linux-kernel - RE: [f2fs-dev][PATCH 3/3 v3] f2fs: fix to truncate inline data in inode page when setattr

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Date:	Tue, 29 Apr 2014 17:02:14 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: RE: [f2fs-dev][PATCH 3/3 v3] f2fs: fix to truncate inline data in
 inode page when setattr

Hi,

2014-04-29 (화), 15:53 +0800, Chao Yu:
> Hi Kim,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk.kim@...sung.com]
> > Sent: Tuesday, April 29, 2014 2:16 PM
> > To: Chao Yu
> > Cc: linux-f2fs-devel@...ts.sourceforge.net; linux-fsdevel@...r.kernel.org;
> > linux-kernel@...r.kernel.org
> > Subject: Re: [f2fs-dev][PATCH 3/3 v3] f2fs: fix to truncate inline data in inode page when setattr
> > 
> > Hi,
> > 
> > 2014-04-29 (화), 14:03 +0800, Chao Yu:
> > > Previous we do not truncate inline data in inode page when setattr, so following
> > > case could still read the inline data which has already truncated:
> > >
> > > 1.write inline data
> > > 2.ftruncate size to 0
> > > 3.ftruncate size to max inline data size
> > > 4.read from offset 0
> > >
> > > This patch introduces truncate_inline_data() to fix this problem.
> > >
> > > change log from v1:
> > >  o fix a bug and do not truncate first page data after truncate inline data.
> > > change log from v2:
> > >  o wait to writeback for inode page if it was already submitted.
> > >
> > > Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> > > ---
> > >  fs/f2fs/f2fs.h   |    1 +
> > >  fs/f2fs/file.c   |    3 +++
> > >  fs/f2fs/inline.c |   19 +++++++++++++++++++
> > >  3 files changed, 23 insertions(+)
> > >
> > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > index 2b67679..676a2c6 100644
> > > --- a/fs/f2fs/f2fs.h
> > > +++ b/fs/f2fs/f2fs.h
> > > @@ -1410,5 +1410,6 @@ bool f2fs_may_inline(struct inode *);
> > >  int f2fs_read_inline_data(struct inode *, struct page *);
> > >  int f2fs_convert_inline_data(struct inode *, pgoff_t);
> > >  int f2fs_write_inline_data(struct inode *, struct page *, unsigned int);
> > > +void truncate_inline_data(struct inode *, u64);
> > >  int recover_inline_data(struct inode *, struct page *);
> > >  #endif
> > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > index b9f4fbf..d97e5c4 100644
> > > --- a/fs/f2fs/file.c
> > > +++ b/fs/f2fs/file.c
> > > @@ -369,6 +369,9 @@ static void truncate_partial_data_page(struct inode *inode, u64 from)
> > >  	unsigned offset = from & (PAGE_CACHE_SIZE - 1);
> > >  	struct page *page;
> > >
> > > +	if (f2fs_has_inline_data(inode))
> > > +		return truncate_inline_data(inode, from);
> > > +
> > >  	if (!offset)
> > >  		return;
> > >
> > > diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> > > index 3258c7c..6a13997 100644
> > > --- a/fs/f2fs/inline.c
> > > +++ b/fs/f2fs/inline.c
> > > @@ -176,6 +176,25 @@ int f2fs_write_inline_data(struct inode *inode,
> > >  	return 0;
> > >  }
> > >
> > > +void truncate_inline_data(struct inode *inode, u64 from)
> > > +{
> > > +	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> > > +	struct page *ipage;
> > > +
> > > +	if (from >= MAX_INLINE_DATA)
> > > +		return;
> > > +
> > > +	ipage = get_node_page(sbi, inode->i_ino);
> > > +	if (IS_ERR(ipage))
> > > +		return;
> > > +
> > > +	f2fs_wait_on_page_writeback(ipage, NODE);
> > 
> > The get_node_page() triggers,
> >  grab_cache_page_write_begin()
> >   -> wait_for_stable_page()
> >      -> wait_on_page_writeback().
> 
> Oh, it's my mistake for this missing, thanks for the mention.:)
> 
> > 
> > Any bugs in there?
> 
> If we wait in grab_cache_page_write_begin(), maybe we will face long time delay
> or potential deadlock caused by f2fs bio cache. So how about use
> grab_cache_page & f2fs_wait_on_page_writeback to avoid this?

Nice catch. :)
IMO, it'd better merge your v2, and let me investigate all the paths to
avoid that.
Is it okay?

> 
> > 
> > > +	zero_user_segment(ipage, INLINE_DATA_OFFSET + from,
> > > +				INLINE_DATA_OFFSET + MAX_INLINE_DATA);
> > > +	set_page_dirty(ipage);
> > > +	f2fs_put_page(ipage, 1);
> > > +}
> > > +
> > >  int recover_inline_data(struct inode *inode, struct page *npage)
> > >  {
> > >  	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> > 
> > --
> > Jaegeuk Kim
> > Samsung
> 
> --
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-- 
Jaegeuk Kim
Samsung

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