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

[zhangqilong via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

> 
> On 2022/9/13 14:10, Chao Yu wrote:
> > 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?
> >>>
Hi,

I may found the reason that truncate_pagecache_range() being called before __exchange_data_block() that does not work.
In the following path:
  -> f2fs_move_file_range
    -> __exchange_data_block
      -> __clone_blkaddrs
       -> f2fs_get_lock_data_page
The source page(s) are read again. So we truncate source page(s) before __exchange_data_block is useless. We need to truncate
source page(s) after __exchange_data_block(). How do you think?

Thanks,

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