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Message-ID: <30e5c9c2-b13a-4b7e-a266-1e03e654f1d3@wanadoo.fr>
Date: Fri, 2 Feb 2024 20:11:56 +0100
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Subject: Re: [PATCH RESEND] nfc: hci: Save a few bytes of memory when
 registering a 'nfc_llc' engine
To: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
 kernel-janitors@vger.kernel.org, netdev@vger.kernel.org
References: <6d2b8c390907dcac2e4dc6e71f1b2db2ef8abef1.1705744530.git.christophe.jaillet@wanadoo.fr>
 <20240131150803.2fec5a5c@kernel.org>
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From: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
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Le 01/02/2024 à 00:08, Jakub Kicinski a écrit :
> On Sat, 27 Jan 2024 10:58:29 +0100 Christophe JAILLET wrote:
>> nfc_llc_register() calls pass a string literal as the 'name' parameter.
>>
>> So kstrdup_const() can be used instead of kfree() to avoid a memory
>> allocation in such cases.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> 
> There is a kfree() call in nfc_llc_exit() that looks suspiciously
> like it may also free the name.
> 
> 

Hi,

you are right.


Should we have something like:

void nfc_llc_exit(void)
{
	struct nfc_llc_engine *llc_engine, *n;

	list_for_each_entry_safe(llc_engine, n, &llc_engines, entry)
		nfc_llc_unregister(&llc_engine->name);
}


It would be slower, but it would reduce code duplication as well.
This is just an _exit() function, so it shouldn't be called that often 
anyway, if called at all.

Or, add another function with the list_del()+kfree_const()+kfree(), that 
would be called from nfc_llc_exit() and nfc_llc_unregister(), to have 
the best of the 2 worlds?

CJ