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

[Linus Torvalds]

On Fri, Aug 30, 2013 at 1:54 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> 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...

Umm? We follow d->d_name.name without d_lock under RCU all the time -
that's what the pathname lookup is all about, after all.

Yes, yes, you haev to be careful and cannot just blindly trust the
length: you also have to check for NUL character as you are copying it
and stop if you hit it. But that's trivial.

Why would d_prepend be any different?

            Linus
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