linux-kernel - Re: [PATCH] f2fs: fix to redirty page if fail to gc data page

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Date:	Fri, 3 Jun 2016 13:13:21 +0800
From:	Chao Yu <yuchao0@...wei.com>
To:	Jaegeuk Kim <jaegeuk@...nel.org>
CC:	Chao Yu <chao@...nel.org>,
	<linux-f2fs-devel@...ts.sourceforge.net>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: fix to redirty page if fail to gc data page

On 2016/6/3 13:08, Jaegeuk Kim wrote:
> On Tue, May 31, 2016 at 02:10:50PM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2016/5/30 10:37, Jaegeuk Kim wrote:
>>> Hi Chao,
>>>
>>> On Sat, May 21, 2016 at 01:19:11PM +0800, Chao Yu wrote:
>>>> From: Chao Yu <yuchao0@...wei.com>
>>>>
>>>> If we fail to move data page during foreground GC, we should give another
>>>> chance to writeback that page which was set dirty previously by writer.
>>>>
>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>> ---
>>>>  fs/f2fs/gc.c | 5 ++++-
>>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>> index 38d56f6..ee213a8 100644
>>>> --- a/fs/f2fs/gc.c
>>>> +++ b/fs/f2fs/gc.c
>>>> @@ -653,12 +653,15 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type)
>>>>  			.page = page,
>>>>  			.encrypted_page = NULL,
>>>>  		};
>>>> +		bool is_dirty = PageDirty(page);
>>>> +
>>>>  		set_page_dirty(page);
>>>>  		f2fs_wait_on_page_writeback(page, DATA, true);
>>>>  		if (clear_page_dirty_for_io(page))
>>>>  			inode_dec_dirty_pages(inode);
>>>>  		set_cold_data(page);
>>>> -		do_write_data_page(&fio);
>>>> +		if (do_write_data_page(&fio) && is_dirty)
>>>> +			set_page_dirty(page);
>>>
>>> If this page is truncated with -ENOENT, we don't need to set it dirty again.
>>
>> Agree
>>
>>> I expect that, if we get an error here, do_garbage_collect() would retry FG_GC
>>
>> IIRC, you have reworked the FG_GC flows changed from an infinite loop to trying
>> do the movement just one time. Here, I think if there are just few of blocks are
>> failed to be moved, we can give one more time for retrying. How do you think?
> 
> Mostly I expected here -ENOENT caused by race condition.

If we hit ENOENT case, we can pass get_valid_blocks check, so we don't need to
worry about this case, right?

> Do we have another expectation?

ENOMEM or EIO?

Thanks,

> 
> Thanks,
> 
>>
>>> again.
>>>
>>> Thanks,
>>>
>>>>  		clear_cold_data(page);
>>>>  	}
>>>>  out:
>>>> -- 
>>>> 2.7.2
>>> .
>>>
> .
>