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Subject: Re: [PATCH] f2fs: add bug_on when f2fs_gc even fails to get one
 victim
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <chao@kernel.org>, <yuchao0@huawei.com>, <yunlong.song@icloud.com>,
        <miaoxie@huawei.com>, <bintian.wang@huawei.com>,
        <linux-fsdevel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <1507729864-118702-1-git-send-email-yunlong.song@huawei.com>
 <20171012232308.GA19689@jaegeuk-macbookpro.roam.corp.google.com>
From:   Yunlong Song <yunlong.song@huawei.com>
Message-ID: <702a755a-1af2-5ddb-9d2f-da5bf67c7705@huawei.com>
Date:   Fri, 13 Oct 2017 09:09:17 +0800
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Hi, Jay,
     I think it should not happen when need_gc == true but total_freed 
==0, so I add it as bug_on to let it panic at once. And even CHECK_FS is 
closed, this can also printk WARNING message for notice.

On 2017/10/13 7:23, Jaegeuk Kim wrote:
> Hi Yunlong,
>
> On 10/11, Yunlong Song wrote:
>> This can help us to debug on some corner case.
>>
>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
>> ---
>>   fs/f2fs/gc.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index 197ebf4..960503e 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -986,6 +986,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>   		.ilist = LIST_HEAD_INIT(gc_list.ilist),
>>   		.iroot = RADIX_TREE_INIT(GFP_NOFS),
>>   	};
>> +	bool need_gc = false;
>>   
>>   	trace_f2fs_gc_begin(sbi->sb, sync, background,
>>   				get_pages(sbi, F2FS_DIRTY_NODES),
>> @@ -1018,8 +1019,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>   			if (ret)
>>   				goto stop;
>>   		}
>> -		if (has_not_enough_free_secs(sbi, 0, 0))
>> +		if (has_not_enough_free_secs(sbi, 0, 0)) {
>>   			gc_type = FG_GC;
>> +			need_gc = true;
>> +		}
>>   	}
>>   
>>   	/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
>> @@ -1028,6 +1031,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>   		goto stop;
>>   	}
>>   	if (!__get_victim(sbi, &segno, gc_type)) {
>> +		f2fs_bug_on(sbi, !total_freed && need_gc);
> How about this, if this is for debugging purpose?
>
> 		if (!total_freed && need_gc)
> 			f2fs_msg(...);
>
> It's not a good way to define a value for f2fs_bug_on(), since it is only
> activated by CHECK_FS config.
>
> Thanks,
>
>>   		ret = -ENODATA;
>>   		goto stop;
>>   	}
>> -- 
>> 1.8.5.2
> .
>

-- 
Thanks,
Yunlong Song


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