linux-kernel - Re: [PATCH] f2fs: avoid false positive of free secs check

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Message-ID: <277e385f-650f-fe29-ac41-ff847a1b7858@huawei.com>
Date:   Thu, 30 Nov 2017 10:42:53 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     Chao Yu <chao@...nel.org>, <jaegeuk@...nel.org>,
        <yuchao0@...wei.com>, <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: avoid false positive of free secs check

SSR can make hot/warm/cold nodes written together, so why should we account
them different?

On 2017/11/29 19:56, Chao Yu wrote:
> On 2017/11/27 14:54, Yunlong Song wrote:
>> Sometimes f2fs_gc is called with no target victim (e.g. xfstest
>> generic/027, ndirty_node:545 ndiry_dent:1 ndirty_imeta:513 rsvd_segs:21
>> free_segs:27, has_not_enough_free_secs will return true). This patch
>> first merges pages and then converts into sections.
> I don't think this could be right, IMO, instead, it would be better to
> account dirty hot/warm/cold nodes or imeta separately, as actually, they
> will use different section, but currently, our calculation way is based
> on that they could be written to same section.
>
> Thanks,
>
>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>> ---
>>   fs/f2fs/f2fs.h    |  9 ---------
>>   fs/f2fs/segment.c | 12 +++++++-----
>>   fs/f2fs/segment.h | 13 +++++++++----
>>   3 files changed, 16 insertions(+), 18 deletions(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index ca6b0c9..e89cff7 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1675,15 +1675,6 @@ static inline int get_dirty_pages(struct inode *inode)
>>   	return atomic_read(&F2FS_I(inode)->dirty_pages);
>>   }
>>   
>> -static inline int get_blocktype_secs(struct f2fs_sb_info *sbi, int block_type)
>> -{
>> -	unsigned int pages_per_sec = sbi->segs_per_sec * sbi->blocks_per_seg;
>> -	unsigned int segs = (get_pages(sbi, block_type) + pages_per_sec - 1) >>
>> -						sbi->log_blocks_per_seg;
>> -
>> -	return segs / sbi->segs_per_sec;
>> -}
>> -
>>   static inline block_t valid_user_blocks(struct f2fs_sb_info *sbi)
>>   {
>>   	return sbi->total_valid_block_count;
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index c117e09..603f805 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -171,17 +171,19 @@ static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
>>   
>>   bool need_SSR(struct f2fs_sb_info *sbi)
>>   {
>> -	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
>> -	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
>> -	int imeta_secs = get_blocktype_secs(sbi, F2FS_DIRTY_IMETA);
>> +	s64 node_pages = get_pages(sbi, F2FS_DIRTY_NODES);
>> +	s64 dent_pages = get_pages(sbi, F2FS_DIRTY_DENTS);
>> +	s64 imeta_pages = get_pages(sbi, F2FS_DIRTY_IMETA);
>>   
>>   	if (test_opt(sbi, LFS))
>>   		return false;
>>   	if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
>>   		return true;
>>   
>> -	return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
>> -			SM_I(sbi)->min_ssr_sections + reserved_sections(sbi));
>> +	return free_sections(sbi) <=
>> +		(PAGE2SEC(sbi, node_pages + imeta_pages) +
>> +		PAGE2SEC(sbi, 2 * dent_pages) +
>> +		SM_I(sbi)->min_ssr_sections + reserved_sections(sbi));
>>   }
>>   
>>   void register_inmem_page(struct inode *inode, struct page *page)
>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>> index d1d394c..723d79e 100644
>> --- a/fs/f2fs/segment.h
>> +++ b/fs/f2fs/segment.h
>> @@ -115,6 +115,10 @@
>>   #define SECTOR_TO_BLOCK(sectors)					\
>>   	((sectors) >> F2FS_LOG_SECTORS_PER_BLOCK)
>>   
>> +#define PAGE2SEC(sbi, pages)				\
>> +	((((pages) + BLKS_PER_SEC(sbi) - 1)		\
>> +	>> sbi->log_blocks_per_seg) / sbi->segs_per_sec)
>> +
>>   /*
>>    * indicate a block allocation direction: RIGHT and LEFT.
>>    * RIGHT means allocating new sections towards the end of volume.
>> @@ -527,9 +531,9 @@ static inline bool has_curseg_enough_space(struct f2fs_sb_info *sbi)
>>   static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi,
>>   					int freed, int needed)
>>   {
>> -	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
>> -	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
>> -	int imeta_secs = get_blocktype_secs(sbi, F2FS_DIRTY_IMETA);
>> +	s64 node_pages = get_pages(sbi, F2FS_DIRTY_NODES);
>> +	s64 dent_pages = get_pages(sbi, F2FS_DIRTY_DENTS);
>> +	s64 imeta_pages = get_pages(sbi, F2FS_DIRTY_IMETA);
>>   
>>   	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
>>   		return false;
>> @@ -538,7 +542,8 @@ static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi,
>>   			has_curseg_enough_space(sbi))
>>   		return false;
>>   	return (free_sections(sbi) + freed) <=
>> -		(node_secs + 2 * dent_secs + imeta_secs +
>> +		(PAGE2SEC(sbi, node_pages + imeta_pages) +
>> +		PAGE2SEC(sbi, 2 * dent_pages) +
>>   		reserved_sections(sbi) + needed);
>>   }
>>   
>>
> .
>

-- 
Thanks,
Yunlong Song