Re: s390/pkey: Use memdup_user() rather than duplicating its implementation

From: Markus Elfring <Markus.Elfring@web.de>
To: Joe Perches <joe@perches.com>,
	linux-s390@vger.kernel.org, kernel-janitors@vger.kernel.org
Cc: "Christian Bornträger" <borntraeger@de.ibm.com>,
	"Harald Freudenberger" <freude@linux.ibm.com>,
	"Heiko Carstens" <heiko.carstens@de.ibm.com>,
	"Ingo Franzki" <ifranzki@linux.ibm.com>,
	"Vasily Gorbik" <gor@linux.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: s390/pkey: Use memdup_user() rather than duplicating its implementation
Date: Wed, 6 Nov 2019 14:00:33 +0100	[thread overview]
Message-ID: <4fa0e106-2565-8610-1356-4adfba08c0a0@web.de> (raw)
In-Reply-To: <6137855bb4170c438c7436cbdb7dfd21639a8855.camel@perches.com>

>> Reuse existing functionality from memdup_user() instead of keeping
>> duplicate source code.
>>
>> Generated by: scripts/coccinelle/api/memdup_user.cocci
…
>> Fixes: f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d ("s390/pkey: add CCA AES cipher key support")
>
> This doesn't fix anything

How would you categorise the proposed source code reduction and software reuse?

> and the Fixes: line is not appropriate.

Will the development opinions vary between contributors?

>> +	return !ukey || keylen < MINKEYBLOBSIZE || keylen > KEYBLOBBUFSIZE
>> +	       ? ERR_PTR(-EINVAL)
>> +	       : memdup_user(ukey, keylen);
>
> This is a very poor use of ternary ?: code.

The conditional operator is applied once more in the intended way,
isn't it?

> This is much more readable for humans.

Readability preferences can vary also for this code structure.

>> +	return uapqns && nr_apqns > 0
>> +	       ? memdup_user(uapqns, nr_apqns * sizeof(struct pkey_apqn))
>> +	       : NULL;
>
> And here you reverse the form of the earlier block.

I kept the previous condition specification.

> Please be consistent and use this style:

Would further developers like to get a more verbose variant for this
software transformation?

Regards,
Markus