linux-kernel - Re: [PATCH v4] mm/ksm: Fix NULL pointer dereference when KSM zero page is enabled

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Message-ID: <e620f913-d0fb-7d48-b6b2-d4c6b433b563@virtuozzo.com>
Date:   Thu, 16 Apr 2020 14:20:24 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     Markus Elfring <Markus.Elfring@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Muchun Song <songmuchun@...edance.com>,
        Xiongchun Duan <duanxiongchun@...edance.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH v4] mm/ksm: Fix NULL pointer dereference when KSM zero
 page is enabled

On 16.04.2020 09:14, Markus Elfring wrote:
> …
>>> +++ b/mm/ksm.c
>>> @@ -2112,8 +2112,15 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
> …
>>> +		if (vma)
>>> +			err = try_to_merge_one_page(vma, page,
>>> +					ZERO_PAGE(rmap_item->address));
>>> +		else
>>> +			/**
>>> +			 * If the vma is out of date, we do not need to
>>> +			 * continue.
>>> +			 */
>>> +			err = 0;
>>>  		up_read(&mm->mmap_sem);
> …
>> It's conventional to put braces around multi-line blocks such as this.
> 
> Are there different views to consider around the usage of single statements
> together with curly brackets in if branches?

For me Andrew's conversion is the best readable. I try to comment the code
the same way myself. I even thought it's kernel default style :)

Kirill