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

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Date:   Tue, 31 Oct 2017 09:59:05 +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 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;
>>   		}
>>   
>