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From: Zoltan Kiss <zoltan.kiss@linaro.org>
To: Olivier Matz <olivier.matz@6wind.com>,
	Zoltan Kiss <zoltan.kiss@schaman.hu>,
	dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mempool: adjust name string size in related data types
Date: Tue, 19 Jul 2016 16:59:28 +0100	[thread overview]
Message-ID: <578E4E60.80802@linaro.org> (raw)
In-Reply-To: <600cac7d-b0aa-7919-93f2-7a396ef7b3ea@6wind.com>



On 19/07/16 16:37, Olivier Matz wrote:
> Hi Zoltan,
>
> On 07/19/2016 04:37 PM, Zoltan Kiss wrote:
>> A recent fix brought up an issue about the size of the 'name' fields:
>>
>> 85cf0079 mem: avoid memzone/mempool/ring name truncation
>>
>> These relations should be observed:
>>
>> RTE_RING_NAMESIZE <= RTE_MEMZONE_NAMESIZE - strlen(RTE_RING_MZ_PREFIX)
>> RTE_MEMPOOL_NAMESIZE <= RTE_RING_NAMESIZE - strlen(RTE_MEMPOOL_MZ_PREFIX)
>>
>> Setting all of them to 32 hides this restriction from the application.
>> This patch increases the memzone string size to accomodate for these
>> prefixes, and the same happens with the ring name string. The ABI needs to
>> be broken to fix this API issue, this way doesn't break applications
>> previously not failing due to the truncating bug now fixed.
>>
>> Signed-off-by: Zoltan Kiss <zoltan.kiss@schaman.hu>
>
> I agree it is a problem for an application because it cannot know what
> is the maximum name length. On the other hand, breaking the ABI for this
> looks a bit overkill. Maybe we could reduce RTE_MEMPOOL_NAMESIZE and
> RTE_RING_NAMESIZE instead of increasing RTE_MEMZONE_NAMESIZE? That way,
> we could keep the ABI as is.

But that would break the ABI too, wouldn't it? Unless you keep the array 
the same size (32 bytes) by using RTE_MEMZONE_NAMESIZE.
And even then, the API breaks anyway. There are applications - I have at 
least some - which use all 32 bytes to store the name. Decrease that 
would cause headache to change the naming scheme, because it's a 30 
character long id, and chopping the last few chars would cause name 
collisions and annoying bugs.

>
> It would even be better to get rid of this static char[] for the
> structure names and replace it by an allocated const char *. I didn't
> check it's feasible for memzones. What do you think?

It would work too, but I don't think it would help a lot. We would still 
need max sizes for the names. Storing them somewhere else won't help us 
in this problem.

>
> In any case, I think it's a bit late for 16.07 for this kind of fix.
>
> Regards,
> Olivier
>

  reply	other threads:[~2016-07-19 15:59 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-19 14:37 [dpdk-dev] [PATCH] mempool: fix lack of free() registration Zoltan Kiss
2016-07-19 14:37 ` [dpdk-dev] [PATCH] mempool: adjust name string size in related data types Zoltan Kiss
2016-07-19 15:37   ` Olivier Matz
2016-07-19 15:59     ` Zoltan Kiss [this message]
2016-07-19 16:17       ` Olivier Matz
2016-07-20 12:41         ` Zoltan Kiss
2016-07-20 13:37           ` Olivier Matz
2016-07-20 14:01             ` Richardson, Bruce
2016-07-20 17:20             ` Zoltan Kiss
2016-07-20 17:16   ` [dpdk-dev] [PATCH v2] " Zoltan Kiss
2016-07-21 13:40     ` Olivier Matz
2016-07-21 13:47       ` Zoltan Kiss
2016-07-21 14:25         ` Olivier Matz
2016-07-21 21:16           ` Thomas Monjalon
2016-07-19 15:26 ` [dpdk-dev] [PATCH] mempool: fix lack of free() registration Olivier Matz
2016-07-19 16:17   ` Zoltan Kiss
2016-07-20 17:14 ` [dpdk-dev] [PATCH v2] mempool: fix lack of free registration Zoltan Kiss
2016-07-21 21:04   ` Thomas Monjalon

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