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

[Chao Yu <chao@kernel.org>]

On 2016/10/15 0:57, Jaegeuk Kim wrote:
> On Fri, Oct 14, 2016 at 09:25:59PM +0800, Chao Yu wrote:
>> 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?
> 
> I found that the above get_sum_page() loop can give a page which is not uptodate
> caused by EIO. Then, we would get the above bug_on, if we move f2fs_cp_error()
> case like this patch.
> 
> Thoughts?

Seems this patch has already been merged into linus' tree...

Anyway, I can understand why you remove f2fs_bug_on & add PageUptodate here, but
why should we repositon below check?

if (get_valid_blocks(sbi, segno, 1) == 0 ||
		unlikely(f2fs_cp_error(sbi)))

Thanks,

> 
> Thanks,
> 

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