linux-kernel - Re: [PATCH 4/5] powerpc-pseries: Return directly after a failed kzalloc_node() in iommu_pseries_alloc

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Date:   Thu, 19 Oct 2017 14:04:43 +0200
From:   SF Markus Elfring <elfring@...rs.sourceforge.net>
To:     Michal Suchánek <msuchanek@...e.de>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Doug Ledford <dledford@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Rob Herring <robh@...nel.org>,
        Sahil Mehta <sahilmehta17@...il.com>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] powerpc-pseries: Return directly after a failed
 kzalloc_node() in iommu_pseries_alloc_group()

>> @@ -61,7 +61,7 @@ static struct iommu_table_group *iommu_pseries_alloc_group(int node) 
>>  	table_group = kzalloc_node(sizeof(*table_group), GFP_KERNEL,
>> node); if (!table_group)
>> -		goto fail_exit;
>> +		return NULL;
>>  
>>  	tbl = kzalloc_node(sizeof(*tbl), GFP_KERNEL, node);
>>  	if (!tbl)
> 
> I have seen quite a few fixes that do inverse of this patch after a
> piece of code allocating some extra piece of memory was added before
> code that just returns on fail because it is the first allocation in
> the function.
> 
> This is not useful.

How do you think about an information from the section “7) Centralized exiting
of functions” in the document “coding-style.rst” then?

“…
If there is no cleanup needed then just return directly.
…”


> A final fail_exit that frees everything that could have been allocated
> is much better.

I got an other software development opinion for such use cases.
I prefer only required function calls there.

Regards,
Markus