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

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Message-Id: <D562EE6A-DE99-4C97-8934-D60682DDE711@konsulko.se>
Date: Tue, 24 Jun 2025 14:15:01 +0200
From: Vitaly Wool <vitaly.wool@...sulko.se>
To: Uladzislau Rezki <urezki@...il.com>
Cc: linux-mm@...ck.org,
 akpm@...ux-foundation.org,
 linux-kernel@...r.kernel.org,
 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 Jun 24, 2025, at 2:02 PM, Uladzislau Rezki <urezki@...il.com> wrote:
> 
> 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.
> 

There’s a patch pending inclusion of this one which will be the user of this change. I was reluctant
to combine these 2 in one series because the second one is on the Rust side, but it can be found
here: https://github.com/vwool/linux-mm/pull/new/realloc-extend.

~Vitaly