Re: [Xen-devel] [PATCH V6 3/8] xen/common: Introduce _xrealloc function

[Oleksandr <olekstysh@gmail.com>]

On 26.09.19 15:19, Jan Beulich wrote:

Hi, Jan

> On 26.09.2019 13:20, Oleksandr Tyshchenko wrote:
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> This patch introduces type-unsafe function which besides
>> re-allocation handles the following corner cases:
>> 1. if requested size is zero, it will behave like xfree
>> 2. if incoming pointer is not valid (NULL or ZERO_BLOCK_PTR),
>>     it will behave like xmalloc
>>
>> If both pointer and size are valid the function will re-allocate and
>> copy only if requested size and alignment don't fit in already
>> allocated space.
>>
>> Subsequent patch will add type-safe helper macros.
>>
>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Thank you!


> preferably with two more cosmetics addressed (can surely be done
> while committing):
>
>> --- a/xen/common/xmalloc_tlsf.c
>> +++ b/xen/common/xmalloc_tlsf.c
>> @@ -549,10 +549,40 @@ static void tlsf_init(void)
>>    * xmalloc()
>>    */
>>   
>> +static void *strip_padding(void *p)
>> +{
>> +    struct bhdr *b = p - BHDR_OVERHEAD;
> Looks like this can (and hence should) be pointer to const.

agree


>
>
>> @@ -593,10 +616,71 @@ void *_xzalloc(unsigned long size, unsigned long align)
>>       return p ? memset(p, 0, size) : p;
>>   }
>>   
>> -void xfree(void *p)
>> +void *_xrealloc(void *ptr, unsigned long size, unsigned long align)
>>   {
>> -    struct bhdr *b;
>> +    unsigned long curr_size;
>> +    void *p;
>> +
>> +    if ( !size )
>> +    {
>> +        xfree(ptr);
>> +        return ZERO_BLOCK_PTR;
>> +    }
>>   
>> +    if ( ptr == NULL || ptr == ZERO_BLOCK_PTR )
>> +        return _xmalloc(size, align);
>> +
>> +    ASSERT(!(align & (align - 1)));
>> +    if ( align < MEM_ALIGN )
>> +        align = MEM_ALIGN;
>> +
>> +    if ( !((unsigned long)ptr & (PAGE_SIZE - 1)) )
>> +    {
>> +        curr_size = (unsigned long)PFN_ORDER(virt_to_page(ptr)) << PAGE_SHIFT;
>> +
>> +        if ( size <= curr_size && !((unsigned long)ptr & (align - 1)) )
>> +            return ptr;
>> +    }
>> +    else
>> +    {
>> +        unsigned long tmp_size;
>> +        struct bhdr *b;
> Same here.

agree


>
>> +        tmp_size = size + align - MEM_ALIGN;
> This could also be the initializer of the variable.

agree

-- 
Regards,

Oleksandr Tyshchenko


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