On Thu, Jan 09, 2014 at 06:59:07PM -0500, Steven Rostedt wrote:
> On Thu, 9 Jan 2014 15:45:37 -0800
> "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> > > static void inode_free_security(struct inode *inode)
> > > {
> > > struct inode_security_struct *isec = inode->i_security;
> > > @@ -244,8 +252,7 @@ static void inode_free_security(struct i
> > > list_del_init(&isec->list);
> > > spin_unlock(&sbsec->isec_lock);
> > >
> > > - inode->i_security = NULL;
> > > - kmem_cache_free(sel_inode_cache, isec);
> > > + call_rcu(&isec->rcu, inode_free_rcu);
> >
> > Does not clearing ->i_security mean that RCU readers can traverse
> > this pointer after the invocation of call_rcu()? If so, this is
> > problematic. (If something else already prevents readers from getting
> > here, no problem.)
>
> This is called when we are about to free the inode. Look at
> destroy_inode(). Basically, this is the same as doing:
>
> call_rcu(&isec->rcu, inode_free_rcu);
> call_rcu(&inode->i_rcu, i_callback);
>
> Where i_callback() does the free of the inode.
>
> If you can access inode->i_security, after a call_rcu, then you can
> also access the inode itself that has just been freed.
>
> Yes, technically, having two separate call_rcu(), the first grace
> period can end before the second, but everything to remove the inode
> from sight has already been set up before that first call_rcu() is
> made. That means when the first call_rcu() is executed, the inode
> should already be invisible to the readers.
Got it, should be fine then, sorry for the noise.
Thanx, Paul
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