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Message-ID: <f132db6d-5b5f-cf18-3e4e-2f3053c93033@bytedance.com>
Date:   Tue, 11 Apr 2023 11:49:56 +0800
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Subject: Re: [PATCH v2] maple_tree: Use correct variable type in sizeof
To:     Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Peng Zhang <zhangpeng.00@bytedance.com>, Liam.Howlett@oracle.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        maple-tree@lists.infradead.org,
        David Binderman <dcb314@hotmail.com>, stable@vger.kernel.org
References: <20230411023513.15227-1-zhangpeng.00@bytedance.com>
 <20230410202935.d1abf62f386eefb1efa36ce4@linux-foundation.org>
 <ZDTXE8jKMz802jqR@casper.infradead.org>
From:   Peng Zhang <zhangpeng.00@bytedance.com>
In-Reply-To: <ZDTXE8jKMz802jqR@casper.infradead.org>
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在 2023/4/11 11:42, Matthew Wilcox 写道:
> On Mon, Apr 10, 2023 at 08:29:35PM -0700, Andrew Morton wrote:
>> On Tue, 11 Apr 2023 10:35:13 +0800 Peng Zhang <zhangpeng.00@bytedance.com> wrote:
>>
>>> The type of variable pointed to by pivs is unsigned long, but the type
>>> used in sizeof is a pointer type. Change it to unsigned long.
>> Thanks, but there's nothing in this changelog which explains why a
>> -stable backport is being proposed.  When fixing a bug, please always
>> describe the user-visible effects of that bug.
> There is no user-visible effect of this bug as the assembly code
> generated will be identical.

Therefore, if this has always been the case, cc stable
is also unnecessary.

>
>>> --- a/lib/maple_tree.c
>>> +++ b/lib/maple_tree.c
>>> @@ -3255,7 +3255,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
>>>   
>>>   		if (tmp < max_p)
>>>   			memset(pivs + tmp, 0,
>>> -			       sizeof(unsigned long *) * (max_p - tmp));
>>> +			       sizeof(unsigned long) * (max_p - tmp));
>>>   
>>>   		if (tmp < mt_slots[mt])
>>>   			memset(slots + tmp, 0, sizeof(void *) * (max_s - tmp));
>> Is there any situation in which
>> sizeof(unsigned long *) != sizeof(unsigned long)?
> Windows 64-bit (pointer 64-bit, unsigned long is 32 bit) is the only
> one I know.  Linux is all ILP32 or LP64.  There may be some embedded
> environments which are different, but I have no idea what they might be.
>