linux-kernel - Re: [PATCH] f2fs: fix to avoid data corruption by forbidding SSR overwrite

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Date:   Tue, 20 Aug 2019 17:16:58 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH] f2fs: fix to avoid data corruption by forbidding SSR
 overwrite

On 2019/8/20 9:00, Jaegeuk Kim wrote:
> On 08/19, Chao Yu wrote:
>> On 2019/8/16 11:03, Chao Yu wrote:
>>> There is one case can cause data corruption.
>>>
>>> - write 4k to fileA
>>> - fsync fileA, 4k data is writebacked to lbaA
>>> - write 4k to fileA
>>> - kworker flushs 4k to lbaB; dnode contain lbaB didn't be persisted yet
>>> - write 4k to fileB
>>> - kworker flush 4k to lbaA due to SSR
>>> - SPOR -> dnode with lbaA will be recovered, however lbaA contains fileB's
>>> data
>>>
>>> One solution is tracking all fsynced file's block history, and disallow
>>> SSR overwrite on newly invalidated block on that file.
>>>
>>> However, during recovery, no matter the dnode is flushed or fsynced, all
>>> previous dnodes until last fsynced one in node chain can be recovered,
>>> that means we need to record all block change in flushed dnode, which
>>> will cause heavy cost, so let's just use simple fix by forbidding SSR
>>> overwrite directly.
>>>
>>
>> Jaegeuk,
>>
>> Please help to add below missed tag to keep this patch being merged in stable
>> kernel.
>>
>> Fixes: 5b6c6be2d878 ("f2fs: use SSR for warm node as well")
> 
> Done.

Thanks! :)

Thanks,