Re: What does this sparse warning mean in posix_acl.h?

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On Sat, Aug 17, 2013 at 09:16:54AM -0700, Linus Torvalds wrote:
> On Sat, Aug 17, 2013 at 7:28 AM, Theodore Ts'o <tytso@xxxxxxxxx> wrote:
> >
> > It apparently has something to do with rcu and "address spaces" but I'm
> > not completely sure what sparse is complaining about --- and whether it
> > is a false positive or a bug in the posix_acl.h.
> 
> I guess we should mark i_acl and i_defauly_acl to be RCU-accessed, and
> then annotate all the accesses properly.

I may be missing something, but it looks like the ACL code isn't
following the RCU rules at _all_.  Even with the missing
rcu_derference() macro invocations which you added in your
proof-of-concept patch, we're still missing the rcu_read_lock() calls
around the use of the rcu pointers.

If so, I'm kind of wondering why we haven't noticed massive problems
here before.

						- Ted
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