Re: [PATCH v2 2/2] mm: kvmalloc: align kvrealloc() with krealloc()

[Vlastimil Babka]

On 7/22/24 6:29 PM, Danilo Krummrich wrote:
> Besides the obvious (and desired) difference between krealloc() and
> kvrealloc(), there is some inconsistency in their function signatures
> and behavior:
> 
>  - krealloc() frees the memory when the requested size is zero, whereas
>    kvrealloc() simply returns a pointer to the existing allocation.
> 
>  - krealloc() behaves like kmalloc() if a NULL pointer is passed, whereas
>    kvrealloc() does not accept a NULL pointer at all and, if passed,
>    would fault instead.
> 
>  - krealloc() is self-contained, whereas kvrealloc() relies on the caller
>    to provide the size of the previous allocation.
> 
> Inconsistent behavior throughout allocation APIs is error prone, hence make
> kvrealloc() behave like krealloc(), which seems superior in all mentioned
> aspects.
> 
> Besides that, implementing kvrealloc() by making use of krealloc() and
> vrealloc() provides oppertunities to grow (and shrink) allocations more
> efficiently. For instance, vrealloc() can be optimized to allocate and
> map additional pages to grow the allocation or unmap and free unused
> pages to shrink the allocation.
> 
> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

with same caveat about the __GFP_ZERO comment on kvrealloc_noprof()