linux-kernel - Re: [f2fs-dev] [PATCH 12/12] f2fs: use extent

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Date:	Fri, 3 Jul 2015 22:16:10 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Chao Yu <yuchaochina@...mail.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 12/12] f2fs: use extent_cache by default

Hi Chao,

On Thu, Jul 02, 2015 at 08:36:16PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@...nel.org]
> > Sent: Tuesday, June 30, 2015 2:40 AM
> > To: linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org;
> > linux-f2fs-devel@...ts.sourceforge.net
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 12/12] f2fs: use extent_cache by default
> > 
> > We don't need to handle the duplicate extent infot showrmation.
> 
> information?

Fixed.

> 
> > 
> > The integrated rule is:
> >  - update on-disk extent with largest one tracked by in-memory extent_cache
> >  - destroy extent_tree for the truncation case
> >  - drop per-inode extent_cache by shrinker
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> 
> [snip]
> 
> > @@ -538,7 +427,11 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
> >  		}
> >  	}
> > 
> > -	return __attach_extent_node(sbi, et, ei, parent, p);
> > +	en = __attach_extent_node(sbi, et, ei, parent, p);
> > +update_out:
> > +	if (en && en->ei.len > et->largest.len)
> > +		et->largest = en->ei;
> 
> IMO, it's better to update cached_en here if it is invalid in
> __detach_extent_node, then cached_en and largest may point different
> extent info, it can expand our region of first level extent cache.

Agreed.

> 
> [snip]
> 
> > +
> > +	/* free all extent info belong to this extent tree */
> > +	f2fs_destroy_extent_node(inode);
> 
> How about returning number of freed extent node for tracing.
> 
> node_cnt = f2fs_destroy_extent_node(inode);

No problem.

> 
> [snip]
> 
> > @@ -237,10 +237,11 @@ void update_inode(struct inode *inode, struct page *node_page)
> >  	ri->i_size = cpu_to_le64(i_size_read(inode));
> >  	ri->i_blocks = cpu_to_le64(inode->i_blocks);
> > 
> > -	read_lock(&F2FS_I(inode)->ext_lock);
> > -	set_raw_extent(&F2FS_I(inode)->ext, &ri->i_ext);
> > -	read_unlock(&F2FS_I(inode)->ext_lock);
> > -
> > +	if (F2FS_I(inode)->extent_tree)
> 
> Could extent cache destroy after above check?

I don't think so.

The extent_tree is assigned as one way.
Once it is assigned, it will be deallocated only after evict_inode.

Thanks,

> 
> Thanks,
> 
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