Re: [PATCH RFC v2 06/19] Add a vmalloc_node_user function

[Christoph Hellwig <hch@infradead.org>]

On Wed, May 29, 2024 at 08:00:41PM +0200, Bernd Schubert wrote:
> This is to have a numa aware vmalloc function for memory exposed to
> userspace. Fuse uring will allocate queue memory using this
> new function.
> 
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> cc: Andrew Morton <akpm@linux-foundation.org>
> cc: linux-mm@kvack.org
> Acked-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>  include/linux/vmalloc.h |  1 +
>  mm/nommu.c              |  6 ++++++
>  mm/vmalloc.c            | 41 +++++++++++++++++++++++++++++++++++++----
>  3 files changed, 44 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 98ea90e90439..e7645702074e 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -141,6 +141,7 @@ static inline unsigned long vmalloc_nr_pages(void) { return 0; }
>  extern void *vmalloc(unsigned long size) __alloc_size(1);
>  extern void *vzalloc(unsigned long size) __alloc_size(1);
>  extern void *vmalloc_user(unsigned long size) __alloc_size(1);
> +extern void *vmalloc_node_user(unsigned long size, int node) __alloc_size(1);
>  extern void *vmalloc_node(unsigned long size, int node) __alloc_size(1);
>  extern void *vzalloc_node(unsigned long size, int node) __alloc_size(1);
>  extern void *vmalloc_32(unsigned long size) __alloc_size(1);
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 5ec8f44e7ce9..207ddf639aa9 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -185,6 +185,12 @@ void *vmalloc_user(unsigned long size)
>  }
>  EXPORT_SYMBOL(vmalloc_user);
>  
> +void *vmalloc_node_user(unsigned long size, int node)
> +{
> +	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
> +}
> +EXPORT_SYMBOL(vmalloc_node_user);
> +
>  struct page *vmalloc_to_page(const void *addr)
>  {
>  	return virt_to_page(addr);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 68fa001648cc..0ac2f44b2b1f 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3958,6 +3958,25 @@ void *vzalloc(unsigned long size)
>  }
>  EXPORT_SYMBOL(vzalloc);
>  
> +/**
> + * _vmalloc_node_user - allocate zeroed virtually contiguous memory for userspace

Please avoid the overly long line.

> + * on the given numa node
> + * @size: allocation size
> + * @node: numa node
> + *
> + * The resulting memory area is zeroed so it can be mapped to userspace
> + * without leaking data.
> + *
> + * Return: pointer to the allocated memory or %NULL on error
> + */
> +static void *_vmalloc_node_user(unsigned long size, int node)

Although for static functions kerneldoc comments are pretty silly
to start with.

>  void *vmalloc_user(unsigned long size)
>  {
> -	return __vmalloc_node_range(size, SHMLBA,  VMALLOC_START, VMALLOC_END,
> -				    GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL,
> -				    VM_USERMAP, NUMA_NO_NODE,
> -				    __builtin_return_address(0));
> +	return _vmalloc_node_user(size, NUMA_NO_NODE);

But I suspect simply adding a gfp_t argument to vmalloc_node might be
a much easier to use interface here, even if it would need a sanity
check to only allow for actually useful to vmalloc flags.