Re: [PATCHv2 05/17] nvme: add Clang context annotations for nvme_ns_head::current_path

[Nilay Shroff <nilay@linux.ibm.com>]

>>>>
>>>> commit 32c1e63fee171f7ed8cc986ec64f576ee80bccab
>>>> Author: Paul E. McKenney <paulmck@kernel.org>
>>>> Date:   Sun Jun 28 09:00:01 2026 -0700
>>>>
>>>>       rcu: Mark __rcu_access_pointer() as context_unsafe()
>>>>
>>>>       A simple comparison of a pointer returned by rcu_access_pointer() results
>>>>       in a context-analysis warning for lockless inspection of the RCU-protected
>>>>       (also known as __rcu-protected) pointer.  This can be suppressed by
>>>>       placing context_unsafe() calls around calls rcu_access_pointer(),
>>>>       but this is messy and distracting.  This commit therefore wraps the
>>>>       underlying __rcu_access_pointer() macro with a call to context_unsafe(),
>>>>       thereby informing the context-analysis code that rcu_access_pointer()
>>>>       may safely be invoked outside of an RCU read-side critical section.
>>>>
>>>>       Reported-by: Christoph Hellwig <hch@lst.de>
>>>>       Suggested-by: Marco Elver <elver@google.com>
>>>>       Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
>>>>
>>>> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
>>>> index 5e95acc33989b6..e40dc2e20c5b1f 100644
>>>> --- a/include/linux/rcupdate.h
>>>> +++ b/include/linux/rcupdate.h
>>>> @@ -490,12 +490,12 @@ context_unsafe(                                                         \
>>>>     */
>>>>    #define unrcu_pointer(p) __unrcu_pointer(p, __UNIQUE_ID(rcu))
>>>>
>>>> -#define __rcu_access_pointer(p, local, space) \
>>>> +#define __rcu_access_pointer(p, local, space) context_unsafe( \
>>>>    ({ \
>>>>        typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \
>>>>        rcu_check_sparse(p, space); \
>>>>        ((typeof(*p) __force __kernel *)(local)); \
>>>> -})
>>>> +}) )
>>>>    #define __rcu_dereference_check(p, local, c, space) \
>>>>    ({ \
>>>>        /* Dependency order vs. p above. */ \
>>>
>>> I have tested the above patch with an __rcu_guarded pointer accessed
>>> outside an RCU read-side critical section while Clang context analysis
>>> is enabled. I can confirm that this change suppresses the context
>>> analysis warning when the pointer is accessed via rcu_access_pointer().
>>>
>>> With that, if you send out this change, please add:
>>>
>>> Tested-by: Nilay Shroff <nilay@linux.ibm.com>
>>
>> Thanks for double-checking.
>>
>> Reviewed-by: Marco Elver <elver@google.com>
> 
> Thank you all!
> 
> By default, I will push this into the upcoming v7.3 merge window.  If you
> need it earlier, we would have to make a case for this being a regression.
> Which I could probably do, but first, is v7.3 too late for you?
> 
> 							Thanx, Paul

I think anyways the current series would not land in the upcoming
kernel v7.2. So if you could push this during v7.3 merge window then
that should be good for us.

Thanks,
--Nilay