linux-kernel - Re: [PATCH 07/32] mm: Bring back vmalloc

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Message-ID: <ZFqOukfefifbfHMb@murray>
Date:   Tue, 9 May 2023 11:19:38 -0700
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-bcachefs@...r.kernel.org,
        Kent Overstreet <kent.overstreet@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>, linux-mm@...ck.org
Subject: Re: [PATCH 07/32] mm: Bring back vmalloc_exec

On Tue, May 09, 2023 at 12:56:32PM -0400, Kent Overstreet wrote:
> From: Kent Overstreet <kent.overstreet@...il.com>
>
> This is needed for bcachefs, which dynamically generates per-btree node
> unpack functions.

Small nits -

Would be good to refer to the original patch that removed it,
i.e. 7a0e27b2a0ce ("mm: remove vmalloc_exec") something like 'patch
... folded vmalloc_exec() into its one user, however bcachefs requires this
as well so revert'.

Would also be good to mention that you are now exporting the function which
the original didn't appear to do.

>
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Uladzislau Rezki <urezki@...il.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: linux-mm@...ck.org

Another nit: I'm a vmalloc reviewer so would be good to get cc'd too :)
(forgivable mistake as very recent change!)

> ---
>  include/linux/vmalloc.h |  1 +
>  kernel/module/main.c    |  4 +---
>  mm/nommu.c              | 18 ++++++++++++++++++
>  mm/vmalloc.c            | 21 +++++++++++++++++++++
>  4 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 69250efa03..ff147fe115 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -145,6 +145,7 @@ extern void *vzalloc(unsigned long size) __alloc_size(1);
>  extern void *vmalloc_user(unsigned long size) __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_exec(unsigned long size, gfp_t gfp_mask) __alloc_size(1);
>  extern void *vmalloc_32(unsigned long size) __alloc_size(1);
>  extern void *vmalloc_32_user(unsigned long size) __alloc_size(1);
>  extern void *__vmalloc(unsigned long size, gfp_t gfp_mask) __alloc_size(1);
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index d3be89de70..9eaa89e84c 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -1607,9 +1607,7 @@ static void dynamic_debug_remove(struct module *mod, struct _ddebug_info *dyndbg
>
>  void * __weak module_alloc(unsigned long size)
>  {
> -	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
> -			GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
> -			NUMA_NO_NODE, __builtin_return_address(0));
> +	return vmalloc_exec(size, GFP_KERNEL);
>  }
>
>  bool __weak module_init_section(const char *name)
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 57ba243c6a..8d9ab19e39 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -280,6 +280,24 @@ void *vzalloc_node(unsigned long size, int node)
>  }
>  EXPORT_SYMBOL(vzalloc_node);
>
> +/**
> + *	vmalloc_exec  -  allocate virtually contiguous, executable memory
> + *	@size:		allocation size
> + *
> + *	Kernel-internal function to allocate enough pages to cover @size
> + *	the page level allocator and map them into contiguous and
> + *	executable kernel virtual space.
> + *
> + *	For tight control over page level allocator and protection flags
> + *	use __vmalloc() instead.
> + */
> +
> +void *vmalloc_exec(unsigned long size, gfp_t gfp_mask)
> +{
> +	return __vmalloc(size, gfp_mask);
> +}
> +EXPORT_SYMBOL_GPL(vmalloc_exec);
> +
>  /**
>   * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
>   *	@size:		allocation size
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 31ff782d36..2ebb9ea7f0 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3401,6 +3401,27 @@ void *vzalloc_node(unsigned long size, int node)
>  }
>  EXPORT_SYMBOL(vzalloc_node);
>
> +/**
> + * vmalloc_exec - allocate virtually contiguous, executable memory
> + * @size:	  allocation size
> + *
> + * Kernel-internal function to allocate enough pages to cover @size
> + * the page level allocator and map them into contiguous and
> + * executable kernel virtual space.
> + *
> + * For tight control over page level allocator and protection flags
> + * use __vmalloc() instead.
> + *
> + * Return: pointer to the allocated memory or %NULL on error
> + */
> +void *vmalloc_exec(unsigned long size, gfp_t gfp_mask)
> +{
> +	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
> +			gfp_mask, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
> +			NUMA_NO_NODE, __builtin_return_address(0));
> +}
> +EXPORT_SYMBOL_GPL(vmalloc_exec);
> +
>  #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
>  #define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL)
>  #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
> --
> 2.40.1
>

Otherwise lgtm, feel free to add:

Acked-by: Lorenzo Stoakes <lstoakes@...il.com>