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Subject: Re: [PATCH] f2fs: fix to avoid data corruption by forbidding SSR
 overwrite
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20190816030334.81035-1-yuchao0@huawei.com>
 <3349ceea-85ac-173a-81a4-1188ce3804ca@huawei.com>
 <20190820010000.GA45681@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <74d1d451-e2a7-dc0f-a218-a05cd4cdcfa8@huawei.com>
Date:   Tue, 20 Aug 2019 17:16:58 +0800
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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,