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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.09.2019 13:20, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> 
> 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@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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.


> @@ -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.

> +        tmp_size = size + align - MEM_ALIGN;

This could also be the initializer of the variable.

Jan

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