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Subject: Re: [PATCH v2] 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>
 <1507901500-162168-1-git-send-email-yunlong.song@huawei.com>
 <20171103034402.GC11335@jaegeuk-macbookpro.roam.corp.google.com>
 <3b26badb-c34e-3c2d-74a2-26ecef1f64ff@huawei.com>
 <20171107023835.GG88544@jaegeuk-macbookpro.roam.corp.google.com>
 <20171107024058.GH88544@jaegeuk-macbookpro.roam.corp.google.com>
From:   Yunlong Song <yunlong.song@huawei.com>
Message-ID: <cafd59c4-1a39-f54b-095e-24430a79437e@huawei.com>
Date:   Tue, 7 Nov 2017 11:16:03 +0800
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Because I find that some out-of-free problem is caused by the failure
of get victim target. For example, chao has pointed out that he has
found out a bug when adding this bug_on last week.

On 2017/11/7 10:40, Jaegeuk Kim wrote:
> On 11/06, Jaegeuk Kim wrote:
>> On 11/06, Yunlong Song wrote:
>>> Agree.
>>>
>>> On 2017/11/3 11:44, Jaegeuk Kim wrote:
>>>> On 10/13, Yunlong Song wrote:
>>>>> This can help us to debug on some corner case.
>>>>>
>>>>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
>>>>> Signed-off-by: Chao Yu <yuchao0@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..2b03202 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_fggc = 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_fggc = 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_fggc);
>>>> Just like this?
>>> That's OK.
>> I'm not quite sure whether this is really a bug_on case.
>> Let me make it WARN_ON() for debugging purpose first.
> BTW, why is this the special case where BG_GC detects FG_GC?
>
>> Thanks,
>>
>>>> 		f2fs_bug_on(sbi, !total_freed && !sync && gc_type == FG_GC);
>>>>
>>>>>    		ret = -ENODATA;
>>>>>    		goto stop;
>>>>>    	}
>>>>> -- 
>>>>> 1.8.5.2
>>>> .
>>>>
>>> -- 
>>> Thanks,
>>> Yunlong Song
>>>
> .
>

-- 
Thanks,
Yunlong Song


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