Re: [PATCH bpf-next 1/6] bpf: rename stack trace map operations

From: Mauricio Vasquez <mauricio.vasquez@polito.it>
To: Song Liu <liu.song.a23@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Networking <netdev@vger.kernel.org>
Subject: Re: [PATCH bpf-next 1/6] bpf: rename stack trace map operations
Date: Tue, 9 Oct 2018 10:34:36 -0500	[thread overview]
Message-ID: <f61ec699-27a4-5503-1029-3fe79adbf137@polito.it> (raw)
In-Reply-To: <CAPhsuW5jKw1cWyZBFMuOpwY1NFcR+kjauovQbY2yx4JJWW4qJA@mail.gmail.com>

On 10/08/2018 08:40 PM, Song Liu wrote:
> Actually, does it make sense to implement a list_map that supports
> both pop_head()
> and pop_tail()? Maybe gate one of the pop operations with options?

The main issue with this approach is the mapping to the system calls.
Adding a flag would complicate things a bit because lookup nor 
lookup_and_delete have a flag argument.

> I am asking because mixing stack with stack trace is still confusing
> after this patch.
>
> Thanks,
> Song
>
> On Mon, Oct 8, 2018 at 12:11 PM Mauricio Vasquez B
> <mauricio.vasquez@polito.it> wrote:
>> In the following patches queue and stack maps (FIFO and LIFO
>> datastructures) will be implemented.  In order to avoid confusion and
>> a possible name clash rename stack_map_ops to stack_trace_map_ops
>>
>> Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>
>> ---
>>   include/linux/bpf_types.h |    2 +-
>>   kernel/bpf/stackmap.c     |    2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
>> index 5432f4c9f50e..658509daacd4 100644
>> --- a/include/linux/bpf_types.h
>> +++ b/include/linux/bpf_types.h
>> @@ -51,7 +51,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_LRU_HASH, htab_lru_map_ops)
>>   BPF_MAP_TYPE(BPF_MAP_TYPE_LRU_PERCPU_HASH, htab_lru_percpu_map_ops)
>>   BPF_MAP_TYPE(BPF_MAP_TYPE_LPM_TRIE, trie_map_ops)
>>   #ifdef CONFIG_PERF_EVENTS
>> -BPF_MAP_TYPE(BPF_MAP_TYPE_STACK_TRACE, stack_map_ops)
>> +BPF_MAP_TYPE(BPF_MAP_TYPE_STACK_TRACE, stack_trace_map_ops)
>>   #endif
>>   BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_of_maps_map_ops)
>>   BPF_MAP_TYPE(BPF_MAP_TYPE_HASH_OF_MAPS, htab_of_maps_map_ops)
>> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
>> index 8061a439ef18..bb41e293418d 100644
>> --- a/kernel/bpf/stackmap.c
>> +++ b/kernel/bpf/stackmap.c
>> @@ -600,7 +600,7 @@ static void stack_map_free(struct bpf_map *map)
>>          put_callchain_buffers();
>>   }
>>
>> -const struct bpf_map_ops stack_map_ops = {
>> +const struct bpf_map_ops stack_trace_map_ops = {
>>          .map_alloc = stack_map_alloc,
>>          .map_free = stack_map_free,
>>          .map_get_next_key = stack_map_get_next_key,
>>