Re: [PATCH v3 bpf RESEND 3/4] module: introduce module_alloc_huge

[Christoph Hellwig <hch@infradead.org>]

On Thu, Apr 14, 2022 at 12:59:13PM -0700, Song Liu wrote:
> Introduce module_alloc_huge, which allocates huge page backed memory in
> module memory space. The primary user of this memory is bpf_prog_pack
> (multiple BPF programs sharing a huge page).
> 
> Signed-off-by: Song Liu <song@kernel.org>
> ---
>  arch/x86/kernel/module.c     | 21 +++++++++++++++++++++
>  include/linux/moduleloader.h |  5 +++++
>  kernel/module.c              |  5 +++++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
> index b98ffcf4d250..63f6a16c70dc 100644
> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -86,6 +86,27 @@ void *module_alloc(unsigned long size)
>  	return p;
>  }
>  
> +void *module_alloc_huge(unsigned long size)
> +{
> +	gfp_t gfp_mask = GFP_KERNEL;
> +	void *p;
> +
> +	if (PAGE_ALIGN(size) > MODULES_LEN)
> +		return NULL;
> +
> +	p = __vmalloc_node_range(size, MODULE_ALIGN,
> +				 MODULES_VADDR + get_module_load_offset(),
> +				 MODULES_END, gfp_mask, PAGE_KERNEL,
> +				 VM_DEFER_KMEMLEAK | VM_ALLOW_HUGE_VMAP,
> +				 NUMA_NO_NODE, __builtin_return_address(0));
> +	if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0)) {
> +		vfree(p);
> +		return NULL;
> +	}
> +
> +	return p;
> +}
> +
>  #ifdef CONFIG_X86_32
>  int apply_relocate(Elf32_Shdr *sechdrs,
>  		   const char *strtab,
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> index 9e09d11ffe5b..d34743a88938 100644
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -26,6 +26,11 @@ unsigned int arch_mod_section_prepend(struct module *mod, unsigned int section);
>     sections.  Returns NULL on failure. */
>  void *module_alloc(unsigned long size);
>  
> +/* Allocator used for allocating memory in module memory space. If size is
> + * greater than PMD_SIZE, allow using huge pages. Returns NULL on failure.
> + */
> +void *module_alloc_huge(unsigned long size);
> +
>  /* Free memory returned from module_alloc. */
>  void module_memfree(void *module_region);
>  
> diff --git a/kernel/module.c b/kernel/module.c
> index 6cea788fd965..b2c6cb682a7d 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2839,6 +2839,11 @@ void * __weak module_alloc(unsigned long size)
>  			NUMA_NO_NODE, __builtin_return_address(0));
>  }
>  
> +void * __weak module_alloc_huge(unsigned long size)
> +{
> +	return vmalloc_huge(size);
> +}

Umm.  This should use the same parameters as module_alloc except for
also passing the new huge page flag.