we needed to truncate the next
>>> dnode during checkpoint, resulting in additional discard or data write.
>>> If we can distinguish this by using crc in addition to cp_version, we can
>>> remove this overhead.
>>>
>>> There is backward compatibility concern where it changes node_footer layout.
>>> But, it only affects the direct nodes written after the last checkpoint.
>>> We simply expect that user would change kernel versions back and forth after
>>> stable checkpoint.
>>
>> Seems with new released v4.8 f2fs, old image with recoverable data could be
>> mounted successfully, but meanwhile all fsynced data which needs to be recovered
>> will be lost w/o any hints?
>>
>> Could we release a new version mkfs paired with new kernel module, so we can tag
>> image as a new layout one, then new kernel module can recognize the image layout
>> and adjust version suited comparing method with old or new image?
> 
> Hmm, how about adding a checkpoint flag like CP_CRC_RECOVERY_FLAG?
> Then, we can proceed crc|cp_ver, if the last checkpoint has this flag.
> 
> Any thought?

Ah, that's better. :)

Thanks,

> 
>>
>> Thanks,
>>
>>
> 
> .
>