linux-kernel - Re: [RFC v7 PATCH 1/4] mm: refactor do_munmap() to extract the common part

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Date:   Fri, 10 Aug 2018 11:23:45 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     mhocko@...nel.org, ldufour@...ux.vnet.ibm.com,
        kirill@...temov.name, vbabka@...e.cz, akpm@...ux-foundation.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v7 PATCH 1/4] mm: refactor do_munmap() to extract the common
 part



On 8/10/18 10:41 AM, Matthew Wilcox wrote:
> On Fri, Aug 10, 2018 at 07:36:00AM +0800, Yang Shi wrote:
>> +static inline bool addr_ok(unsigned long start, size_t len)
> Maybe munmap_range_ok()?  Otherwise some of the conditions here don't make
> sense for such a generic sounding function.

I don't know. I think the argument is about munmap_ prefix should be used.

>
>>   {
>> -	unsigned long end;
>> -	struct vm_area_struct *vma, *prev, *last;
>> -
>>   	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
>> -		return -EINVAL;
>> +		return false;
>>   
>> -	len = PAGE_ALIGN(len);
>> -	if (len == 0)
>> -		return -EINVAL;
>> +	if (PAGE_ALIGN(len) == 0)
>> +		return false;
>> +
>> +	return true;
>> +}
>> +
>> +/*
>> + * munmap_lookup_vma: find the first overlap vma and split overlap vmas.
>> + * @mm: mm_struct
>> + * @start: start address
>> + * @end: end address
>> + *
>> + * returns the pointer to vma, NULL or err ptr when spilt_vma returns error.
> kernel-doc prefers:
>
>   * Return: %NULL if no VMA overlaps this range.  An ERR_PTR if an
>   * overlapping VMA could not be split.  Otherwise a pointer to the first
>   * VMA which overlaps the range.

Ok, will fix it.

>
>> + */
>> +static struct vm_area_struct *munmap_lookup_vma(struct mm_struct *mm,
>> +			unsigned long start, unsigned long end)
>> +{
>> +	struct vm_area_struct *vma, *prev, *last;
>>   
>>   	/* Find the first overlapping VMA */
>>   	vma = find_vma(mm, start);
>>   	if (!vma)
>> -		return 0;
>> -	prev = vma->vm_prev;
>> -	/* we have  start < vma->vm_end  */
>> +		return NULL;
>>   
>> +	/* we have  start < vma->vm_end  */
> Can you remove the duplicate spaces here?

Sure

Thanks,
Yang