Re: [PATCH] f2fs: fix wrong sum_page pointer in f2fs_gc

[Chao Yu <chao@kernel.org>]

On 2016/10/14 1:14, Jaegeuk Kim wrote:
> On Thu, Oct 13, 2016 at 06:33:19PM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2016/10/13 7:23, Jaegeuk Kim wrote:
>>> This patch fixes using a wrong pointer for sum_page in f2fs_gc.
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>>  fs/f2fs/gc.c | 10 +++++-----
>>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index e48142f..9c18917 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -854,16 +854,16 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>  
>>>  	for (segno = start_segno; segno < end_segno; segno++) {
>>>  
>>> -		if (get_valid_blocks(sbi, segno, 1) == 0 ||
>>> -					unlikely(f2fs_cp_error(sbi)))
>>> -			goto next;
>>> -
>>>  		/* find segment summary of victim */
>>>  		sum_page = find_get_page(META_MAPPING(sbi),
>>>  					GET_SUM_BLOCK(sbi, segno));
>>> -		f2fs_bug_on(sbi, !PageUptodate(sum_page));
>>>  		f2fs_put_page(sum_page, 0);
>>>  
>>> +		if (get_valid_blocks(sbi, segno, 1) == 0 ||
>>> +				!PageUptodate(sum_page) ||
>>
>> Why uptodate flag of summary page can be cleared? someone truncates it?
> 
> Well, it looks like no problem to remove this, since it will hit
> f2fs_cp_error(). I just intended to handle the above f2fs_bug_on here.

If summary page becomes non-uptodate, it seems there is a bug in vfs/mm/f2fs,
why not keep it there to detect bug?

Thanks,

> 
> I found you added the above bug_on, but it's not a big deal to remain tho. :)
> 
> 718e53fa: f2fs: enhance foreground GC
> 
> Thanks,
> 
>>
>> Thanks,
>>
>>> +				unlikely(f2fs_cp_error(sbi)))
>>> +			goto next;
>>> +
>>>  		sum = page_address(sum_page);
>>>  		f2fs_bug_on(sbi, type != GET_SUM_TYPE((&sum->footer)));
>>>  
>>>
> 
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