linux-kernel - Re: [PATCH] f2fs: let f2fs also gc atomic file to avoid loop gc

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Date:   Fri, 17 Nov 2017 10:49:48 +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] f2fs: let f2fs also gc atomic file to avoid loop gc

On 2017/11/17 8:58, Yunlong Song wrote:
> Is there any problem if just deleting the judgement condition in this patch?

IIRC, dirty node comes from data segment GC can be writebacked & flushed during
atomic commit, but related data will still be in inner bio cache, after later
SPOR, data would be inconsistent.

Thanks,

> 
> On 2017/11/8 17:28, Chao Yu wrote:
>> On 2017/11/8 10:34, Yunlong Song wrote:
>>> If some files are opened with atomic flag and have not commited yet, at
>>> the same time, if all the target victim segments have at least one page
>>> of these atomic files, then f2fs gc will fail to do gc and hangs in the
>>> process of go to gc_more, since gc_date_segment will not move any data
>>> and get_valid_blocks will never be 0, then do_garbage_collect will
>>> always return 0.
>> Oh, I added this judgment condition to avoid ruining atomic write by data
>> GC, could we find another way to solve this issue? BTW, if there is direct
>> IO, we will also skip data segment GC.
>>
>> Thanks,
>>
>>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>> ---
>>>   fs/f2fs/gc.c | 6 ------
>>>   1 file changed, 6 deletions(-)
>>>
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index 5d5bba4..3fdcd04 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -621,9 +621,6 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>   	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>   		goto out;
>>>   
>>> -	if (f2fs_is_atomic_file(inode))
>>> -		goto out;
>>> -
>>>   	set_new_dnode(&dn, inode, NULL, NULL, 0);
>>>   	err = get_dnode_of_data(&dn, bidx, LOOKUP_NODE);
>>>   	if (err)
>>> @@ -718,9 +715,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>   	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>   		goto out;
>>>   
>>> -	if (f2fs_is_atomic_file(inode))
>>> -		goto out;
>>> -
>>>   	if (gc_type == BG_GC) {
>>>   		if (PageWriteback(page))
>>>   			goto out;
>>>
>>
>> .
>>
>