linux-kernel - Re: [PATCH 14/18] fs: Protect inode->i_state with th einode->i

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Message-ID: <20101009080537.GA15724@infradead.org>
Date:	Sat, 9 Oct 2010 04:05:37 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/18] fs: Protect inode->i_state with th einode->i_lock

On Fri, Oct 08, 2010 at 07:04:28PM +1100, Dave Chinner wrote:
> > >  		inode->i_ino = ++last_ino;
> > >  		inode->i_state = 0;
> > > +		__inode_add_to_lists(sb, NULL, inode);
> > >  		spin_unlock(&inode_lock);
> > >  	}
> > >  	return inode;
> > 
> > What's the point in doing this move?
> 
> hmmmm, let me think on that....
> 
> > 
> > > @@ -953,8 +966,8 @@ static struct inode *get_new_inode(struct super_block *sb,
> > >  			if (set(inode, data))
> > >  				goto set_failed;
> > >  
> > > -			__inode_add_to_lists(sb, b, inode);
> > >  			inode->i_state = I_NEW;
> > > +			__inode_add_to_lists(sb, b, inode);
> > 
> > Same here.
> 
> Ah, done thinking now! I was so the i_state field had been set
> before the inode was added to various lists and potentially
> accessable to other threads. I should probably add a comment to that
> effect, right?

In addition to the comment get_new_inode_fast also needs the same
treatment.  I also wonder if we need to set I_NEW in new_inode and
then later call unlock_new_inode on it.  It's not on the hash at that
point, but it is on the per-sbi list which we use for a few things.
With current callers it seems safe, but the whole thing also is rather
fragile.  Better left for another patch, though.
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