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Subject: Re: [PATCH] e2fsprogs: Try again to solve unreliable io case
From:   Zhiqiang Liu <liuzhiqiang26@huawei.com>
To:     Theodore Ts'o <tytso@mit.edu>
CC:     Haotian Li <lihaotian9@huawei.com>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>,
        "harshad shirwadkar," <harshadshirwadkar@gmail.com>,
        linfeilong <linfeilong@huawei.com>
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Date:   Mon, 10 May 2021 11:35:59 +0800
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friendly ping ...

On 2021/4/24 12:46, Zhiqiang Liu wrote:
>
> On 2021/4/23 23:46, Theodore Ts'o wrote:
>> On Fri, Apr 23, 2021 at 10:18:09AM +0800, Zhiqiang Liu wrote:
>>> Thanks for your reply.
>>> Actually, we have met the problem in ipsan situation.
>>> When exec 'fsck -a <remote-device>', short-term fluctuations or
>>> abnormalities may occur on the network. Despite the driver has
>>> do the best effort, some IO errors may occur. So add retrying in
>>> e2fsprogs can further improve the reliability of the repair
>>> process.
>> But why doesn't this happen when the file system is mounted, and why
>> is that acceptable?   And why not change the driver to do more retries?
>>
>>    		      	      	  - Ted
>>
> Actually, this may happen when the filesystem is mounted. The difference
> is that the mounted filesystem can ensure the consistency with journal.
>
> For example, if the IO error occurs when calling io_channel_write_byte()
> to update superblock, the checksum may be not written to the disk successfully.
> Then the checksum error will occur, and the filesystem cannot be
> repaired with 'fsck -y|a|f'.
>
> This situation has a very low probability. For improving the reliability of
> the repair process, the retries in e2fsprogs may be necessary.
>
> Regards
> Zhiqiang Liu.
>
>> .
>>
>
> .