On Fri, Jul 22, 2011 at 8:29 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
>> + * Under RCU walk, we cannot even do a "get_cached_acl()",
>> + * because that involves locking and getting a refcount on
>> + * a cached ACL.
>
> ... why is that a problem? Locking there is mere ->i_lock and getting
> a refcount is atomic_inc(). Grabbing a reference might be Not Nice from
> the cacheline bouncing POV, but...
I agree in theory, but it's not something we've done before. Some of
the posix-acl code is pretty disgusting, I didn't even want to go
there.
And the case that tends to really *matter* is the "no acls" case
anyway, and that's the case that is guaranteed to have no nasty races
or odd issues with having to allocate/de-allocate any acl structures.
But yes, this could be looked at.
Linus
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