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

[Yunlong Song]

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@xxxxxxxxxx>
> > ---
> >   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