Re: [f2fs-dev] 答复: 答复: [PATCH -next] f2fs: adding truncate page cache after being moved

[Chao Yu <chao@kernel.org>]

On 2022/9/13 12:37, zhangqilong wrote:
>>
>> On 2022/9/13 11:41, zhangqilong wrote:
>>>> On 2022/9/13 11:05, Zhang Qilong wrote:
>>>>> If we do not truncate source page cache, user can still see the
>>>>> previous source data after being moved. We fix it by adding
>>>>> truncating after __exchange_data_block.
>>>>>
>>>>> Fixes:4dd6f977fc778 ("f2fs: support an ioctl to move a range of data
>>>>> blocks")
>>>>> Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
>>>>> ---
>>>>>     fs/f2fs/file.c | 4 ++++
>>>>>     1 file changed, 4 insertions(+)
>>>>>
>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index
>>>>> 771f1f7f3690..e3ff648aa496 100644
>>>>> --- a/fs/f2fs/file.c
>>>>> +++ b/fs/f2fs/file.c
>>>>> @@ -2789,6 +2789,10 @@ static int f2fs_move_file_range(struct file
>>>> *file_in, loff_t pos_in,
>>>>>     	}
>>>>>     	f2fs_unlock_op(sbi);
>>>>>
>>>>> +	filemap_invalidate_lock(src->i_mapping);
>>>>
>>>> invalidate lock should cover __exchange_data_block()?
>>>>
>>>>> +	truncate_pagecache_range(src, pos_in, pos_in + len - 1);
>>>>
>>>> truncate_pagecache_range() should be called before
>>>> __exchange_data_block()?
>>>
>>> I have tried it, but it do not work. So I move the truncate operation
>>> to the back of __exchange_data_block that it works well. I don't know
>>> much enough, what do you think of this issue.
>>
>> Can you describe details about the testcase?
>>
>> Thanks,
>>
> 
> Process 1 						process 2
> -> open A
> -> mmap
> 	Read the data and save
> 								-> ioctl with F2FS_IOC_MOVE_RANGE   A  ->  B

The ioctl only change the data on target file (B), so Process 1 needs to
read and check data of source file (B)?

Thanks,

> 
> -> mmap
> 	Read the data that offset is same with first time and save
> 
> Compare the consistency of the data that read twice.
> 


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