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SubjectRe: [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:
> > > @@ -884,9 +897,9 @@ struct inode *new_inode(struct super_block *sb)
> > > inode = alloc_inode(sb);
> > > if (inode) {
> > > spin_lock(&inode_lock);
> > > - __inode_add_to_lists(sb, NULL, inode);
> > > 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?

If that can happen, don't we need a wmb() between the assignment to
i_state and the list_add too? If so, that's a good comment :-)

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."


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