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From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org, Andrew Rybchenko <arybchenko@solarflare.com>,
	stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH] mempool: fix mempool virt populate with small chunks
Date: Thu, 9 Jan 2020 14:29:08 +0000
Message-ID: <6e43ec20-4fa5-55fa-6ca9-2ffca9bcf7dc@intel.com> (raw)
In-Reply-To: <20200109142351.GJ22738@platinum>

On 09-Jan-20 2:23 PM, Olivier Matz wrote:
> On Thu, Jan 09, 2020 at 01:52:41PM +0000, Burakov, Anatoly wrote:
>> On 09-Jan-20 1:27 PM, Olivier Matz wrote:
>>> To populate a mempool with a virtual area, the mempool code calls
>>> rte_mempool_populate_iova() for each iova-contiguous area. It happens
>>> (rarely) that this area is too small to store one object. In this case,
>>> rte_mempool_populate_iova() returns an error, which is forwarded by
>>> rte_mempool_populate_virt().
>>>
>>> This case should not throw an error in
>>> rte_mempool_populate_virt(). Instead, the area that is too small should
>>> just be ignored.
>>>
>>> To fix this issue, change the return value of
>>> rte_mempool_populate_iova() to -ENOBUFS when no object can be populated,
>>> so it can be ignored by the caller. As this would be an API change, add
>>> a compat wrapper to keep the current API unchanged. The wrapper will be
>>> removed for 20.11.
>>>
>>> Fixes: 354788b60cfd ("mempool: allow populating with unaligned virtual area")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
>>> ---
>>>
>>
>> The approach fixes the issue on my end, so
>>
>> Tested-by: Anatoly Burakov <anatoly.burakov@intel.com>
>>
>>> Is there a simple way to ensure that we won't forget to remove the
>>> wrapper for 20.11? Anatoly suggested me to use versioned symbols, but
>>> it's not clear to me how.
>>>
>>
>> Yes, i'd like to do better than "ah shur we won't forget pinky swear".
>>
>> Can't we do this with ABI versioning? E.g.
>>
>> rte_populate_iova_v20() ... returns EINVAL
>>
>> rte_populate_iova_v21() ... returns ENOBUFS
>>
>> I'm pretty sure, even if it doesn't break, it will still be more likely to
>> not be forgotten because there's almost a guarantee that someone will grep
>> for symbol versioning macros across the codebase around 20.11 timeframe.
> 
> Without using symbol versionning, would this be ok too?
> 
>    int
>    rte_mempool_populate_iova(struct rte_mempool *mp, char *vaddr,
>           rte_iova_t iova, size_t len, rte_mempool_memchunk_free_cb_t *free_cb,
>           void *opaque)
>    {
>           int ret;
> 
>           ret = __rte_mempool_populate_iova(mp, vaddr, iova, len, free_cb, opaque);
> 
>    #if RTE_VERSION < RTE_VERSION_NUM(20, 11, 0, 0)
>           if (ret == -ENOBUFS)
>                   ret = -EINVAL;
>    #endif
> 
>           return ret;
>    }
> 
> 

Well it would certainly work :) it just makes it more likely that this 
will be missed.

How about, we leave your patch as is, and then you submit another patch 
marked for [20.11] and mark it as Deferred straight away? This is 
probably the best method to not forget that i can think of, if you're so 
averse to symbol versioning :D

> 
>> -- 
>> Thanks,
>> Anatoly


-- 
Thanks,
Anatoly

  reply	other threads:[~2020-01-09 14:29 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-09 13:27 Olivier Matz
2020-01-09 13:40 ` [dpdk-stable] [dpdk-dev] " David Marchand
2020-01-09 13:46   ` Olivier Matz
2020-01-09 13:52 ` [dpdk-stable] " Burakov, Anatoly
2020-01-09 14:23   ` Olivier Matz
2020-01-09 14:29     ` Burakov, Anatoly [this message]
2020-01-09 14:58       ` [dpdk-stable] [dpdk-dev] " Bruce Richardson
2020-01-17 14:57 ` [dpdk-stable] [PATCH v2 0/3] " Olivier Matz
2020-01-17 14:57   ` [dpdk-stable] [PATCH v2 1/3] " Olivier Matz
2020-01-17 14:57   ` [dpdk-stable] [PATCH v2 2/3] doc: announce API change for mempool IOVA populate Olivier Matz
2020-01-17 20:32     ` David Marchand
2020-01-17 14:57   ` [dpdk-stable] [PATCH v2 3/3] [20.05] mempool: return 0 if area is too small on populate Olivier Matz
2020-01-17 20:32     ` David Marchand
2020-01-20 12:02   ` [dpdk-stable] [dpdk-dev] [PATCH v2 0/3] mempool: fix mempool virt populate with small chunks Thomas Monjalon

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