linux-kernel - Re: [PATCH v2] f2fs: collect prefree segments to avoild write checkpoint fail

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Date:   Tue, 31 Oct 2017 10:56:00 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Yunlong Song <yunlong.song@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] f2fs: collect prefree segments to avoild write
 checkpoint fail

On 2017/10/31 10:05, Yunlong Song wrote:
> So I use CHECK_FS config to control it. When CHECK_FS is off, all the 
> other f2fs_bug_on also
> only printk WARNING info rather than trigger BUG_ON.

If this runing out-of-free-segments issue explicitly happens, IMO, its better
to face and fix it.

BTW, it's better to add bug_on here to detect the issue?

Thanks,

> 
> On 2017/10/31 9:59, Chao Yu wrote:
>> On 2017/10/31 9:33, Yunlong Song wrote:
>>> ping...
>>>
>>> On 2017/9/1 20:00, Yunlong Song wrote:
>>>> In come corner case, the reserved segments are used to do gc, and there are
>>>> not enough free segments for write checkpoint to finish its job, then the
>>>> gc process will fail to change the prefree segments to free segments.
>> I agreed to use this in production for robustness, but for upstream, it's better
>> to investigate and fix this issue rather than covering up it.
>>
>> Thanks,
>>
>>>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>>> ---
>>>>    fs/f2fs/gc.c | 10 ++++++++++
>>>>    1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>> index cd147e7..6552b04 100644
>>>> --- a/fs/f2fs/gc.c
>>>> +++ b/fs/f2fs/gc.c
>>>> @@ -1056,6 +1056,16 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>>>    	if (!sync) {
>>>>    		if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
>>>>    			segno = NULL_SEGNO;
>>>> +#ifndef CONFIG_F2FS_CHECK_FS
>>>> +			if (prefree_segments(sbi) &&
>>>> +				has_not_enough_free_secs(sbi,
>>>> +					reserved_sections(sbi), 0)) {
>>>> +				ret = write_checkpoint(sbi, &cpc);
>>>> +				if (ret)
>>>> +					goto stop;
>>>> +				sec_freed = 0;
>>>> +			}
>>>> +#endif
>>>>    			goto gc_more;
>>>>    		}
>>>>    
>>
>> .
>>
>