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SubjectRe: [f2fs-dev] [PATCH] f2fs: clear cold data flag if IO is not counted
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On 2018/10/16 7:08, Jaegeuk Kim wrote:
> On 10/15, Chao Yu wrote:
>> On 2018/10/11 5:22, Jaegeuk Kim wrote:
>>> If we clear the cold data flag out of the writeback flow, we can miscount
>>> -1 by end_io.
>>
>> I didn't get it, which count do you mean?
>
> It's the number of dirty pages.
>
> Balancing F2FS Async:
> - IO (CP: 1, Data: -1, Flush: ( 0 0 1), Discard: ( 0 129304)) cmd: 0 undiscard: 0
>

So I guess the race should be:

GC thread: IRQ
- move_data_page()
- set_page_dirty()
- clear_cold_data()
- f2fs_write_end_io()
- type = WB_DATA_TYPE(page);
here, we get wrong type
- dec_page_count(sbi, type);
- f2fs_wait_on_page_writeback()

How about relocate wait_writeback & set_page_dirty to avoid above race:

move_data_page()

retry:
f2fs_wait_on_page_writeback(page, DATA, true);
set_page_dirty(page);

Thanks,

>>
>> Thanks,
>>
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>> fs/f2fs/data.c | 4 ----
>>> 1 file changed, 4 deletions(-)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 29a9d3b8f709..4102799b5558 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2636,10 +2636,6 @@ static int f2fs_set_data_page_dirty(struct page *page)
>>> if (!PageUptodate(page))
>>> SetPageUptodate(page);
>>>
>>> - /* don't remain PG_checked flag which was set during GC */
>>> - if (is_cold_data(page))
>>> - clear_cold_data(page);
>>> -
>>> if (f2fs_is_atomic_file(inode) && !f2fs_is_commit_atomic_write(inode)) {
>>> if (!IS_ATOMIC_WRITTEN_PAGE(page)) {
>>> f2fs_register_inmem_page(inode, page);
>>>
>
> .
>

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