Re: [PATCH v7 1/4] spinlock: A new lockref structure for locklessupdate of refcount

[Waiman Long]

On 08/30/2013 04:54 PM, Al Viro wrote:
> On Fri, Aug 30, 2013 at 01:43:11PM -0700, Linus Torvalds wrote:
> > On Fri, Aug 30, 2013 at 1:15 PM, Waiman Long<waiman.long@xxxxxx>  wrote:
> > > The prepend_path() isn't all due to getcwd. The correct profile should be
> > Ugh. I really think that prepend_path() should just be rewritten to
> > run entirely under RCU.
> >
> > Then we can remove *all* the stupid locking, and replace it with doing
> > a read-lock on the rename sequence count, and repeating if requited.
> >
> > That shouldn't even be hard to do, it just requires mindless massaging
> > and being careful.
> Not really.  Sure, you'll retry it if you race with d_move(); that's not
> the real problem - access past the end of the object containing ->d_name.name
> would screw you and that's what ->d_lock is preventing there.  Delayed freeing
> of what ->d_name is pointing into is fine, but it's not the only way to get
> hurt there...

Actually, prepend_path() was called with rename_lock taken. So d_move() 
couldn't be run at the same time. Am I right?

Regards,
Longman
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