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Balbir Singh wrote:
> <snip>
>
>> if (slot->slots[i]) {
>>- results[nr_found++] = slot->slots[i];
>>+ results[nr_found++] = &slot->slots[i];
>> if (nr_found == max_items)
>> goto out;
>> }
>
>
> A quick clarification - Shouldn't accesses to slot->slots[i] above be
> protected using rcu_derefence()?
>
I think we're safe here -- this is the _address_ of the pointer.
However, when dereferencing this address in _gang_lookup,
I think we do need rcu_dereference indeed.
Note that _gang_lookup_slot doesn't do this for us, however --
the caller must do that when dereferencing the pointer to the
item (eg. see page_cache_get_speculative in 2/3).
That said, I'm not 100% sure I have the rcu memory barriers in
the right places (well I'm sure I don't, given the _gang_lookup
bug you exposed!).
Thanks,
Nick
--
SUSE Labs, Novell Inc.
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