linux-kernel - Re: [PATCH] mm/migrate: Fix NULL movable_ops if CONFIG

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Message-ID: <07b17e1c-92e6-432a-9af6-13d3fc8246bc@redhat.com>
Date: Sat, 16 Aug 2025 19:04:01 +0200
From: David Hildenbrand <david@...hat.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Huacai Chen <chenhuacai@...nel.org>, Huacai Chen
 <chenhuacai@...ngson.cn>, Andrew Morton <akpm@...ux-foundation.org>,
 linux-mm@...ck.org, Zi Yan <ziy@...dia.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Harry Yoo <harry.yoo@...cle.com>, linux-kernel@...r.kernel.org,
 Minchan Kim <minchan@...nel.org>,
 Sergey Senozhatsky <senozhatsky@...omium.org>,
 "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH] mm/migrate: Fix NULL movable_ops if CONFIG_ZSMALLOC=m

On 16.08.25 19:02, David Hildenbrand wrote:
> On 16.08.25 18:23, Matthew Wilcox wrote:
>> On Sat, Aug 16, 2025 at 12:54:52PM +0200, David Hildenbrand wrote:
>>> +++ b/mm/balloon_compaction.c
>>> @@ -256,8 +256,10 @@ const struct movable_operations balloon_mops = {
>>>    static int __init balloon_init(void)
>>>    {
>>> -	movable_ops[MOVABLE_BALLOON] = &balloon_mops;
>>> -	return 0;
>>> +	int rc;
>>> +
>>> +	rc = register_movable_ops(&balloon_mops, PGTY_offline);
>>> +	return rc;
>>
>> Using 'rc' as the name of this variable is an anti-pattern.  All it
>> tells you is "this is the return value".  Calling it 'err' is far
>> better because now we know it's an error number (or zero for success,
>> of course).
> 
> I know, we all have our things to complain about. Some about Cc: above
> --, others about the name of error variables :P
> 
> $ git grep "int rc" | wc -l
> 12730
> $ git grep "int ret" | wc -l
> 80386
> $ git grep "int error" | wc -l
> 4349
> $ git grep "int err " | wc -l
> 6117
> 
>>
>> It seems to be a particularly IBM derived antipattern ;-)
> 
> Careful miser :D

"mister". No idea if "miser" exist and if so, whether it could be 
considered offensive ;)

-- 
Cheers

David / dhildenb