linux-kernel - Re: [PATCH] mm/vmalloc: allow to set node and align in vrealloc

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Message-ID: <aFqT1mK7SYsYd3DZ@pc636>
Date: Tue, 24 Jun 2025 14:02:30 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Vitaly Wool <vitaly.wool@...sulko.se>
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Uladzislau Rezki <urezki@...il.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: allow to set node and align in vrealloc

On Tue, Jun 24, 2025 at 11:51:21AM +0200, Vitaly Wool wrote:
> Reimplement vrealloc() to be able to set node and alignment should
> a user need to do so. Rename the function to vrealloc_node() to
> better match what it actually does now and introduce a macro for
> vrealloc() for backward compatibility.
> 
> With that change we also provide the ability for the Rust part of
> the kernel to set node and aligmnent in its allocations.
> 
> Signed-off-by: Vitaly Wool <vitaly.wool@...sulko.se>
> ---
>  include/linux/vmalloc.h |  8 +++++---
>  mm/vmalloc.c            | 16 +++++++++++++---
>  2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index fdc9aeb74a44..7d5251287687 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -197,9 +197,11 @@ extern void *__vcalloc_noprof(size_t n, size_t size, gfp_t flags) __alloc_size(1
>  extern void *vcalloc_noprof(size_t n, size_t size) __alloc_size(1, 2);
>  #define vcalloc(...)		alloc_hooks(vcalloc_noprof(__VA_ARGS__))
>  
> -void * __must_check vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> -		__realloc_size(2);
> -#define vrealloc(...)		alloc_hooks(vrealloc_noprof(__VA_ARGS__))
> +void *__must_check vrealloc_node_noprof(const void *p, size_t size,
> +		unsigned long align, gfp_t flags, int nid) __realloc_size(2);
> +#define vrealloc_noprof(p, s, f)	vrealloc_node_noprof(p, s, 1, f, NUMA_NO_NODE)
> +#define vrealloc_node(...)		alloc_hooks(vrealloc_node_noprof(__VA_ARGS__))
> +#define vrealloc(...)			alloc_hooks(vrealloc_noprof(__VA_ARGS__))
>  
>  extern void vfree(const void *addr);
>  extern void vfree_atomic(const void *addr);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ab986dd09b6a..117894301db1 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -4081,10 +4081,12 @@ void *vzalloc_node_noprof(unsigned long size, int node)
>  EXPORT_SYMBOL(vzalloc_node_noprof);
>  
>  /**
> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
> + * vrealloc_node - reallocate virtually contiguous memory; contents remain unchanged
>   * @p: object to reallocate memory for
>   * @size: the size to reallocate
> + * @align: requested alignment
>   * @flags: the flags for the page level allocator
> + * @nid: node id
>   *
>   * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is 0 and
>   * @p is not a %NULL pointer, the object pointed to is freed.
> @@ -4103,7 +4105,7 @@ EXPORT_SYMBOL(vzalloc_node_noprof);
>   * Return: pointer to the allocated memory; %NULL if @size is zero or in case of
>   *         failure
>   */
> -void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> +void *vrealloc_node_noprof(const void *p, size_t size, unsigned long align, gfp_t flags, int nid)
>  {
>  	struct vm_struct *vm = NULL;
>  	size_t alloced_size = 0;
> @@ -4127,6 +4129,13 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
>  		if (WARN(alloced_size < old_size,
>  			 "vrealloc() has mismatched area vs requested sizes (%p)\n", p))
>  			return NULL;
> +		if (WARN(nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)),
> +			 "vrealloc() has mismatched nids\n"))
> +			return NULL;
> +		if (WARN((uintptr_t)p & (align - 1),
> +			 "will not reallocate with a bigger alignment (0x%lx)\n",
> +			 align))
> +			return NULL;
>  	}
>  
>  	/*
> @@ -4158,7 +4167,8 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
>  	}
>  
>  	/* TODO: Grow the vm_area, i.e. allocate and map additional pages. */
> -	n = __vmalloc_noprof(size, flags);
> +	n = __vmalloc_node_noprof(size, align, flags, nid, __builtin_return_address(0));
> +
>  	if (!n)
>  		return NULL;
>  
> -- 
> 2.39.2
> 
Do we have users which require alignment and nid? I see that it is part
of kvrealloc() API only.

--
Uladzislau Rezki