Re: [f2fs-dev] [PATCH 3/3] f2fs: load largest extent all the time

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Chao,

On Tue, Dec 29, 2015 at 05:23:55PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Tuesday, December 29, 2015 7:32 AM
> > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > linux-f2fs-devel@lists.sourceforge.net
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 3/3] f2fs: load largest extent all the time
> > 
> > Otherwise, we can get mismatched largest extent information.
> > 
> > One example is:
> > 1. mount f2fs w/ extent_cache
> > 2. make a small extent
> > 3. umount
> > 4. mount f2fs w/o extent_cache
> > 5. update the largest extent
> > 6. umount
> > 7. mount f2fs w/ extent_cache
> > 8. get the old extent made by #2
> 
> Good catch!
> 
> It's a pity to drop it since it may provide some help if we
> can reuse it.

Indeed, but I expect it's not a common case.

Thanks,

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/extent_cache.c | 18 +++++++++++++-----
> >  fs/f2fs/f2fs.h         |  2 +-
> >  fs/f2fs/inode.c        |  3 ++-
> >  3 files changed, 16 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
> > index e7b6548..23e7c82 100644
> > --- a/fs/f2fs/extent_cache.c
> > +++ b/fs/f2fs/extent_cache.c
> > @@ -166,20 +166,27 @@ static void __drop_largest_extent(struct inode *inode,
> >  		largest->len = 0;
> >  }
> > 
> > -void f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext)
> > +/* return true, if inode page is changed */
> > +bool f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext)
> >  {
> >  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >  	struct extent_tree *et;
> >  	struct extent_node *en;
> >  	struct extent_info ei;
> > 
> > -	if (!f2fs_may_extent_tree(inode))
> > -		return;
> > +	if (!f2fs_may_extent_tree(inode)) {
> > +		/* drop largest extent */
> > +		if (i_ext && i_ext->len) {
> > +			i_ext->len = 0;
> > +			return true;
> > +		}
> > +		return false;
> > +	}
> > 
> >  	et = __grab_extent_tree(inode);
> > 
> > -	if (!i_ext || le32_to_cpu(i_ext->len) < F2FS_MIN_EXTENT_LEN)
> > -		return;
> > +	if (!i_ext || !i_ext->len)
> > +		return false;
> > 
> >  	set_extent_info(&ei, le32_to_cpu(i_ext->fofs),
> >  		le32_to_cpu(i_ext->blk), le32_to_cpu(i_ext->len));
> > @@ -196,6 +203,7 @@ void f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext)
> >  	}
> >  out:
> >  	write_unlock(&et->lock);
> > +	return false;
> >  }
> > 
> >  static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index e04b2be..a339508 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -2083,7 +2083,7 @@ void f2fs_leave_shrinker(struct f2fs_sb_info *);
> >   * extent_cache.c
> >   */
> >  unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *, int);
> > -void f2fs_init_extent_tree(struct inode *, struct f2fs_extent *);
> > +bool f2fs_init_extent_tree(struct inode *, struct f2fs_extent *);
> >  unsigned int f2fs_destroy_extent_node(struct inode *);
> >  void f2fs_destroy_extent_tree(struct inode *);
> >  bool f2fs_lookup_extent_cache(struct inode *, pgoff_t, struct extent_info *);
> > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > index ec3fb32..e955008 100644
> > --- a/fs/f2fs/inode.c
> > +++ b/fs/f2fs/inode.c
> > @@ -138,7 +138,8 @@ static int do_read_inode(struct inode *inode)
> >  	fi->i_pino = le32_to_cpu(ri->i_pino);
> >  	fi->i_dir_level = ri->i_dir_level;
> > 
> > -	f2fs_init_extent_tree(inode, &ri->i_ext);
> > +	if (f2fs_init_extent_tree(inode, &ri->i_ext))
> > +		set_page_dirty(node_page);
> > 
> >  	get_inline_info(fi, ri);
> > 
> > --
> > 2.5.4 (Apple Git-61)
> > 
> > 
> > ------------------------------------------------------------------------------
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