[dpdk-dev] [PATCH v2] mempool: adjust name string size in related data types

[Olivier Matz]

Hi Zoltan,


On 07/20/2016 07:16 PM, Zoltan Kiss wrote:
> A recent patch brought up an issue about the size of the 'name' fields:
> 
> 85cf0079 mem: avoid memzone/mempool/ring name truncation
> 
> These relations should be observed:
> 
> 1. Each ring creates a memzone with a prefixed name:
> RTE_RING_NAMESIZE <= RTE_MEMZONE_NAMESIZE - strlen(RTE_RING_MZ_PREFIX)
> 
> 2. There are some mempool handlers which create a ring with a prefixed
> name:
> RTE_MEMPOOL_NAMESIZE <= RTE_RING_NAMESIZE - strlen(RTE_MEMPOOL_MZ_PREFIX)
> 
> 3. A mempool can create up to RTE_MAX_MEMZONE pre and postfixed memzones:
> sprintf(postfix, "_%d", RTE_MAX_MEMZONE)
> RTE_MEMPOOL_NAMESIZE <= RTE_MEMZONE_NAMESIZE -
> 	strlen(RTE_MEMPOOL_MZ_PREFIX) - strlen(postfix)
> 
> Setting all of them to 32 hides this restriction from the application.
> This patch decreases the mempool and ring string size to accommodate for
> these prefixes, but it doesn't apply the 3rd constraint. Applications
> relying on these constants need to be recompiled, otherwise they'll run
> into ENAMETOOLONG issues.
> The size of the arrays are kept 32 for ABI compatibility, it can be
> decreased next time the ABI changes.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss at schaman.hu>

Looks like to be a good compromise for the 16.07 release. One question
however: why not taking in account the 3rd constraint? Because it may
not completly fix the issue if the mempool is fragmented.

We could define RTE_MEMPOOL_NAMESIZE to 24
 = 32 - len('mp_') - len('_0123'))

Thanks,
Olivier