linux-kernel - Re: [PATCH 2/2] f2fs: fix the inconsistent state of data pages

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Message-id: <1368592895.11843.13.camel@kjgkr>
Date:	Wed, 15 May 2013 13:41:35 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 2/2] f2fs: fix the inconsistent state of data pages

2013-05-15 (수), 13:04 +0900, Namjae Jeon:
> 2013/5/15, Jaegeuk Kim <jaegeuk.kim@...sung.com>:
> > In get_lock_data_page, if there is a data race between get_dnode_of_data
> > for
> > node and grab_cache_page for data, f2fs is able to face with the following
> > BUG_ON(dn.data_blkaddr == NEW_ADDR).
> >
> > kernel BUG at /home/zeus/f2fs_test/src/fs/f2fs/data.c:251!
> >  [<ffffffffa044966c>] get_lock_data_page+0x1ec/0x210 [f2fs]
> > Call Trace:
> >  [<ffffffffa043b089>] f2fs_readdir+0x89/0x210 [f2fs]
> >  [<ffffffff811a0920>] ? fillonedir+0x100/0x100
> >  [<ffffffff811a0920>] ? fillonedir+0x100/0x100
> >  [<ffffffff811a07f8>] vfs_readdir+0xb8/0xe0
> >  [<ffffffff811a0b4f>] sys_getdents+0x8f/0x110
> >  [<ffffffff816d7999>] system_call_fastpath+0x16/0x1b
> >
> > This bug is able to be occurred when the block address of the data block is
> > changed after f2fs_put_dnode().
> > In order to avoid that, this patch fixes the lock order of node and data
> > blocks in which the node block lock is covered by the data block lock.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> > ---
> >  fs/f2fs/data.c | 17 +++++++++++------
> >  1 file changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 91ff93b..05fb5c6 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -233,18 +233,23 @@ struct page *get_lock_data_page(struct inode *inode,
> > pgoff_t index)
> >  	struct page *page;
> >  	int err;
> >
> > +repeat:
> > +	page = grab_cache_page(mapping, index);
> > +	if (!page)
> > +		return ERR_PTR(-ENOMEM);
> > +
> >  	set_new_dnode(&dn, inode, NULL, NULL, 0);
> >  	err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
> > -	if (err)
> > +	if (err) {
> > +		f2fs_put_page(page, 1);
> >  		return ERR_PTR(err);
> > +	}
> >  	f2fs_put_dnode(&dn);
> >
> > -	if (dn.data_blkaddr == NULL_ADDR)
> > +	if (dn.data_blkaddr == NULL_ADDR) {
> > +		f2fs_put_page(page, 1);
> >  		return ERR_PTR(-ENOENT);
> > -repeat:
> > -	page = grab_cache_page(mapping, index);
> > -	if (!page)
> > -		return ERR_PTR(-ENOMEM);
> > +	}
> >
> >  	if (PageUptodate(page))
> >  		return page;
> Is there no need to move PageUptodate condition checking to
> grab_cache_page next ?

For the data consistency, I'd like to check index in its node block
prior to this.
Thanks,

> 
> Thanks.
> > --
> > 1.8.1.3.566.gaa39828
> >
> > --
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> >

-- 
Jaegeuk Kim
Samsung

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