[PATCH v9 0/4] support large align and nid in Rust allocators

[PATCH v9 0/4] support large align and nid in Rust allocators

[Vitaly Wool]

The coming patches provide the ability for Rust allocators to set
NUMA node and large alignment.

Changelog:
v2 -> v3:
* fixed the build breakage for non-MMU configs
v3 -> v4:
* added NUMA node support for k[v]realloc (patch #2)
* removed extra logic in Rust helpers
* patch for Rust allocators split into 2 (align: patch #3 and
  NUMA ids: patch #4)
v4 -> v5:
* reworked NUMA node support for k[v]realloc for all 3 <alloc>_node
  functions to have the same signature
* all 3 <alloc>_node slab/vmalloc functions now support alignment
  specification
* Rust helpers are extended with new functions, the old ones are left
  intact
* Rust support for NUMA nodes comes first now (as patch #3)
v5 -> v6:
* added <alloc>_node_align functions to keep the existing interfaces
  intact
* clearer separation for Rust support of MUNA ids and large alignments
v6 -> v7:
* NUMA identifier as a new Rust type (NumaNode)
* better documentation for changed and new functions and constants
v7 -> v8:
* removed NumaError
* small cleanups per reviewers' comments
v8 -> v9:
* realloc functions can now reallocate memory for a different NUMA
  node
* better comments/explanations in the Rust part

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>

[PATCH v9 1/4] mm/vmalloc: allow to set node and align in vrealloc

[Vitaly Wool]

Reimplement vrealloc() to be able to set node and alignment should
a user need to do so. Rename the function to vrealloc_node_align()
to better match what it actually does now and introduce macros for
vrealloc() and friends 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@konsulko.se>
---
 include/linux/vmalloc.h | 12 +++++++++---
 mm/vmalloc.c            | 19 +++++++++++++++----
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index fdc9aeb74a44..68791f7cb3ba 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -197,9 +197,15 @@ 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_align_noprof(const void *p, size_t size,
+		unsigned long align, gfp_t flags, int nid) __realloc_size(2);
+#define vrealloc_node_noprof(_p, _s, _f, _nid)	\
+	vrealloc_node_align_noprof(_p, _s, 1, _f, _nid)
+#define vrealloc_noprof(_p, _s, _f)		\
+	vrealloc_node_align_noprof(_p, _s, 1, _f, NUMA_NO_NODE)
+#define vrealloc_node_align(...)		alloc_hooks(vrealloc_node_align_noprof(__VA_ARGS__))
+#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 6dbcdceecae1..776c68f84ce2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4089,12 +4089,15 @@ void *vzalloc_node_noprof(unsigned long size, int node)
 EXPORT_SYMBOL(vzalloc_node_noprof);
 
 /**
- * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
+ * vrealloc_node_align_noprof - 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
+ * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If @size is 0 and
  * @p is not a %NULL pointer, the object pointed to is freed.
  *
  * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
@@ -4111,7 +4114,8 @@ 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_align_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;
@@ -4135,6 +4139,11 @@ 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(!IS_ALIGNED((unsigned long)p, align),
+			 "will not reallocate with a bigger alignment (0x%lx)\n", align))
+			return NULL;
+		if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
+			goto need_realloc;
 	}
 
 	/*
@@ -4165,8 +4174,10 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
 		return (void *)p;
 	}
 
+need_realloc:
 	/* 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

Re: [PATCH v9 1/4] mm/vmalloc: allow to set node and align in vrealloc

[Uladzislau Rezki]

On Tue, Jul 01, 2025 at 12:16:15AM +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_align()
> to better match what it actually does now and introduce macros for
> vrealloc() and friends 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@konsulko.se>
> ---
>  include/linux/vmalloc.h | 12 +++++++++---
>  mm/vmalloc.c            | 19 +++++++++++++++----
>  2 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index fdc9aeb74a44..68791f7cb3ba 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -197,9 +197,15 @@ 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_align_noprof(const void *p, size_t size,
> +		unsigned long align, gfp_t flags, int nid) __realloc_size(2);
> +#define vrealloc_node_noprof(_p, _s, _f, _nid)	\
> +	vrealloc_node_align_noprof(_p, _s, 1, _f, _nid)
> +#define vrealloc_noprof(_p, _s, _f)		\
> +	vrealloc_node_align_noprof(_p, _s, 1, _f, NUMA_NO_NODE)
> +#define vrealloc_node_align(...)		alloc_hooks(vrealloc_node_align_noprof(__VA_ARGS__))
> +#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 6dbcdceecae1..776c68f84ce2 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -4089,12 +4089,15 @@ void *vzalloc_node_noprof(unsigned long size, int node)
>  EXPORT_SYMBOL(vzalloc_node_noprof);
>  
>  /**
> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
> + * vrealloc_node_align_noprof - 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
> + * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If @size is 0 and
>   * @p is not a %NULL pointer, the object pointed to is freed.
>   *
>   * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
> @@ -4111,7 +4114,8 @@ 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_align_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;
> @@ -4135,6 +4139,11 @@ 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(!IS_ALIGNED((unsigned long)p, align),
> +			 "will not reallocate with a bigger alignment (0x%lx)\n", align))
> +			return NULL;
> +		if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
> +			goto need_realloc;
>
By this goto change, you bypass the two important checks below. For
example if you shrink the allocated size, you do not need to perform
any allocations. Instead the patch goes and allocates a new area.

You just need to remove:

-		if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
-			goto need_realloc;

to make it working.

--
Uladzislau Rezki

Re: [PATCH v9 1/4] mm/vmalloc: allow to set node and align in vrealloc

[Vitaly Wool]

> On Jul 1, 2025, at 12:50 PM, Uladzislau Rezki <urezki@gmail.com> wrote:
> 
> On Tue, Jul 01, 2025 at 12:16:15AM +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_align()
>> to better match what it actually does now and introduce macros for
>> vrealloc() and friends 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@konsulko.se>
>> ---
>> include/linux/vmalloc.h | 12 +++++++++---
>> mm/vmalloc.c            | 19 +++++++++++++++----
>> 2 files changed, 24 insertions(+), 7 deletions(-)
>> 
>> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
>> index fdc9aeb74a44..68791f7cb3ba 100644
>> --- a/include/linux/vmalloc.h
>> +++ b/include/linux/vmalloc.h
>> @@ -197,9 +197,15 @@ 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_align_noprof(const void *p, size_t size,
>> + unsigned long align, gfp_t flags, int nid) __realloc_size(2);
>> +#define vrealloc_node_noprof(_p, _s, _f, _nid) \
>> + vrealloc_node_align_noprof(_p, _s, 1, _f, _nid)
>> +#define vrealloc_noprof(_p, _s, _f) \
>> + vrealloc_node_align_noprof(_p, _s, 1, _f, NUMA_NO_NODE)
>> +#define vrealloc_node_align(...) alloc_hooks(vrealloc_node_align_noprof(__VA_ARGS__))
>> +#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 6dbcdceecae1..776c68f84ce2 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -4089,12 +4089,15 @@ void *vzalloc_node_noprof(unsigned long size, int node)
>> EXPORT_SYMBOL(vzalloc_node_noprof);
>> 
>> /**
>> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
>> + * vrealloc_node_align_noprof - 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
>> + * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If @size is 0 and
>>  * @p is not a %NULL pointer, the object pointed to is freed.
>>  *
>>  * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
>> @@ -4111,7 +4114,8 @@ 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_align_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;
>> @@ -4135,6 +4139,11 @@ 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(!IS_ALIGNED((unsigned long)p, align),
>> + "will not reallocate with a bigger alignment (0x%lx)\n", align))
>> + return NULL;
>> + if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
>> + goto need_realloc;
>> 
> By this goto change, you bypass the two important checks below. For
> example if you shrink the allocated size, you do not need to perform
> any allocations. Instead the patch goes and allocates a new area.
> 
> You just need to remove:
> 
> - if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
> - goto need_realloc;
> 
> to make it working.
> 

I am not sure I’m following. If we get a request to reallocate for a different node then we should either reject it or do the new allocation for this new node and copy the data to the new place. Shrinking the allocation on the old node doesn’t seem to be right. Or am I missing something?

~Vitaly

Re: [PATCH v9 1/4] mm/vmalloc: allow to set node and align in vrealloc

[Uladzislau Rezki]

On Tue, Jul 01, 2025 at 12:54:36PM +0200, Vitaly Wool wrote:
> 
> 
> > On Jul 1, 2025, at 12:50 PM, Uladzislau Rezki <urezki@gmail.com> wrote:
> > 
> > On Tue, Jul 01, 2025 at 12:16:15AM +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_align()
> >> to better match what it actually does now and introduce macros for
> >> vrealloc() and friends 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@konsulko.se>
> >> ---
> >> include/linux/vmalloc.h | 12 +++++++++---
> >> mm/vmalloc.c            | 19 +++++++++++++++----
> >> 2 files changed, 24 insertions(+), 7 deletions(-)
> >> 
> >> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> >> index fdc9aeb74a44..68791f7cb3ba 100644
> >> --- a/include/linux/vmalloc.h
> >> +++ b/include/linux/vmalloc.h
> >> @@ -197,9 +197,15 @@ 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_align_noprof(const void *p, size_t size,
> >> + unsigned long align, gfp_t flags, int nid) __realloc_size(2);
> >> +#define vrealloc_node_noprof(_p, _s, _f, _nid) \
> >> + vrealloc_node_align_noprof(_p, _s, 1, _f, _nid)
> >> +#define vrealloc_noprof(_p, _s, _f) \
> >> + vrealloc_node_align_noprof(_p, _s, 1, _f, NUMA_NO_NODE)
> >> +#define vrealloc_node_align(...) alloc_hooks(vrealloc_node_align_noprof(__VA_ARGS__))
> >> +#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 6dbcdceecae1..776c68f84ce2 100644
> >> --- a/mm/vmalloc.c
> >> +++ b/mm/vmalloc.c
> >> @@ -4089,12 +4089,15 @@ void *vzalloc_node_noprof(unsigned long size, int node)
> >> EXPORT_SYMBOL(vzalloc_node_noprof);
> >> 
> >> /**
> >> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
> >> + * vrealloc_node_align_noprof - 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
> >> + * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If @size is 0 and
> >>  * @p is not a %NULL pointer, the object pointed to is freed.
> >>  *
> >>  * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
> >> @@ -4111,7 +4114,8 @@ 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_align_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;
> >> @@ -4135,6 +4139,11 @@ 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(!IS_ALIGNED((unsigned long)p, align),
> >> + "will not reallocate with a bigger alignment (0x%lx)\n", align))
> >> + return NULL;
> >> + if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
> >> + goto need_realloc;
> >> 
> > By this goto change, you bypass the two important checks below. For
> > example if you shrink the allocated size, you do not need to perform
> > any allocations. Instead the patch goes and allocates a new area.
> > 
> > You just need to remove:
> > 
> > - if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
> > - goto need_realloc;
> > 
> > to make it working.
> > 
> 
> I am not sure I’m following. If we get a request to reallocate for a different node then we should either reject it or do the new allocation for this new node and copy the data to the new place. Shrinking the allocation on the old node doesn’t seem to be right. Or am I missing something?
> 
If your process migrates to a new NODE, which is fine, it does not mean
that you have to perform all this bouncing movement(reallocate on a new node).
Next time it can be migrated back. Process are allowed to migrate and access
to a remote memory.

Let's keep it simple.

--
Uladzislau Rezki

Re: [PATCH v9 1/4] mm/vmalloc: allow to set node and align in vrealloc

[Vitaly Wool]

> On Jul 1, 2025, at 1:16 PM, Uladzislau Rezki <urezki@gmail.com> wrote:
> 
> On Tue, Jul 01, 2025 at 12:54:36PM +0200, Vitaly Wool wrote:
>> 
>> 
>>> On Jul 1, 2025, at 12:50 PM, Uladzislau Rezki <urezki@gmail.com> wrote:
>>> 
>>> On Tue, Jul 01, 2025 at 12:16:15AM +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_align()
>>>> to better match what it actually does now and introduce macros for
>>>> vrealloc() and friends 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@konsulko.se>
>>>> ---
>>>> include/linux/vmalloc.h | 12 +++++++++---
>>>> mm/vmalloc.c            | 19 +++++++++++++++----
>>>> 2 files changed, 24 insertions(+), 7 deletions(-)
>>>> 
>>>> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
>>>> index fdc9aeb74a44..68791f7cb3ba 100644
>>>> --- a/include/linux/vmalloc.h
>>>> +++ b/include/linux/vmalloc.h
>>>> @@ -197,9 +197,15 @@ 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_align_noprof(const void *p, size_t size,
>>>> + unsigned long align, gfp_t flags, int nid) __realloc_size(2);
>>>> +#define vrealloc_node_noprof(_p, _s, _f, _nid) \
>>>> + vrealloc_node_align_noprof(_p, _s, 1, _f, _nid)
>>>> +#define vrealloc_noprof(_p, _s, _f) \
>>>> + vrealloc_node_align_noprof(_p, _s, 1, _f, NUMA_NO_NODE)
>>>> +#define vrealloc_node_align(...) alloc_hooks(vrealloc_node_align_noprof(__VA_ARGS__))
>>>> +#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 6dbcdceecae1..776c68f84ce2 100644
>>>> --- a/mm/vmalloc.c
>>>> +++ b/mm/vmalloc.c
>>>> @@ -4089,12 +4089,15 @@ void *vzalloc_node_noprof(unsigned long size, int node)
>>>> EXPORT_SYMBOL(vzalloc_node_noprof);
>>>> 
>>>> /**
>>>> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
>>>> + * vrealloc_node_align_noprof - 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
>>>> + * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If @size is 0 and
>>>> * @p is not a %NULL pointer, the object pointed to is freed.
>>>> *
>>>> * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
>>>> @@ -4111,7 +4114,8 @@ 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_align_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;
>>>> @@ -4135,6 +4139,11 @@ 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(!IS_ALIGNED((unsigned long)p, align),
>>>> + "will not reallocate with a bigger alignment (0x%lx)\n", align))
>>>> + return NULL;
>>>> + if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
>>>> + goto need_realloc;
>>>> 
>>> By this goto change, you bypass the two important checks below. For
>>> example if you shrink the allocated size, you do not need to perform
>>> any allocations. Instead the patch goes and allocates a new area.
>>> 
>>> You just need to remove:
>>> 
>>> - if (nid != NUMA_NO_NODE && nid != page_to_nid(vmalloc_to_page(p)))
>>> - goto need_realloc;
>>> 
>>> to make it working.
>>> 
>> 
>> I am not sure I’m following. If we get a request to reallocate for a different node then we should either reject it or do the new allocation for this new node and copy the data to the new place. Shrinking the allocation on the old node doesn’t seem to be right. Or am I missing something?
>> 
> If your process migrates to a new NODE, which is fine, it does not mean
> that you have to perform all this bouncing movement(reallocate on a new node).
> Next time it can be migrated back. Process are allowed to migrate and access
> to a remote memory.
> 

Indeed, but in that case the caller is expected to specify NUMA_NO_NODE in vrealloc_node_align(). If the caller did specify an exact node we can’t just silently disregard that, we should either respect that or fail.

~Vitaly

[PATCH v9 2/4] mm/slub: allow to set node and align in k[v]realloc

[Vitaly Wool]

Reimplement k[v]realloc_node() to be able to set node and
alignment should a user need to do so. In order to do that while
retaining the maximal backward compatibility, add
k[v]realloc_node_align() functions and redefine the rest of API
using these new ones.

With that change we also provide the ability for the Rust part of
the kernel to set node and aligmnent in its K[v]xxx
[re]allocations.

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
---
 include/linux/slab.h | 40 ++++++++++++++++++++----------
 mm/nommu.c           |  3 ++-
 mm/slub.c            | 58 +++++++++++++++++++++++++++++---------------
 3 files changed, 67 insertions(+), 34 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index d5a8ab98035c..13abcf4ada22 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -465,9 +465,15 @@ int kmem_cache_shrink(struct kmem_cache *s);
 /*
  * Common kmalloc functions provided by all allocators
  */
-void * __must_check krealloc_noprof(const void *objp, size_t new_size,
-				    gfp_t flags) __realloc_size(2);
-#define krealloc(...)				alloc_hooks(krealloc_noprof(__VA_ARGS__))
+void * __must_check krealloc_node_align_noprof(const void *objp, size_t new_size,
+					       unsigned long align,
+					       gfp_t flags, int nid) __realloc_size(2);
+#define krealloc_node_noprof(_p, _s, _f, _n) \
+	krealloc_node_align_noprof(_p, _s, 1, _f, _n)
+#define krealloc_noprof(...)		krealloc_node_noprof(__VA_ARGS__, NUMA_NO_NODE)
+#define krealloc_node_align(...)	alloc_hooks(krealloc_node_align_noprof(__VA_ARGS__))
+#define krealloc_node(...)		alloc_hooks(krealloc_node_noprof(__VA_ARGS__))
+#define krealloc(...)			alloc_hooks(krealloc_noprof(__VA_ARGS__))
 
 void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
@@ -1041,18 +1047,23 @@ static inline __alloc_size(1) void *kzalloc_noprof(size_t size, gfp_t flags)
 #define kzalloc(...)				alloc_hooks(kzalloc_noprof(__VA_ARGS__))
 #define kzalloc_node(_size, _flags, _node)	kmalloc_node(_size, (_flags)|__GFP_ZERO, _node)
 
-void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node) __alloc_size(1);
-#define kvmalloc_node_noprof(size, flags, node)	\
-	__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(size, NULL), flags, node)
+void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align,
+			     gfp_t flags, int node) __alloc_size(1);
+#define kvmalloc_node_align_noprof(_size, _align, _flags, _node)	\
+	__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(_size, NULL), _align, _flags, _node)
+#define kvmalloc_node_noprof(_size, _flags, _node)	\
+	kvmalloc_node_align_noprof(_size, 1, _flags, _node)
+#define kvmalloc_node_align(...)		\
+	alloc_hooks(kvmalloc_node_align_noprof(__VA_ARGS__))
 #define kvmalloc_node(...)			alloc_hooks(kvmalloc_node_noprof(__VA_ARGS__))
 
-#define kvmalloc(_size, _flags)			kvmalloc_node(_size, _flags, NUMA_NO_NODE)
-#define kvmalloc_noprof(_size, _flags)		kvmalloc_node_noprof(_size, _flags, NUMA_NO_NODE)
+#define kvmalloc_noprof(...)			kvmalloc_node_noprof(__VA_ARGS__, NUMA_NO_NODE)
+#define kvmalloc(...)				alloc_hooks(kvmalloc_noprof(__VA_ARGS__))
 #define kvzalloc(_size, _flags)			kvmalloc(_size, (_flags)|__GFP_ZERO)
 
-#define kvzalloc_node(_size, _flags, _node)	kvmalloc_node(_size, (_flags)|__GFP_ZERO, _node)
+#define kvzalloc_node(_s, _f, _n)		kvmalloc_node(_s, (_f)|__GFP_ZERO, _n)
 #define kmem_buckets_valloc(_b, _size, _flags)	\
-	alloc_hooks(__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(_size, _b), _flags, NUMA_NO_NODE))
+	alloc_hooks(__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(_size, _b), 1, _flags, NUMA_NO_NODE))
 
 static inline __alloc_size(1, 2) void *
 kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node)
@@ -1068,13 +1079,16 @@ kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node)
 #define kvmalloc_array_noprof(...)		kvmalloc_array_node_noprof(__VA_ARGS__, NUMA_NO_NODE)
 #define kvcalloc_node_noprof(_n,_s,_f,_node)	kvmalloc_array_node_noprof(_n,_s,(_f)|__GFP_ZERO,_node)
 #define kvcalloc_noprof(...)			kvcalloc_node_noprof(__VA_ARGS__, NUMA_NO_NODE)
-
 #define kvmalloc_array(...)			alloc_hooks(kvmalloc_array_noprof(__VA_ARGS__))
 #define kvcalloc_node(...)			alloc_hooks(kvcalloc_node_noprof(__VA_ARGS__))
 #define kvcalloc(...)				alloc_hooks(kvcalloc_noprof(__VA_ARGS__))
 
-void *kvrealloc_noprof(const void *p, size_t size, gfp_t flags)
-		__realloc_size(2);
+void *kvrealloc_node_align_noprof(const void *p, size_t size, unsigned long align,
+				  gfp_t flags, int nid) __realloc_size(2);
+#define kvrealloc_node_align(...)		kvrealloc_node_align_noprof(__VA_ARGS__)
+#define kvrealloc_node_noprof(_p, _s, _f, _n)	kvrealloc_node_align_noprof(_p, _s, 1, _f, _n)
+#define kvrealloc_node(...)			alloc_hooks(kvrealloc_node_noprof(__VA_ARGS__))
+#define kvrealloc_noprof(...)			kvrealloc_node_noprof(__VA_ARGS__, NUMA_NO_NODE)
 #define kvrealloc(...)				alloc_hooks(kvrealloc_noprof(__VA_ARGS__))
 
 extern void kvfree(const void *addr);
diff --git a/mm/nommu.c b/mm/nommu.c
index 87e1acab0d64..8359b2025b9f 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -119,7 +119,8 @@ void *__vmalloc_noprof(unsigned long size, gfp_t gfp_mask)
 }
 EXPORT_SYMBOL(__vmalloc_noprof);
 
-void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
+void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align,
+				 gfp_t flags, int node)
 {
 	return krealloc_noprof(p, size, (flags | __GFP_COMP) & ~__GFP_HIGHMEM);
 }
diff --git a/mm/slub.c b/mm/slub.c
index c4b64821e680..2caf94f27dc5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4845,7 +4845,7 @@ void kfree(const void *object)
 EXPORT_SYMBOL(kfree);
 
 static __always_inline __realloc_size(2) void *
-__do_krealloc(const void *p, size_t new_size, gfp_t flags)
+__do_krealloc(const void *p, size_t new_size, unsigned long align, gfp_t flags, int nid)
 {
 	void *ret;
 	size_t ks = 0;
@@ -4859,6 +4859,14 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags)
 	if (!kasan_check_byte(p))
 		return NULL;
 
+	/* refuse to proceed if alignment is bigger than what kmalloc() provides */
+	if (!IS_ALIGNED((unsigned long)p, align) || new_size < align)
+		return NULL;
+
+	/* different NUMA id requested => new allocation required */
+	if (nid != NUMA_NO_NODE && nid != page_to_nid(virt_to_page(p)))
+		goto alloc_new;
+
 	if (is_kfence_address(p)) {
 		ks = orig_size = kfence_ksize(p);
 	} else {
@@ -4903,7 +4911,7 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags)
 	return (void *)p;
 
 alloc_new:
-	ret = kmalloc_node_track_caller_noprof(new_size, flags, NUMA_NO_NODE, _RET_IP_);
+	ret = kmalloc_node_track_caller_noprof(new_size, flags, nid, _RET_IP_);
 	if (ret && p) {
 		/* Disable KASAN checks as the object's redzone is accessed. */
 		kasan_disable_current();
@@ -4915,10 +4923,12 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags)
 }
 
 /**
- * krealloc - reallocate memory. The contents will remain unchanged.
+ * krealloc_node_align - reallocate memory. The contents will remain unchanged.
  * @p: object to reallocate memory for.
  * @new_size: how many bytes of memory are required.
+ * @align: desired alignment.
  * @flags: the type of memory to allocate.
+ * @nid: NUMA node or NUMA_NO_NODE
  *
  * If @p is %NULL, krealloc() behaves exactly like kmalloc().  If @new_size
  * is 0 and @p is not a %NULL pointer, the object pointed to is freed.
@@ -4947,7 +4957,8 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags)
  *
  * Return: pointer to the allocated memory or %NULL in case of error
  */
-void *krealloc_noprof(const void *p, size_t new_size, gfp_t flags)
+void *krealloc_node_align_noprof(const void *p, size_t new_size, unsigned long align,
+				 gfp_t flags, int nid)
 {
 	void *ret;
 
@@ -4956,13 +4967,13 @@ void *krealloc_noprof(const void *p, size_t new_size, gfp_t flags)
 		return ZERO_SIZE_PTR;
 	}
 
-	ret = __do_krealloc(p, new_size, flags);
+	ret = __do_krealloc(p, new_size, align, flags, nid);
 	if (ret && kasan_reset_tag(p) != kasan_reset_tag(ret))
 		kfree(p);
 
 	return ret;
 }
-EXPORT_SYMBOL(krealloc_noprof);
+EXPORT_SYMBOL(krealloc_node_align_noprof);
 
 static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size)
 {
@@ -4993,6 +5004,7 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size)
  * failure, fall back to non-contiguous (vmalloc) allocation.
  * @size: size of the request.
  * @b: which set of kmalloc buckets to allocate from.
+ * @align: desired alignment.
  * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
  * @node: numa node to allocate from
  *
@@ -5005,19 +5017,22 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size)
  *
  * Return: pointer to the allocated memory of %NULL in case of failure
  */
-void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node)
+void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align,
+			     gfp_t flags, int node)
 {
 	void *ret;
 
 	/*
 	 * It doesn't really make sense to fallback to vmalloc for sub page
-	 * requests
+	 * requests and small alignments
 	 */
-	ret = __do_kmalloc_node(size, PASS_BUCKET_PARAM(b),
-				kmalloc_gfp_adjust(flags, size),
-				node, _RET_IP_);
-	if (ret || size <= PAGE_SIZE)
-		return ret;
+	if (size >= align) {
+		ret = __do_kmalloc_node(size, PASS_BUCKET_PARAM(b),
+					kmalloc_gfp_adjust(flags, size),
+					node, _RET_IP_);
+		if (ret || size <= PAGE_SIZE)
+			return ret;
+	}
 
 	/* non-sleeping allocations are not supported by vmalloc */
 	if (!gfpflags_allow_blocking(flags))
@@ -5035,7 +5050,7 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node)
 	 * about the resulting pointer, and cannot play
 	 * protection games.
 	 */
-	return __vmalloc_node_range_noprof(size, 1, VMALLOC_START, VMALLOC_END,
+	return __vmalloc_node_range_noprof(size, align, VMALLOC_START, VMALLOC_END,
 			flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
 			node, __builtin_return_address(0));
 }
@@ -5079,10 +5094,12 @@ void kvfree_sensitive(const void *addr, size_t len)
 EXPORT_SYMBOL(kvfree_sensitive);
 
 /**
- * kvrealloc - reallocate memory; contents remain unchanged
+ * kvrealloc_node_align - reallocate memory; contents remain unchanged
  * @p: object to reallocate memory for
  * @size: the size to reallocate
+ * @align: desired alignment
  * @flags: the flags for the page level allocator
+ * @nid: NUMA node id
  *
  * If @p is %NULL, kvrealloc() behaves exactly like kvmalloc(). If @size is 0
  * and @p is not a %NULL pointer, the object pointed to is freed.
@@ -5100,17 +5117,18 @@ EXPORT_SYMBOL(kvfree_sensitive);
  *
  * Return: pointer to the allocated memory or %NULL in case of error
  */
-void *kvrealloc_noprof(const void *p, size_t size, gfp_t flags)
+void *kvrealloc_node_align_noprof(const void *p, size_t size, unsigned long align,
+				  gfp_t flags, int nid)
 {
 	void *n;
 
 	if (is_vmalloc_addr(p))
-		return vrealloc_noprof(p, size, flags);
+		return vrealloc_node_align_noprof(p, size, align, flags, nid);
 
-	n = krealloc_noprof(p, size, kmalloc_gfp_adjust(flags, size));
+	n = krealloc_node_align_noprof(p, size, align, kmalloc_gfp_adjust(flags, size), nid);
 	if (!n) {
 		/* We failed to krealloc(), fall back to kvmalloc(). */
-		n = kvmalloc_noprof(size, flags);
+		n = kvmalloc_node_align_noprof(size, align, flags, nid);
 		if (!n)
 			return NULL;
 
@@ -5126,7 +5144,7 @@ void *kvrealloc_noprof(const void *p, size_t size, gfp_t flags)
 
 	return n;
 }
-EXPORT_SYMBOL(kvrealloc_noprof);
+EXPORT_SYMBOL(kvrealloc_node_align_noprof);
 
 struct detached_freelist {
 	struct slab *slab;
-- 
2.39.2

Re: [PATCH v9 2/4] mm/slub: allow to set node and align in k[v]realloc

[Tamir Duberstein]

On Mon, Jun 30, 2025 at 6:16 PM Vitaly Wool <vitaly.wool@konsulko.se> wrote:
>
> Reimplement k[v]realloc_node() to be able to set node and
> alignment should a user need to do so. In order to do that while
> retaining the maximal backward compatibility, add
> k[v]realloc_node_align() functions and redefine the rest of API
> using these new ones.
>
> With that change we also provide the ability for the Rust part of
> the kernel to set node and aligmnent in its K[v]xxx
> [re]allocations.
>
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>

The typo (slub) snuck back in.

Re: [PATCH v9 2/4] mm/slub: allow to set node and align in k[v]realloc

[Vitaly Wool]

> On Jul 1, 2025, at 1:41 AM, Tamir Duberstein <tamird@gmail.com> wrote:
> 
> On Mon, Jun 30, 2025 at 6:16 PM Vitaly Wool <vitaly.wool@konsulko.se> wrote:
>> 
>> Reimplement k[v]realloc_node() to be able to set node and
>> alignment should a user need to do so. In order to do that while
>> retaining the maximal backward compatibility, add
>> k[v]realloc_node_align() functions and redefine the rest of API
>> using these new ones.
>> 
>> With that change we also provide the ability for the Rust part of
>> the kernel to set node and aligmnent in its K[v]xxx
>> [re]allocations.
>> 
>> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
> 
> The typo (slub) snuck back in.

Bummer. ;)

Thanks for pointing that out. I’ll fix it in the anniversary patchset, hopefully this will be the only thing to fix.

~Vitaly

[PATCH v9 3/4] rust: add support for NUMA ids in allocations

[Vitaly Wool]

Add a new type to support specifying NUMA identifiers in Rust
allocators and extend the allocators to have NUMA id as a
parameter. Thus, modify ReallocFunc to use the new extended realloc
primitives from the C side of the kernel (i. e.
k[v]realloc_node_align/vrealloc_node_align) and add the new function
alloc_node to the Allocator trait while keeping the existing one
(alloc) for backward compatibility.

This will allow to specify node to use for allocation of e. g.
{KV}Box, as well as for future NUMA aware users of the API.

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
---
 rust/helpers/slab.c            |  8 ++--
 rust/helpers/vmalloc.c         |  4 +-
 rust/kernel/alloc.rs           | 80 ++++++++++++++++++++++++++++++++--
 rust/kernel/alloc/allocator.rs | 42 ++++++++++--------
 4 files changed, 107 insertions(+), 27 deletions(-)

diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index a842bfbddcba..8472370a4338 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -3,13 +3,13 @@
 #include <linux/slab.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
+rust_helper_krealloc_node(const void *objp, size_t new_size, gfp_t flags, int node)
 {
-	return krealloc(objp, new_size, flags);
+	return krealloc_node(objp, new_size, flags, node);
 }
 
 void * __must_check __realloc_size(2)
-rust_helper_kvrealloc(const void *p, size_t size, gfp_t flags)
+rust_helper_kvrealloc_node(const void *p, size_t size, gfp_t flags, int node)
 {
-	return kvrealloc(p, size, flags);
+	return kvrealloc_node(p, size, flags, node);
 }
diff --git a/rust/helpers/vmalloc.c b/rust/helpers/vmalloc.c
index 80d34501bbc0..62d30db9a1a6 100644
--- a/rust/helpers/vmalloc.c
+++ b/rust/helpers/vmalloc.c
@@ -3,7 +3,7 @@
 #include <linux/vmalloc.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
+rust_helper_vrealloc_node(const void *p, size_t size, gfp_t flags, int node)
 {
-	return vrealloc(p, size, flags);
+	return vrealloc_node(p, size, flags, node);
 }
diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index a2c49e5494d3..e886ab31108f 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -28,7 +28,9 @@
 /// Indicates an allocation error.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct AllocError;
+
 use core::{alloc::Layout, ptr::NonNull};
+use crate::error::{code::EINVAL, Result};
 
 /// Flags to be used when allocating memory.
 ///
@@ -115,6 +117,31 @@ pub mod flags {
     pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN);
 }
 
+/// Non Uniform Memory Access (NUMA) node identifier
+#[derive(Clone, Copy, PartialEq)]
+pub struct NumaNode(i32);
+
+impl NumaNode {
+    /// create a new NUMA node identifer (non-negative integer)
+    /// returns EINVAL if a negative id or an id exceeding MAX_NUMNODES is specified
+    pub fn new(node: i32) -> Result<Self> {
+        // SAFETY: MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10
+        if node < 0 || node >= bindings::MAX_NUMNODES as i32 {
+            return Err(EINVAL);
+        }
+        Ok(Self(node))
+    }
+}
+
+/// Specify necessary constant to pass the information to Allocator that the caller doesn't care
+/// about the NUMA node to allocate memory from.
+pub mod numa {
+    use super::NumaNode;
+
+    /// No preference for NUMA node
+    pub const NUMA_NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
+}
+
 /// The kernel's [`Allocator`] trait.
 ///
 /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described
@@ -148,7 +175,7 @@ pub unsafe trait Allocator {
     ///
     /// When the return value is `Ok(ptr)`, then `ptr` is
     /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
-    ///   [`Allocator::free`] or [`Allocator::realloc`],
+    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
     /// - aligned to `layout.align()`,
     ///
     /// Additionally, `Flags` are honored as documented in
@@ -159,7 +186,38 @@ fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
         unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) }
     }
 
-    /// Re-allocate an existing memory allocation to satisfy the requested `layout`.
+    /// Allocate memory based on `layout`, `flags` and `nid`.
+    ///
+    /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
+    /// constraints (i.e. minimum size and alignment as specified by `layout`).
+    ///
+    /// This function is equivalent to `realloc_node` when called with `None`.
+    ///
+    /// # Guarantees
+    ///
+    /// When the return value is `Ok(ptr)`, then `ptr` is
+    /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
+    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
+    /// - aligned to `layout.align()`,
+    ///
+    /// Additionally, `Flags` are honored as documented in
+    /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>.
+    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
+                -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: Passing `None` to `realloc_node` is valid by its safety requirements and
+        // asks for a new memory allocation.
+        unsafe { Self::realloc_node(None, layout, Layout::new::<()>(), flags, nid) }
+    }
+
+    /// Re-allocate an existing memory allocation to satisfy the requested `layout` and
+    /// a specific NUMA node request to allocate the memory for.
+    ///
+    /// Systems employing a Non Uniform Memory Access (NUMA) architecture contain collections of
+    /// hardware resources including processors, memory, and I/O buses, that comprise what is
+    /// commonly known as a NUMA node.
+    ///
+    /// `nid` stands for NUMA id, i. e. NUMA node identifier, which is a non-negative
+    /// integer if a node needs to be specified, or NUMA_NO_NODE if the caller doesn't care.
     ///
     /// If the requested size is zero, `realloc` behaves equivalent to `free`.
     ///
@@ -191,13 +249,29 @@ fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
     ///   and old size, i.e. `ret_ptr[0..min(layout.size(), old_layout.size())] ==
     ///   p[0..min(layout.size(), old_layout.size())]`.
     /// - when the return value is `Err(AllocError)`, then `ptr` is still valid.
-    unsafe fn realloc(
+    unsafe fn realloc_node(
         ptr: Option<NonNull<u8>>,
         layout: Layout,
         old_layout: Layout,
         flags: Flags,
+        nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError>;
 
+
+    /// Re-allocate an existing memory allocation to satisfy the requested `layout`. This
+    /// function works exactly as realloc_node() but it doesn't give the ability to specify
+    /// the NUMA node in the call.
+    unsafe fn realloc(
+        ptr: Option<NonNull<u8>>,
+        layout: Layout,
+        old_layout: Layout,
+        flags: Flags,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: guaranteed by realloc_node()
+        unsafe { Self::realloc_node(ptr, layout, old_layout, flags, numa::NUMA_NO_NODE) }
+    }
+
+
     /// Free an existing memory allocation.
     ///
     /// # Safety
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index aa2dfa9dca4c..2e86e9839a1b 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -13,7 +13,7 @@
 use core::ptr;
 use core::ptr::NonNull;
 
-use crate::alloc::{AllocError, Allocator};
+use crate::alloc::{AllocError, Allocator, NumaNode};
 use crate::bindings;
 use crate::pr_warn;
 
@@ -58,18 +58,20 @@ fn aligned_size(new_layout: Layout) -> usize {
 ///
 /// One of the following: `krealloc`, `vrealloc`, `kvrealloc`.
 struct ReallocFunc(
-    unsafe extern "C" fn(*const crate::ffi::c_void, usize, u32) -> *mut crate::ffi::c_void,
+    unsafe extern "C" fn(
+        *const crate::ffi::c_void, usize,  u32, crate::ffi::c_int,
+    ) -> *mut crate::ffi::c_void,
 );
 
 impl ReallocFunc {
-    // INVARIANT: `krealloc` satisfies the type invariants.
-    const KREALLOC: Self = Self(bindings::krealloc);
+    // INVARIANT: `krealloc_node` satisfies the type invariants.
+    const KREALLOC: Self = Self(bindings::krealloc_node);
 
-    // INVARIANT: `vrealloc` satisfies the type invariants.
-    const VREALLOC: Self = Self(bindings::vrealloc);
+    // INVARIANT: `vrealloc_node` satisfies the type invariants.
+    const VREALLOC: Self = Self(bindings::vrealloc_node);
 
-    // INVARIANT: `kvrealloc` satisfies the type invariants.
-    const KVREALLOC: Self = Self(bindings::kvrealloc);
+    // INVARIANT: `kvrealloc_node` satisfies the type invariants.
+    const KVREALLOC: Self = Self(bindings::kvrealloc_node);
 
     /// # Safety
     ///
@@ -87,6 +89,7 @@ unsafe fn call(
         layout: Layout,
         old_layout: Layout,
         flags: Flags,
+        nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
         let size = aligned_size(layout);
         let ptr = match ptr {
@@ -110,7 +113,7 @@ unsafe fn call(
         // - Those functions provide the guarantees of this function.
         let raw_ptr = unsafe {
             // If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
-            self.0(ptr.cast(), size, flags.0).cast()
+            self.0(ptr.cast(), size, flags.0, nid.0).cast()
         };
 
         let ptr = if size == 0 {
@@ -123,34 +126,36 @@ unsafe fn call(
     }
 }
 
-// SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that
+// SAFETY: `realloc_node` delegates to `ReallocFunc::call`, which guarantees that
 // - memory remains valid until it is explicitly freed,
 // - passing a pointer to a valid memory allocation is OK,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for Kmalloc {
     #[inline]
-    unsafe fn realloc(
+    unsafe fn realloc_node(
         ptr: Option<NonNull<u8>>,
         layout: Layout,
         old_layout: Layout,
         flags: Flags,
+        nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
         // SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`.
-        unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) }
+        unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags, nid) }
     }
 }
 
-// SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that
+// SAFETY: `realloc_node` delegates to `ReallocFunc::call`, which guarantees that
 // - memory remains valid until it is explicitly freed,
 // - passing a pointer to a valid memory allocation is OK,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for Vmalloc {
     #[inline]
-    unsafe fn realloc(
+    unsafe fn realloc_node(
         ptr: Option<NonNull<u8>>,
         layout: Layout,
         old_layout: Layout,
         flags: Flags,
+        nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
         // TODO: Support alignments larger than PAGE_SIZE.
         if layout.align() > bindings::PAGE_SIZE {
@@ -160,21 +165,22 @@ unsafe fn realloc(
 
         // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
         // allocated with this `Allocator`.
-        unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags) }
+        unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags, nid) }
     }
 }
 
-// SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that
+// SAFETY: `realloc_node` delegates to `ReallocFunc::call`, which guarantees that
 // - memory remains valid until it is explicitly freed,
 // - passing a pointer to a valid memory allocation is OK,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for KVmalloc {
     #[inline]
-    unsafe fn realloc(
+    unsafe fn realloc_node(
         ptr: Option<NonNull<u8>>,
         layout: Layout,
         old_layout: Layout,
         flags: Flags,
+        nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
         // TODO: Support alignments larger than PAGE_SIZE.
         if layout.align() > bindings::PAGE_SIZE {
@@ -184,6 +190,6 @@ unsafe fn realloc(
 
         // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
         // allocated with this `Allocator`.
-        unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags) }
+        unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags, nid) }
     }
 }
-- 
2.39.2

Re: [PATCH v9 3/4] rust: add support for NUMA ids in allocations

[Alice Ryhl]

On Tue, Jul 01, 2025 at 12:16:40AM +0200, Vitaly Wool wrote:
> Add a new type to support specifying NUMA identifiers in Rust
> allocators and extend the allocators to have NUMA id as a
> parameter. Thus, modify ReallocFunc to use the new extended realloc
> primitives from the C side of the kernel (i. e.
> k[v]realloc_node_align/vrealloc_node_align) and add the new function
> alloc_node to the Allocator trait while keeping the existing one
> (alloc) for backward compatibility.
> 
> This will allow to specify node to use for allocation of e. g.
> {KV}Box, as well as for future NUMA aware users of the API.
> 
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>

My main feedback is that we should consider introducing a new trait
instead of modifying Allocator. What we could do is have a NodeAllocator
trait that is a super-trait of Allocator and has additional methods with
a node parameter.

A sketch:

pub unsafe trait NodeAllocator: Allocator {
    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
                -> Result<NonNull<[u8]>, AllocError>;

    unsafe fn realloc_node(
        ptr: Option<NonNull<u8>>,
        layout: Layout,
        old_layout: Layout,
        flags: Flags,
        nid: NumaNode,
    ) -> Result<NonNull<[u8]>, AllocError>;
}

By doing this, it's possible to have allocators that do not support
specifying the numa node which only implement Allocator, and to have
other allocators that implement both Allocator and NumaAllocator where
you are able to specify the node.

If all allocators in the kernel support numa nodes, then you can ignore
this.
> +/// Non Uniform Memory Access (NUMA) node identifier
> +#[derive(Clone, Copy, PartialEq)]
> +pub struct NumaNode(i32);
> +
> +impl NumaNode {
> +    /// create a new NUMA node identifer (non-negative integer)
> +    /// returns EINVAL if a negative id or an id exceeding MAX_NUMNODES is specified
> +    pub fn new(node: i32) -> Result<Self> {
> +        // SAFETY: MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10
> +        if node < 0 || node >= bindings::MAX_NUMNODES as i32 {
> +            return Err(EINVAL);
> +        }
> +        Ok(Self(node))
> +    }
> +}
> +
> +/// Specify necessary constant to pass the information to Allocator that the caller doesn't care
> +/// about the NUMA node to allocate memory from.
> +pub mod numa {
> +    use super::NumaNode;
> +
> +    /// No preference for NUMA node
> +    pub const NUMA_NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
> +}

Instead of using a module, you can make it an associated constant of the
struct.

impl NumaNode {
    pub const NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
}

This way you can access the constant as NumaNode::NO_NODE.

>  /// The kernel's [`Allocator`] trait.
>  ///
>  /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described
> @@ -148,7 +175,7 @@ pub unsafe trait Allocator {
>      ///
>      /// When the return value is `Ok(ptr)`, then `ptr` is
>      /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
> -    ///   [`Allocator::free`] or [`Allocator::realloc`],
> +    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
>      /// - aligned to `layout.align()`,
>      ///
>      /// Additionally, `Flags` are honored as documented in
> @@ -159,7 +186,38 @@ fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
>          unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) }
>      }
>  
> -    /// Re-allocate an existing memory allocation to satisfy the requested `layout`.
> +    /// Allocate memory based on `layout`, `flags` and `nid`.
> +    ///
> +    /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
> +    /// constraints (i.e. minimum size and alignment as specified by `layout`).
> +    ///
> +    /// This function is equivalent to `realloc_node` when called with `None`.
> +    ///
> +    /// # Guarantees
> +    ///
> +    /// When the return value is `Ok(ptr)`, then `ptr` is
> +    /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
> +    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
> +    /// - aligned to `layout.align()`,
> +    ///
> +    /// Additionally, `Flags` are honored as documented in
> +    /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>.
> +    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
> +                -> Result<NonNull<[u8]>, AllocError> {

I don't think this is how rustfmt would format this. Can you run rustfmt
on your patch?

Alice

Re: [PATCH v9 3/4] rust: add support for NUMA ids in allocations

[Vitaly Wool]

> On Jul 1, 2025, at 12:34 PM, Alice Ryhl <aliceryhl@google.com> wrote:
> 
> On Tue, Jul 01, 2025 at 12:16:40AM +0200, Vitaly Wool wrote:
>> Add a new type to support specifying NUMA identifiers in Rust
>> allocators and extend the allocators to have NUMA id as a
>> parameter. Thus, modify ReallocFunc to use the new extended realloc
>> primitives from the C side of the kernel (i. e.
>> k[v]realloc_node_align/vrealloc_node_align) and add the new function
>> alloc_node to the Allocator trait while keeping the existing one
>> (alloc) for backward compatibility.
>> 
>> This will allow to specify node to use for allocation of e. g.
>> {KV}Box, as well as for future NUMA aware users of the API.
>> 
>> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
> 
> My main feedback is that we should consider introducing a new trait
> instead of modifying Allocator. What we could do is have a NodeAllocator
> trait that is a super-trait of Allocator and has additional methods with
> a node parameter.
> 
> A sketch:
> 
> pub unsafe trait NodeAllocator: Allocator {
>    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
>                -> Result<NonNull<[u8]>, AllocError>;
> 
>    unsafe fn realloc_node(
>        ptr: Option<NonNull<u8>>,
>        layout: Layout,
>        old_layout: Layout,
>        flags: Flags,
>        nid: NumaNode,
>    ) -> Result<NonNull<[u8]>, AllocError>;
> }
> 
> By doing this, it's possible to have allocators that do not support
> specifying the numa node which only implement Allocator, and to have
> other allocators that implement both Allocator and NumaAllocator where
> you are able to specify the node.
> 
> If all allocators in the kernel support numa nodes, then you can ignore
> this.

This is an elegant solution indeed but I think that keeping the existing approach goes better with the overall kernel trend of having better NUMA support. My point is, if we add NodeAllocator as a super-trait and in a foreseeable future all the Rust allocators will want/be required to support NUMA (which is likely to happen), we’ll have to “flatten” the traits and effectively go back to the approach expressed in this patch.

>> +/// Non Uniform Memory Access (NUMA) node identifier
>> +#[derive(Clone, Copy, PartialEq)]
>> +pub struct NumaNode(i32);
>> +
>> +impl NumaNode {
>> +    /// create a new NUMA node identifer (non-negative integer)
>> +    /// returns EINVAL if a negative id or an id exceeding MAX_NUMNODES is specified
>> +    pub fn new(node: i32) -> Result<Self> {
>> +        // SAFETY: MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10
>> +        if node < 0 || node >= bindings::MAX_NUMNODES as i32 {
>> +            return Err(EINVAL);
>> +        }
>> +        Ok(Self(node))
>> +    }
>> +}
>> +
>> +/// Specify necessary constant to pass the information to Allocator that the caller doesn't care
>> +/// about the NUMA node to allocate memory from.
>> +pub mod numa {
>> +    use super::NumaNode;
>> +
>> +    /// No preference for NUMA node
>> +    pub const NUMA_NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
>> +}
> 
> Instead of using a module, you can make it an associated constant of the
> struct.
> 
> impl NumaNode {
>    pub const NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
> }
> 
> This way you can access the constant as NumaNode::NO_NODE.

Thanks, noted.

> 
>> /// The kernel's [`Allocator`] trait.
>> ///
>> /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described
>> @@ -148,7 +175,7 @@ pub unsafe trait Allocator {
>>     ///
>>     /// When the return value is `Ok(ptr)`, then `ptr` is
>>     /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
>> -    ///   [`Allocator::free`] or [`Allocator::realloc`],
>> +    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
>>     /// - aligned to `layout.align()`,
>>     ///
>>     /// Additionally, `Flags` are honored as documented in
>> @@ -159,7 +186,38 @@ fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
>>         unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) }
>>     }
>> 
>> -    /// Re-allocate an existing memory allocation to satisfy the requested `layout`.
>> +    /// Allocate memory based on `layout`, `flags` and `nid`.
>> +    ///
>> +    /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
>> +    /// constraints (i.e. minimum size and alignment as specified by `layout`).
>> +    ///
>> +    /// This function is equivalent to `realloc_node` when called with `None`.
>> +    ///
>> +    /// # Guarantees
>> +    ///
>> +    /// When the return value is `Ok(ptr)`, then `ptr` is
>> +    /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
>> +    ///   [`Allocator::free`], [`Allocator::realloc`] or [`Allocator::realloc_node`],
>> +    /// - aligned to `layout.align()`,
>> +    ///
>> +    /// Additionally, `Flags` are honored as documented in
>> +    /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>.
>> +    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
>> +                -> Result<NonNull<[u8]>, AllocError> {
> 
> I don't think this is how rustfmt would format this. Can you run rustfmt
> on your patch?
> 
> 
Will do, thanks.

~Vitaly

Re: [PATCH v9 3/4] rust: add support for NUMA ids in allocations

[Alice Ryhl]

On Tue, Jul 1, 2025 at 1:19 PM Vitaly Wool <vitaly.wool@konsulko.se> wrote:
>
>
>
> > On Jul 1, 2025, at 12:34 PM, Alice Ryhl <aliceryhl@google.com> wrote:
> >
> > On Tue, Jul 01, 2025 at 12:16:40AM +0200, Vitaly Wool wrote:
> >> Add a new type to support specifying NUMA identifiers in Rust
> >> allocators and extend the allocators to have NUMA id as a
> >> parameter. Thus, modify ReallocFunc to use the new extended realloc
> >> primitives from the C side of the kernel (i. e.
> >> k[v]realloc_node_align/vrealloc_node_align) and add the new function
> >> alloc_node to the Allocator trait while keeping the existing one
> >> (alloc) for backward compatibility.
> >>
> >> This will allow to specify node to use for allocation of e. g.
> >> {KV}Box, as well as for future NUMA aware users of the API.
> >>
> >> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
> >
> > My main feedback is that we should consider introducing a new trait
> > instead of modifying Allocator. What we could do is have a NodeAllocator
> > trait that is a super-trait of Allocator and has additional methods with
> > a node parameter.
> >
> > A sketch:
> >
> > pub unsafe trait NodeAllocator: Allocator {
> >    fn alloc_node(layout: Layout, flags: Flags, nid: NumaNode)
> >                -> Result<NonNull<[u8]>, AllocError>;
> >
> >    unsafe fn realloc_node(
> >        ptr: Option<NonNull<u8>>,
> >        layout: Layout,
> >        old_layout: Layout,
> >        flags: Flags,
> >        nid: NumaNode,
> >    ) -> Result<NonNull<[u8]>, AllocError>;
> > }
> >
> > By doing this, it's possible to have allocators that do not support
> > specifying the numa node which only implement Allocator, and to have
> > other allocators that implement both Allocator and NumaAllocator where
> > you are able to specify the node.
> >
> > If all allocators in the kernel support numa nodes, then you can ignore
> > this.
>
> This is an elegant solution indeed but I think that keeping the existing approach goes better with the overall kernel trend of having better NUMA support. My point is, if we add NodeAllocator as a super-trait and in a foreseeable future all the Rust allocators will want/be required to support NUMA (which is likely to happen), we’ll have to “flatten” the traits and effectively go back to the approach expressed in this patch.

If we are not going to have allocators without numa support, then what
you did is reasonable. Though in that case I would consider just
changing the existing methods instead of having methods both with and
without a numa node argument.

Alice

[PATCH v4 4/4] rust: support large alignments in allocations

[Vitaly Wool]

Add support for large (> PAGE_SIZE) alignments in Rust allocators.
All the preparations on the C side are already done, we just need
to add bindings for <alloc>_node_align() functions and start
using those.

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
---
 rust/helpers/slab.c            | 10 ++++++----
 rust/helpers/vmalloc.c         |  5 +++--
 rust/kernel/alloc/allocator.rs | 28 ++++++++--------------------
 3 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index 8472370a4338..d729be798f31 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -3,13 +3,15 @@
 #include <linux/slab.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_krealloc_node(const void *objp, size_t new_size, gfp_t flags, int node)
+rust_helper_krealloc_node_align(const void *objp, size_t new_size, unsigned long align,
+				gfp_t flags, int node)
 {
-	return krealloc_node(objp, new_size, flags, node);
+	return krealloc_node_align(objp, new_size, align, flags, node);
 }
 
 void * __must_check __realloc_size(2)
-rust_helper_kvrealloc_node(const void *p, size_t size, gfp_t flags, int node)
+rust_helper_kvrealloc_node_align(const void *p, size_t size, unsigned long align,
+				gfp_t flags, int node)
 {
-	return kvrealloc_node(p, size, flags, node);
+	return kvrealloc_node_align(p, size, align, flags, node);
 }
diff --git a/rust/helpers/vmalloc.c b/rust/helpers/vmalloc.c
index 62d30db9a1a6..7d7f7336b3d2 100644
--- a/rust/helpers/vmalloc.c
+++ b/rust/helpers/vmalloc.c
@@ -3,7 +3,8 @@
 #include <linux/vmalloc.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_vrealloc_node(const void *p, size_t size, gfp_t flags, int node)
+rust_helper_vrealloc_node_align(const void *p, size_t size, unsigned long align,
+				gfp_t flags, int node)
 {
-	return vrealloc_node(p, size, flags, node);
+	return vrealloc_node_align(p, size, align, flags, node);
 }
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 2e86e9839a1b..58e5bf78c159 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -59,19 +59,19 @@ fn aligned_size(new_layout: Layout) -> usize {
 /// One of the following: `krealloc`, `vrealloc`, `kvrealloc`.
 struct ReallocFunc(
     unsafe extern "C" fn(
-        *const crate::ffi::c_void, usize,  u32, crate::ffi::c_int,
+        *const crate::ffi::c_void, usize, crate::ffi::c_ulong, u32, crate::ffi::c_int,
     ) -> *mut crate::ffi::c_void,
 );
 
 impl ReallocFunc {
-    // INVARIANT: `krealloc_node` satisfies the type invariants.
-    const KREALLOC: Self = Self(bindings::krealloc_node);
+    // INVARIANT: `krealloc_node_align` satisfies the type invariants.
+    const KREALLOC: Self = Self(bindings::krealloc_node_align);
 
-    // INVARIANT: `vrealloc_node` satisfies the type invariants.
-    const VREALLOC: Self = Self(bindings::vrealloc_node);
+    // INVARIANT: `vrealloc_node_align` satisfies the type invariants.
+    const VREALLOC: Self = Self(bindings::vrealloc_node_align);
 
-    // INVARIANT: `kvrealloc_node` satisfies the type invariants.
-    const KVREALLOC: Self = Self(bindings::kvrealloc_node);
+    // INVARIANT: `kvrealloc_node_align` satisfies the type invariants.
+    const KVREALLOC: Self = Self(bindings::kvrealloc_node_align);
 
     /// # Safety
     ///
@@ -113,7 +113,7 @@ unsafe fn call(
         // - Those functions provide the guarantees of this function.
         let raw_ptr = unsafe {
             // If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
-            self.0(ptr.cast(), size, flags.0, nid.0).cast()
+            self.0(ptr.cast(), size, layout.align(), flags.0, nid.0).cast()
         };
 
         let ptr = if size == 0 {
@@ -157,12 +157,6 @@ unsafe fn realloc_node(
         flags: Flags,
         nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
-        // TODO: Support alignments larger than PAGE_SIZE.
-        if layout.align() > bindings::PAGE_SIZE {
-            pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
-            return Err(AllocError);
-        }
-
         // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
         // allocated with this `Allocator`.
         unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags, nid) }
@@ -182,12 +176,6 @@ unsafe fn realloc_node(
         flags: Flags,
         nid: NumaNode,
     ) -> Result<NonNull<[u8]>, AllocError> {
-        // TODO: Support alignments larger than PAGE_SIZE.
-        if layout.align() > bindings::PAGE_SIZE {
-            pr_warn!("KVmalloc does not support alignments larger than PAGE_SIZE yet.\n");
-            return Err(AllocError);
-        }
-
         // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
         // allocated with this `Allocator`.
         unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags, nid) }
-- 
2.39.2