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SubjectRe: [PATCH] net: openvswitch: pass NULL for unused parameters
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On 8/30/20 1:02 PM, Andy Shevchenko wrote:
> On Sun, Aug 30, 2020 at 6:17 PM <trix@redhat.com> wrote:
>> From: Tom Rix <trix@redhat.com>
>>
>> clang static analysis flags these problems
>>
>> flow_table.c:713:2: warning: The expression is an uninitialized
>> value. The computed value will also be garbage
>> (*n_mask_hit)++;
>> ^~~~~~~~~~~~~~~
>> flow_table.c:748:5: warning: The expression is an uninitialized
>> value. The computed value will also be garbage
>> (*n_cache_hit)++;
>> ^~~~~~~~~~~~~~~~
>>
>> These are not problems because neither pararmeter is used
> parameter
Too many ar's, it must be talk like a pirate day.
>
>> by the calling function.
>>
>> Looking at all of the calling functions, there are many
>> cases where the results are unused. Passing unused
>> parameters is a waste.
>>
>> To avoid passing unused parameters, rework the
>> masked_flow_lookup() and flow_lookup() routines to check
>> for NULL parameters and change the unused parameters to NULL.
>>
>> Signed-off-by: Tom Rix <trix@redhat.com>
>> ---
>> net/openvswitch/flow_table.c | 16 +++++++---------
>> 1 file changed, 7 insertions(+), 9 deletions(-)
>>
>> diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
>> index e2235849a57e..18e7fa3aa67e 100644
>> --- a/net/openvswitch/flow_table.c
>> +++ b/net/openvswitch/flow_table.c
>> @@ -710,7 +710,8 @@ static struct sw_flow *masked_flow_lookup(struct table_instance *ti,
>> ovs_flow_mask_key(&masked_key, unmasked, false, mask);
>> hash = flow_hash(&masked_key, &mask->range);
>> head = find_bucket(ti, hash);
>> - (*n_mask_hit)++;
>> + if (n_mask_hit)
>> + (*n_mask_hit)++;
>>
>> hlist_for_each_entry_rcu(flow, head, flow_table.node[ti->node_ver],
>> lockdep_ovsl_is_held()) {
>> @@ -745,7 +746,8 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl,
>> u64_stats_update_begin(&ma->syncp);
>> usage_counters[*index]++;
>> u64_stats_update_end(&ma->syncp);
>> - (*n_cache_hit)++;
>> + if (n_cache_hit)
>> + (*n_cache_hit)++;
>> return flow;
>> }
>> }
>> @@ -798,9 +800,8 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
>> *n_cache_hit = 0;
>> if (unlikely(!skb_hash || mc->cache_size == 0)) {
>> u32 mask_index = 0;
>> - u32 cache = 0;
>>
>> - return flow_lookup(tbl, ti, ma, key, n_mask_hit, &cache,
>> + return flow_lookup(tbl, ti, ma, key, n_mask_hit, NULL,
>> &mask_index);
> Can it be done for mask_index as well?

Yes, it's a bit more complicated but doable.

Tom

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