linux-kernel - Re: [PATCH v3 4/6] modules: Add CONFIG_ARCH_WANTS_MODULES_DATA_IN

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Date:   Wed, 2 Feb 2022 16:01:53 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Aaron Tomlin <atomlin@...hat.com>
Cc:     Jessica Yu <jeyu@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v3 4/6] modules: Add
 CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC

On Sat, Jan 29, 2022 at 05:02:09PM +0000, Christophe Leroy wrote:
> diff --git a/kernel/module.c b/kernel/module.c
> index 11f51e17fb9f..f3758115ebaa 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -81,7 +81,9 @@
>  /* If this is set, the section belongs in the init part of the module */
>  #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>  
> +#ifndef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
>  #define	data_layout core_layout
> +#endif
>  
>  /*
>   * Mutex protects:
> @@ -111,6 +113,12 @@ static struct mod_tree_root {
>  #define module_addr_min mod_tree.addr_min
>  #define module_addr_max mod_tree.addr_max
>  
> +#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
> +static struct mod_tree_root mod_data_tree __cacheline_aligned = {
> +	.addr_min = -1UL,
> +};
> +#endif
> +
>  #ifdef CONFIG_MODULES_TREE_LOOKUP
>  
>  /*
> @@ -186,6 +194,11 @@ static void mod_tree_insert(struct module *mod)
>  	__mod_tree_insert(&mod->core_layout.mtn, &mod_tree);
>  	if (mod->init_layout.size)
>  		__mod_tree_insert(&mod->init_layout.mtn, &mod_tree);
> +
> +#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
> +	mod->data_layout.mtn.mod = mod;
> +	__mod_tree_insert(&mod->data_layout.mtn, &mod_data_tree);
> +#endif


kernel/ directory has quite a few files, module.c is the second to
largest file, and it has tons of stuff. Aaron is doing work to
split things out to make code easier to read and so that its easier
to review changes. See:

https://lkml.kernel.org/r/20220130213214.1042497-1-atomlin@redhat.com

I think this is a good patch example which could benefit from that work.
So I'd much prefer to see that work go in first than this, so to see if
we can make the below changes more compartamentalized.

Curious, how much testing has been put into this series?

  Luis