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Subject: Re: [PATCH v4] mm/ksm: Fix NULL pointer dereference when KSM zero
 page is enabled
To:     Markus Elfring <Markus.Elfring@web.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Xiongchun Duan <duanxiongchun@bytedance.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        David Hildenbrand <david@redhat.com>,
        Yang Shi <yang.shi@linux.alibaba.com>
References: <20200416025034.29780-1-songmuchun@bytedance.com>
 <20200415195841.da4361916f662a0136a271a5@linux-foundation.org>
 <516df5d7-b514-11dc-130e-f1a2edce0108@web.de>
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
Message-ID: <e620f913-d0fb-7d48-b6b2-d4c6b433b563@virtuozzo.com>
Date:   Thu, 16 Apr 2020 14:20:24 +0300
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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 +			 * If the vma is out of date, we do not need to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