Re: [dpdk-dev] [PATCH v7 1/1] fbarray: fix duplicated fbarray file in secondary

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 26-Nov-19 7:40 PM, Yasufumi Ogawa wrote:
> Hi David,
> 
> Sorry for slow reply.
> 
> On 2019/11/14 21:27, David Marchand wrote:
>> On Thu, Nov 14, 2019 at 12:42 PM Yasufumi Ogawa <yasufum.o@gmail.com> 
>> wrote:
>>>
>>> On 2019/11/14 2:01, Burakov, Anatoly wrote:
>>>> On 13-Nov-19 9:43 PM, yasufum.o@gmail.com wrote:
>>>>> From: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>>>>>
>>>>> In secondary_msl_create_walk(), it creates a file for fbarrays with 
>>>>> its
>>>>> PID for reserving unique name among secondary processes. However, it
>>>>> does not work if several secondaries run as app containers because 
>>>>> each
>>>>> of containerized secondary has PID 1, and failed to reserve unique 
>>>>> name
>>>>> other than first one. To reserve unique name in each of containers, 
>>>>> use
>>>>> hostname in addition to PID.
>>>>>
>>>>> Cc: stable@dpdk.org
>>>>>
>>>>> Signed-off-by: Yasufumi Ogawa <yasufum.o@gmail.com>
>>>>> ---
>>>>>    lib/librte_eal/linux/eal/eal_memalloc.c | 16 +++++++++++++---
>>>>>    1 file changed, 13 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/lib/librte_eal/linux/eal/eal_memalloc.c
>>>>> b/lib/librte_eal/linux/eal/eal_memalloc.c
>>>>> index af6d0d023..11de6d4d6 100644
>>>>> --- a/lib/librte_eal/linux/eal/eal_memalloc.c
>>>>> +++ b/lib/librte_eal/linux/eal/eal_memalloc.c
>>>>> @@ -1365,6 +1365,12 @@ secondary_msl_create_walk(const struct
>>>>> rte_memseg_list *msl,
>>>>>        struct rte_memseg_list *primary_msl, *local_msl;
>>>>>        char name[PATH_MAX];
>>>>>        int msl_idx, ret;
>>>>> +    char hostname[HOST_NAME_MAX+1] = { 0 };
>>>>> +    /* filename of secondary's fbarray is defined such as
>>>>> +     * "fbarray_memseg-1048576k-0-0_PID_HOSTNAME" and length of PID
>>>>> +     * can be 7 digits maximumly.
>>>>> +     */
>>>>> +    int fbarray_sec_name_len = 32 + 7 + 1 + HOST_NAME_MAX + 1;
>>>>
>>>> What does 32 stand for? Maybe #define both 32 and 7 values?
>>> Hi Anatoly,
>>>
>>> Thank you for your comments! If my understanding is correct, the prefix
>>> "fbarray_memseg-1048576k-0-0_" is 28 digits and it could be larger if
>>> using the size of hugepage or the number of NUMA nodes are larger
>>> possibly. However, I think 32 digits is still enough.
>>>
>>>   > Maybe #define both 32 and 7 values?
>>> Yes. I think it should be better to use #define if this values are
>>> referred several times.
>>
>>
>> We can truncate to RTE_FBARRAY_NAME_LEN in all cases.
>> And iiuc, rte_fbarray_init will refuse any longer name anyway.
> Could I confirm the issue? I've understood that it is failed to validate 
> the name of fbarray in fully_validate() at 
> "lib/librte_eal/common/eal_common_fbarray.c:697".
> 
> static int
> fully_validate(const char *name, unsigned int elt_sz, unsigned int len)
> {
>          if (name == NULL || elt_sz == 0 || len == 0 || len > INT_MAX) {
>                  rte_errno = EINVAL;
>                  return -1;
>          }
> 
>          if (strnlen(name, RTE_FBARRAY_NAME_LEN) == RTE_FBARRAY_NAME_LEN) {
>                  rte_errno = ENAMETOOLONG;
>                  return -1;
>          }
>          return 0;
> }
> 
> I should overwrite the definition of RTE_FBARRAY_NAME_LEN as previous 
> patch in this case, and it causes an ABI breakage, right? If so, I would 
> like to make the change and give up to update stable release.
> 
> Thanks,
> Yasufumi
> 

It seems we're getting into bikeshedding...

We can do this without ABI breakage. You could have just used 
RTE_FBARRAY_NAME_LEN as max fbarray name length for fbarray_sec_name_len 
(i.e. that would include hostname + pid + whatever else there is). The 
name, as David has pointed out, would be truncated to 
RTE_FBARRAY_NAME_LEN anyway (or, more precisely, it will be refused if 
it's longer than that), so this is the most you can have - so you can 
just use that as the maximum.

-- 
Thanks,
Anatoly