On Thu 14 Feb 2019 at 20:34, Stefano Brivio <sbri...@redhat.com> wrote:
> On Thu, 14 Feb 2019 09:47:02 +0200
> Vlad Buslov <vla...@mellanox.com> wrote:
>
>> As a preparation for using classifier spinlock instead of relying on
>> external rtnl lock, rearrange code in fl_change. The goal is to group the
>> code which changes classifier state in single block in order to allow
>> following commits in this set to protect it from parallel modification with
>> tp->lock. Data structures that require tp->lock protection are mask
>> hashtable and filters list, and classifier handle_idr.
>>
>> fl_hw_replace_filter() is a sleeping function and cannot be called while
>> holding a spinlock. In order to execute all sequence of changes to shared
>> classifier data structures atomically, call fl_hw_replace_filter() before
>> modifying them.
>>
>> Signed-off-by: Vlad Buslov <vla...@mellanox.com>
>> Acked-by: Jiri Pirko <j...@mellanox.com>
>> ---
>> net/sched/cls_flower.c | 85
>> ++++++++++++++++++++++++++------------------------
>> 1 file changed, 44 insertions(+), 41 deletions(-)
>>
>> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
>> index 88d7af78ba7e..91596a6271f8 100644
>> --- a/net/sched/cls_flower.c
>> +++ b/net/sched/cls_flower.c
>> @@ -1354,90 +1354,93 @@ static int fl_change(struct net *net, struct sk_buff
>> *in_skb,
>> if (err < 0)
>> goto errout;
>>
>> - if (!handle) {
>> - handle = 1;
>> - err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
>> - INT_MAX, GFP_KERNEL);
>> - } else if (!fold) {
>> - /* user specifies a handle and it doesn't exist */
>> - err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
>> - handle, GFP_KERNEL);
>> - }
>> - if (err)
>> - goto errout;
>> - fnew->handle = handle;
>> -
>>
>> [...]
>>
>> if (fold) {
>> + fnew->handle = handle;
>
> I'm probably missing something, but what if fold is passed and the
> handle isn't specified? That can still happen, right? In that case we
> wouldn't be allocating the handle.
Hi Stefano,
Thank you for reviewing my code.
Cls API lookups fold by handle, so this pointer can only be not NULL
when user specified a handle and filter with such handle exists on tp.
>
>> +
>> + err = rhashtable_insert_fast(&fnew->mask->ht, &fnew->ht_node,
>> + fnew->mask->filter_ht_params);
>> + if (err)
>> + goto errout_hw;
>> +
>> rhashtable_remove_fast(&fold->mask->ht,
>> &fold->ht_node,
>> fold->mask->filter_ht_params);
>> - if (!tc_skip_hw(fold->flags))
>> - fl_hw_destroy_filter(tp, fold, NULL);
>> - }
>> -
>> - *arg = fnew;
>> -
>> - if (fold) {
>> idr_replace(&head->handle_idr, fnew, fnew->handle);
>> list_replace_rcu(&fold->list, &fnew->list);
>> +
>> + if (!tc_skip_hw(fold->flags))
>> + fl_hw_destroy_filter(tp, fold, NULL);
>> tcf_unbind_filter(tp, &fold->res);
>> tcf_exts_get_net(&fold->exts);
>> tcf_queue_work(&fold->rwork, fl_destroy_filter_work);
>> } else {
>> + if (__fl_lookup(fnew->mask, &fnew->mkey)) {
>> + err = -EEXIST;
>> + goto errout_hw;
>> + }
>> +
>> + if (handle) {
>> + /* user specifies a handle and it doesn't exist */
>> + err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
>> + handle, GFP_ATOMIC);
>> + } else {
>> + handle = 1;
>> + err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
>> + INT_MAX, GFP_ATOMIC);
>> + }
>> + if (err)
>> + goto errout_hw;
>
> Just if you respin: a newline here would be nice to have.
Agree.
>
>> + fnew->handle = handle;
>> +
>> + err = rhashtable_insert_fast(&fnew->mask->ht, &fnew->ht_node,
>> + fnew->mask->filter_ht_params);
>> + if (err)
>> + goto errout_idr;
>> +
>> list_add_tail_rcu(&fnew->list, &fnew->mask->filters);
>> }
>>
>> + *arg = fnew;
>> +
>> kfree(tb);
>> kfree(mask);
>> return 0;
>>
>> -errout_mask_ht:
>> - rhashtable_remove_fast(&fnew->mask->ht, &fnew->ht_node,
>> - fnew->mask->filter_ht_params);
>> -
>> -errout_mask:
>> - fl_mask_put(head, fnew->mask, false);
>> -
>> errout_idr:
>> if (!fold)
>
> This check could go away, I guess (not a strong preference though).
Yes, it seems that after this change errout_idr lable is only accessed
from else branch of if(fold) conditional so the check is redundant.
>
>> idr_remove(&head->handle_idr, fnew->handle);
>> +errout_hw:
>> + if (!tc_skip_hw(fnew->flags))
>> + fl_hw_destroy_filter(tp, fnew, NULL);
>> +errout_mask:
>> + fl_mask_put(head, fnew->mask, false);
>> errout:
>> tcf_exts_destroy(&fnew->exts);
>> kfree(fnew);
